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1 /* Copyright (c) 2014, 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 #include <openssl/base.h>
16 
17 #include <string>
18 #include <vector>
19 
20 #include <errno.h>
21 #include <limits.h>
22 #include <stddef.h>
23 #include <stdlib.h>
24 #include <string.h>
25 #include <sys/types.h>
26 
27 #if !defined(OPENSSL_WINDOWS)
28 #include <arpa/inet.h>
29 #include <fcntl.h>
30 #include <netdb.h>
31 #include <netinet/in.h>
32 #include <sys/select.h>
33 #include <sys/socket.h>
34 #include <unistd.h>
35 #else
36 #include <io.h>
37 OPENSSL_MSVC_PRAGMA(warning(push, 3))
38 #include <winsock2.h>
39 #include <ws2tcpip.h>
40 OPENSSL_MSVC_PRAGMA(warning(pop))
41 
42 typedef int ssize_t;
43 OPENSSL_MSVC_PRAGMA(comment(lib, "Ws2_32.lib"))
44 #endif
45 
46 #include <openssl/err.h>
47 #include <openssl/ssl.h>
48 #include <openssl/x509.h>
49 
50 #include "../crypto/internal.h"
51 #include "internal.h"
52 #include "transport_common.h"
53 
54 
55 #if !defined(OPENSSL_WINDOWS)
closesocket(int sock)56 static int closesocket(int sock) {
57   return close(sock);
58 }
59 #endif
60 
InitSocketLibrary()61 bool InitSocketLibrary() {
62 #if defined(OPENSSL_WINDOWS)
63   WSADATA wsaData;
64   int err = WSAStartup(MAKEWORD(2, 2), &wsaData);
65   if (err != 0) {
66     fprintf(stderr, "WSAStartup failed with error %d\n", err);
67     return false;
68   }
69 #endif
70   return true;
71 }
72 
SplitHostPort(std::string * out_hostname,std::string * out_port,const std::string & hostname_and_port)73 static void SplitHostPort(std::string *out_hostname, std::string *out_port,
74                           const std::string &hostname_and_port) {
75   size_t colon_offset = hostname_and_port.find_last_of(':');
76   const size_t bracket_offset = hostname_and_port.find_last_of(']');
77   std::string hostname, port;
78 
79   // An IPv6 literal may have colons internally, guarded by square brackets.
80   if (bracket_offset != std::string::npos &&
81       colon_offset != std::string::npos && bracket_offset > colon_offset) {
82     colon_offset = std::string::npos;
83   }
84 
85   if (colon_offset == std::string::npos) {
86     *out_hostname = hostname_and_port;
87     *out_port = "443";
88   } else {
89     *out_hostname = hostname_and_port.substr(0, colon_offset);
90     *out_port = hostname_and_port.substr(colon_offset + 1);
91   }
92 }
93 
94 // Connect sets |*out_sock| to be a socket connected to the destination given
95 // in |hostname_and_port|, which should be of the form "www.example.com:123".
96 // It returns true on success and false otherwise.
Connect(int * out_sock,const std::string & hostname_and_port)97 bool Connect(int *out_sock, const std::string &hostname_and_port) {
98   std::string hostname, port;
99   SplitHostPort(&hostname, &port, hostname_and_port);
100 
101   // Handle IPv6 literals.
