1:mod:`!ssl` --- TLS/SSL wrapper for socket objects 2================================================== 3 4.. module:: ssl 5 :synopsis: TLS/SSL wrapper for socket objects 6 7.. moduleauthor:: Bill Janssen <bill.janssen@gmail.com> 8.. sectionauthor:: Bill Janssen <bill.janssen@gmail.com> 9 10**Source code:** :source:`Lib/ssl.py` 11 12.. index:: single: OpenSSL; (use in module ssl) 13 14.. index:: TLS, SSL, Transport Layer Security, Secure Sockets Layer 15 16-------------- 17 18This module provides access to Transport Layer Security (often known as "Secure 19Sockets Layer") encryption and peer authentication facilities for network 20sockets, both client-side and server-side. This module uses the OpenSSL 21library. It is available on all modern Unix systems, Windows, macOS, and 22probably additional platforms, as long as OpenSSL is installed on that platform. 23 24.. note:: 25 26 Some behavior may be platform dependent, since calls are made to the 27 operating system socket APIs. The installed version of OpenSSL may also 28 cause variations in behavior. For example, TLSv1.3 comes with OpenSSL version 29 1.1.1. 30 31.. warning:: 32 Don't use this module without reading the :ref:`ssl-security`. Doing so 33 may lead to a false sense of security, as the default settings of the 34 ssl module are not necessarily appropriate for your application. 35 36.. include:: ../includes/wasm-notavail.rst 37 38This section documents the objects and functions in the ``ssl`` module; for more 39general information about TLS, SSL, and certificates, the reader is referred to 40the documents in the "See Also" section at the bottom. 41 42This module provides a class, :class:`ssl.SSLSocket`, which is derived from the 43:class:`socket.socket` type, and provides a socket-like wrapper that also 44encrypts and decrypts the data going over the socket with SSL. It supports 45additional methods such as :meth:`getpeercert`, which retrieves the 46certificate of the other side of the connection, :meth:`cipher`, which 47retrieves the cipher being used for the secure connection or 48:meth:`get_verified_chain`, :meth:`get_unverified_chain` which retrieves 49certificate chain. 50 51For more sophisticated applications, the :class:`ssl.SSLContext` class 52helps manage settings and certificates, which can then be inherited 53by SSL sockets created through the :meth:`SSLContext.wrap_socket` method. 54 55.. versionchanged:: 3.5.3 56 Updated to support linking with OpenSSL 1.1.0 57 58.. versionchanged:: 3.6 59 60 OpenSSL 0.9.8, 1.0.0 and 1.0.1 are deprecated and no longer supported. 61 In the future the ssl module will require at least OpenSSL 1.0.2 or 62 1.1.0. 63 64.. versionchanged:: 3.10 65 66 :pep:`644` has been implemented. The ssl module requires OpenSSL 1.1.1 67 or newer. 68 69 Use of deprecated constants and functions result in deprecation warnings. 70 71 72Functions, Constants, and Exceptions 73------------------------------------ 74 75 76Socket creation 77^^^^^^^^^^^^^^^ 78 79Instances of :class:`SSLSocket` must be created using the 80:meth:`SSLContext.wrap_socket` method. The helper function 81:func:`create_default_context` returns a new context with secure default 82settings. 83 84Client socket example with default context and IPv4/IPv6 dual stack:: 85 86 import socket 87 import ssl 88 89 hostname = 'www.python.org' 90 context = ssl.create_default_context() 91 92 with socket.create_connection((hostname, 443)) as sock: 93 with context.wrap_socket(sock, server_hostname=hostname) as ssock: 94 print(ssock.version()) 95 96 97Client socket example with custom context and IPv4:: 98 99 hostname = 'www.python.org' 100 # PROTOCOL_TLS_CLIENT requires valid cert chain and hostname 101 context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) 102 context.load_verify_locations('path/to/cabundle.pem') 103 104 with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock: 105 with context.wrap_socket(sock, server_hostname=hostname) as ssock: 106 print(ssock.version()) 107 108 109Server socket example listening on localhost IPv4:: 110 111 context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER) 112 context.load_cert_chain('/path/to/certchain.pem', '/path/to/private.key') 113 114 with socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0) as sock: 115 sock.bind(('127.0.0.1', 8443)) 116 sock.listen(5) 117 with context.wrap_socket(sock, server_side=True) as ssock: 118 conn, addr = ssock.accept() 119 ... 120 121 122Context creation 123^^^^^^^^^^^^^^^^ 124 125A convenience function helps create :class:`SSLContext` objects for common 126purposes. 127 128.. function:: create_default_context(purpose=Purpose.SERVER_AUTH, cafile=None, capath=None, cadata=None) 129 130 Return a new :class:`SSLContext` object with default settings for 131 the given *purpose*. The settings are chosen by the :mod:`ssl` module, 132 and usually represent a higher security level than when calling the 133 :class:`SSLContext` constructor directly. 134 135 *cafile*, *capath*, *cadata* represent optional CA certificates to 136 trust for certificate verification, as in 137 :meth:`SSLContext.load_verify_locations`. If all three are 138 :const:`None`, this function can choose to trust the system's default 139 CA certificates instead. 140 141 The settings are: :data:`PROTOCOL_TLS_CLIENT` or 142 :data:`PROTOCOL_TLS_SERVER`, :data:`OP_NO_SSLv2`, and :data:`OP_NO_SSLv3` 143 with high encryption cipher suites without RC4 and 144 without unauthenticated cipher suites. Passing :const:`~Purpose.SERVER_AUTH` 145 as *purpose* sets :data:`~SSLContext.verify_mode` to :data:`CERT_REQUIRED` 146 and either loads CA certificates (when at least one of *cafile*, *capath* or 147 *cadata* is given) or uses :meth:`SSLContext.load_default_certs` to load 148 default CA certificates. 149 150 When :attr:`~SSLContext.keylog_filename` is supported and the environment 151 variable :envvar:`SSLKEYLOGFILE` is set, :func:`create_default_context` 152 enables key logging. 153 154 The default settings for this context include 155 :data:`VERIFY_X509_PARTIAL_CHAIN` and :data:`VERIFY_X509_STRICT`. 156 These make the underlying OpenSSL implementation behave more like 157 a conforming implementation of :rfc:`5280`, in exchange for a small 158 amount of incompatibility with older X.509 certificates. 159 160 .. note:: 161 The protocol, options, cipher and other settings may change to more 162 restrictive values anytime without prior deprecation. The values 163 represent a fair balance between compatibility and security. 164 165 If your application needs specific settings, you should create a 166 :class:`SSLContext` and apply the settings yourself. 167 168 .. note:: 169 If you find that when certain older clients or servers attempt to connect 170 with a :class:`SSLContext` created by this function that they get an error 171 stating "Protocol or cipher suite mismatch", it may be that they only 172 support SSL3.0 which this function excludes using the 173 :data:`OP_NO_SSLv3`. SSL3.0 is widely considered to be `completely broken 174 <https://en.wikipedia.org/wiki/POODLE>`_. If you still wish to continue to 175 use this function but still allow SSL 3.0 connections you can re-enable 176 them using:: 177 178 ctx = ssl.create_default_context(Purpose.CLIENT_AUTH) 179 ctx.options &= ~ssl.OP_NO_SSLv3 180 181 .. note:: 182 This context enables :data:`VERIFY_X509_STRICT` by default, which 183 may reject pre-:rfc:`5280` or malformed certificates that the 184 underlying OpenSSL implementation otherwise would accept. While disabling 185 this is not recommended, you can do so using:: 186 187 ctx = ssl.create_default_context() 188 ctx.verify_flags &= ~ssl.VERIFY_X509_STRICT 189 190 .. versionadded:: 3.4 191 192 .. versionchanged:: 3.4.4 193 194 RC4 was dropped from the default cipher string. 195 196 .. versionchanged:: 3.6 197 198 ChaCha20/Poly1305 was added to the default cipher string. 199 200 3DES was dropped from the default cipher string. 201 202 .. versionchanged:: 3.8 203 204 Support for key logging to :envvar:`SSLKEYLOGFILE` was added. 205 206 .. versionchanged:: 3.10 207 208 The context now uses :data:`PROTOCOL_TLS_CLIENT` or 209 :data:`PROTOCOL_TLS_SERVER` protocol instead of generic 210 :data:`PROTOCOL_TLS`. 211 212 .. versionchanged:: 3.13 213 214 The context now uses :data:`VERIFY_X509_PARTIAL_CHAIN` and 215 :data:`VERIFY_X509_STRICT` in its default verify flags. 216 217 218Exceptions 219^^^^^^^^^^ 220 221.. exception:: SSLError 222 223 Raised to signal an error from the underlying SSL implementation 224 (currently provided by the OpenSSL library). This signifies some 225 problem in the higher-level encryption and authentication layer that's 226 superimposed on the underlying network connection. This error 227 is a subtype of :exc:`OSError`. The error code and message of 228 :exc:`SSLError` instances are provided by the OpenSSL library. 229 230 .. versionchanged:: 3.3 231 :exc:`SSLError` used to be a subtype of :exc:`socket.error`. 232 233 .. attribute:: library 234 235 A string mnemonic designating the OpenSSL submodule in which the error 236 occurred, such as ``SSL``, ``PEM`` or ``X509``. The range of possible 237 values depends on the OpenSSL version. 238 239 .. versionadded:: 3.3 240 241 .. attribute:: reason 242 243 A string mnemonic designating the reason this error occurred, for 244 example ``CERTIFICATE_VERIFY_FAILED``. The range of possible 245 values depends on the OpenSSL version. 246 247 .. versionadded:: 3.3 248 249.. exception:: SSLZeroReturnError 250 251 A subclass of :exc:`SSLError` raised when trying to read or write and 252 the SSL connection has been closed cleanly. Note that this doesn't 253 mean that the underlying transport (read TCP) has been closed. 254 255 .. versionadded:: 3.3 256 257.. exception:: SSLWantReadError 258 259 A subclass of :exc:`SSLError` raised by a :ref:`non-blocking SSL socket 260 <ssl-nonblocking>` when trying to read or write data, but more data needs 261 to be received on the underlying TCP transport before the request can be 262 fulfilled. 263 264 .. versionadded:: 3.3 265 266.. exception:: SSLWantWriteError 267 268 A subclass of :exc:`SSLError` raised by a :ref:`non-blocking SSL socket 269 <ssl-nonblocking>` when trying to read or write data, but more data needs 270 to be sent on the underlying TCP transport before the request can be 271 fulfilled. 272 273 .. versionadded:: 3.3 274 275.. exception:: SSLSyscallError 276 277 A subclass of :exc:`SSLError` raised when a system error was encountered 278 while trying to fulfill an operation on a SSL socket. Unfortunately, 279 there is no easy way to inspect the original errno number. 280 281 .. versionadded:: 3.3 282 283.. exception:: SSLEOFError 284 285 A subclass of :exc:`SSLError` raised when the SSL connection has been 286 terminated abruptly. Generally, you shouldn't try to reuse the underlying 287 transport when this error is encountered. 288 289 .. versionadded:: 3.3 290 291.. exception:: SSLCertVerificationError 292 293 A subclass of :exc:`SSLError` raised when certificate validation has 294 failed. 295 296 .. versionadded:: 3.7 297 298 .. attribute:: verify_code 299 300 A numeric error number that denotes the verification error. 301 302 .. attribute:: verify_message 303 304 A human readable string of the verification error. 305 306.. exception:: CertificateError 307 308 An alias for :exc:`SSLCertVerificationError`. 309 310 .. versionchanged:: 3.7 311 The exception is now an alias for :exc:`SSLCertVerificationError`. 312 313 314Random generation 315^^^^^^^^^^^^^^^^^ 316 317.. function:: RAND_bytes(num) 318 319 Return *num* cryptographically strong pseudo-random bytes. Raises an 320 :class:`SSLError` if the PRNG has not been seeded with enough data or if the 321 operation is not supported by the current RAND method. :func:`RAND_status` 322 can be used to check the status of the PRNG and :func:`RAND_add` can be used 323 to seed the PRNG. 324 325 For almost all applications :func:`os.urandom` is preferable. 326 327 Read the Wikipedia article, `Cryptographically secure pseudorandom number 328 generator (CSPRNG) 329 <https://en.wikipedia.org/wiki/Cryptographically_secure_pseudorandom_number_generator>`_, 330 to get the requirements of a cryptographically strong generator. 331 332 .. versionadded:: 3.3 333 334.. function:: RAND_status() 335 336 Return ``True`` if the SSL pseudo-random number generator has been seeded 337 with 'enough' randomness, and ``False`` otherwise. You can use 338 :func:`ssl.RAND_egd` and :func:`ssl.RAND_add` to increase the randomness of 339 the pseudo-random number generator. 340 341.. function:: RAND_add(bytes, entropy) 342 343 Mix the given *bytes* into the SSL pseudo-random number generator. The 344 parameter *entropy* (a float) is a lower bound on the entropy contained in 345 string (so you can always use ``0.0``). See :rfc:`1750` for more 346 information on sources of entropy. 347 348 .. versionchanged:: 3.5 349 Writable :term:`bytes-like object` is now accepted. 350 351Certificate handling 352^^^^^^^^^^^^^^^^^^^^ 353 354.. testsetup:: 355 356 import ssl 357 358.. function:: cert_time_to_seconds(cert_time) 359 360 Return the time in seconds since the Epoch, given the ``cert_time`` 361 string representing the "notBefore" or "notAfter" date from a 362 certificate in ``"%b %d %H:%M:%S %Y %Z"`` strptime format (C 363 locale). 364 365 Here's an example: 366 367 .. doctest:: newcontext 368 369 >>> import ssl 370 >>> timestamp = ssl.cert_time_to_seconds("Jan 5 09:34:43 2018 GMT") 371 >>> timestamp # doctest: +SKIP 372 1515144883 373 >>> from datetime import datetime 374 >>> print(datetime.utcfromtimestamp(timestamp)) # doctest: +SKIP 375 2018-01-05 09:34:43 376 377 "notBefore" or "notAfter" dates must use GMT (:rfc:`5280`). 