doc/man3/BIO_f_ssl.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 BIO_do_handshake,
   6 BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode,
   7 BIO_set_ssl_renegotiate_bytes,
   8 BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
   9 BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id,
  10 BIO_ssl_shutdown - SSL BIO
  11
  12 =head1 SYNOPSIS
  13
  14 =for openssl multiple includes
  15
  16  #include <openssl/bio.h>
  17  #include <openssl/ssl.h>
  18
  19  const BIO_METHOD *BIO_f_ssl(void);
  20
  21  long BIO_set_ssl(BIO *b, SSL *ssl, long c);
  22  long BIO_get_ssl(BIO *b, SSL **sslp);
  23  long BIO_set_ssl_mode(BIO *b, long client);
  24  long BIO_set_ssl_renegotiate_bytes(BIO *b, long num);
  25  long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
  26  long BIO_get_num_renegotiates(BIO *b);
  27
  28  BIO *BIO_new_ssl(SSL_CTX *ctx, int client);
  29  BIO *BIO_new_ssl_connect(SSL_CTX *ctx);
  30  BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx);
  31  int BIO_ssl_copy_session_id(BIO *to, BIO *from);
  32  void BIO_ssl_shutdown(BIO *bio);
  33
  34  long BIO_do_handshake(BIO *b);
  35
  36 =head1 DESCRIPTION
  37
  38 BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which
  39 is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to
  40 SSL I/O.
  41
  42 I/O performed on an SSL BIO communicates using the SSL protocol with
  43 the SSLs read and write BIOs. If an SSL connection is not established
  44 then an attempt is made to establish one on the first I/O call.
  45
  46 If a BIO is appended to an SSL BIO using BIO_push() it is automatically
  47 used as the SSL BIOs read and write BIOs.
  48
  49 Calling BIO_reset() on an SSL BIO closes down any current SSL connection
  50 by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in
  51 the chain: this will typically disconnect the underlying transport.
  52 The SSL BIO is then reset to the initial accept or connect state.
  53
  54 If the close flag is set when an SSL BIO is freed then the internal
  55 SSL structure is also freed using SSL_free().
  56
  57 BIO_set_ssl() sets the internal SSL pointer of BIO B<b> to B<ssl> using
  58 the close flag B<c>.
  59
  60 BIO_get_ssl() retrieves the SSL pointer of BIO B<b>, it can then be
  61 manipulated using the standard SSL library functions.
  62
  63 BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client>
  64 is 1 client mode is set. If B<client> is 0 server mode is set.
  65
  66 BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count
  67 to B<num>. When set after every B<num> bytes of I/O (read and write)
  68 the SSL session is automatically renegotiated. B<num> must be at
  69 least 512 bytes.
  70
  71 BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout to
  72 B<seconds>. When the renegotiate timeout elapses the session is
  73 automatically renegotiated.
  74
  75 BIO_get_num_renegotiates() returns the total number of session
  76 renegotiations due to I/O or timeout.
  77
  78 BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using
  79 client mode if B<client> is non zero.
  80
  81 BIO_new_ssl_connect() creates a new BIO chain consisting of an
  82 SSL BIO (using B<ctx>) followed by a connect BIO.
  83
  84 BIO_new_buffer_ssl_connect() creates a new BIO chain consisting
  85 of a buffering BIO, an SSL BIO (using B<ctx>) and a connect
  86 BIO.
  87
  88 BIO_ssl_copy_session_id() copies an SSL session id between
  89 BIO chains B<from> and B<to>. It does this by locating the
  90 SSL BIOs in each chain and calling SSL_copy_session_id() on
  91 the internal SSL pointer.
  92
  93 BIO_ssl_shutdown() closes down an SSL connection on BIO
  94 chain B<bio>. It does this by locating the SSL BIO in the
  95 chain and calling SSL_shutdown() on its internal SSL
  96 pointer.
  97
  98 BIO_do_handshake() attempts to complete an SSL handshake on the
  99 -supplied BIO and establish the SSL connection.
 100 For non-SSL BIOs the connection is done typically at TCP level.
 101 If domain name resolution yields multiple IP addresses all of them are tried
 102 after connect() failures.
 103 The function returns 1 if the connection was established successfully.
 104 A zero or negative value is returned if the connection could not be established.
 105 The call BIO_should_retry() should be used for nonblocking connect BIOs
 106 to determine if the call should be retried.
 107 If a connection has already been established this call has no effect.
 108
 109 =head1 NOTES
 110
 111 SSL BIOs are exceptional in that if the underlying transport
 112 is non blocking they can still request a retry in exceptional
 113 circumstances. Specifically this will happen if a session
 114 renegotiation takes place during a BIO_read_ex() operation, one
 115 case where this happens is when step up occurs.
 116
 117 The SSL flag SSL_AUTO_RETRY can be
 118 set to disable this behaviour. That is when this flag is set
 119 an SSL BIO using a blocking transport will never request a
 120 retry.
 121
 122 Since unknown BIO_ctrl() operations are sent through filter
 123 BIOs the servers name and port can be set using BIO_set_host()
 124 on the BIO returned by BIO_new_ssl_connect() without having
 125 to locate the connect BIO first.
 126
 127 Applications do not have to call BIO_do_handshake() but may wish
 128 to do so to separate the handshake process from other I/O
 129 processing.
 130
 131 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
 132 BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
 133 BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.
 134
 135 =head1 RETURN VALUES
 136
 137 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.
 138
 139 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
 140 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
 141 success or a value which is less than or equal to 0 if an error occurred.
 142
 143 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
 144 a valid B<BIO> structure on success or B<NULL> if an error occurred.