102   if (hostname.size() >= 2 && hostname[0] == '[' &&
103       hostname[hostname.size() - 1] == ']') {
104     hostname = hostname.substr(1, hostname.size() - 2);
105   }
106 
107   struct addrinfo hint, *result;
108   OPENSSL_memset(&hint, 0, sizeof(hint));
109   hint.ai_family = AF_UNSPEC;
110   hint.ai_socktype = SOCK_STREAM;
111 
112   int ret = getaddrinfo(hostname.c_str(), port.c_str(), &hint, &result);
113   if (ret != 0) {
114     fprintf(stderr, "getaddrinfo returned: %s\n", gai_strerror(ret));
115     return false;
116   }
117 
118   bool ok = false;
119   char buf[256];
120 
121   *out_sock =
122       socket(result->ai_family, result->ai_socktype, result->ai_protocol);
123   if (*out_sock < 0) {
124     perror("socket");
125     goto out;
126   }
127 
128   switch (result->ai_family) {
129     case AF_INET: {
130       struct sockaddr_in *sin =
131           reinterpret_cast<struct sockaddr_in *>(result->ai_addr);
132       fprintf(stderr, "Connecting to %s:%d\n",
133               inet_ntop(result->ai_family, &sin->sin_addr, buf, sizeof(buf)),
134               ntohs(sin->sin_port));
135       break;
136     }
137     case AF_INET6: {
138       struct sockaddr_in6 *sin6 =
139           reinterpret_cast<struct sockaddr_in6 *>(result->ai_addr);
140       fprintf(stderr, "Connecting to [%s]:%d\n",
141               inet_ntop(result->ai_family, &sin6->sin6_addr, buf, sizeof(buf)),
142               ntohs(sin6->sin6_port));
143       break;
144     }
145   }
146 
147   if (connect(*out_sock, result->ai_addr, result->ai_addrlen) != 0) {
148     perror("connect");
149     goto out;
150   }
151   ok = true;
152 
153 out:
154   freeaddrinfo(result);
155   return ok;
156 }
157 
~Listener()158 Listener::~Listener() {
159   if (server_sock_ >= 0) {
160     closesocket(server_sock_);
161   }
162 }
163 
Init(const std::string & port)164 bool Listener::Init(const std::string &port) {
165   if (server_sock_ >= 0) {
166     return false;
167   }
168 
169   struct sockaddr_in6 addr;
170   OPENSSL_memset(&addr, 0, sizeof(addr));
171 
172   addr.sin6_family = AF_INET6;
173   addr.sin6_addr = IN6ADDR_ANY_INIT;
174   addr.sin6_port = htons(atoi(port.c_str()));
175 
176 #if defined(OPENSSL_WINDOWS)
177   const BOOL enable = TRUE;
178 #else
179   const int enable = 1;
180 #endif
181 
182   server_sock_ = socket(addr.sin6_family, SOCK_STREAM, 0);
183   if (server_sock_ < 0) {
184     perror("socket");
185     return false;
186   }
187 
188   if (setsockopt(server_sock_, SOL_SOCKET, SO_REUSEADDR, (const char *)&enable,
189                  sizeof(enable)) < 0) {
190     perror("setsockopt");
191     return false;
192   }
193 
194   if (bind(server_sock_, (struct sockaddr *)&addr, sizeof(addr)) != 0) {
195     perror("connect");
196     return false;
197   }
198 
199   listen(server_sock_, SOMAXCONN);
200   return true;
201 }
202 
Accept(int * out_sock)203 bool Listener::Accept(int *out_sock) {
204   struct sockaddr_in6 addr;
205   socklen_t addr_len = sizeof(addr);
206   *out_sock = accept(server_sock_, (struct sockaddr *)&addr, &addr_len);
207   return *out_sock >= 0;
208 }
209 
VersionFromString(uint16_t * out_version,const std::string & version)210 bool VersionFromString(uint16_t *out_version, const std::string &version) {
211   if (version == "ssl3") {
212     *out_version = SSL3_VERSION;
213     return true;
214   } else if (version == "tls1" || version == "tls1.0") {
215     *out_version = TLS1_VERSION;
216     return true;
217   } else if (version == "tls1.1") {
218     *out_version = TLS1_1_VERSION;
219     return true;
220   } else if (version == "tls1.2") {
221     *out_version = TLS1_2_VERSION;
222     return true;
223   } else if (version == "tls1.3") {