378 379 .. versionchanged:: 3.5 380 Interpret the input time as a time in UTC as specified by 'GMT' 381 timezone in the input string. Local timezone was used 382 previously. Return an integer (no fractions of a second in the 383 input format) 384 385.. function:: get_server_certificate(addr, ssl_version=PROTOCOL_TLS_CLIENT, \ 386 ca_certs=None[, timeout]) 387 388 Given the address ``addr`` of an SSL-protected server, as a (*hostname*, 389 *port-number*) pair, fetches the server's certificate, and returns it as a 390 PEM-encoded string. If ``ssl_version`` is specified, uses that version of 391 the SSL protocol to attempt to connect to the server. If *ca_certs* is 392 specified, it should be a file containing a list of root certificates, the 393 same format as used for the *cafile* parameter in 394 :meth:`SSLContext.load_verify_locations`. The call will attempt to validate the 395 server certificate against that set of root certificates, and will fail 396 if the validation attempt fails. A timeout can be specified with the 397 ``timeout`` parameter. 398 399 .. versionchanged:: 3.3 400 This function is now IPv6-compatible. 401 402 .. versionchanged:: 3.5 403 The default *ssl_version* is changed from :data:`PROTOCOL_SSLv3` to 404 :data:`PROTOCOL_TLS` for maximum compatibility with modern servers. 405 406 .. versionchanged:: 3.10 407 The *timeout* parameter was added. 408 409.. function:: DER_cert_to_PEM_cert(DER_cert_bytes) 410 411 Given a certificate as a DER-encoded blob of bytes, returns a PEM-encoded 412 string version of the same certificate. 413 414.. function:: PEM_cert_to_DER_cert(PEM_cert_string) 415 416 Given a certificate as an ASCII PEM string, returns a DER-encoded sequence of 417 bytes for that same certificate. 418 419.. function:: get_default_verify_paths() 420 421 Returns a named tuple with paths to OpenSSL's default cafile and capath. 422 The paths are the same as used by 423 :meth:`SSLContext.set_default_verify_paths`. The return value is a 424 :term:`named tuple` ``DefaultVerifyPaths``: 425 426 * :attr:`cafile` - resolved path to cafile or ``None`` if the file doesn't exist, 427 * :attr:`capath` - resolved path to capath or ``None`` if the directory doesn't exist, 428 * :attr:`openssl_cafile_env` - OpenSSL's environment key that points to a cafile, 429 * :attr:`openssl_cafile` - hard coded path to a cafile, 430 * :attr:`openssl_capath_env` - OpenSSL's environment key that points to a capath, 431 * :attr:`openssl_capath` - hard coded path to a capath directory 432 433 .. versionadded:: 3.4 434 435.. function:: enum_certificates(store_name) 436 437 Retrieve certificates from Windows' system cert store. *store_name* may be 438 one of ``CA``, ``ROOT`` or ``MY``. Windows may provide additional cert 439 stores, too. 440 441 The function returns a list of (cert_bytes, encoding_type, trust) tuples. 442 The encoding_type specifies the encoding of cert_bytes. It is either 443 :const:`x509_asn` for X.509 ASN.1 data or :const:`pkcs_7_asn` for 444 PKCS#7 ASN.1 data. Trust specifies the purpose of the certificate as a set 445 of OIDS or exactly ``True`` if the certificate is trustworthy for all 446 purposes. 447 448 Example:: 449 450 >>> ssl.enum_certificates("CA") 451 [(b'data...', 'x509_asn', {'1.3.6.1.5.5.7.3.1', '1.3.6.1.5.5.7.3.2'}), 452 (b'data...', 'x509_asn', True)] 453 454 .. availability:: Windows. 455 456 .. versionadded:: 3.4 457 458.. function:: enum_crls(store_name) 459 460 Retrieve CRLs from Windows' system cert store. *store_name* may be 461 one of ``CA``, ``ROOT`` or ``MY``. Windows may provide additional cert 462 stores, too. 463 464 The function returns a list of (cert_bytes, encoding_type, trust) tuples. 465 The encoding_type specifies the encoding of cert_bytes. It is either 466 :const:`x509_asn` for X.509 ASN.1 data or :const:`pkcs_7_asn` for 467 PKCS#7 ASN.1 data. 468 469 .. availability:: Windows. 470 471 .. versionadded:: 3.4 472 473 474Constants 475^^^^^^^^^ 476 477 All constants are now :class:`enum.IntEnum` or :class:`enum.IntFlag` collections. 478 479 .. versionadded:: 3.6 480 481.. data:: CERT_NONE 482 483 Possible value for :attr:`SSLContext.verify_mode`. 484 Except for :const:`PROTOCOL_TLS_CLIENT`, 485 it is the default mode. With client-side sockets, just about any 486 cert is accepted. Validation errors, such as untrusted or expired cert, 487 are ignored and do not abort the TLS/SSL handshake. 488 489 In server mode, no certificate is requested from the client, so the client 490 does not send any for client cert authentication. 491 492 See the discussion of :ref:`ssl-security` below. 493 494.. data:: CERT_OPTIONAL 495 496 Possible value for :attr:`SSLContext.verify_mode`. 497 In client mode, :const:`CERT_OPTIONAL` 498 has the same meaning as :const:`CERT_REQUIRED`. It is recommended to 499 use :const:`CERT_REQUIRED` for client-side sockets instead. 500 501 In server mode, a client certificate request is sent to the client. The 502 client may either ignore the request or send a certificate in order 503 perform TLS client cert authentication. If the client chooses to send 504 a certificate, it is verified. Any verification error immediately aborts 505 the TLS handshake. 506 507 Use of this setting requires a valid set of CA certificates to 508 be passed to :meth:`SSLContext.load_verify_locations`. 509 510.. data:: CERT_REQUIRED 511 512 Possible value for :attr:`SSLContext.verify_mode`. 513 In this mode, certificates are 514 required from the other side of the socket connection; an :class:`SSLError` 515 will be raised if no certificate is provided, or if its validation fails. 516 This mode is **not** sufficient to verify a certificate in client mode as 517 it does not match hostnames. :attr:`~SSLContext.check_hostname` must be 518 enabled as well to verify the authenticity of a cert. 519 :const:`PROTOCOL_TLS_CLIENT` uses :const:`CERT_REQUIRED` and 520 enables :attr:`~SSLContext.check_hostname` by default. 521 522 With server socket, this mode provides mandatory TLS client cert 523 authentication. A client certificate request is sent to the client and 524 the client must provide a valid and trusted certificate. 525 526 Use of this setting requires a valid set of CA certificates to 527 be passed to :meth:`SSLContext.load_verify_locations`. 528 529.. class:: VerifyMode 530 531 :class:`enum.IntEnum` collection of CERT_* constants. 532 533 .. versionadded:: 3.6 534 535.. data:: VERIFY_DEFAULT 536 537 Possible value for :attr:`SSLContext.verify_flags`. In this mode, certificate 538 revocation lists (CRLs) are not checked. By default OpenSSL does neither 539 require nor verify CRLs. 540 541 .. versionadded:: 3.4 542 543.. data:: VERIFY_CRL_CHECK_LEAF 544 545 Possible value for :attr:`SSLContext.verify_flags`. In this mode, only the 546 peer cert is checked but none of the intermediate CA certificates. The mode 547 requires a valid CRL that is signed by the peer cert's issuer (its direct 548 ancestor CA). If no proper CRL has been loaded with 549 :attr:`SSLContext.load_verify_locations`, validation will fail. 550 551 .. versionadded:: 3.4 552 553.. data:: VERIFY_CRL_CHECK_CHAIN 554 555 Possible value for :attr:`SSLContext.verify_flags`. In this mode, CRLs of 556 all certificates in the peer cert chain are checked. 557 558 .. versionadded:: 3.4 559 560.. data:: VERIFY_X509_STRICT 561 562 Possible value for :attr:`SSLContext.verify_flags` to disable workarounds 563 for broken X.509 certificates. 564 565 .. versionadded:: 3.4 566 567.. data:: VERIFY_ALLOW_PROXY_CERTS 568 569 Possible value for :attr:`SSLContext.verify_flags` to enables proxy 570 certificate verification. 571 572 .. versionadded:: 3.10 573 574.. data:: VERIFY_X509_TRUSTED_FIRST 575 576 Possible value for :attr:`SSLContext.verify_flags`. It instructs OpenSSL to 577 prefer trusted certificates when building the trust chain to validate a 578 certificate. This flag is enabled by default. 579 580 .. versionadded:: 3.4.4 581 582.. data:: VERIFY_X509_PARTIAL_CHAIN 583 584 Possible value for :attr:`SSLContext.verify_flags`. It instructs OpenSSL to 585 accept intermediate CAs in the trust store to be treated as trust-anchors, 586 in the same way as the self-signed root CA certificates. This makes it 587 possible to trust certificates issued by an intermediate CA without having 588 to trust its ancestor root CA. 589 590 .. versionadded:: 3.10 591 592 593.. class:: VerifyFlags 594 595 :class:`enum.IntFlag` collection of VERIFY_* constants. 596 597 .. versionadded:: 3.6 598 599.. data:: PROTOCOL_TLS 600 601 Selects the highest protocol version that both the client and server support. 602 Despite the name, this option can select both "SSL" and "TLS" protocols. 603 604 .. versionadded:: 3.6 605 606 .. deprecated:: 3.10 607 608 TLS clients and servers require different default settings for secure 609 communication. The generic TLS protocol constant is deprecated in 610 favor of :data:`PROTOCOL_TLS_CLIENT` and :data:`PROTOCOL_TLS_SERVER`. 611 612.. data:: PROTOCOL_TLS_CLIENT 613 614 Auto-negotiate the highest protocol version that both the client and 615 server support, and configure the context client-side connections. The 616 protocol enables :data:`CERT_REQUIRED` and 617 :attr:`~SSLContext.check_hostname` by default. 618 619 .. versionadded:: 3.6 620 621.. data:: PROTOCOL_TLS_SERVER 622 623 Auto-negotiate the highest protocol version that both the client and 624 server support, and configure the context server-side connections. 625 626 .. versionadded:: 3.6 627 628.. data:: PROTOCOL_SSLv23 629 630 Alias for :data:`PROTOCOL_TLS`. 631 632 .. deprecated:: 3.6 633 634 Use :data:`PROTOCOL_TLS` instead. 635 636.. data:: PROTOCOL_SSLv3 637 638 Selects SSL version 3 as the channel encryption protocol. 639 640 This protocol is not available if OpenSSL is compiled with the 641 ``no-ssl3`` option. 642 643 .. warning:: 644 645 SSL version 3 is insecure. Its use is highly discouraged. 646 647 .. deprecated:: 3.6 648 649 OpenSSL has deprecated all version specific protocols. Use the default 650 protocol :data:`PROTOCOL_TLS_SERVER` or :data:`PROTOCOL_TLS_CLIENT` 651 with :attr:`SSLContext.minimum_version` and 652 :attr:`SSLContext.maximum_version` instead. 653 654 655.. data:: PROTOCOL_TLSv1 656 657 Selects TLS version 1.0 as the channel encryption protocol. 658 659 .. deprecated:: 3.6 660 661 OpenSSL has deprecated all version specific protocols. 662 663.. data:: PROTOCOL_TLSv1_1 664 665 Selects TLS version 1.1 as the channel encryption protocol. 666 Available only with openssl version 1.0.1+. 667 668 .. versionadded:: 3.4 669 670 .. deprecated:: 3.6 671 672 OpenSSL has deprecated all version specific protocols. 673 674.. data:: PROTOCOL_TLSv1_2 675 676 Selects TLS version 1.2 as the channel encryption protocol. 677 Available only with openssl version 1.0.1+. 678 679 .. versionadded:: 3.4 680 681 .. deprecated:: 3.6 682 683 OpenSSL has deprecated all version specific protocols. 684 685.. data:: OP_ALL 686 687 Enables workarounds for various bugs present in other SSL implementations. 688 This option is set by default. It does not necessarily set the same 689 flags as OpenSSL's ``SSL_OP_ALL`` constant. 690 691 .. versionadded:: 3.2 692 693.. data:: OP_NO_SSLv2 694 695 Prevents an SSLv2 connection. This option is only applicable in 696 conjunction with :const:`PROTOCOL_TLS`. It prevents the peers from 697 choosing SSLv2 as the protocol version. 698 699 .. versionadded:: 3.2 700 701 .. deprecated:: 3.6 702 703 SSLv2 is deprecated 704 705.. data:: OP_NO_SSLv3 706 707 Prevents an SSLv3 connection. This option is only applicable in 708 conjunction with :const:`PROTOCOL_TLS`. It prevents the peers from 709 choosing SSLv3 as the protocol version. 710 711 .. versionadded:: 3.2 712 713 .. deprecated:: 3.6 714 715 SSLv3 is deprecated 716 717.. data:: OP_NO_TLSv1 718 719 Prevents a TLSv1 connection. This option is only applicable in 720 conjunction with :const:`PROTOCOL_TLS`. It prevents the peers from 721 choosing TLSv1 as the protocol version. 722 723 .. versionadded:: 3.2 724 725 .. deprecated:: 3.7 726 The option is deprecated since OpenSSL 1.1.0, use the new 727 :attr:`SSLContext.minimum_version` and 728 :attr:`SSLContext.maximum_version` instead. 729 730.. data:: OP_NO_TLSv1_1 731 732 Prevents a TLSv1.1 connection. This option is only applicable in conjunction 733 with :const:`PROTOCOL_TLS`. It prevents the peers from choosing TLSv1.1 as 734 the protocol version. Available only with openssl version 1.0.1+. 735 736 .. versionadded:: 3.4 737 738 .. deprecated:: 3.7 739 The option is deprecated since OpenSSL 1.1.0. 740 741.. data:: OP_NO_TLSv1_2 742 743 Prevents a TLSv1.2 connection. This option is only applicable in conjunction 744 with :const:`PROTOCOL_TLS`. It prevents the peers from choosing TLSv1.2 as 745 the protocol version. Available only with openssl version 1.0.1+. 746 747 .. versionadded:: 3.4 748 749 .. deprecated:: 3.7 750 The option is deprecated since OpenSSL 1.1.0. 751 752.. data:: OP_NO_TLSv1_3 753 754 Prevents a TLSv1.3 connection. This option is only applicable in conjunction 755 with :const:`PROTOCOL_TLS`. It prevents the peers from choosing TLSv1.3 as 756 the protocol version. TLS 1.3 is available with OpenSSL 1.1.1 or later. 757 When Python has been compiled against an older version of OpenSSL, the 758 flag defaults to *0*. 759 760 .. versionadded:: 3.6.3 761 762 .. deprecated:: 3.7 763 The option is deprecated since OpenSSL 1.1.0. It was added to 2.7.15 and 764 3.6.3 for backwards compatibility with OpenSSL 1.0.2. 765 766.. data:: OP_NO_RENEGOTIATION 767 768 Disable all renegotiation in TLSv1.2 and earlier. Do not send 769 HelloRequest messages, and ignore renegotiation requests via ClientHello. 770 771 This option is only available with OpenSSL 1.1.0h and later. 772 773 .. versionadded:: 3.7 774 775.. data:: OP_CIPHER_SERVER_PREFERENCE 776 777 Use the server's cipher ordering preference, rather than the client's. 778 This option has no effect on client sockets and SSLv2 server sockets. 779 780 .. versionadded:: 3.3 781 782.. data:: OP_SINGLE_DH_USE 783 784 Prevents reuse of the same DH key for distinct SSL sessions. This 785 improves forward secrecy but requires more computational resources. 786 This option only applies to server sockets. 