• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
1 /* Copyright (c) 2015, Google Inc.
2  *
3  * Permission to use, copy, modify, and/or distribute this software for any
4  * purpose with or without fee is hereby granted, provided that the above
5  * copyright notice and this permission notice appear in all copies.
6  *
7  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10  * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12  * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13  * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
14 
15 #ifndef OPENSSL_HEADER_CURVE25519_H
16 #define OPENSSL_HEADER_CURVE25519_H
17 
18 #include <openssl/base.h>
19 
20 #if defined(__cplusplus)
21 extern "C" {
22 #endif
23 
24 
25 // Curve25519.
26 //
27 // Curve25519 is an elliptic curve. See https://tools.ietf.org/html/rfc7748.
28 
29 
30 // X25519.
31 //
32 // X25519 is the Diffie-Hellman primitive built from curve25519. It is
33 // sometimes referred to as “curve25519”, but “X25519” is a more precise name.
34 // See http://cr.yp.to/ecdh.html and https://tools.ietf.org/html/rfc7748.
35 
36 #define X25519_PRIVATE_KEY_LEN 32
37 #define X25519_PUBLIC_VALUE_LEN 32
38 #define X25519_SHARED_KEY_LEN 32
39 
40 // X25519_keypair sets |out_public_value| and |out_private_key| to a freshly
41 // generated, public–private key pair.
42 OPENSSL_EXPORT void X25519_keypair(uint8_t out_public_value[32],
43                                    uint8_t out_private_key[32]);
44 
45 // X25519 writes a shared key to |out_shared_key| that is calculated from the
46 // given private key and the peer's public value. It returns one on success and
47 // zero on error.
48 //
49 // Don't use the shared key directly, rather use a KDF and also include the two
50 // public values as inputs.
51 OPENSSL_EXPORT int X25519(uint8_t out_shared_key[32],
52                           const uint8_t private_key[32],
53                           const uint8_t peer_public_value[32]);
54 
55 // X25519_public_from_private calculates a Diffie-Hellman public value from the
56 // given private key and writes it to |out_public_value|.
57 OPENSSL_EXPORT void X25519_public_from_private(uint8_t out_public_value[32],
58                                                const uint8_t private_key[32]);
59 
60 
61 // Ed25519.
62 //
63 // Ed25519 is a signature scheme using a twisted-Edwards curve that is
64 // birationally equivalent to curve25519.
65 //
66 // Note that, unlike RFC 8032's formulation, our private key representation
67 // includes a public key suffix to make multiple key signing operations with the
68 // same key more efficient. The RFC 8032 private key is referred to in this
69 // implementation as the "seed" and is the first 32 bytes of our private key.
70 
71 #define ED25519_PRIVATE_KEY_LEN 64
72 #define ED25519_PUBLIC_KEY_LEN 32
73 #define ED25519_SIGNATURE_LEN 64
74 
75 // ED25519_keypair sets |out_public_key| and |out_private_key| to a freshly
76 // generated, public–private key pair.
77 OPENSSL_EXPORT void ED25519_keypair(uint8_t out_public_key[32],
78                                     uint8_t out_private_key[64]);
79 
80 // ED25519_sign sets |out_sig| to be a signature of |message_len| bytes from
81 // |message| using |private_key|. It returns one on success or zero on
82 // allocation failure.
83 OPENSSL_EXPORT int ED25519_sign(uint8_t out_sig[64], const uint8_t *message,
84                                 size_t message_len,
85                                 const uint8_t private_key[64]);
86 
87 // ED25519_verify returns one iff |signature| is a valid signature, by
88 // |public_key| of |message_len| bytes from |message|. It returns zero
89 // otherwise.
90 OPENSSL_EXPORT int ED25519_verify(const uint8_t *message, size_t message_len,
91                                   const uint8_t signature[64],
92                                   const uint8_t public_key[32]);
93 
94 // ED25519_keypair_from_seed calculates a public and private key from an
95 // Ed25519 “seed”. Seed values are not exposed by this API (although they
96 // happen to be the first 32 bytes of a private key) so this function is for
97 // interoperating with systems that may store just a seed instead of a full
98 // private key.
99 OPENSSL_EXPORT void ED25519_keypair_from_seed(uint8_t out_public_key[32],
100                                               uint8_t out_private_key[64],
101                                               const uint8_t seed[32]);
102 
103 
104 // SPAKE2.
105 //
106 // SPAKE2 is a password-authenticated key-exchange. It allows two parties,
107 // who share a low-entropy secret (i.e. password), to agree on a shared key.