224     *out_version = TLS1_3_VERSION;
225     return true;
226   }
227   return false;
228 }
229 
SignatureAlgorithmToString(uint16_t version,uint16_t sigalg)230 static const char *SignatureAlgorithmToString(uint16_t version, uint16_t sigalg) {
231   const bool is_tls12 = version == TLS1_2_VERSION || version == DTLS1_2_VERSION;
232   switch (sigalg) {
233     case SSL_SIGN_RSA_PKCS1_SHA1:
234       return "rsa_pkcs1_sha1";
235     case SSL_SIGN_RSA_PKCS1_SHA256:
236       return "rsa_pkcs1_sha256";
237     case SSL_SIGN_RSA_PKCS1_SHA384:
238       return "rsa_pkcs1_sha384";
239     case SSL_SIGN_RSA_PKCS1_SHA512:
240       return "rsa_pkcs1_sha512";
241     case SSL_SIGN_ECDSA_SHA1:
242       return "ecdsa_sha1";
243     case SSL_SIGN_ECDSA_SECP256R1_SHA256:
244       return is_tls12 ? "ecdsa_sha256" : "ecdsa_secp256r1_sha256";
245     case SSL_SIGN_ECDSA_SECP384R1_SHA384:
246       return is_tls12 ? "ecdsa_sha384" : "ecdsa_secp384r1_sha384";
247     case SSL_SIGN_ECDSA_SECP521R1_SHA512:
248       return is_tls12 ? "ecdsa_sha512" : "ecdsa_secp521r1_sha512";
249     case SSL_SIGN_RSA_PSS_SHA256:
250       return "rsa_pss_sha256";
251     case SSL_SIGN_RSA_PSS_SHA384:
252       return "rsa_pss_sha384";
253     case SSL_SIGN_RSA_PSS_SHA512:
254       return "rsa_pss_sha512";
255     case SSL_SIGN_ED25519:
256       return "ed25519";
257     default:
258       return "(unknown)";
259   }
260 }
261 
PrintConnectionInfo(const SSL * ssl)262 void PrintConnectionInfo(const SSL *ssl) {
263   const SSL_CIPHER *cipher = SSL_get_current_cipher(ssl);
264 
265   fprintf(stderr, "  Version: %s\n", SSL_get_version(ssl));
266   fprintf(stderr, "  Resumed session: %s\n",
267           SSL_session_reused(ssl) ? "yes" : "no");
268   fprintf(stderr, "  Cipher: %s\n", SSL_CIPHER_standard_name(cipher));
269   uint16_t curve = SSL_get_curve_id(ssl);
270   if (curve != 0) {
271     fprintf(stderr, "  ECDHE curve: %s\n", SSL_get_curve_name(curve));
272   }
273   uint16_t sigalg = SSL_get_peer_signature_algorithm(ssl);
274   if (sigalg != 0) {
275     fprintf(stderr, "  Signature algorithm: %s\n",
276             SignatureAlgorithmToString(SSL_version(ssl), sigalg));
277   }
278   fprintf(stderr, "  Secure renegotiation: %s\n",
279           SSL_get_secure_renegotiation_support(ssl) ? "yes" : "no");
280   fprintf(stderr, "  Extended master secret: %s\n",
281           SSL_get_extms_support(ssl) ? "yes" : "no");
282 
283   const uint8_t *next_proto;
284   unsigned next_proto_len;
285   SSL_get0_next_proto_negotiated(ssl, &next_proto, &next_proto_len);
286   fprintf(stderr, "  Next protocol negotiated: %.*s\n", next_proto_len,
287           next_proto);
288 
289   const uint8_t *alpn;
290   unsigned alpn_len;
291   SSL_get0_alpn_selected(ssl, &alpn, &alpn_len);
292   fprintf(stderr, "  ALPN protocol: %.*s\n", alpn_len, alpn);
293 
294   const char *host_name = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
295   if (host_name != nullptr && SSL_is_server(ssl)) {
296     fprintf(stderr, "  Client sent SNI: %s\n", host_name);
297   }
298 
299   if (!SSL_is_server(ssl)) {
300     const uint8_t *ocsp_staple;
301     size_t ocsp_staple_len;
302     SSL_get0_ocsp_response(ssl, &ocsp_staple, &ocsp_staple_len);
303     fprintf(stderr, "  OCSP staple: %s\n", ocsp_staple_len > 0 ? "yes" : "no");
304 
305     const uint8_t *sct_list;
306     size_t sct_list_len;
307     SSL_get0_signed_cert_timestamp_list(ssl, &sct_list, &sct_list_len);
308     fprintf(stderr, "  SCT list: %s\n", sct_list_len > 0 ? "yes" : "no");
309   }
310 
311   fprintf(stderr, "  Early data: %s\n",
312           SSL_early_data_accepted(ssl) ? "yes" : "no");
313 
314   // Print the server cert subject and issuer names.