787 788 .. versionadded:: 3.3 789 790.. data:: OP_SINGLE_ECDH_USE 791 792 Prevents reuse of the same ECDH key for distinct SSL sessions. This 793 improves forward secrecy but requires more computational resources. 794 This option only applies to server sockets. 795 796 .. versionadded:: 3.3 797 798.. data:: OP_ENABLE_MIDDLEBOX_COMPAT 799 800 Send dummy Change Cipher Spec (CCS) messages in TLS 1.3 handshake to make 801 a TLS 1.3 connection look more like a TLS 1.2 connection. 802 803 This option is only available with OpenSSL 1.1.1 and later. 804 805 .. versionadded:: 3.8 806 807.. data:: OP_NO_COMPRESSION 808 809 Disable compression on the SSL channel. This is useful if the application 810 protocol supports its own compression scheme. 811 812 .. versionadded:: 3.3 813 814.. class:: Options 815 816 :class:`enum.IntFlag` collection of OP_* constants. 817 818.. data:: OP_NO_TICKET 819 820 Prevent client side from requesting a session ticket. 821 822 .. versionadded:: 3.6 823 824.. data:: OP_IGNORE_UNEXPECTED_EOF 825 826 Ignore unexpected shutdown of TLS connections. 827 828 This option is only available with OpenSSL 3.0.0 and later. 829 830 .. versionadded:: 3.10 831 832.. data:: OP_ENABLE_KTLS 833 834 Enable the use of the kernel TLS. To benefit from the feature, OpenSSL must 835 have been compiled with support for it, and the negotiated cipher suites and 836 extensions must be supported by it (a list of supported ones may vary by 837 platform and kernel version). 838 839 Note that with enabled kernel TLS some cryptographic operations are 840 performed by the kernel directly and not via any available OpenSSL 841 Providers. This might be undesirable if, for example, the application 842 requires all cryptographic operations to be performed by the FIPS provider. 843 844 This option is only available with OpenSSL 3.0.0 and later. 845 846 .. versionadded:: 3.12 847 848.. data:: OP_LEGACY_SERVER_CONNECT 849 850 Allow legacy insecure renegotiation between OpenSSL and unpatched servers 851 only. 852 853 .. versionadded:: 3.12 854 855.. data:: HAS_ALPN 856 857 Whether the OpenSSL library has built-in support for the *Application-Layer 858 Protocol Negotiation* TLS extension as described in :rfc:`7301`. 859 860 .. versionadded:: 3.5 861 862.. data:: HAS_NEVER_CHECK_COMMON_NAME 863 864 Whether the OpenSSL library has built-in support not checking subject 865 common name and :attr:`SSLContext.hostname_checks_common_name` is 866 writeable. 867 868 .. versionadded:: 3.7 869 870.. data:: HAS_ECDH 871 872 Whether the OpenSSL library has built-in support for the Elliptic Curve-based 873 Diffie-Hellman key exchange. This should be true unless the feature was 874 explicitly disabled by the distributor. 875 876 .. versionadded:: 3.3 877 878.. data:: HAS_SNI 879 880 Whether the OpenSSL library has built-in support for the *Server Name 881 Indication* extension (as defined in :rfc:`6066`). 882 883 .. versionadded:: 3.2 884 885.. data:: HAS_NPN 886 887 Whether the OpenSSL library has built-in support for the *Next Protocol 888 Negotiation* as described in the `Application Layer Protocol 889 Negotiation <https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation>`_. 890 When true, you can use the :meth:`SSLContext.set_npn_protocols` method to advertise 891 which protocols you want to support. 892 893 .. versionadded:: 3.3 894 895.. data:: HAS_SSLv2 896 897 Whether the OpenSSL library has built-in support for the SSL 2.0 protocol. 898 899 .. versionadded:: 3.7 900 901.. data:: HAS_SSLv3 902 903 Whether the OpenSSL library has built-in support for the SSL 3.0 protocol. 904 905 .. versionadded:: 3.7 906 907.. data:: HAS_TLSv1 908 909 Whether the OpenSSL library has built-in support for the TLS 1.0 protocol. 910 911 .. versionadded:: 3.7 912 913.. data:: HAS_TLSv1_1 914 915 Whether the OpenSSL library has built-in support for the TLS 1.1 protocol. 916 917 .. versionadded:: 3.7 918 919.. data:: HAS_TLSv1_2 920 921 Whether the OpenSSL library has built-in support for the TLS 1.2 protocol. 922 923 .. versionadded:: 3.7 924 925.. data:: HAS_TLSv1_3 926 927 Whether the OpenSSL library has built-in support for the TLS 1.3 protocol. 928 929 .. versionadded:: 3.7 930 931.. data:: HAS_PSK 932 933 Whether the OpenSSL library has built-in support for TLS-PSK. 934 935 .. versionadded:: 3.13 936 937.. data:: CHANNEL_BINDING_TYPES 938 939 List of supported TLS channel binding types. Strings in this list 940 can be used as arguments to :meth:`SSLSocket.get_channel_binding`. 941 942 .. versionadded:: 3.3 943 944.. data:: OPENSSL_VERSION 945 946 The version string of the OpenSSL library loaded by the interpreter:: 947 948 >>> ssl.OPENSSL_VERSION 949 'OpenSSL 1.0.2k 26 Jan 2017' 950 951 .. versionadded:: 3.2 952 953.. data:: OPENSSL_VERSION_INFO 954 955 A tuple of five integers representing version information about the 956 OpenSSL library:: 957 958 >>> ssl.OPENSSL_VERSION_INFO 959 (1, 0, 2, 11, 15) 960 961 .. versionadded:: 3.2 962 963.. data:: OPENSSL_VERSION_NUMBER 964 965 The raw version number of the OpenSSL library, as a single integer:: 966 967 >>> ssl.OPENSSL_VERSION_NUMBER 968 268443839 969 >>> hex(ssl.OPENSSL_VERSION_NUMBER) 970 '0x100020bf' 971 972 .. versionadded:: 3.2 973 974.. data:: ALERT_DESCRIPTION_HANDSHAKE_FAILURE 975 ALERT_DESCRIPTION_INTERNAL_ERROR 976 ALERT_DESCRIPTION_* 977 978 Alert Descriptions from :rfc:`5246` and others. The `IANA TLS Alert Registry 979 <https://www.iana.org/assignments/tls-parameters/tls-parameters.xml#tls-parameters-6>`_ 980 contains this list and references to the RFCs where their meaning is defined. 981 982 Used as the return value of the callback function in 983 :meth:`SSLContext.set_servername_callback`. 984 985 .. versionadded:: 3.4 986 987.. class:: AlertDescription 988 989 :class:`enum.IntEnum` collection of ALERT_DESCRIPTION_* constants. 990 991 .. versionadded:: 3.6 992 993.. data:: Purpose.SERVER_AUTH 994 995 Option for :func:`create_default_context` and 996 :meth:`SSLContext.load_default_certs`. This value indicates that the 997 context may be used to authenticate web servers (therefore, it will 998 be used to create client-side sockets). 999 1000 .. versionadded:: 3.4 1001 1002.. data:: Purpose.CLIENT_AUTH 1003 1004 Option for :func:`create_default_context` and 1005 :meth:`SSLContext.load_default_certs`. This value indicates that the 1006 context may be used to authenticate web clients (therefore, it will 1007 be used to create server-side sockets). 1008 1009 .. versionadded:: 3.4 1010 1011.. class:: SSLErrorNumber 1012 1013 :class:`enum.IntEnum` collection of SSL_ERROR_* constants. 1014 1015 .. versionadded:: 3.6 1016 1017.. class:: TLSVersion 1018 1019 :class:`enum.IntEnum` collection of SSL and TLS versions for 1020 :attr:`SSLContext.maximum_version` and :attr:`SSLContext.minimum_version`. 1021 1022 .. versionadded:: 3.7 1023 1024.. attribute:: TLSVersion.MINIMUM_SUPPORTED 1025.. attribute:: TLSVersion.MAXIMUM_SUPPORTED 1026 1027 The minimum or maximum supported SSL or TLS version. These are magic 1028 constants. Their values don't reflect the lowest and highest available 1029 TLS/SSL versions. 1030 1031.. attribute:: TLSVersion.SSLv3 1032.. attribute:: TLSVersion.TLSv1 1033.. attribute:: TLSVersion.TLSv1_1 1034.. attribute:: TLSVersion.TLSv1_2 1035.. attribute:: TLSVersion.TLSv1_3 1036 1037 SSL 3.0 to TLS 1.3. 1038 1039 .. deprecated:: 3.10 1040 1041 All :class:`TLSVersion` members except :attr:`TLSVersion.TLSv1_2` and 1042 :attr:`TLSVersion.TLSv1_3` are deprecated. 1043 1044 1045SSL Sockets 1046----------- 1047 1048.. class:: SSLSocket(socket.socket) 1049 1050 SSL sockets provide the following methods of :ref:`socket-objects`: 1051 1052 - :meth:`~socket.socket.accept` 1053 - :meth:`~socket.socket.bind` 1054 - :meth:`~socket.socket.close` 1055 - :meth:`~socket.socket.connect` 1056 - :meth:`~socket.socket.detach` 1057 - :meth:`~socket.socket.fileno` 1058 - :meth:`~socket.socket.getpeername`, :meth:`~socket.socket.getsockname` 1059 - :meth:`~socket.socket.getsockopt`, :meth:`~socket.socket.setsockopt` 1060 - :meth:`~socket.socket.gettimeout`, :meth:`~socket.socket.settimeout`, 1061 :meth:`~socket.socket.setblocking` 1062 - :meth:`~socket.socket.listen` 1063 - :meth:`~socket.socket.makefile` 1064 - :meth:`~socket.socket.recv`, :meth:`~socket.socket.recv_into` 1065 (but passing a non-zero ``flags`` argument is not allowed) 1066 - :meth:`~socket.socket.send`, :meth:`~socket.socket.sendall` (with 1067 the same limitation) 1068 - :meth:`~socket.socket.sendfile` (but :mod:`os.sendfile` will be used 1069 for plain-text sockets only, else :meth:`~socket.socket.send` will be used) 1070 - :meth:`~socket.socket.shutdown` 1071 1072 However, since the SSL (and TLS) protocol has its own framing atop 1073 of TCP, the SSL sockets abstraction can, in certain respects, diverge from 1074 the specification of normal, OS-level sockets. See especially the 1075 :ref:`notes on non-blocking sockets <ssl-nonblocking>`. 1076 1077 Instances of :class:`SSLSocket` must be created using the 1078 :meth:`SSLContext.wrap_socket` method. 1079 1080 .. versionchanged:: 3.5 1081 The :meth:`sendfile` method was added. 1082 1083 .. versionchanged:: 3.5 1084 The :meth:`shutdown` does not reset the socket timeout each time bytes 1085 are received or sent. The socket timeout is now the maximum total duration 1086 of the shutdown. 1087 1088 .. deprecated:: 3.6 1089 It is deprecated to create a :class:`SSLSocket` instance directly, use 1090 :meth:`SSLContext.wrap_socket` to wrap a socket. 1091 1092 .. versionchanged:: 3.7 1093 :class:`SSLSocket` instances must to created with 1094 :meth:`~SSLContext.wrap_socket`. In earlier versions, it was possible 1095 to create instances directly. This was never documented or officially 1096 supported. 1097 1098 .. versionchanged:: 3.10 1099 Python now uses ``SSL_read_ex`` and ``SSL_write_ex`` internally. The 1100 functions support reading and writing of data larger than 2 GB. Writing 1101 zero-length data no longer fails with a protocol violation error. 1102 1103SSL sockets also have the following additional methods and attributes: 1104 1105.. method:: SSLSocket.read(len=1024, buffer=None) 1106 1107 Read up to *len* bytes of data from the SSL socket and return the result as 1108 a ``bytes`` instance. If *buffer* is specified, then read into the buffer 1109 instead, and return the number of bytes read. 1110 1111 Raise :exc:`SSLWantReadError` or :exc:`SSLWantWriteError` if the socket is 1112 :ref:`non-blocking <ssl-nonblocking>` and the read would block. 1113 1114 As at any time a re-negotiation is possible, a call to :meth:`read` can also 1115 cause write operations. 1116 1117 .. versionchanged:: 3.5 1118 The socket timeout is no longer reset each time bytes are received or sent. 1119 The socket timeout is now the maximum total duration to read up to *len* 1120 bytes. 1121 1122 .. deprecated:: 3.6 1123 Use :meth:`~SSLSocket.recv` instead of :meth:`~SSLSocket.read`. 1124 1125.. method:: SSLSocket.write(buf) 1126 1127 Write *buf* to the SSL socket and return the number of bytes written. The 1128 *buf* argument must be an object supporting the buffer interface. 1129 1130 Raise :exc:`SSLWantReadError` or :exc:`SSLWantWriteError` if the socket is 1131 :ref:`non-blocking <ssl-nonblocking>` and the write would block. 1132 1133 As at any time a re-negotiation is possible, a call to :meth:`write` can 1134 also cause read operations. 1135 1136 .. versionchanged:: 3.5 1137 The socket timeout is no longer reset each time bytes are received or sent. 1138 The socket timeout is now the maximum total duration to write *buf*. 1139 1140 .. deprecated:: 3.6 1141 Use :meth:`~SSLSocket.send` instead of :meth:`~SSLSocket.write`. 1142 1143.. note:: 1144 1145 The :meth:`~SSLSocket.read` and :meth:`~SSLSocket.write` methods are the 1146 low-level methods that read and write unencrypted, application-level data 1147 and decrypt/encrypt it to encrypted, wire-level data. These methods 1148 require an active SSL connection, i.e. the handshake was completed and 1149 :meth:`SSLSocket.unwrap` was not called. 1150 1151 Normally you should use the socket API methods like 1152 :meth:`~socket.socket.recv` and :meth:`~socket.socket.send` instead of these 1153 methods. 1154 1155.. method:: SSLSocket.do_handshake() 1156 1157 Perform the SSL setup handshake. 1158 1159 .. versionchanged:: 3.4 1160 The handshake method also performs :func:`match_hostname` when the 1161 :attr:`~SSLContext.check_hostname` attribute of the socket's 1162 :attr:`~SSLSocket.context` is true. 1163 1164 .. versionchanged:: 3.5 1165 The socket timeout is no longer reset each time bytes are received or sent. 1166 The socket timeout is now the maximum total duration of the handshake. 1167 1168 .. versionchanged:: 3.7 1169 Hostname or IP address is matched by OpenSSL during handshake. The 1170 function :func:`match_hostname` is no longer used. In case OpenSSL 1171 refuses a hostname or IP address, the handshake is aborted early and 1172 a TLS alert message is sent to the peer. 1173 1174.. method:: SSLSocket.getpeercert(binary_form=False) 1175 1176 If there is no certificate for the peer on the other end of the connection, 1177 return ``None``. If the SSL handshake hasn't been done yet, raise 1178 :exc:`ValueError`. 1179 1180 If the ``binary_form`` parameter is :const:`False`, and a certificate was 1181 received from the peer, this method returns a :class:`dict` instance. If the 1182 certificate was not validated, the dict is empty. If the certificate was 1183 validated, it returns a dict with several keys, amongst them ``subject`` 1184 (the principal for which the certificate was issued) and ``issuer`` 1185 (the principal issuing the certificate). If a certificate contains an 1186 instance of the *Subject Alternative Name* extension (see :rfc:`3280`), 1187 there will also be a ``subjectAltName`` key in the dictionary. 