doc/man3/BIO_f_ssl.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 BIO_do_handshake,
 BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode,
 BIO_set_ssl_renegotiate_bytes,
 BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
 BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id,
 BIO_ssl_shutdown - SSL BIO

 =head1 SYNOPSIS

 =for openssl multiple includes

  #include <openssl/bio.h>
  #include <openssl/ssl.h>

  const BIO_METHOD *BIO_f_ssl(void);

  long BIO_set_ssl(BIO *b, SSL *ssl, long c);
  long BIO_get_ssl(BIO *b, SSL **sslp);
  long BIO_set_ssl_mode(BIO *b, long client);
  long BIO_set_ssl_renegotiate_bytes(BIO *b, long num);
  long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
  long BIO_get_num_renegotiates(BIO *b);

  BIO *BIO_new_ssl(SSL_CTX *ctx, int client);
  BIO *BIO_new_ssl_connect(SSL_CTX *ctx);
  BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx);
  int BIO_ssl_copy_session_id(BIO *to, BIO *from);
  void BIO_ssl_shutdown(BIO *bio);

  long BIO_do_handshake(BIO *b);

 =head1 DESCRIPTION

 BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which
 is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to
 SSL I/O.

 I/O performed on an SSL BIO communicates using the SSL protocol with
 the SSLs read and write BIOs. If an SSL connection is not established
 then an attempt is made to establish one on the first I/O call.

 If a BIO is appended to an SSL BIO using BIO_push() it is automatically
 used as the SSL BIOs read and write BIOs.

 Calling BIO_reset() on an SSL BIO closes down any current SSL connection
 by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in
 the chain: this will typically disconnect the underlying transport.
 The SSL BIO is then reset to the initial accept or connect state.

 If the close flag is set when an SSL BIO is freed then the internal
 SSL structure is also freed using SSL_free().

 BIO_set_ssl() sets the internal SSL pointer of SSL BIO B<b> to B<ssl> using
 the close flag B<c>.

 BIO_get_ssl() retrieves the SSL pointer of SSL BIO B<b>, it can then be
 manipulated using the standard SSL library functions.

 BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client>
 is 1 client mode is set. If B<client> is 0 server mode is set.

 BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count of SSL BIO B<b>
 to B<num>. When set after every B<num> bytes of I/O (read and write)
 the SSL session is automatically renegotiated. B<num> must be at
 least 512 bytes.

 BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout of SSL BIO B<b>
 to B<seconds>.
 When the renegotiate timeout elapses the session is automatically renegotiated.

 BIO_get_num_renegotiates() returns the total number of session
 renegotiations due to I/O or timeout of SSL BIO B<b>.

 BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using
 client mode if B<client> is non zero.

 BIO_new_ssl_connect() creates a new BIO chain consisting of an
 SSL BIO (using B<ctx>) followed by a connect BIO.

 BIO_new_buffer_ssl_connect() creates a new BIO chain consisting
 of a buffering BIO, an SSL BIO (using B<ctx>), and a connect BIO.

 BIO_ssl_copy_session_id() copies an SSL session id between
 BIO chains B<from> and B<to>. It does this by locating the
 SSL BIOs in each chain and calling SSL_copy_session_id() on
 the internal SSL pointer.

 BIO_ssl_shutdown() closes down an SSL connection on BIO
 chain B<bio>. It does this by locating the SSL BIO in the
 chain and calling SSL_shutdown() on its internal SSL
 pointer.

 BIO_do_handshake() attempts to complete an SSL handshake on the
 supplied BIO and establish the SSL connection.
 For non-SSL BIOs the connection is done typically at TCP level.
 If domain name resolution yields multiple IP addresses all of them are tried
 after connect() failures.
 The function returns 1 if the connection was established successfully.
 A zero or negative value is returned if the connection could not be established.
 The call BIO_should_retry() should be used for nonblocking connect BIOs
 to determine if the call should be retried.
 If a connection has already been established this call has no effect.