315   bssl::UniquePtr<X509> peer(SSL_get_peer_certificate(ssl));
316   if (peer != nullptr) {
317     fprintf(stderr, "  Cert subject: ");
318     X509_NAME_print_ex_fp(stderr, X509_get_subject_name(peer.get()), 0,
319                           XN_FLAG_ONELINE);
320     fprintf(stderr, "\n  Cert issuer: ");
321     X509_NAME_print_ex_fp(stderr, X509_get_issuer_name(peer.get()), 0,
322                           XN_FLAG_ONELINE);
323     fprintf(stderr, "\n");
324   }
325 }
326 
SocketSetNonBlocking(int sock,bool is_non_blocking)327 bool SocketSetNonBlocking(int sock, bool is_non_blocking) {
328   bool ok;
329 
330 #if defined(OPENSSL_WINDOWS)
331   u_long arg = is_non_blocking;
332   ok = 0 == ioctlsocket(sock, FIONBIO, &arg);
333 #else
334   int flags = fcntl(sock, F_GETFL, 0);
335   if (flags < 0) {
336     return false;
337   }
338   if (is_non_blocking) {
339     flags |= O_NONBLOCK;
340   } else {
341     flags &= ~O_NONBLOCK;
342   }
343   ok = 0 == fcntl(sock, F_SETFL, flags);
344 #endif
345   if (!ok) {
346     fprintf(stderr, "Failed to set socket non-blocking.\n");
347   }
348   return ok;
349 }
350 
351 // PrintErrorCallback is a callback function from OpenSSL's
352 // |ERR_print_errors_cb| that writes errors to a given |FILE*|.
PrintErrorCallback(const char * str,size_t len,void * ctx)353 int PrintErrorCallback(const char *str, size_t len, void *ctx) {
354   fwrite(str, len, 1, reinterpret_cast<FILE*>(ctx));
355   return 1;
356 }
357 
TransferData(SSL * ssl,int sock)358 bool TransferData(SSL *ssl, int sock) {
359   bool stdin_open = true;
360 
361   fd_set read_fds;
362   FD_ZERO(&read_fds);
363 
364   if (!SocketSetNonBlocking(sock, true)) {
365     return false;
366   }
367 
368   for (;;) {
369     if (stdin_open) {
370       FD_SET(0, &read_fds);
371     }
372     FD_SET(sock, &read_fds);
373 
374     int ret = select(sock + 1, &read_fds, NULL, NULL, NULL);
375     if (ret <= 0) {
376       perror("select");
377       return false;
378     }
379 
380     if (FD_ISSET(0, &read_fds)) {
381       uint8_t buffer[512];
382       ssize_t n;
383 
384       do {
385         n = BORINGSSL_READ(0, buffer, sizeof(buffer));
386       } while (n == -1 && errno == EINTR);
387 
388       if (n == 0) {
389         FD_CLR(0, &read_fds);
390         stdin_open = false;
391 #if !defined(OPENSSL_WINDOWS)
392         shutdown(sock, SHUT_WR);
393 #else
394         shutdown(sock, SD_SEND);
395 #endif
396         continue;
397       } else if (n < 0) {
398         perror("read from stdin");
399         return false;
400       }
401 
402       if (!SocketSetNonBlocking(sock, false)) {
403         return false;
404       }
405       int ssl_ret = SSL_write(ssl, buffer, n);
406       if (!SocketSetNonBlocking(sock, true)) {
407         return false;
408       }
409 
410       if (ssl_ret <= 0) {
411         int ssl_err = SSL_get_error(ssl, ssl_ret);
412         fprintf(stderr, "Error while writing: %d\n", ssl_err);
413         ERR_print_errors_cb(PrintErrorCallback, stderr);
414         return false;
415       } else if (ssl_ret != n) {
416         fprintf(stderr, "Short write from SSL_write.\n");
417         return false;
418       }
419     }
420 
421     if (FD_ISSET(sock, &read_fds)) {
422       uint8_t buffer[512];
423       int ssl_ret = SSL_read(ssl, buffer, sizeof(buffer));
424 
425       if (ssl_ret < 0) {
426         int ssl_err = SSL_get_error(ssl, ssl_ret);
427         if (ssl_err == SSL_ERROR_WANT_READ) {
428           continue;
429         }
430         fprintf(stderr, "Error while reading: %d\n", ssl_err);
431         ERR_print_errors_cb(PrintErrorCallback, stderr);
432         return false;
433       } else if (ssl_ret == 0) {
434         return true;
435       }
436 
437       ssize_t n;
438       do {
439         n = BORINGSSL_WRITE(1, buffer, ssl_ret);
440       } while (n == -1 && errno == EINTR);
441 
442       if (n != ssl_ret) {
443         fprintf(stderr, "Short write to stderr.\n");
444         return false;
445       }
446     }
447   }
448 }
449 
450 // SocketLineReader wraps a small buffer around a socket for line-orientated
451 // protocols.