1188 1189 The ``subject`` and ``issuer`` fields are tuples containing the sequence 1190 of relative distinguished names (RDNs) given in the certificate's data 1191 structure for the respective fields, and each RDN is a sequence of 1192 name-value pairs. Here is a real-world example:: 1193 1194 {'issuer': ((('countryName', 'IL'),), 1195 (('organizationName', 'StartCom Ltd.'),), 1196 (('organizationalUnitName', 1197 'Secure Digital Certificate Signing'),), 1198 (('commonName', 1199 'StartCom Class 2 Primary Intermediate Server CA'),)), 1200 'notAfter': 'Nov 22 08:15:19 2013 GMT', 1201 'notBefore': 'Nov 21 03:09:52 2011 GMT', 1202 'serialNumber': '95F0', 1203 'subject': ((('description', '571208-SLe257oHY9fVQ07Z'),), 1204 (('countryName', 'US'),), 1205 (('stateOrProvinceName', 'California'),), 1206 (('localityName', 'San Francisco'),), 1207 (('organizationName', 'Electronic Frontier Foundation, Inc.'),), 1208 (('commonName', '*.eff.org'),), 1209 (('emailAddress', 'hostmaster@eff.org'),)), 1210 'subjectAltName': (('DNS', '*.eff.org'), ('DNS', 'eff.org')), 1211 'version': 3} 1212 1213 If the ``binary_form`` parameter is :const:`True`, and a certificate was 1214 provided, this method returns the DER-encoded form of the entire certificate 1215 as a sequence of bytes, or :const:`None` if the peer did not provide a 1216 certificate. Whether the peer provides a certificate depends on the SSL 1217 socket's role: 1218 1219 * for a client SSL socket, the server will always provide a certificate, 1220 regardless of whether validation was required; 1221 1222 * for a server SSL socket, the client will only provide a certificate 1223 when requested by the server; therefore :meth:`getpeercert` will return 1224 :const:`None` if you used :const:`CERT_NONE` (rather than 1225 :const:`CERT_OPTIONAL` or :const:`CERT_REQUIRED`). 1226 1227 See also :attr:`SSLContext.check_hostname`. 1228 1229 .. versionchanged:: 3.2 1230 The returned dictionary includes additional items such as ``issuer`` 1231 and ``notBefore``. 1232 1233 .. versionchanged:: 3.4 1234 :exc:`ValueError` is raised when the handshake isn't done. 1235 The returned dictionary includes additional X509v3 extension items 1236 such as ``crlDistributionPoints``, ``caIssuers`` and ``OCSP`` URIs. 1237 1238 .. versionchanged:: 3.9 1239 IPv6 address strings no longer have a trailing new line. 1240 1241.. method:: SSLSocket.get_verified_chain() 1242 1243 Returns verified certificate chain provided by the other 1244 end of the SSL channel as a list of DER-encoded bytes. 1245 If certificate verification was disabled method acts the same as 1246 :meth:`~SSLSocket.get_unverified_chain`. 1247 1248 .. versionadded:: 3.13 1249 1250.. method:: SSLSocket.get_unverified_chain() 1251 1252 Returns raw certificate chain provided by the other 1253 end of the SSL channel as a list of DER-encoded bytes. 1254 1255 .. versionadded:: 3.13 1256 1257.. method:: SSLSocket.cipher() 1258 1259 Returns a three-value tuple containing the name of the cipher being used, the 1260 version of the SSL protocol that defines its use, and the number of secret 1261 bits being used. If no connection has been established, returns ``None``. 1262 1263.. method:: SSLSocket.shared_ciphers() 1264 1265 Return the list of ciphers available in both the client and server. Each 1266 entry of the returned list is a three-value tuple containing the name of the 1267 cipher, the version of the SSL protocol that defines its use, and the number 1268 of secret bits the cipher uses. :meth:`~SSLSocket.shared_ciphers` returns 1269 ``None`` if no connection has been established or the socket is a client 1270 socket. 1271 1272 .. versionadded:: 3.5 1273 1274.. method:: SSLSocket.compression() 1275 1276 Return the compression algorithm being used as a string, or ``None`` 1277 if the connection isn't compressed. 1278 1279 If the higher-level protocol supports its own compression mechanism, 1280 you can use :data:`OP_NO_COMPRESSION` to disable SSL-level compression. 1281 1282 .. versionadded:: 3.3 1283 1284.. method:: SSLSocket.get_channel_binding(cb_type="tls-unique") 1285 1286 Get channel binding data for current connection, as a bytes object. Returns 1287 ``None`` if not connected or the handshake has not been completed. 1288 1289 The *cb_type* parameter allow selection of the desired channel binding 1290 type. Valid channel binding types are listed in the 1291 :data:`CHANNEL_BINDING_TYPES` list. Currently only the 'tls-unique' channel 1292 binding, defined by :rfc:`5929`, is supported. :exc:`ValueError` will be 1293 raised if an unsupported channel binding type is requested. 1294 1295 .. versionadded:: 3.3 1296 1297.. method:: SSLSocket.selected_alpn_protocol() 1298 1299 Return the protocol that was selected during the TLS handshake. If 1300 :meth:`SSLContext.set_alpn_protocols` was not called, if the other party does 1301 not support ALPN, if this socket does not support any of the client's 1302 proposed protocols, or if the handshake has not happened yet, ``None`` is 1303 returned. 1304 1305 .. versionadded:: 3.5 1306 1307.. method:: SSLSocket.selected_npn_protocol() 1308 1309 Return the higher-level protocol that was selected during the TLS/SSL 1310 handshake. If :meth:`SSLContext.set_npn_protocols` was not called, or 1311 if the other party does not support NPN, or if the handshake has not yet 1312 happened, this will return ``None``. 1313 1314 .. versionadded:: 3.3 1315 1316 .. deprecated:: 3.10 1317 1318 NPN has been superseded by ALPN 1319 1320.. method:: SSLSocket.unwrap() 1321 1322 Performs the SSL shutdown handshake, which removes the TLS layer from the 1323 underlying socket, and returns the underlying socket object. This can be 1324 used to go from encrypted operation over a connection to unencrypted. The 1325 returned socket should always be used for further communication with the 1326 other side of the connection, rather than the original socket. 1327 1328.. method:: SSLSocket.verify_client_post_handshake() 1329 1330 Requests post-handshake authentication (PHA) from a TLS 1.3 client. PHA 1331 can only be initiated for a TLS 1.3 connection from a server-side socket, 1332 after the initial TLS handshake and with PHA enabled on both sides, see 1333 :attr:`SSLContext.post_handshake_auth`. 1334 1335 The method does not perform a cert exchange immediately. The server-side 1336 sends a CertificateRequest during the next write event and expects the 1337 client to respond with a certificate on the next read event. 1338 1339 If any precondition isn't met (e.g. not TLS 1.3, PHA not enabled), an 1340 :exc:`SSLError` is raised. 1341 1342 .. note:: 1343 Only available with OpenSSL 1.1.1 and TLS 1.3 enabled. Without TLS 1.3 1344 support, the method raises :exc:`NotImplementedError`. 1345 1346 .. versionadded:: 3.8 1347 1348.. method:: SSLSocket.version() 1349 1350 Return the actual SSL protocol version negotiated by the connection 1351 as a string, or ``None`` if no secure connection is established. 1352 As of this writing, possible return values include ``"SSLv2"``, 1353 ``"SSLv3"``, ``"TLSv1"``, ``"TLSv1.1"`` and ``"TLSv1.2"``. 1354 Recent OpenSSL versions may define more return values. 1355 1356 .. versionadded:: 3.5 1357 1358.. method:: SSLSocket.pending() 1359 1360 Returns the number of already decrypted bytes available for read, pending on 1361 the connection. 1362 1363.. attribute:: SSLSocket.context 1364 1365 The :class:`SSLContext` object this SSL socket is tied to. 1366 1367 .. versionadded:: 3.2 1368 1369.. attribute:: SSLSocket.server_side 1370 1371 A boolean which is ``True`` for server-side sockets and ``False`` for 1372 client-side sockets. 1373 1374 .. versionadded:: 3.2 1375 1376.. attribute:: SSLSocket.server_hostname 1377 1378 Hostname of the server: :class:`str` type, or ``None`` for server-side 1379 socket or if the hostname was not specified in the constructor. 1380 1381 .. versionadded:: 3.2 1382 1383 .. versionchanged:: 3.7 1384 The attribute is now always ASCII text. When ``server_hostname`` is 1385 an internationalized domain name (IDN), this attribute now stores the 1386 A-label form (``"xn--pythn-mua.org"``), rather than the U-label form 1387 (``"pythön.org"``). 1388 1389.. attribute:: SSLSocket.session 1390 1391 The :class:`SSLSession` for this SSL connection. The session is available 1392 for client and server side sockets after the TLS handshake has been 1393 performed. For client sockets the session can be set before 1394 :meth:`~SSLSocket.do_handshake` has been called to reuse a session. 1395 1396 .. versionadded:: 3.6 1397 1398.. attribute:: SSLSocket.session_reused 1399 1400 .. versionadded:: 3.6 1401 1402 1403SSL Contexts 1404------------ 1405 1406.. versionadded:: 3.2 1407 1408An SSL context holds various data longer-lived than single SSL connections, 1409such as SSL configuration options, certificate(s) and private key(s). 1410It also manages a cache of SSL sessions for server-side sockets, in order 1411to speed up repeated connections from the same clients. 1412 1413.. class:: SSLContext(protocol=None) 1414 1415 Create a new SSL context. You may pass *protocol* which must be one 1416 of the ``PROTOCOL_*`` constants defined in this module. The parameter 1417 specifies which version of the SSL protocol to use. Typically, the 1418 server chooses a particular protocol version, and the client must adapt 1419 to the server's choice. Most of the versions are not interoperable 1420 with the other versions. If not specified, the default is 1421 :data:`PROTOCOL_TLS`; it provides the most compatibility with other 1422 versions. 1423 1424 Here's a table showing which versions in a client (down the side) can connect 1425 to which versions in a server (along the top): 1426 1427 .. table:: 1428 1429 ======================== ============ ============ ============= ========= =========== =========== 1430 *client* / **server** **SSLv2** **SSLv3** **TLS** [3]_ **TLSv1** **TLSv1.1** **TLSv1.2** 1431 ------------------------ ------------ ------------ ------------- --------- ----------- ----------- 1432 *SSLv2* yes no no [1]_ no no no 1433 *SSLv3* no yes no [2]_ no no no 1434 *TLS* (*SSLv23*) [3]_ no [1]_ no [2]_ yes yes yes yes 1435 *TLSv1* no no yes yes no no 1436 *TLSv1.1* no no yes no yes no 1437 *TLSv1.2* no no yes no no yes 1438 ======================== ============ ============ ============= ========= =========== =========== 1439 1440 .. rubric:: Footnotes 1441 .. [1] :class:`SSLContext` disables SSLv2 with :data:`OP_NO_SSLv2` by default. 1442 .. [2] :class:`SSLContext` disables SSLv3 with :data:`OP_NO_SSLv3` by default. 1443 .. [3] TLS 1.3 protocol will be available with :data:`PROTOCOL_TLS` in 1444 OpenSSL >= 1.1.1. There is no dedicated PROTOCOL constant for just 1445 TLS 1.3. 1446 1447 .. seealso:: 1448 :func:`create_default_context` lets the :mod:`ssl` module choose 1449 security settings for a given purpose. 1450 1451 .. versionchanged:: 3.6 1452 1453 The context is created with secure default values. The options 1454 :data:`OP_NO_COMPRESSION`, :data:`OP_CIPHER_SERVER_PREFERENCE`, 1455 :data:`OP_SINGLE_DH_USE`, :data:`OP_SINGLE_ECDH_USE`, 1456 :data:`OP_NO_SSLv2`, 1457 and :data:`OP_NO_SSLv3` (except for :data:`PROTOCOL_SSLv3`) are 1458 set by default. The initial cipher suite list contains only ``HIGH`` 1459 ciphers, no ``NULL`` ciphers and no ``MD5`` ciphers. 1460 1461 .. deprecated:: 3.10 1462 1463 :class:`SSLContext` without protocol argument is deprecated. The 1464 context class will either require :data:`PROTOCOL_TLS_CLIENT` or 1465 :data:`PROTOCOL_TLS_SERVER` protocol in the future. 1466 1467 .. versionchanged:: 3.10 1468 1469 The default cipher suites now include only secure AES and ChaCha20 1470 ciphers with forward secrecy and security level 2. RSA and DH keys with 1471 less than 2048 bits and ECC keys with less than 224 bits are prohibited. 1472 :data:`PROTOCOL_TLS`, :data:`PROTOCOL_TLS_CLIENT`, and 1473 :data:`PROTOCOL_TLS_SERVER` use TLS 1.2 as minimum TLS version. 1474 1475 .. note:: 1476 1477 :class:`SSLContext` only supports limited mutation once it has been used 1478 by a connection. Adding new certificates to the internal trust store is 1479 allowed, but changing ciphers, verification settings, or mTLS 1480 certificates may result in surprising behavior. 1481 1482 .. note:: 1483 1484 :class:`SSLContext` is designed to be shared and used by multiple 1485 connections. 1486 Thus, it is thread-safe as long as it is not reconfigured after being 1487 used by a connection. 1488 1489:class:`SSLContext` objects have the following methods and attributes: 1490 1491.. method:: SSLContext.cert_store_stats() 1492 1493 Get statistics about quantities of loaded X.509 certificates, count of 1494 X.509 certificates flagged as CA certificates and certificate revocation 1495 lists as dictionary. 1496 1497 Example for a context with one CA cert and one other cert:: 1498 1499 >>> context.cert_store_stats() 1500 {'crl': 0, 'x509_ca': 1, 'x509': 2} 1501 1502 .. versionadded:: 3.4 1503 1504 1505.. method:: SSLContext.load_cert_chain(certfile, keyfile=None, password=None) 1506 1507 Load a private key and the corresponding certificate. The *certfile* 1508 string must be the path to a single file in PEM format containing the 1509 certificate as well as any number of CA certificates needed to establish 1510 the certificate's authenticity. The *keyfile* string, if present, must 1511 point to a file containing the private key. Otherwise the private 1512 key will be taken from *certfile* as well. See the discussion of 1513 :ref:`ssl-certificates` for more information on how the certificate 1514 is stored in the *certfile*. 1515 1516 The *password* argument may be a function to call to get the password for 1517 decrypting the private key. It will only be called if the private key is 1518 encrypted and a password is necessary. It will be called with no arguments, 1519 and it should return a string, bytes, or bytearray. If the return value is 1520 a string it will be encoded as UTF-8 before using it to decrypt the key. 1521 Alternatively a string, bytes, or bytearray value may be supplied directly 1522 as the *password* argument. It will be ignored if the private key is not 1523 encrypted and no password is needed. 