108 // An attacker can only make one guess of the password per execution of the
109 // protocol.
110 //
111 // See https://tools.ietf.org/html/draft-irtf-cfrg-spake2-02.
112 
113 // spake2_role_t enumerates the different “roles” in SPAKE2. The protocol
114 // requires that the symmetry of the two parties be broken so one participant
115 // must be “Alice” and the other be “Bob”.
116 enum spake2_role_t {
117   spake2_role_alice,
118   spake2_role_bob,
119 };
120 
121 // SPAKE2_CTX_new creates a new |SPAKE2_CTX| (which can only be used for a
122 // single execution of the protocol). SPAKE2 requires the symmetry of the two
123 // parties to be broken which is indicated via |my_role| – each party must pass
124 // a different value for this argument.
125 //
126 // The |my_name| and |their_name| arguments allow optional, opaque names to be
127 // bound into the protocol. For example MAC addresses, hostnames, usernames
128 // etc. These values are not exposed and can avoid context-confusion attacks
129 // when a password is shared between several devices.
130 OPENSSL_EXPORT SPAKE2_CTX *SPAKE2_CTX_new(
131     enum spake2_role_t my_role,
132     const uint8_t *my_name, size_t my_name_len,
133     const uint8_t *their_name, size_t their_name_len);
134 
135 // SPAKE2_CTX_free frees |ctx| and all the resources that it has allocated.
136 OPENSSL_EXPORT void SPAKE2_CTX_free(SPAKE2_CTX *ctx);
137 
138 // SPAKE2_MAX_MSG_SIZE is the maximum size of a SPAKE2 message.
139 #define SPAKE2_MAX_MSG_SIZE 32
140 
141 // SPAKE2_generate_msg generates a SPAKE2 message given |password|, writes
142 // it to |out| and sets |*out_len| to the number of bytes written.
143 //
144 // At most |max_out_len| bytes are written to |out| and, in order to ensure
145 // success, |max_out_len| should be at least |SPAKE2_MAX_MSG_SIZE| bytes.
146 //
147 // This function can only be called once for a given |SPAKE2_CTX|.
148 //
149 // It returns one on success and zero on error.
150 OPENSSL_EXPORT int SPAKE2_generate_msg(SPAKE2_CTX *ctx, uint8_t *out,
151                                        size_t *out_len, size_t max_out_len,
152                                        const uint8_t *password,
153                                        size_t password_len);
154 
155 // SPAKE2_MAX_KEY_SIZE is the maximum amount of key material that SPAKE2 will
156 // produce.
157 #define SPAKE2_MAX_KEY_SIZE 64
158 
159 // SPAKE2_process_msg completes the SPAKE2 exchange given the peer's message in
160 // |their_msg|, writes at most |max_out_key_len| bytes to |out_key| and sets
161 // |*out_key_len| to the number of bytes written.
162 //
163 // The resulting keying material is suitable for:
164 //   a) Using directly in a key-confirmation step: i.e. each side could
165 //      transmit a hash of their role, a channel-binding value and the key
166 //      material to prove to the other side that they know the shared key.
167 //   b) Using as input keying material to HKDF to generate a variety of subkeys
168 //      for encryption etc.
169 //
170 // If |max_out_key_key| is smaller than the amount of key material generated
171 // then the key is silently truncated. If you want to ensure that no truncation
172 // occurs then |max_out_key| should be at least |SPAKE2_MAX_KEY_SIZE|.
173 //
174 // You must call |SPAKE2_generate_msg| on a given |SPAKE2_CTX| before calling
175 // this function. On successful return, |ctx| is complete and calling
176 // |SPAKE2_CTX_free| is the only acceptable operation on it.
177 //
178 // Returns one on success or zero on error.
179 OPENSSL_EXPORT int SPAKE2_process_msg(SPAKE2_CTX *ctx, uint8_t *out_key,
180                                       size_t *out_key_len,
181                                       size_t max_out_key_len,
182                                       const uint8_t *their_msg,
183                                       size_t their_msg_len);
184 
185 
186 #if defined(__cplusplus)
187 }  // extern C
188 
189 extern "C++" {
190 
191 BSSL_NAMESPACE_BEGIN
192 
193 BORINGSSL_MAKE_DELETER(SPAKE2_CTX, SPAKE2_CTX_free)
194 
195 BSSL_NAMESPACE_END
196 
197 }  // extern C++
198 
199 #endif
200 
201 #endif  // OPENSSL_HEADER_CURVE25519_H
202