 =head1 NOTES

 SSL BIOs are exceptional in that if the underlying transport
 is non blocking they can still request a retry in exceptional
 circumstances. Specifically this will happen if a session
 renegotiation takes place during a BIO_read_ex() operation, one
 case where this happens is when step up occurs.

 The SSL flag SSL_AUTO_RETRY can be
 set to disable this behaviour. That is when this flag is set
 an SSL BIO using a blocking transport will never request a
 retry.

 Since unknown BIO_ctrl() operations are sent through filter
 BIOs the servers name and port can be set using BIO_set_host()
 on the BIO returned by BIO_new_ssl_connect() without having
 to locate the connect BIO first.

 Applications do not have to call BIO_do_handshake() but may wish
 to do so to separate the handshake process from other I/O
 processing.

 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
 BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
 BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.

 =head1 RETURN VALUES

 BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.

 BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
 BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
 success or a value which is less than or equal to 0 if an error occurred.

 BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
 a valid B<BIO> structure on success or B<NULL> if an error occurred.

 BIO_ssl_copy_session_id() returns 1 on success or 0 on error.

 BIO_do_handshake() returns 1 if the connection was established successfully.
 A zero or negative value is returned if the connection could not be established.

 =head1 EXAMPLES

 This SSL/TLS client example attempts to retrieve a page from an
 SSL/TLS web server. The I/O routines are identical to those of the
 unencrypted example in L<BIO_s_connect(3)>.

  BIO *sbio, *out;
  int len;
  char tmpbuf[1024];
  SSL_CTX *ctx;
  SSL *ssl;

  /* XXX Seed the PRNG if needed. */

  ctx = SSL_CTX_new(TLS_client_method());

  /* XXX Set verify paths and mode here. */

  sbio = BIO_new_ssl_connect(ctx);
  BIO_get_ssl(sbio, &ssl);
  if (ssl == NULL) {
      fprintf(stderr, "Can't locate SSL pointer\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  /* XXX We might want to do other things with ssl here */

  /* An empty host part means the loopback address */
  BIO_set_conn_hostname(sbio, ":https");

  out = BIO_new_fp(stdout, BIO_NOCLOSE);
  if (BIO_do_connect(sbio) <= 0) {
      fprintf(stderr, "Error connecting to server\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  /* XXX Could examine ssl here to get connection info */

  BIO_puts(sbio, "GET / HTTP/1.0\n\n");
  for (;;) {
      len = BIO_read(sbio, tmpbuf, 1024);
      if (len <= 0)
          break;
      BIO_write(out, tmpbuf, len);
  }
  BIO_free_all(sbio);
  BIO_free(out);

 Here is a simple server example. It makes use of a buffering
 BIO to allow lines to be read from the SSL BIO using BIO_gets.
 It creates a pseudo web page containing the actual request from
 a client and also echoes the request to standard output.

  BIO *sbio, *bbio, *acpt, *out;
  int len;
  char tmpbuf[1024];
  SSL_CTX *ctx;
  SSL *ssl;

  /* XXX Seed the PRNG if needed. */

  ctx = SSL_CTX_new(TLS_server_method());
  if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
          || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
          || !SSL_CTX_check_private_key(ctx)) {
      fprintf(stderr, "Error setting up SSL_CTX\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  /* XXX Other things like set verify locations, EDH temp callbacks. */

  /* New SSL BIO setup as server */
  sbio = BIO_new_ssl(ctx, 0);
  BIO_get_ssl(sbio, &ssl);
  if (ssl == NULL) {
      fprintf(stderr, "Can't locate SSL pointer\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  bbio = BIO_new(BIO_f_buffer());
  sbio = BIO_push(bbio, sbio);
  acpt = BIO_new_accept("4433");