1524 1525 If the *password* argument is not specified and a password is required, 1526 OpenSSL's built-in password prompting mechanism will be used to 1527 interactively prompt the user for a password. 1528 1529 An :class:`SSLError` is raised if the private key doesn't 1530 match with the certificate. 1531 1532 .. versionchanged:: 3.3 1533 New optional argument *password*. 1534 1535.. method:: SSLContext.load_default_certs(purpose=Purpose.SERVER_AUTH) 1536 1537 Load a set of default "certification authority" (CA) certificates from 1538 default locations. On Windows it loads CA certs from the ``CA`` and 1539 ``ROOT`` system stores. On all systems it calls 1540 :meth:`SSLContext.set_default_verify_paths`. In the future the method may 1541 load CA certificates from other locations, too. 1542 1543 The *purpose* flag specifies what kind of CA certificates are loaded. The 1544 default settings :const:`Purpose.SERVER_AUTH` loads certificates, that are 1545 flagged and trusted for TLS web server authentication (client side 1546 sockets). :const:`Purpose.CLIENT_AUTH` loads CA certificates for client 1547 certificate verification on the server side. 1548 1549 .. versionadded:: 3.4 1550 1551.. method:: SSLContext.load_verify_locations(cafile=None, capath=None, cadata=None) 1552 1553 Load a set of "certification authority" (CA) certificates used to validate 1554 other peers' certificates when :data:`verify_mode` is other than 1555 :data:`CERT_NONE`. At least one of *cafile* or *capath* must be specified. 1556 1557 This method can also load certification revocation lists (CRLs) in PEM or 1558 DER format. In order to make use of CRLs, :attr:`SSLContext.verify_flags` 1559 must be configured properly. 1560 1561 The *cafile* string, if present, is the path to a file of concatenated 1562 CA certificates in PEM format. See the discussion of 1563 :ref:`ssl-certificates` for more information about how to arrange the 1564 certificates in this file. 1565 1566 The *capath* string, if present, is 1567 the path to a directory containing several CA certificates in PEM format, 1568 following an `OpenSSL specific layout 1569 <https://docs.openssl.org/master/man3/SSL_CTX_load_verify_locations/>`_. 1570 1571 The *cadata* object, if present, is either an ASCII string of one or more 1572 PEM-encoded certificates or a :term:`bytes-like object` of DER-encoded 1573 certificates. Like with *capath* extra lines around PEM-encoded 1574 certificates are ignored but at least one certificate must be present. 1575 1576 .. versionchanged:: 3.4 1577 New optional argument *cadata* 1578 1579.. method:: SSLContext.get_ca_certs(binary_form=False) 1580 1581 Get a list of loaded "certification authority" (CA) certificates. If the 1582 ``binary_form`` parameter is :const:`False` each list 1583 entry is a dict like the output of :meth:`SSLSocket.getpeercert`. Otherwise 1584 the method returns a list of DER-encoded certificates. The returned list 1585 does not contain certificates from *capath* unless a certificate was 1586 requested and loaded by a SSL connection. 1587 1588 .. note:: 1589 Certificates in a capath directory aren't loaded unless they have 1590 been used at least once. 1591 1592 .. versionadded:: 3.4 1593 1594.. method:: SSLContext.get_ciphers() 1595 1596 Get a list of enabled ciphers. The list is in order of cipher priority. 1597 See :meth:`SSLContext.set_ciphers`. 1598 1599 Example:: 1600 1601 >>> ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23) 1602 >>> ctx.set_ciphers('ECDHE+AESGCM:!ECDSA') 1603 >>> ctx.get_ciphers() 1604 [{'aead': True, 1605 'alg_bits': 256, 1606 'auth': 'auth-rsa', 1607 'description': 'ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=RSA ' 1608 'Enc=AESGCM(256) Mac=AEAD', 1609 'digest': None, 1610 'id': 50380848, 1611 'kea': 'kx-ecdhe', 1612 'name': 'ECDHE-RSA-AES256-GCM-SHA384', 1613 'protocol': 'TLSv1.2', 1614 'strength_bits': 256, 1615 'symmetric': 'aes-256-gcm'}, 1616 {'aead': True, 1617 'alg_bits': 128, 1618 'auth': 'auth-rsa', 1619 'description': 'ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=RSA ' 1620 'Enc=AESGCM(128) Mac=AEAD', 1621 'digest': None, 1622 'id': 50380847, 1623 'kea': 'kx-ecdhe', 1624 'name': 'ECDHE-RSA-AES128-GCM-SHA256', 1625 'protocol': 'TLSv1.2', 1626 'strength_bits': 128, 1627 'symmetric': 'aes-128-gcm'}] 1628 1629 .. versionadded:: 3.6 1630 1631.. method:: SSLContext.set_default_verify_paths() 1632 1633 Load a set of default "certification authority" (CA) certificates from 1634 a filesystem path defined when building the OpenSSL library. Unfortunately, 1635 there's no easy way to know whether this method succeeds: no error is 1636 returned if no certificates are to be found. When the OpenSSL library is 1637 provided as part of the operating system, though, it is likely to be 1638 configured properly. 1639 1640.. method:: SSLContext.set_ciphers(ciphers) 1641 1642 Set the available ciphers for sockets created with this context. 1643 It should be a string in the `OpenSSL cipher list format 1644 <https://docs.openssl.org/master/man1/ciphers/>`_. 1645 If no cipher can be selected (because compile-time options or other 1646 configuration forbids use of all the specified ciphers), an 1647 :class:`SSLError` will be raised. 1648 1649 .. note:: 1650 when connected, the :meth:`SSLSocket.cipher` method of SSL sockets will 1651 give the currently selected cipher. 1652 1653 TLS 1.3 cipher suites cannot be disabled with 1654 :meth:`~SSLContext.set_ciphers`. 1655 1656.. method:: SSLContext.set_alpn_protocols(protocols) 1657 1658 Specify which protocols the socket should advertise during the SSL/TLS 1659 handshake. It should be a list of ASCII strings, like ``['http/1.1', 1660 'spdy/2']``, ordered by preference. The selection of a protocol will happen 1661 during the handshake, and will play out according to :rfc:`7301`. After a 1662 successful handshake, the :meth:`SSLSocket.selected_alpn_protocol` method will 1663 return the agreed-upon protocol. 1664 1665 This method will raise :exc:`NotImplementedError` if :data:`HAS_ALPN` is 1666 ``False``. 1667 1668 .. versionadded:: 3.5 1669 1670.. method:: SSLContext.set_npn_protocols(protocols) 1671 1672 Specify which protocols the socket should advertise during the SSL/TLS 1673 handshake. It should be a list of strings, like ``['http/1.1', 'spdy/2']``, 1674 ordered by preference. The selection of a protocol will happen during the 1675 handshake, and will play out according to the `Application Layer Protocol Negotiation 1676 <https://en.wikipedia.org/wiki/Application-Layer_Protocol_Negotiation>`_. After a 1677 successful handshake, the :meth:`SSLSocket.selected_npn_protocol` method will 1678 return the agreed-upon protocol. 1679 1680 This method will raise :exc:`NotImplementedError` if :data:`HAS_NPN` is 1681 ``False``. 1682 1683 .. versionadded:: 3.3 1684 1685 .. deprecated:: 3.10 1686 1687 NPN has been superseded by ALPN 1688 1689.. attribute:: SSLContext.sni_callback 1690 1691 Register a callback function that will be called after the TLS Client Hello 1692 handshake message has been received by the SSL/TLS server when the TLS client 1693 specifies a server name indication. The server name indication mechanism 1694 is specified in :rfc:`6066` section 3 - Server Name Indication. 1695 1696 Only one callback can be set per ``SSLContext``. If *sni_callback* 1697 is set to ``None`` then the callback is disabled. Calling this function a 1698 subsequent time will disable the previously registered callback. 1699 1700 The callback function will be called with three 1701 arguments; the first being the :class:`ssl.SSLSocket`, the second is a string 1702 that represents the server name that the client is intending to communicate 1703 (or :const:`None` if the TLS Client Hello does not contain a server name) 1704 and the third argument is the original :class:`SSLContext`. The server name 1705 argument is text. For internationalized domain name, the server 1706 name is an IDN A-label (``"xn--pythn-mua.org"``). 1707 1708 A typical use of this callback is to change the :class:`ssl.SSLSocket`'s 1709 :attr:`SSLSocket.context` attribute to a new object of type 1710 :class:`SSLContext` representing a certificate chain that matches the server 1711 name. 1712 1713 Due to the early negotiation phase of the TLS connection, only limited 1714 methods and attributes are usable like 1715 :meth:`SSLSocket.selected_alpn_protocol` and :attr:`SSLSocket.context`. 1716 The :meth:`SSLSocket.getpeercert`, :meth:`SSLSocket.get_verified_chain`, 1717 :meth:`SSLSocket.get_unverified_chain` :meth:`SSLSocket.cipher` 1718 and :meth:`SSLSocket.compression` methods require that 1719 the TLS connection has progressed beyond the TLS Client Hello and therefore 1720 will not return meaningful values nor can they be called safely. 1721 1722 The *sni_callback* function must return ``None`` to allow the 1723 TLS negotiation to continue. If a TLS failure is required, a constant 1724 :const:`ALERT_DESCRIPTION_* <ALERT_DESCRIPTION_INTERNAL_ERROR>` can be 1725 returned. Other return values will result in a TLS fatal error with 1726 :const:`ALERT_DESCRIPTION_INTERNAL_ERROR`. 1727 1728 If an exception is raised from the *sni_callback* function the TLS 1729 connection will terminate with a fatal TLS alert message 1730 :const:`ALERT_DESCRIPTION_HANDSHAKE_FAILURE`. 1731 1732 This method will raise :exc:`NotImplementedError` if the OpenSSL library 1733 had OPENSSL_NO_TLSEXT defined when it was built. 1734 1735 .. versionadded:: 3.7 1736 1737.. attribute:: SSLContext.set_servername_callback(server_name_callback) 1738 1739 This is a legacy API retained for backwards compatibility. When possible, 1740 you should use :attr:`sni_callback` instead. The given *server_name_callback* 1741 is similar to *sni_callback*, except that when the server hostname is an 1742 IDN-encoded internationalized domain name, the *server_name_callback* 1743 receives a decoded U-label (``"pythön.org"``). 1744 1745 If there is a decoding error on the server name, the TLS connection will 1746 terminate with an :const:`ALERT_DESCRIPTION_INTERNAL_ERROR` fatal TLS 1747 alert message to the client. 1748 1749 .. versionadded:: 3.4 1750 1751.. method:: SSLContext.load_dh_params(dhfile) 1752 1753 Load the key generation parameters for Diffie-Hellman (DH) key exchange. 1754 Using DH key exchange improves forward secrecy at the expense of 1755 computational resources (both on the server and on the client). 1756 The *dhfile* parameter should be the path to a file containing DH 1757 parameters in PEM format. 1758 1759 This setting doesn't apply to client sockets. You can also use the 1760 :data:`OP_SINGLE_DH_USE` option to further improve security. 1761 1762 .. versionadded:: 3.3 1763 1764.. method:: SSLContext.set_ecdh_curve(curve_name) 1765 1766 Set the curve name for Elliptic Curve-based Diffie-Hellman (ECDH) key 1767 exchange. ECDH is significantly faster than regular DH while arguably 1768 as secure. The *curve_name* parameter should be a string describing 1769 a well-known elliptic curve, for example ``prime256v1`` for a widely 1770 supported curve. 1771 1772 This setting doesn't apply to client sockets. You can also use the 1773 :data:`OP_SINGLE_ECDH_USE` option to further improve security. 1774 1775 This method is not available if :data:`HAS_ECDH` is ``False``. 1776 1777 .. versionadded:: 3.3 1778 1779 .. seealso:: 1780 `SSL/TLS & Perfect Forward Secrecy <https://vincent.bernat.ch/en/blog/2011-ssl-perfect-forward-secrecy>`_ 1781 Vincent Bernat. 1782 1783.. method:: SSLContext.wrap_socket(sock, server_side=False, \ 1784 do_handshake_on_connect=True, suppress_ragged_eofs=True, \ 1785 server_hostname=None, session=None) 1786 1787 Wrap an existing Python socket *sock* and return an instance of 1788 :attr:`SSLContext.sslsocket_class` (default :class:`SSLSocket`). The 1789 returned SSL socket is tied to the context, its settings and certificates. 1790 *sock* must be a :const:`~socket.SOCK_STREAM` socket; other 1791 socket types are unsupported. 1792 1793 The parameter ``server_side`` is a boolean which identifies whether 1794 server-side or client-side behavior is desired from this socket. 1795 1796 For client-side sockets, the context construction is lazy; if the 1797 underlying socket isn't connected yet, the context construction will be 1798 performed after :meth:`connect` is called on the socket. For 1799 server-side sockets, if the socket has no remote peer, it is assumed 1800 to be a listening socket, and the server-side SSL wrapping is 1801 automatically performed on client connections accepted via the 1802 :meth:`accept` method. The method may raise :exc:`SSLError`. 1803 1804 On client connections, the optional parameter *server_hostname* specifies 1805 the hostname of the service which we are connecting to. This allows a 1806 single server to host multiple SSL-based services with distinct certificates, 1807 quite similarly to HTTP virtual hosts. Specifying *server_hostname* will 1808 raise a :exc:`ValueError` if *server_side* is true. 1809 1810 The parameter ``do_handshake_on_connect`` specifies whether to do the SSL 1811 handshake automatically after doing a :meth:`socket.connect`, or whether the 1812 application program will call it explicitly, by invoking the 1813 :meth:`SSLSocket.do_handshake` method. Calling 1814 :meth:`SSLSocket.do_handshake` explicitly gives the program control over the 1815 blocking behavior of the socket I/O involved in the handshake. 1816 1817 The parameter ``suppress_ragged_eofs`` specifies how the 1818 :meth:`SSLSocket.recv` method should signal unexpected EOF from the other end 1819 of the connection. If specified as :const:`True` (the default), it returns a 1820 normal EOF (an empty bytes object) in response to unexpected EOF errors 1821 raised from the underlying socket; if :const:`False`, it will raise the 1822 exceptions back to the caller. 1823 1824 *session*, see :attr:`~SSLSocket.session`. 1825 1826 To wrap an :class:`SSLSocket` in another :class:`SSLSocket`, use 1827 :meth:`SSLContext.wrap_bio`. 