452 class SocketLineReader {
453  public:
SocketLineReader(int sock)454   explicit SocketLineReader(int sock) : sock_(sock) {}
455 
456   // Next reads a '\n'- or '\r\n'-terminated line from the socket and, on
457   // success, sets |*out_line| to it and returns true. Otherwise it returns
458   // false.
Next(std::string * out_line)459   bool Next(std::string *out_line) {
460     for (;;) {
461       for (size_t i = 0; i < buf_len_; i++) {
462         if (buf_[i] != '\n') {
463           continue;
464         }
465 
466         size_t length = i;
467         if (i > 0 && buf_[i - 1] == '\r') {
468           length--;
469         }
470 
471         out_line->assign(buf_, length);
472         buf_len_ -= i + 1;
473         OPENSSL_memmove(buf_, &buf_[i + 1], buf_len_);
474 
475         return true;
476       }
477 
478       if (buf_len_ == sizeof(buf_)) {
479         fprintf(stderr, "Received line too long!\n");
480         return false;
481       }
482 
483       ssize_t n;
484       do {
485         n = recv(sock_, &buf_[buf_len_], sizeof(buf_) - buf_len_, 0);
486       } while (n == -1 && errno == EINTR);
487 
488       if (n < 0) {
489         fprintf(stderr, "Read error from socket\n");
490         return false;
491       }
492 
493       buf_len_ += n;
494     }
495   }
496 
497   // ReadSMTPReply reads one or more lines that make up an SMTP reply. On
498   // success, it sets |*out_code| to the reply's code (e.g. 250) and
499   // |*out_content| to the body of the reply (e.g. "OK") and returns true.
500   // Otherwise it returns false.
501   //
502   // See https://tools.ietf.org/html/rfc821#page-48
ReadSMTPReply(unsigned * out_code,std::string * out_content)503   bool ReadSMTPReply(unsigned *out_code, std::string *out_content) {
504     out_content->clear();
505 
506     // kMaxLines is the maximum number of lines that we'll accept in an SMTP
507     // reply.
508     static const unsigned kMaxLines = 512;
509     for (unsigned i = 0; i < kMaxLines; i++) {
510       std::string line;
511       if (!Next(&line)) {
512         return false;
513       }
514 
515       if (line.size() < 4) {
516         fprintf(stderr, "Short line from SMTP server: %s\n", line.c_str());
517         return false;
518       }
519 
520       const std::string code_str = line.substr(0, 3);
521       char *endptr;
522       const unsigned long code = strtoul(code_str.c_str(), &endptr, 10);
523       if (*endptr || code > UINT_MAX) {
524         fprintf(stderr, "Failed to parse code from line: %s\n", line.c_str());
525         return false;
526       }
527 
528       if (i == 0) {
529         *out_code = code;
530       } else if (code != *out_code) {
531         fprintf(stderr,
532                 "Reply code varied within a single reply: was %u, now %u\n",
533                 *out_code, static_cast<unsigned>(code));
534         return false;
535       }
536 
537       if (line[3] == ' ') {
538         // End of reply.
539         *out_content += line.substr(4, std::string::npos);
540         return true;
541       } else if (line[3] == '-') {
542         // Another line of reply will follow this one.