  /*
   * By doing this when a new connection is established
   * we automatically have sbio inserted into it. The
   * BIO chain is now 'swallowed' by the accept BIO and
   * will be freed when the accept BIO is freed.
   */
  BIO_set_accept_bios(acpt, sbio);
  out = BIO_new_fp(stdout, BIO_NOCLOSE);

  /* Setup accept BIO */
  if (BIO_do_accept(acpt) <= 0) {
      fprintf(stderr, "Error setting up accept BIO\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  /* We only want one connection so remove and free accept BIO */
  sbio = BIO_pop(acpt);
  BIO_free_all(acpt);

  if (BIO_do_handshake(sbio) <= 0) {
      fprintf(stderr, "Error in SSL handshake\n");
      ERR_print_errors_fp(stderr);
      exit(1);
  }

  BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
  BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
  BIO_puts(sbio, "--------------------------------------------------\r\n");

  for (;;) {
      len = BIO_gets(sbio, tmpbuf, 1024);
      if (len <= 0)
          break;
      BIO_write(sbio, tmpbuf, len);
      BIO_write(out, tmpbuf, len);
      /* Look for blank line signifying end of headers*/
      if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n')
          break;
  }

  BIO_puts(sbio, "--------------------------------------------------\r\n");
  BIO_puts(sbio, "\r\n");
  BIO_flush(sbio);
  BIO_free_all(sbio);

 =head1 HISTORY

 In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
 the I/O BIO reference count was incorrectly incremented (instead of
 decremented) and dissociated with the SSL BIO even if the SSL BIO was not
 explicitly being popped (e.g. a pop higher up the chain). Applications which
 included workarounds for this bug (e.g. freeing BIOs more than once) should
 be modified to handle this fix or they may free up an already freed BIO.

 =head1 COPYRIGHT

 Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

 Licensed under the Apache License 2.0 (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy
 in the file LICENSE in the source distribution or at
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

	BIO_do_handshake,
	BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode,
	BIO_set_ssl_renegotiate_bytes,
	BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl,
	BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id,
	BIO_ssl_shutdown - SSL BIO

	=head1 SYNOPSIS

	=for openssl multiple includes

	#include <openssl/bio.h>
	#include <openssl/ssl.h>

	const BIO_METHOD *BIO_f_ssl(void);

	long BIO_set_ssl(BIO b, SSL ssl, long c);
	long BIO_get_ssl(BIO b, SSL *sslp);
	long BIO_set_ssl_mode(BIO *b, long client);
	long BIO_set_ssl_renegotiate_bytes(BIO *b, long num);
	long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds);
	long BIO_get_num_renegotiates(BIO *b);

	BIO BIO_new_ssl(SSL_CTX ctx, int client);
	BIO BIO_new_ssl_connect(SSL_CTX ctx);
	BIO BIO_new_buffer_ssl_connect(SSL_CTX ctx);
	int BIO_ssl_copy_session_id(BIO to, BIO from);
	void BIO_ssl_shutdown(BIO *bio);

	long BIO_do_handshake(BIO *b);

	=head1 DESCRIPTION

	BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which
	is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to
	SSL I/O.

	I/O performed on an SSL BIO communicates using the SSL protocol with
	the SSLs read and write BIOs. If an SSL connection is not established
	then an attempt is made to establish one on the first I/O call.

	If a BIO is appended to an SSL BIO using BIO_push() it is automatically
	used as the SSL BIOs read and write BIOs.

	Calling BIO_reset() on an SSL BIO closes down any current SSL connection
	by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in
	the chain: this will typically disconnect the underlying transport.
	The SSL BIO is then reset to the initial accept or connect state.

	If the close flag is set when an SSL BIO is freed then the internal
	SSL structure is also freed using SSL_free().

	BIO_set_ssl() sets the internal SSL pointer of SSL BIO B<b> to B<ssl> using
	the close flag B<c>.

	BIO_get_ssl() retrieves the SSL pointer of SSL BIO B<b>, it can then be
	manipulated using the standard SSL library functions.

	BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client>
	is 1 client mode is set. If B<client> is 0 server mode is set.

	BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count of SSL BIO B<b>
	to B<num>. When set after every B<num> bytes of I/O (read and write)
	the SSL session is automatically renegotiated. B<num> must be at
	least 512 bytes.

	BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout of SSL BIO B<b>
	to B<seconds>.
	When the renegotiate timeout elapses the session is automatically renegotiated.

	BIO_get_num_renegotiates() returns the total number of session
	renegotiations due to I/O or timeout of SSL BIO B<b>.

	BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using
	client mode if B<client> is non zero.

	BIO_new_ssl_connect() creates a new BIO chain consisting of an
	SSL BIO (using B<ctx>) followed by a connect BIO.

	BIO_new_buffer_ssl_connect() creates a new BIO chain consisting
	of a buffering BIO, an SSL BIO (using B<ctx>), and a connect BIO.

	BIO_ssl_copy_session_id() copies an SSL session id between
	BIO chains B<from> and B<to>. It does this by locating the
	SSL BIOs in each chain and calling SSL_copy_session_id() on
	the internal SSL pointer.

	BIO_ssl_shutdown() closes down an SSL connection on BIO
	chain B<bio>. It does this by locating the SSL BIO in the
	chain and calling SSL_shutdown() on its internal SSL
	pointer.

	BIO_do_handshake() attempts to complete an SSL handshake on the
	supplied BIO and establish the SSL connection.
	For non-SSL BIOs the connection is done typically at TCP level.
	If domain name resolution yields multiple IP addresses all of them are tried
	after connect() failures.
	The function returns 1 if the connection was established successfully.
	A zero or negative value is returned if the connection could not be established.
	The call BIO_should_retry() should be used for nonblocking connect BIOs
	to determine if the call should be retried.
	If a connection has already been established this call has no effect.

	=head1 NOTES

	SSL BIOs are exceptional in that if the underlying transport
	is non blocking they can still request a retry in exceptional
	circumstances. Specifically this will happen if a session
	renegotiation takes place during a BIO_read_ex() operation, one
	case where this happens is when step up occurs.

	The SSL flag SSL_AUTO_RETRY can be
	set to disable this behaviour. That is when this flag is set
	an SSL BIO using a blocking transport will never request a
	retry.

	Since unknown BIO_ctrl() operations are sent through filter
	BIOs the servers name and port can be set using BIO_set_host()
	on the BIO returned by BIO_new_ssl_connect() without having
	to locate the connect BIO first.

	Applications do not have to call BIO_do_handshake() but may wish
	to do so to separate the handshake process from other I/O
	processing.

	BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(),
	BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(),
	BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros.

	=head1 RETURN VALUES

	BIO_f_ssl() returns the SSL B<BIO_METHOD> structure.

	BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(),
	BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on
	success or a value which is less than or equal to 0 if an error occurred.

	BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return
	a valid B<BIO> structure on success or B<NULL> if an error occurred.

	BIO_ssl_copy_session_id() returns 1 on success or 0 on error.

	BIO_do_handshake() returns 1 if the connection was established successfully.
	A zero or negative value is returned if the connection could not be established.

	=head1 EXAMPLES

	This SSL/TLS client example attempts to retrieve a page from an
	SSL/TLS web server. The I/O routines are identical to those of the
	unencrypted example in L<BIO_s_connect(3)>.