1828 1829 .. versionchanged:: 3.5 1830 Always allow a server_hostname to be passed, even if OpenSSL does not 1831 have SNI. 1832 1833 .. versionchanged:: 3.6 1834 *session* argument was added. 1835 1836 .. versionchanged:: 3.7 1837 The method returns an instance of :attr:`SSLContext.sslsocket_class` 1838 instead of hard-coded :class:`SSLSocket`. 1839 1840.. attribute:: SSLContext.sslsocket_class 1841 1842 The return type of :meth:`SSLContext.wrap_socket`, defaults to 1843 :class:`SSLSocket`. The attribute can be overridden on instance of class 1844 in order to return a custom subclass of :class:`SSLSocket`. 1845 1846 .. versionadded:: 3.7 1847 1848.. method:: SSLContext.wrap_bio(incoming, outgoing, server_side=False, \ 1849 server_hostname=None, session=None) 1850 1851 Wrap the BIO objects *incoming* and *outgoing* and return an instance of 1852 :attr:`SSLContext.sslobject_class` (default :class:`SSLObject`). The SSL 1853 routines will read input data from the incoming BIO and write data to the 1854 outgoing BIO. 1855 1856 The *server_side*, *server_hostname* and *session* parameters have the 1857 same meaning as in :meth:`SSLContext.wrap_socket`. 1858 1859 .. versionchanged:: 3.6 1860 *session* argument was added. 1861 1862 .. versionchanged:: 3.7 1863 The method returns an instance of :attr:`SSLContext.sslobject_class` 1864 instead of hard-coded :class:`SSLObject`. 1865 1866.. attribute:: SSLContext.sslobject_class 1867 1868 The return type of :meth:`SSLContext.wrap_bio`, defaults to 1869 :class:`SSLObject`. The attribute can be overridden on instance of class 1870 in order to return a custom subclass of :class:`SSLObject`. 1871 1872 .. versionadded:: 3.7 1873 1874.. method:: SSLContext.session_stats() 1875 1876 Get statistics about the SSL sessions created or managed by this context. 1877 A dictionary is returned which maps the names of each `piece of information <https://docs.openssl.org/1.1.1/man3/SSL_CTX_sess_number/>`_ to their 1878 numeric values. For example, here is the total number of hits and misses 1879 in the session cache since the context was created:: 1880 1881 >>> stats = context.session_stats() 1882 >>> stats['hits'], stats['misses'] 1883 (0, 0) 1884 1885.. attribute:: SSLContext.check_hostname 1886 1887 Whether to match the peer cert's hostname in 1888 :meth:`SSLSocket.do_handshake`. The context's 1889 :attr:`~SSLContext.verify_mode` must be set to :data:`CERT_OPTIONAL` or 1890 :data:`CERT_REQUIRED`, and you must pass *server_hostname* to 1891 :meth:`~SSLContext.wrap_socket` in order to match the hostname. Enabling 1892 hostname checking automatically sets :attr:`~SSLContext.verify_mode` from 1893 :data:`CERT_NONE` to :data:`CERT_REQUIRED`. It cannot be set back to 1894 :data:`CERT_NONE` as long as hostname checking is enabled. The 1895 :data:`PROTOCOL_TLS_CLIENT` protocol enables hostname checking by default. 1896 With other protocols, hostname checking must be enabled explicitly. 1897 1898 Example:: 1899 1900 import socket, ssl 1901 1902 context = ssl.SSLContext(ssl.PROTOCOL_TLSv1_2) 1903 context.verify_mode = ssl.CERT_REQUIRED 1904 context.check_hostname = True 1905 context.load_default_certs() 1906 1907 s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 1908 ssl_sock = context.wrap_socket(s, server_hostname='www.verisign.com') 1909 ssl_sock.connect(('www.verisign.com', 443)) 1910 1911 .. versionadded:: 3.4 1912 1913 .. versionchanged:: 3.7 1914 1915 :attr:`~SSLContext.verify_mode` is now automatically changed 1916 to :data:`CERT_REQUIRED` when hostname checking is enabled and 1917 :attr:`~SSLContext.verify_mode` is :data:`CERT_NONE`. Previously 1918 the same operation would have failed with a :exc:`ValueError`. 1919 1920.. attribute:: SSLContext.keylog_filename 1921 1922 Write TLS keys to a keylog file, whenever key material is generated or 1923 received. The keylog file is designed for debugging purposes only. The 1924 file format is specified by NSS and used by many traffic analyzers such 1925 as Wireshark. The log file is opened in append-only mode. Writes are 1926 synchronized between threads, but not between processes. 1927 1928 .. versionadded:: 3.8 1929 1930.. attribute:: SSLContext.maximum_version 1931 1932 A :class:`TLSVersion` enum member representing the highest supported 1933 TLS version. The value defaults to :attr:`TLSVersion.MAXIMUM_SUPPORTED`. 1934 The attribute is read-only for protocols other than :attr:`PROTOCOL_TLS`, 1935 :attr:`PROTOCOL_TLS_CLIENT`, and :attr:`PROTOCOL_TLS_SERVER`. 1936 1937 The attributes :attr:`~SSLContext.maximum_version`, 1938 :attr:`~SSLContext.minimum_version` and 1939 :attr:`SSLContext.options` all affect the supported SSL 1940 and TLS versions of the context. The implementation does not prevent 1941 invalid combination. For example a context with 1942 :attr:`OP_NO_TLSv1_2` in :attr:`~SSLContext.options` and 1943 :attr:`~SSLContext.maximum_version` set to :attr:`TLSVersion.TLSv1_2` 1944 will not be able to establish a TLS 1.2 connection. 1945 1946 .. versionadded:: 3.7 1947 1948.. attribute:: SSLContext.minimum_version 1949 1950 Like :attr:`SSLContext.maximum_version` except it is the lowest 1951 supported version or :attr:`TLSVersion.MINIMUM_SUPPORTED`. 1952 1953 .. versionadded:: 3.7 1954 1955.. attribute:: SSLContext.num_tickets 1956 1957 Control the number of TLS 1.3 session tickets of a 1958 :attr:`PROTOCOL_TLS_SERVER` context. The setting has no impact on TLS 1959 1.0 to 1.2 connections. 1960 1961 .. versionadded:: 3.8 1962 1963.. attribute:: SSLContext.options 1964 1965 An integer representing the set of SSL options enabled on this context. 1966 The default value is :data:`OP_ALL`, but you can specify other options 1967 such as :data:`OP_NO_SSLv2` by ORing them together. 1968 1969 .. versionchanged:: 3.6 1970 :attr:`SSLContext.options` returns :class:`Options` flags: 1971 1972 >>> ssl.create_default_context().options # doctest: +SKIP 1973 <Options.OP_ALL|OP_NO_SSLv3|OP_NO_SSLv2|OP_NO_COMPRESSION: 2197947391> 1974 1975 .. deprecated:: 3.7 1976 1977 All ``OP_NO_SSL*`` and ``OP_NO_TLS*`` options have been deprecated since 1978 Python 3.7. Use :attr:`SSLContext.minimum_version` and 1979 :attr:`SSLContext.maximum_version` instead. 1980 1981.. attribute:: SSLContext.post_handshake_auth 1982 1983 Enable TLS 1.3 post-handshake client authentication. Post-handshake auth 1984 is disabled by default and a server can only request a TLS client 1985 certificate during the initial handshake. When enabled, a server may 1986 request a TLS client certificate at any time after the handshake. 1987 1988 When enabled on client-side sockets, the client signals the server that 1989 it supports post-handshake authentication. 1990 1991 When enabled on server-side sockets, :attr:`SSLContext.verify_mode` must 1992 be set to :data:`CERT_OPTIONAL` or :data:`CERT_REQUIRED`, too. The 1993 actual client cert exchange is delayed until 1994 :meth:`SSLSocket.verify_client_post_handshake` is called and some I/O is 1995 performed. 1996 1997 .. versionadded:: 3.8 1998 1999.. attribute:: SSLContext.protocol 2000 2001 The protocol version chosen when constructing the context. This attribute 2002 is read-only. 2003 2004.. attribute:: SSLContext.hostname_checks_common_name 2005 2006 Whether :attr:`~SSLContext.check_hostname` falls back to verify the cert's 2007 subject common name in the absence of a subject alternative name 2008 extension (default: true). 2009 2010 .. versionadded:: 3.7 2011 2012 .. versionchanged:: 3.10 2013 2014 The flag had no effect with OpenSSL before version 1.1.1l. Python 3.8.9, 2015 3.9.3, and 3.10 include workarounds for previous versions. 2016 2017.. attribute:: SSLContext.security_level 2018 2019 An integer representing the `security level 2020 <https://docs.openssl.org/master/man3/SSL_CTX_get_security_level/>`_ 2021 for the context. This attribute is read-only. 2022 2023 .. versionadded:: 3.10 2024 2025.. attribute:: SSLContext.verify_flags 2026 2027 The flags for certificate verification operations. You can set flags like 2028 :data:`VERIFY_CRL_CHECK_LEAF` by ORing them together. By default OpenSSL 2029 does neither require nor verify certificate revocation lists (CRLs). 2030 2031 .. versionadded:: 3.4 2032 2033 .. versionchanged:: 3.6 2034 :attr:`SSLContext.verify_flags` returns :class:`VerifyFlags` flags: 2035 2036 >>> ssl.create_default_context().verify_flags # doctest: +SKIP 2037 <VerifyFlags.VERIFY_X509_TRUSTED_FIRST: 32768> 2038 2039.. attribute:: SSLContext.verify_mode 2040 2041 Whether to try to verify other peers' certificates and how to behave 2042 if verification fails. This attribute must be one of 2043 :data:`CERT_NONE`, :data:`CERT_OPTIONAL` or :data:`CERT_REQUIRED`. 2044 2045 .. versionchanged:: 3.6 2046 :attr:`SSLContext.verify_mode` returns :class:`VerifyMode` enum: 2047 2048 >>> ssl.create_default_context().verify_mode # doctest: +SKIP 2049 <VerifyMode.CERT_REQUIRED: 2> 2050 2051.. method:: SSLContext.set_psk_client_callback(callback) 2052 2053 Enables TLS-PSK (pre-shared key) authentication on a client-side connection. 2054 2055 In general, certificate based authentication should be preferred over this method. 2056 2057 The parameter ``callback`` is a callable object with the signature: 2058 ``def callback(hint: str | None) -> tuple[str | None, bytes]``. 2059 The ``hint`` parameter is an optional identity hint sent by the server. 2060 The return value is a tuple in the form (client-identity, psk). 2061 Client-identity is an optional string which may be used by the server to 2062 select a corresponding PSK for the client. The string must be less than or 2063 equal to ``256`` octets when UTF-8 encoded. PSK is a 2064 :term:`bytes-like object` representing the pre-shared key. Return a zero 2065 length PSK to reject the connection. 2066 2067 Setting ``callback`` to :const:`None` removes any existing callback. 2068 2069 .. note:: 2070 When using TLS 1.3: 2071 2072 - the ``hint`` parameter is always :const:`None`. 2073 - client-identity must be a non-empty string. 2074 2075 Example usage:: 2076 2077 context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) 2078 context.check_hostname = False 2079 context.verify_mode = ssl.CERT_NONE 2080 context.maximum_version = ssl.TLSVersion.TLSv1_2 2081 context.set_ciphers('PSK') 2082 2083 # A simple lambda: 2084 psk = bytes.fromhex('c0ffee') 2085 context.set_psk_client_callback(lambda hint: (None, psk)) 2086 2087 # A table using the hint from the server: 2088 psk_table = { 'ServerId_1': bytes.fromhex('c0ffee'), 2089 'ServerId_2': bytes.fromhex('facade') 2090 } 2091 def callback(hint): 2092 return 'ClientId_1', psk_table.get(hint, b'') 2093 context.set_psk_client_callback(callback) 2094 2095 This method will raise :exc:`NotImplementedError` if :data:`HAS_PSK` is 2096 ``False``. 2097 2098 .. versionadded:: 3.13 2099 2100.. method:: SSLContext.set_psk_server_callback(callback, identity_hint=None) 2101 2102 Enables TLS-PSK (pre-shared key) authentication on a server-side connection. 2103 2104 In general, certificate based authentication should be preferred over this method. 2105 2106 The parameter ``callback`` is a callable object with the signature: 2107 ``def callback(identity: str | None) -> bytes``. 2108 The ``identity`` parameter is an optional identity sent by the client which can 2109 be used to select a corresponding PSK. 2110 The return value is a :term:`bytes-like object` representing the pre-shared key. 2111 Return a zero length PSK to reject the connection. 2112 2113 Setting ``callback`` to :const:`None` removes any existing callback. 2114 2115 The parameter ``identity_hint`` is an optional identity hint string sent to 2116 the client. The string must be less than or equal to ``256`` octets when 2117 UTF-8 encoded. 2118 2119 .. note:: 2120 When using TLS 1.3 the ``identity_hint`` parameter is not sent to the client. 2121 2122 Example usage:: 2123 2124 context = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER) 2125 context.maximum_version = ssl.TLSVersion.TLSv1_2 2126 context.set_ciphers('PSK') 2127 2128 # A simple lambda: 2129 psk = bytes.fromhex('c0ffee') 2130 context.set_psk_server_callback(lambda identity: psk) 2131 2132 # A table using the identity of the client: 2133 psk_table = { 'ClientId_1': bytes.fromhex('c0ffee'), 2134 'ClientId_2': bytes.fromhex('facade') 2135 } 2136 def callback(identity): 2137 return psk_table.get(identity, b'') 2138 context.set_psk_server_callback(callback, 'ServerId_1') 2139 2140 This method will raise :exc:`NotImplementedError` if :data:`HAS_PSK` is 2141 ``False``. 2142 2143 .. versionadded:: 3.13 2144 2145.. index:: single: certificates 2146 2147.. index:: single: X509 certificate 2148 2149.. _ssl-certificates: 2150 2151Certificates 2152------------ 2153 2154Certificates in general are part of a public-key / private-key system. In this 2155system, each *principal*, (which may be a machine, or a person, or an 2156organization) is assigned a unique two-part encryption key. One part of the key 2157is public, and is called the *public key*; the other part is kept secret, and is 2158called the *private key*. The two parts are related, in that if you encrypt a 2159message with one of the parts, you can decrypt it with the other part, and 2160**only** with the other part. 2161 2162A certificate contains information about two principals. It contains the name 2163of a *subject*, and the subject's public key. It also contains a statement by a 2164second principal, the *issuer*, that the subject is who they claim to be, and 2165that this is indeed the subject's public key. The issuer's statement is signed 2166with the issuer's private key, which only the issuer knows. However, anyone can 2167verify the issuer's statement by finding the issuer's public key, decrypting the 2168statement with it, and comparing it to the other information in the certificate. 2169The certificate also contains information about the time period over which it is 2170valid. This is expressed as two fields, called "notBefore" and "notAfter". 