543         *out_content += line.substr(4, std::string::npos);
544         out_content->push_back('\n');
545       } else {
546         fprintf(stderr, "Bad character after code in SMTP reply: %s\n",
547                 line.c_str());
548         return false;
549       }
550     }
551 
552     fprintf(stderr, "Rejected SMTP reply of more then %u lines\n", kMaxLines);
553     return false;
554   }
555 
556  private:
557   const int sock_;
558   char buf_[512];
559   size_t buf_len_ = 0;
560 };
561 
562 // SendAll writes |data_len| bytes from |data| to |sock|. It returns true on
563 // success and false otherwise.
SendAll(int sock,const char * data,size_t data_len)564 static bool SendAll(int sock, const char *data, size_t data_len) {
565   size_t done = 0;
566 
567   while (done < data_len) {
568     ssize_t n;
569     do {
570       n = send(sock, &data[done], data_len - done, 0);
571     } while (n == -1 && errno == EINTR);
572 
573     if (n < 0) {
574       fprintf(stderr, "Error while writing to socket\n");
575       return false;
576     }
577 
578     done += n;
579   }
580 
581   return true;
582 }
583 
DoSMTPStartTLS(int sock)584 bool DoSMTPStartTLS(int sock) {
585   SocketLineReader line_reader(sock);
586 
587   unsigned code_220 = 0;
588   std::string reply_220;
589   if (!line_reader.ReadSMTPReply(&code_220, &reply_220)) {
590     return false;
591   }
592 
593   if (code_220 != 220) {
594     fprintf(stderr, "Expected 220 line from SMTP server but got code %u\n",
595             code_220);
596     return false;
597   }
598 
599   static const char kHelloLine[] = "EHLO BoringSSL\r\n";
600   if (!SendAll(sock, kHelloLine, sizeof(kHelloLine) - 1)) {
601     return false;
602   }
603 
604   unsigned code_250 = 0;
605   std::string reply_250;
606   if (!line_reader.ReadSMTPReply(&code_250, &reply_250)) {
607     return false;
608   }
609 
610   if (code_250 != 250) {
611     fprintf(stderr, "Expected 250 line after EHLO but got code %u\n", code_250);
612     return false;
613   }
614 
615   // https://tools.ietf.org/html/rfc1869#section-4.3
616   if (("\n" + reply_250 + "\n").find("\nSTARTTLS\n") == std::string::npos) {
617     fprintf(stderr, "Server does not support STARTTLS\n");
618     return false;
619   }
620 
621   static const char kSTARTTLSLine[] = "STARTTLS\r\n";
622   if (!SendAll(sock, kSTARTTLSLine, sizeof(kSTARTTLSLine) - 1)) {
623     return false;
624   }
625 
626   if (!line_reader.ReadSMTPReply(&code_220, &reply_220)) {
627     return false;
628   }
629 
630   if (code_220 != 220) {
631     fprintf(
632         stderr,
633         "Expected 220 line from SMTP server after STARTTLS, but got code %u\n",
634         code_220);
635     return false;
636   }
637 
638   return true;
639 }
640 
DoHTTPTunnel(int sock,const std::string & hostname_and_port)641 bool DoHTTPTunnel(int sock, const std::string &hostname_and_port) {
642   std::string hostname, port;
643   SplitHostPort(&hostname, &port, hostname_and_port);
644 
645   fprintf(stderr, "Establishing HTTP tunnel to %s:%s.\n", hostname.c_str(),
646           port.c_str());
647   char buf[1024];
648   snprintf(buf, sizeof(buf), "CONNECT %s:%s HTTP/1.0\r\n\r\n", hostname.c_str(),
649            port.c_str());
650   if (!SendAll(sock, buf, strlen(buf))) {
651     return false;
652   }
653 
654   SocketLineReader line_reader(sock);
655 
656   // Read until an empty line, signaling the end of the HTTP response.
657   std::string line;
658   for (;;) {
659     if (!line_reader.Next(&line)) {
660       return false;
661     }
662     if (line.empty()) {
663       return true;
664     }
665     fprintf(stderr, "%s\n", line.c_str());
666   }
667 }
668