	BIO sbio, out;
	int len;
	char tmpbuf[1024];
	SSL_CTX *ctx;
	SSL *ssl;

	/* XXX Seed the PRNG if needed. */

	ctx = SSL_CTX_new(TLS_client_method());

	/* XXX Set verify paths and mode here. */

	sbio = BIO_new_ssl_connect(ctx);
	BIO_get_ssl(sbio, &ssl);
	if (ssl == NULL) {
	fprintf(stderr, "Can't locate SSL pointer\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	/* XXX We might want to do other things with ssl here */

	/* An empty host part means the loopback address */
	BIO_set_conn_hostname(sbio, ":https");

	out = BIO_new_fp(stdout, BIO_NOCLOSE);
	if (BIO_do_connect(sbio) <= 0) {
	fprintf(stderr, "Error connecting to server\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	/* XXX Could examine ssl here to get connection info */

	BIO_puts(sbio, "GET / HTTP/1.0\n\n");
	for (;;) {
	len = BIO_read(sbio, tmpbuf, 1024);
	if (len <= 0)
	break;
	BIO_write(out, tmpbuf, len);
	}
	BIO_free_all(sbio);
	BIO_free(out);

	Here is a simple server example. It makes use of a buffering
	BIO to allow lines to be read from the SSL BIO using BIO_gets.
	It creates a pseudo web page containing the actual request from
	a client and also echoes the request to standard output.

	BIO sbio, bbio, acpt, out;
	int len;
	char tmpbuf[1024];
	SSL_CTX *ctx;
	SSL *ssl;

	/* XXX Seed the PRNG if needed. */

	ctx = SSL_CTX_new(TLS_server_method());
	if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM)
	\|\| !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM)
	\|\| !SSL_CTX_check_private_key(ctx)) {
	fprintf(stderr, "Error setting up SSL_CTX\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	/* XXX Other things like set verify locations, EDH temp callbacks. */

	/* New SSL BIO setup as server */
	sbio = BIO_new_ssl(ctx, 0);
	BIO_get_ssl(sbio, &ssl);
	if (ssl == NULL) {
	fprintf(stderr, "Can't locate SSL pointer\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	bbio = BIO_new(BIO_f_buffer());
	sbio = BIO_push(bbio, sbio);
	acpt = BIO_new_accept("4433");

	/*
	* By doing this when a new connection is established
	* we automatically have sbio inserted into it. The
	* BIO chain is now 'swallowed' by the accept BIO and
	* will be freed when the accept BIO is freed.
	*/
	BIO_set_accept_bios(acpt, sbio);
	out = BIO_new_fp(stdout, BIO_NOCLOSE);

	/* Setup accept BIO */
	if (BIO_do_accept(acpt) <= 0) {
	fprintf(stderr, "Error setting up accept BIO\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	/* We only want one connection so remove and free accept BIO */
	sbio = BIO_pop(acpt);
	BIO_free_all(acpt);

	if (BIO_do_handshake(sbio) <= 0) {
	fprintf(stderr, "Error in SSL handshake\n");
	ERR_print_errors_fp(stderr);
	exit(1);
	}

	BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n");
	BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n");
	BIO_puts(sbio, "--------------------------------------------------\r\n");

	for (;;) {
	len = BIO_gets(sbio, tmpbuf, 1024);
	if (len <= 0)
	break;
	BIO_write(sbio, tmpbuf, len);
	BIO_write(out, tmpbuf, len);
	/* Look for blank line signifying end of headers*/
	if (tmpbuf[0] == '\r' \|\| tmpbuf[0] == '\n')
	break;
	}

	BIO_puts(sbio, "--------------------------------------------------\r\n");
	BIO_puts(sbio, "\r\n");
	BIO_flush(sbio);
	BIO_free_all(sbio);

	=head1 HISTORY

	In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly,
	the I/O BIO reference count was incorrectly incremented (instead of
	decremented) and dissociated with the SSL BIO even if the SSL BIO was not
	explicitly being popped (e.g. a pop higher up the chain). Applications which
	included workarounds for this bug (e.g. freeing BIOs more than once) should
	be modified to handle this fix or they may free up an already freed BIO.

	=head1 COPYRIGHT

	Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

	Licensed under the Apache License 2.0 (the "License"). You may not use
	this file except in compliance with the License. You can obtain a copy
	in the file LICENSE in the source distribution or at
	L<https://www.openssl.org/source/license.html>.

	=cut