2171 2172In the Python use of certificates, a client or server can use a certificate to 2173prove who they are. The other side of a network connection can also be required 2174to produce a certificate, and that certificate can be validated to the 2175satisfaction of the client or server that requires such validation. The 2176connection attempt can be set to raise an exception if the validation fails. 2177Validation is done automatically, by the underlying OpenSSL framework; the 2178application need not concern itself with its mechanics. But the application 2179does usually need to provide sets of certificates to allow this process to take 2180place. 2181 2182Python uses files to contain certificates. They should be formatted as "PEM" 2183(see :rfc:`1422`), which is a base-64 encoded form wrapped with a header line 2184and a footer line:: 2185 2186 -----BEGIN CERTIFICATE----- 2187 ... (certificate in base64 PEM encoding) ... 2188 -----END CERTIFICATE----- 2189 2190Certificate chains 2191^^^^^^^^^^^^^^^^^^ 2192 2193The Python files which contain certificates can contain a sequence of 2194certificates, sometimes called a *certificate chain*. This chain should start 2195with the specific certificate for the principal who "is" the client or server, 2196and then the certificate for the issuer of that certificate, and then the 2197certificate for the issuer of *that* certificate, and so on up the chain till 2198you get to a certificate which is *self-signed*, that is, a certificate which 2199has the same subject and issuer, sometimes called a *root certificate*. The 2200certificates should just be concatenated together in the certificate file. For 2201example, suppose we had a three certificate chain, from our server certificate 2202to the certificate of the certification authority that signed our server 2203certificate, to the root certificate of the agency which issued the 2204certification authority's certificate:: 2205 2206 -----BEGIN CERTIFICATE----- 2207 ... (certificate for your server)... 2208 -----END CERTIFICATE----- 2209 -----BEGIN CERTIFICATE----- 2210 ... (the certificate for the CA)... 2211 -----END CERTIFICATE----- 2212 -----BEGIN CERTIFICATE----- 2213 ... (the root certificate for the CA's issuer)... 2214 -----END CERTIFICATE----- 2215 2216CA certificates 2217^^^^^^^^^^^^^^^ 2218 2219If you are going to require validation of the other side of the connection's 2220certificate, you need to provide a "CA certs" file, filled with the certificate 2221chains for each issuer you are willing to trust. Again, this file just contains 2222these chains concatenated together. For validation, Python will use the first 2223chain it finds in the file which matches. The platform's certificates file can 2224be used by calling :meth:`SSLContext.load_default_certs`, this is done 2225automatically with :func:`.create_default_context`. 2226 2227Combined key and certificate 2228^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2229 2230Often the private key is stored in the same file as the certificate; in this 2231case, only the ``certfile`` parameter to :meth:`SSLContext.load_cert_chain` 2232needs to be passed. If the private key is stored 2233with the certificate, it should come before the first certificate in 2234the certificate chain:: 2235 2236 -----BEGIN RSA PRIVATE KEY----- 2237 ... (private key in base64 encoding) ... 2238 -----END RSA PRIVATE KEY----- 2239 -----BEGIN CERTIFICATE----- 2240 ... (certificate in base64 PEM encoding) ... 2241 -----END CERTIFICATE----- 2242 2243Self-signed certificates 2244^^^^^^^^^^^^^^^^^^^^^^^^ 2245 2246If you are going to create a server that provides SSL-encrypted connection 2247services, you will need to acquire a certificate for that service. There are 2248many ways of acquiring appropriate certificates, such as buying one from a 2249certification authority. Another common practice is to generate a self-signed 2250certificate. The simplest way to do this is with the OpenSSL package, using 2251something like the following:: 2252 2253 % openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.pem 2254 Generating a 1024 bit RSA private key 2255 .......++++++ 2256 .............................++++++ 2257 writing new private key to 'cert.pem' 2258 ----- 2259 You are about to be asked to enter information that will be incorporated 2260 into your certificate request. 2261 What you are about to enter is what is called a Distinguished Name or a DN. 2262 There are quite a few fields but you can leave some blank 2263 For some fields there will be a default value, 2264 If you enter '.', the field will be left blank. 2265 ----- 2266 Country Name (2 letter code) [AU]:US 2267 State or Province Name (full name) [Some-State]:MyState 2268 Locality Name (eg, city) []:Some City 2269 Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Organization, Inc. 2270 Organizational Unit Name (eg, section) []:My Group 2271 Common Name (eg, YOUR name) []:myserver.mygroup.myorganization.com 2272 Email Address []:ops@myserver.mygroup.myorganization.com 2273 % 2274 2275The disadvantage of a self-signed certificate is that it is its own root 2276certificate, and no one else will have it in their cache of known (and trusted) 2277root certificates. 2278 2279 2280Examples 2281-------- 2282 2283Testing for SSL support 2284^^^^^^^^^^^^^^^^^^^^^^^ 2285 2286To test for the presence of SSL support in a Python installation, user code 2287should use the following idiom:: 2288 2289 try: 2290 import ssl 2291 except ImportError: 2292 pass 2293 else: 2294 ... # do something that requires SSL support 2295 2296Client-side operation 2297^^^^^^^^^^^^^^^^^^^^^ 2298 2299This example creates a SSL context with the recommended security settings 2300for client sockets, including automatic certificate verification:: 2301 2302 >>> context = ssl.create_default_context() 2303 2304If you prefer to tune security settings yourself, you might create 2305a context from scratch (but beware that you might not get the settings 2306right):: 2307 2308 >>> context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) 2309 >>> context.load_verify_locations("/etc/ssl/certs/ca-bundle.crt") 2310 2311(this snippet assumes your operating system places a bundle of all CA 2312certificates in ``/etc/ssl/certs/ca-bundle.crt``; if not, you'll get an 2313error and have to adjust the location) 2314 2315The :data:`PROTOCOL_TLS_CLIENT` protocol configures the context for cert 2316validation and hostname verification. :attr:`~SSLContext.verify_mode` is 2317set to :data:`CERT_REQUIRED` and :attr:`~SSLContext.check_hostname` is set 2318to ``True``. All other protocols create SSL contexts with insecure defaults. 2319 2320When you use the context to connect to a server, :const:`CERT_REQUIRED` 2321and :attr:`~SSLContext.check_hostname` validate the server certificate: it 2322ensures that the server certificate was signed with one of the CA 2323certificates, checks the signature for correctness, and verifies other 2324properties like validity and identity of the hostname:: 2325 2326 >>> conn = context.wrap_socket(socket.socket(socket.AF_INET), 2327 ... server_hostname="www.python.org") 2328 >>> conn.connect(("www.python.org", 443)) 2329 2330You may then fetch the certificate:: 2331 2332 >>> cert = conn.getpeercert() 2333 2334Visual inspection shows that the certificate does identify the desired service 2335(that is, the HTTPS host ``www.python.org``):: 2336 2337 >>> pprint.pprint(cert) 2338 {'OCSP': ('http://ocsp.digicert.com',), 2339 'caIssuers': ('http://cacerts.digicert.com/DigiCertSHA2ExtendedValidationServerCA.crt',), 2340 'crlDistributionPoints': ('http://crl3.digicert.com/sha2-ev-server-g1.crl', 2341 'http://crl4.digicert.com/sha2-ev-server-g1.crl'), 2342 'issuer': ((('countryName', 'US'),), 2343 (('organizationName', 'DigiCert Inc'),), 2344 (('organizationalUnitName', 'www.digicert.com'),), 2345 (('commonName', 'DigiCert SHA2 Extended Validation Server CA'),)), 2346 'notAfter': 'Sep 9 12:00:00 2016 GMT', 2347 'notBefore': 'Sep 5 00:00:00 2014 GMT', 2348 'serialNumber': '01BB6F00122B177F36CAB49CEA8B6B26', 2349 'subject': ((('businessCategory', 'Private Organization'),), 2350 (('1.3.6.1.4.1.311.60.2.1.3', 'US'),), 2351 (('1.3.6.1.4.1.311.60.2.1.2', 'Delaware'),), 2352 (('serialNumber', '3359300'),), 2353 (('streetAddress', '16 Allen Rd'),), 2354 (('postalCode', '03894-4801'),), 2355 (('countryName', 'US'),), 2356 (('stateOrProvinceName', 'NH'),), 2357 (('localityName', 'Wolfeboro'),), 2358 (('organizationName', 'Python Software Foundation'),), 2359 (('commonName', 'www.python.org'),)), 2360 'subjectAltName': (('DNS', 'www.python.org'), 2361 ('DNS', 'python.org'), 2362 ('DNS', 'pypi.org'), 2363 ('DNS', 'docs.python.org'), 2364 ('DNS', 'testpypi.org'), 2365 ('DNS', 'bugs.python.org'), 2366 ('DNS', 'wiki.python.org'), 2367 ('DNS', 'hg.python.org'), 2368 ('DNS', 'mail.python.org'), 2369 ('DNS', 'packaging.python.org'), 2370 ('DNS', 'pythonhosted.org'), 2371 ('DNS', 'www.pythonhosted.org'), 2372 ('DNS', 'test.pythonhosted.org'), 2373 ('DNS', 'us.pycon.org'), 2374 ('DNS', 'id.python.org')), 2375 'version': 3} 2376 2377Now the SSL channel is established and the certificate verified, you can 2378proceed to talk with the server:: 2379 2380 >>> conn.sendall(b"HEAD / HTTP/1.0\r\nHost: linuxfr.org\r\n\r\n") 2381 >>> pprint.pprint(conn.recv(1024).split(b"\r\n")) 2382 [b'HTTP/1.1 200 OK', 2383 b'Date: Sat, 18 Oct 2014 18:27:20 GMT', 2384 b'Server: nginx', 2385 b'Content-Type: text/html; charset=utf-8', 2386 b'X-Frame-Options: SAMEORIGIN', 2387 b'Content-Length: 45679', 2388 b'Accept-Ranges: bytes', 2389 b'Via: 1.1 varnish', 2390 b'Age: 2188', 2391 b'X-Served-By: cache-lcy1134-LCY', 2392 b'X-Cache: HIT', 2393 b'X-Cache-Hits: 11', 2394 b'Vary: Cookie', 2395 b'Strict-Transport-Security: max-age=63072000; includeSubDomains', 2396 b'Connection: close', 2397 b'', 2398 b''] 2399 2400See the discussion of :ref:`ssl-security` below. 2401 2402 2403Server-side operation 2404^^^^^^^^^^^^^^^^^^^^^ 2405 2406For server operation, typically you'll need to have a server certificate, and 2407private key, each in a file. You'll first create a context holding the key 2408and the certificate, so that clients can check your authenticity. Then 2409you'll open a socket, bind it to a port, call :meth:`listen` on it, and start 2410waiting for clients to connect:: 2411 2412 import socket, ssl 2413 2414 context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH) 2415 context.load_cert_chain(certfile="mycertfile", keyfile="mykeyfile") 2416 2417 bindsocket = socket.socket() 2418 bindsocket.bind(('myaddr.example.com', 10023)) 2419 bindsocket.listen(5) 2420 2421When a client connects, you'll call :meth:`accept` on the socket to get the 2422new socket from the other end, and use the context's :meth:`SSLContext.wrap_socket` 2423method to create a server-side SSL socket for the connection:: 2424 2425 while True: 2426 newsocket, fromaddr = bindsocket.accept() 2427 connstream = context.wrap_socket(newsocket, server_side=True) 2428 try: 2429 deal_with_client(connstream) 2430 finally: 2431 connstream.shutdown(socket.SHUT_RDWR) 2432 connstream.close() 2433 2434Then you'll read data from the ``connstream`` and do something with it till you 2435are finished with the client (or the client is finished with you):: 2436 2437 def deal_with_client(connstream): 2438 data = connstream.recv(1024) 2439 # empty data means the client is finished with us 2440 while data: 2441 if not do_something(connstream, data): 2442 # we'll assume do_something returns False 2443 # when we're finished with client 2444 break 2445 data = connstream.recv(1024) 2446 # finished with client 2447 2448And go back to listening for new client connections (of course, a real server 2449would probably handle each client connection in a separate thread, or put 2450the sockets in :ref:`non-blocking mode <ssl-nonblocking>` and use an event loop). 2451 2452 2453.. _ssl-nonblocking: 2454 2455Notes on non-blocking sockets 2456----------------------------- 2457 2458SSL sockets behave slightly different than regular sockets in 2459non-blocking mode. When working with non-blocking sockets, there are 2460thus several things you need to be aware of: 2461 2462- Most :class:`SSLSocket` methods will raise either 2463 :exc:`SSLWantWriteError` or :exc:`SSLWantReadError` instead of 2464 :exc:`BlockingIOError` if an I/O operation would 2465 block. :exc:`SSLWantReadError` will be raised if a read operation on 2466 the underlying socket is necessary, and :exc:`SSLWantWriteError` for 2467 a write operation on the underlying socket. Note that attempts to 2468 *write* to an SSL socket may require *reading* from the underlying 2469 socket first, and attempts to *read* from the SSL socket may require 2470 a prior *write* to the underlying socket. 2471 2472 .. versionchanged:: 3.5 2473 2474 In earlier Python versions, the :meth:`!SSLSocket.send` method 2475 returned zero instead of raising :exc:`SSLWantWriteError` or 2476 :exc:`SSLWantReadError`. 2477 2478- Calling :func:`~select.select` tells you that the OS-level socket can be 2479 read from (or written to), but it does not imply that there is sufficient 2480 data at the upper SSL layer. For example, only part of an SSL frame might 2481 have arrived. Therefore, you must be ready to handle :meth:`SSLSocket.recv` 2482 and :meth:`SSLSocket.send` failures, and retry after another call to 2483 :func:`~select.select`. 2484 2485- Conversely, since the SSL layer has its own framing, a SSL socket may 2486 still have data available for reading without :func:`~select.select` 2487 being aware of it. Therefore, you should first call 2488 :meth:`SSLSocket.recv` to drain any potentially available data, and then 2489 only block on a :func:`~select.select` call if still necessary. 