 145
 146 BIO_ssl_copy_session_id() returns 1 on success or 0 on error.
 147
 148 BIO_do_handshake() returns 1 if the connection was established successfully.
 149 A zero or negative value is returned if the connection could not be established.
 150
 151 =head1 EXAMPLES
 152
 153 This SSL/TLS client example attempts to retrieve a page from an
 154 SSL/TLS web server. The I/O routines are identical to those of the
 155 unencrypted example in L<BIO_s_connect(3)>.
 156
 157  BIO *sbio, *out;
 158  int len;
 159  char tmpbuf[1024];
 160  SSL_CTX *ctx;
 161  SSL *ssl;
 162
 163  /* XXX Seed the PRNG if needed. */
 164
 165  ctx = SSL_CTX_new(TLS_client_method());
 166
 167  /* XXX Set verify paths and mode here. */
 168
 169  sbio = BIO_new_ssl_connect(ctx);
 170  BIO_get_ssl(sbio, &ssl);
 171  if (ssl == NULL) {
 172      fprintf(stderr, "Can't locate SSL pointer\n");
 173      ERR_print_errors_fp(stderr);
 174      exit(1);
 175  }
 176
 177  /* XXX We might want to do other things with ssl here */
 178
 179  /* An empty host part means the loopback address */
 180  BIO_set_conn_hostname(sbio, ":https");
 181
 182  out = BIO_new_fp(stdout, BIO_NOCLOSE);
 183  if (BIO_do_connect(sbio) <= 0) {
 184      fprintf(stderr, "Error connecting to server\n");
 185      ERR_print_errors_fp(stderr);
 186      exit(1);
 187  }
 188
 189  /* XXX Could examine ssl here to get connection info */
 190
 191  BIO_puts(sbio, "GET / HTTP/1.0\n\n");
 192  for (;;) {
 193      len = BIO_read(sbio, tmpbuf, 1024);
 194      if (len <= 0)
 195          break;
 196      BIO_write(out, tmpbuf, len);
 197  }
 198  BIO_free_all(sbio);
 199  BIO_free(out);
 200
 201 Here is a simple server example. It makes use of a buffering
 202 BIO to allow lines to be read from the SSL BIO using BIO_gets.
 203 It creates a pseudo web page containing the actual request from
 204 a client and also echoes the request to standard output.
 205
 206  BIO *sbio, *bbio, *acpt, *out;
 207  int len;
 208  char tmpbuf[1024];
 209  SSL_CTX *ctx;
 210  SSL *ssl;
 211
 212  /* XXX Seed the PRNG if needed. */
 213
 214  ctx = SSL_CTX_new(TLS_server_method());
 215  if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
 216          || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
 217          || !SSL_CTX_check_private_key(ctx)) {
 218      fprintf(stderr, "Error setting up SSL_CTX\n");
 219      ERR_print_errors_fp(stderr);
 220      exit(1);
 221  }
 222
 223  /* XXX Other things like set verify locations, EDH temp callbacks. */
 224
 225  /* New SSL BIO setup as server */
 226  sbio = BIO_new_ssl(ctx, 0);
 227  BIO_get_ssl(sbio, &ssl);
 228  if (ssl == NULL) {
 229      fprintf(stderr, "Can't locate SSL pointer\n");
 230      ERR_print_errors_fp(stderr);
 231      exit(1);
 232  }
 233
 234  bbio = BIO_new(BIO_f_buffer());
 235  sbio = BIO_push(bbio, sbio);
 236  acpt = BIO_new_accept("4433");
 237
 238  /*
 239   * By doing this when a new connection is established
 240   * we automatically have sbio inserted into it. The
 241   * BIO chain is now 'swallowed' by the accept BIO and
 242   * will be freed when the accept BIO is freed.
 243   */
 244  BIO_set_accept_bios(acpt, sbio);
 245  out = BIO_new_fp(stdout, BIO_NOCLOSE);
 246
 247  /* Setup accept BIO */
 248  if (BIO_do_accept(acpt) <= 0) {
 249      fprintf(stderr, "Error setting up accept BIO\n");
 250      ERR_print_errors_fp(stderr);
 251      exit(1);
 252  }
 253
 254  /* We only want one connection so remove and free accept BIO */
 255  sbio = BIO_pop(acpt);
 256  BIO_free_all(acpt);
 257
 258  if (BIO_do_handshake(sbio) <= 0) {
 259      fprintf(stderr, "Error in SSL handshake\n");
 260      ERR_print_errors_fp(stderr);
 261      exit(1);
 262  }
 263
 264  BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
 265  BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
 266  BIO_puts(sbio, "--------------------------------------------------\r\n");
 267
 268  for (;;) {
 269      len = BIO_gets(sbio, tmpbuf, 1024);
 270      if (len <= 0)
 271          break;
 272      BIO_write(sbio, tmpbuf, len);
 273      BIO_write(out, tmpbuf, len);
 274      /* Look for blank line signifying end of headers*/
 275      if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
 276          break;
 277  }
 278
 279  BIO_puts(sbio, "--------------------------------------------------\r\n");
 280  BIO_puts(sbio, "\r\n");
 281  BIO_flush(sbio);
 282  BIO_free_all(sbio);
 283
 284 =head1 HISTORY
 285
 286 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
 287 the I/O BIO reference count was incorrectly incremented (instead of
 288 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
 289 explicitly being popped (e.g. a pop higher up the chain). Applications which
 290 included workarounds for this bug (e.g. freeing BIOs more than once) should
 291 be modified to handle this fix or they may free up an already freed BIO.
 292
 293 =head1 COPYRIGHT
 294
 295 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
 296
 297 Licensed under the Apache License 2.0 (the "License").  You may not use
 298 this file except in compliance with the License.  You can obtain a copy
 299 in the file LICENSE in the source distribution or at
 300 L<https://www.openssl.org/source/license.html>.
 301
 302 =cut