2490 2491 (of course, similar provisions apply when using other primitives such as 2492 :func:`~select.poll`, or those in the :mod:`selectors` module) 2493 2494- The SSL handshake itself will be non-blocking: the 2495 :meth:`SSLSocket.do_handshake` method has to be retried until it returns 2496 successfully. Here is a synopsis using :func:`~select.select` to wait for 2497 the socket's readiness:: 2498 2499 while True: 2500 try: 2501 sock.do_handshake() 2502 break 2503 except ssl.SSLWantReadError: 2504 select.select([sock], [], []) 2505 except ssl.SSLWantWriteError: 2506 select.select([], [sock], []) 2507 2508.. seealso:: 2509 2510 The :mod:`asyncio` module supports :ref:`non-blocking SSL sockets 2511 <ssl-nonblocking>` and provides a 2512 higher level API. It polls for events using the :mod:`selectors` module and 2513 handles :exc:`SSLWantWriteError`, :exc:`SSLWantReadError` and 2514 :exc:`BlockingIOError` exceptions. It runs the SSL handshake asynchronously 2515 as well. 2516 2517 2518Memory BIO Support 2519------------------ 2520 2521.. versionadded:: 3.5 2522 2523Ever since the SSL module was introduced in Python 2.6, the :class:`SSLSocket` 2524class has provided two related but distinct areas of functionality: 2525 2526- SSL protocol handling 2527- Network IO 2528 2529The network IO API is identical to that provided by :class:`socket.socket`, 2530from which :class:`SSLSocket` also inherits. This allows an SSL socket to be 2531used as a drop-in replacement for a regular socket, making it very easy to add 2532SSL support to an existing application. 2533 2534Combining SSL protocol handling and network IO usually works well, but there 2535are some cases where it doesn't. An example is async IO frameworks that want to 2536use a different IO multiplexing model than the "select/poll on a file 2537descriptor" (readiness based) model that is assumed by :class:`socket.socket` 2538and by the internal OpenSSL socket IO routines. This is mostly relevant for 2539platforms like Windows where this model is not efficient. For this purpose, a 2540reduced scope variant of :class:`SSLSocket` called :class:`SSLObject` is 2541provided. 2542 2543.. class:: SSLObject 2544 2545 A reduced-scope variant of :class:`SSLSocket` representing an SSL protocol 2546 instance that does not contain any network IO methods. This class is 2547 typically used by framework authors that want to implement asynchronous IO 2548 for SSL through memory buffers. 2549 2550 This class implements an interface on top of a low-level SSL object as 2551 implemented by OpenSSL. This object captures the state of an SSL connection 2552 but does not provide any network IO itself. IO needs to be performed through 2553 separate "BIO" objects which are OpenSSL's IO abstraction layer. 2554 2555 This class has no public constructor. An :class:`SSLObject` instance 2556 must be created using the :meth:`~SSLContext.wrap_bio` method. This 2557 method will create the :class:`SSLObject` instance and bind it to a 2558 pair of BIOs. The *incoming* BIO is used to pass data from Python to the 2559 SSL protocol instance, while the *outgoing* BIO is used to pass data the 2560 other way around. 2561 2562 The following methods are available: 2563 2564 - :attr:`~SSLSocket.context` 2565 - :attr:`~SSLSocket.server_side` 2566 - :attr:`~SSLSocket.server_hostname` 2567 - :attr:`~SSLSocket.session` 2568 - :attr:`~SSLSocket.session_reused` 2569 - :meth:`~SSLSocket.read` 2570 - :meth:`~SSLSocket.write` 2571 - :meth:`~SSLSocket.getpeercert` 2572 - :meth:`~SSLSocket.get_verified_chain` 2573 - :meth:`~SSLSocket.get_unverified_chain` 2574 - :meth:`~SSLSocket.selected_alpn_protocol` 2575 - :meth:`~SSLSocket.selected_npn_protocol` 2576 - :meth:`~SSLSocket.cipher` 2577 - :meth:`~SSLSocket.shared_ciphers` 2578 - :meth:`~SSLSocket.compression` 2579 - :meth:`~SSLSocket.pending` 2580 - :meth:`~SSLSocket.do_handshake` 2581 - :meth:`~SSLSocket.verify_client_post_handshake` 2582 - :meth:`~SSLSocket.unwrap` 2583 - :meth:`~SSLSocket.get_channel_binding` 2584 - :meth:`~SSLSocket.version` 2585 2586 When compared to :class:`SSLSocket`, this object lacks the following 2587 features: 2588 2589 - Any form of network IO; ``recv()`` and ``send()`` read and write only to 2590 the underlying :class:`MemoryBIO` buffers. 2591 2592 - There is no *do_handshake_on_connect* machinery. You must always manually 2593 call :meth:`~SSLSocket.do_handshake` to start the handshake. 2594 2595 - There is no handling of *suppress_ragged_eofs*. All end-of-file conditions 2596 that are in violation of the protocol are reported via the 2597 :exc:`SSLEOFError` exception. 2598 2599 - The method :meth:`~SSLSocket.unwrap` call does not return anything, 2600 unlike for an SSL socket where it returns the underlying socket. 2601 2602 - The *server_name_callback* callback passed to 2603 :meth:`SSLContext.set_servername_callback` will get an :class:`SSLObject` 2604 instance instead of a :class:`SSLSocket` instance as its first parameter. 2605 2606 Some notes related to the use of :class:`SSLObject`: 2607 2608 - All IO on an :class:`SSLObject` is :ref:`non-blocking <ssl-nonblocking>`. 2609 This means that for example :meth:`~SSLSocket.read` will raise an 2610 :exc:`SSLWantReadError` if it needs more data than the incoming BIO has 2611 available. 2612 2613 .. versionchanged:: 3.7 2614 :class:`SSLObject` instances must be created with 2615 :meth:`~SSLContext.wrap_bio`. In earlier versions, it was possible to 2616 create instances directly. This was never documented or officially 2617 supported. 2618 2619An SSLObject communicates with the outside world using memory buffers. The 2620class :class:`MemoryBIO` provides a memory buffer that can be used for this 2621purpose. It wraps an OpenSSL memory BIO (Basic IO) object: 2622 2623.. class:: MemoryBIO 2624 2625 A memory buffer that can be used to pass data between Python and an SSL 2626 protocol instance. 2627 2628 .. attribute:: MemoryBIO.pending 2629 2630 Return the number of bytes currently in the memory buffer. 2631 2632 .. attribute:: MemoryBIO.eof 2633 2634 A boolean indicating whether the memory BIO is current at the end-of-file 2635 position. 2636 2637 .. method:: MemoryBIO.read(n=-1) 2638 2639 Read up to *n* bytes from the memory buffer. If *n* is not specified or 2640 negative, all bytes are returned. 2641 2642 .. method:: MemoryBIO.write(buf) 2643 2644 Write the bytes from *buf* to the memory BIO. The *buf* argument must be an 2645 object supporting the buffer protocol. 2646 2647 The return value is the number of bytes written, which is always equal to 2648 the length of *buf*. 2649 2650 .. method:: MemoryBIO.write_eof() 2651 2652 Write an EOF marker to the memory BIO. After this method has been called, it 2653 is illegal to call :meth:`~MemoryBIO.write`. The attribute :attr:`eof` will 2654 become true after all data currently in the buffer has been read. 2655 2656 2657SSL session 2658----------- 2659 2660.. versionadded:: 3.6 2661 2662.. class:: SSLSession 2663 2664 Session object used by :attr:`~SSLSocket.session`. 2665 2666 .. attribute:: id 2667 .. attribute:: time 2668 .. attribute:: timeout 2669 .. attribute:: ticket_lifetime_hint 2670 .. attribute:: has_ticket 2671 2672 2673.. _ssl-security: 2674 2675Security considerations 2676----------------------- 2677 2678Best defaults 2679^^^^^^^^^^^^^ 2680 2681For **client use**, if you don't have any special requirements for your 2682security policy, it is highly recommended that you use the 2683:func:`create_default_context` function to create your SSL context. 2684It will load the system's trusted CA certificates, enable certificate 2685validation and hostname checking, and try to choose reasonably secure 2686protocol and cipher settings. 2687 2688For example, here is how you would use the :class:`smtplib.SMTP` class to 2689create a trusted, secure connection to a SMTP server:: 2690 2691 >>> import ssl, smtplib 2692 >>> smtp = smtplib.SMTP("mail.python.org", port=587) 2693 >>> context = ssl.create_default_context() 2694 >>> smtp.starttls(context=context) 2695 (220, b'2.0.0 Ready to start TLS') 2696 2697If a client certificate is needed for the connection, it can be added with 2698:meth:`SSLContext.load_cert_chain`. 2699 2700By contrast, if you create the SSL context by calling the :class:`SSLContext` 2701constructor yourself, it will not have certificate validation nor hostname 2702checking enabled by default. If you do so, please read the paragraphs below 2703to achieve a good security level. 2704 2705Manual settings 2706^^^^^^^^^^^^^^^ 2707 2708Verifying certificates 2709'''''''''''''''''''''' 2710 2711When calling the :class:`SSLContext` constructor directly, 2712:const:`CERT_NONE` is the default. Since it does not authenticate the other 2713peer, it can be insecure, especially in client mode where most of the time you 2714would like to ensure the authenticity of the server you're talking to. 2715Therefore, when in client mode, it is highly recommended to use 2716:const:`CERT_REQUIRED`. However, it is in itself not sufficient; you also 2717have to check that the server certificate, which can be obtained by calling 2718:meth:`SSLSocket.getpeercert`, matches the desired service. For many 2719protocols and applications, the service can be identified by the hostname. 2720This common check is automatically performed when 2721:attr:`SSLContext.check_hostname` is enabled. 2722 2723.. versionchanged:: 3.7 2724 Hostname matchings is now performed by OpenSSL. Python no longer uses 2725 :func:`match_hostname`. 2726 2727In server mode, if you want to authenticate your clients using the SSL layer 2728(rather than using a higher-level authentication mechanism), you'll also have 2729to specify :const:`CERT_REQUIRED` and similarly check the client certificate. 2730 2731 2732Protocol versions 2733''''''''''''''''' 2734 2735SSL versions 2 and 3 are considered insecure and are therefore dangerous to 2736use. If you want maximum compatibility between clients and servers, it is 2737recommended to use :const:`PROTOCOL_TLS_CLIENT` or 2738:const:`PROTOCOL_TLS_SERVER` as the protocol version. SSLv2 and SSLv3 are 2739disabled by default. 2740 2741:: 2742 2743 >>> client_context = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT) 2744 >>> client_context.minimum_version = ssl.TLSVersion.TLSv1_3 2745 >>> client_context.maximum_version = ssl.TLSVersion.TLSv1_3 2746 2747 2748The SSL context created above will only allow TLSv1.3 and later (if 2749supported by your system) connections to a server. :const:`PROTOCOL_TLS_CLIENT` 2750implies certificate validation and hostname checks by default. You have to 2751load certificates into the context. 2752 2753 2754Cipher selection 2755'''''''''''''''' 2756 2757If you have advanced security requirements, fine-tuning of the ciphers 2758enabled when negotiating a SSL session is possible through the 2759:meth:`SSLContext.set_ciphers` method. Starting from Python 3.2.3, the 2760ssl module disables certain weak ciphers by default, but you may want 2761to further restrict the cipher choice. Be sure to read OpenSSL's documentation 2762about the `cipher list format <https://docs.openssl.org/1.1.1/man1/ciphers/#cipher-list-format>`_. 2763If you want to check which ciphers are enabled by a given cipher list, use 2764:meth:`SSLContext.get_ciphers` or the ``openssl ciphers`` command on your 2765system. 2766 2767Multi-processing 2768^^^^^^^^^^^^^^^^ 2769 2770If using this module as part of a multi-processed application (using, 2771for example the :mod:`multiprocessing` or :mod:`concurrent.futures` modules), 2772be aware that OpenSSL's internal random number generator does not properly 2773handle forked processes. Applications must change the PRNG state of the 2774parent process if they use any SSL feature with :func:`os.fork`. Any 2775successful call of :func:`~ssl.RAND_add` or :func:`~ssl.RAND_bytes` is 2776sufficient. 2777 2778 2779.. _ssl-tlsv1_3: 2780 2781TLS 1.3 2782------- 2783 2784.. versionadded:: 3.7 2785 2786The TLS 1.3 protocol behaves slightly differently than previous version 2787of TLS/SSL. Some new TLS 1.3 features are not yet available. 2788 2789- TLS 1.3 uses a disjunct set of cipher suites. All AES-GCM and 2790 ChaCha20 cipher suites are enabled by default. The method 2791 :meth:`SSLContext.set_ciphers` cannot enable or disable any TLS 1.3 2792 ciphers yet, but :meth:`SSLContext.get_ciphers` returns them. 2793- Session tickets are no longer sent as part of the initial handshake and 2794 are handled differently. :attr:`SSLSocket.session` and :class:`SSLSession` 2795 are not compatible with TLS 1.3. 2796- Client-side certificates are also no longer verified during the initial 2797 handshake. A server can request a certificate at any time. Clients 2798 process certificate requests while they send or receive application data 2799 from the server. 2800- TLS 1.3 features like early data, deferred TLS client cert request, 2801 signature algorithm configuration, and rekeying are not supported yet. 2802 2803 2804.. seealso:: 2805 2806 Class :class:`socket.socket` 2807 Documentation of underlying :mod:`socket` class 2808 2809 `SSL/TLS Strong Encryption: An Introduction <https://httpd.apache.org/docs/trunk/en/ssl/ssl_intro.html>`_ 2810 Intro from the Apache HTTP Server documentation 2811 2812 :rfc:`RFC 1422: Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management <1422>` 2813 Steve Kent 2814 2815 :rfc:`RFC 4086: Randomness Requirements for Security <4086>` 2816 Donald E., Jeffrey I. Schiller 2817 2818 :rfc:`RFC 5280: Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile <5280>` 2819 D. Cooper 2820 2821 :rfc:`RFC 5246: The Transport Layer Security (TLS) Protocol Version 1.2 <5246>` 2822 T. Dierks et. al. 2823 2824 :rfc:`RFC 6066: Transport Layer Security (TLS) Extensions <6066>` 2825 D. Eastlake 2826 2827 `IANA TLS: Transport Layer Security (TLS) Parameters <https://www.iana.org/assignments/tls-parameters/tls-parameters.xml>`_ 2828 IANA 2829 2830 :rfc:`RFC 7525: Recommendations for Secure Use of Transport Layer Security (TLS) and Datagram Transport Layer Security (DTLS) <7525>` 2831 IETF 2832 2833 `Mozilla's Server Side TLS recommendations <https://wiki.mozilla.org/Security/Server_Side_TLS>`_ 2834 Mozilla 2835