.\" $OpenBSD: BIO_f_ssl.3,v 1.16 2024/01/13 18:37:51 tb Exp $ .\" full merge up to: OpenSSL f672aee4 Feb 9 11:52:40 2016 -0500 .\" selective merge up to: OpenSSL 61f805c1 Jan 16 01:01:46 2018 +0800 .\" .\" This file was written by Dr. Stephen Henson . .\" Copyright (c) 2000, 2003, 2009, 2014-2016 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. 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IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: January 13 2024 $ .Dt BIO_F_SSL 3 .Os .Sh NAME .Nm BIO_f_ssl , .Nm BIO_set_ssl , .Nm BIO_get_ssl , .Nm BIO_set_ssl_mode , .Nm BIO_set_ssl_renegotiate_bytes , .Nm BIO_get_num_renegotiates , .Nm BIO_set_ssl_renegotiate_timeout , .Nm BIO_new_ssl , .Nm BIO_new_ssl_connect , .Nm BIO_new_buffer_ssl_connect , .Nm BIO_ssl_copy_session_id , .Nm BIO_ssl_shutdown , .Nm BIO_do_handshake .Nd SSL BIO .Sh SYNOPSIS .In openssl/bio.h .In openssl/ssl.h .Ft const BIO_METHOD * .Fn BIO_f_ssl void .Ft long .Fo BIO_set_ssl .Fa "BIO *b" .Fa "SSL *ssl" .Fa "long c" .Fc .Ft long .Fo BIO_get_ssl .Fa "BIO *b" .Fa "SSL *sslp" .Fc .Ft long .Fo BIO_set_ssl_mode .Fa "BIO *b" .Fa "long client" .Fc .Ft long .Fo BIO_set_ssl_renegotiate_bytes .Fa "BIO *b" .Fa "long num" .Fc .Ft long .Fo BIO_set_ssl_renegotiate_timeout .Fa "BIO *b" .Fa "long seconds" .Fc .Ft long .Fo BIO_get_num_renegotiates .Fa "BIO *b" .Fc .Ft BIO * .Fn BIO_new_ssl "SSL_CTX *ctx" "int client" .Ft BIO * .Fn BIO_new_ssl_connect "SSL_CTX *ctx" .Ft BIO * .Fn BIO_new_buffer_ssl_connect "SSL_CTX *ctx" .Ft int .Fn BIO_ssl_copy_session_id "BIO *to" "BIO *from" .Ft void .Fn BIO_ssl_shutdown "BIO *bio" .Ft long .Fn BIO_do_handshake "BIO *b" .Sh DESCRIPTION .Fn BIO_f_ssl returns the .Vt SSL .Vt BIO method. This is a filter .Vt BIO which is a wrapper around the OpenSSL .Vt SSL routines adding a .Vt BIO .Dq flavor to SSL I/O. .Pp I/O performed on an .Vt SSL .Vt BIO communicates using the SSL protocol with the .Vt SSL Ns 's read and write .Vt BIO Ns s . If an SSL connection is not established then an attempt is made to establish one on the first I/O call. .Pp If a .Vt BIO is appended to an .Vt SSL .Vt BIO using .Xr BIO_push 3 , it is automatically used as the .Vt SSL .Vt BIO Ns 's read and write .Vt BIO Ns s . .Pp Calling .Xr BIO_reset 3 on an .Vt SSL .Vt BIO closes down any current SSL connection by calling .Xr SSL_shutdown 3 . .Xr BIO_reset 3 is then sent to the next .Vt BIO in the chain; this will typically disconnect the underlying transport. The .Vt SSL .Vt BIO is then reset to the initial accept or connect state. .Pp If the close flag is set when an .Vt SSL .Vt BIO is freed then the internal .Vt SSL structure is also freed using .Xr SSL_free 3 . .Pp .Fn BIO_set_ssl sets the internal .Vt SSL pointer of .Vt BIO .Fa b to .Fa ssl using the close flag .Fa c . .Pp .Fn BIO_get_ssl retrieves the .Vt SSL pointer of .Vt BIO .Fa b ; it can then be manipulated using the standard SSL library functions. .Pp .Fn BIO_set_ssl_mode sets the .Vt SSL .Vt BIO mode to .Fa client . If .Fa client is 1, client mode is set. If .Fa client is 0, server mode is set. .Pp .Fn BIO_set_ssl_renegotiate_bytes sets the renegotiate byte count to .Fa num . When set, after every .Fa num bytes of I/O (read and write) the SSL session is automatically renegotiated. .Fa num must be at least 512 bytes. .Pp .Fn BIO_set_ssl_renegotiate_timeout sets the renegotiate timeout to .Fa seconds . When the renegotiate timeout elapses, the session is automatically renegotiated. .Pp .Fn BIO_get_num_renegotiates returns the total number of session renegotiations due to I/O or timeout. .Pp .Fn BIO_new_ssl allocates an .Vt SSL .Vt BIO using .Vt SSL_CTX .Va ctx and using client mode if .Fa client is nonzero. .Pp .Fn BIO_new_ssl_connect creates a new .Vt BIO chain consisting of an .Vt SSL .Vt BIO (using .Fa ctx ) followed by a connect BIO. .Pp .Fn BIO_new_buffer_ssl_connect creates a new .Vt BIO chain consisting of a buffering .Vt BIO , an .Vt SSL .Vt BIO (using .Fa ctx ) and a connect .Vt BIO . .Pp .Fn BIO_ssl_copy_session_id copies an SSL session id between .Vt BIO chains .Fa from and .Fa to . It does this by locating the .Vt SSL .Vt BIO Ns s in each chain and calling .Xr SSL_copy_session_id 3 on the internal .Vt SSL pointer. .Pp .Fn BIO_ssl_shutdown closes down an SSL connection on .Vt BIO chain .Fa bio . It does this by locating the .Vt SSL .Vt BIO in the chain and calling .Xr SSL_shutdown 3 on its internal .Vt SSL pointer. .Pp .Fn BIO_do_handshake attempts to complete an SSL handshake on the supplied .Vt BIO and establish the SSL connection. It returns 1 if the connection was established successfully. A zero or negative value is returned if the connection could not be established; the call .Xr BIO_should_retry 3 should be used for non blocking connect .Vt BIO Ns s to determine if the call should be retried. If an SSL connection has already been established, this call has no effect. .Pp When a chain containing an SSL BIO is copied with .Xr BIO_dup_chain 3 , .Xr SSL_dup 3 is called internally to copy the .Vt SSL object from the existing BIO object to the new BIO object, and the internal data related to .Fn BIO_set_ssl_renegotiate_bytes and .Fn BIO_set_ssl_renegotiate_timeout is also copied. .Pp .Vt SSL .Vt BIO Ns s 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 .Xr BIO_read 3 operation. One case where this happens is when step up occurs. .Pp In OpenSSL 0.9.6 and later the SSL flag .Dv SSL_AUTO_RETRY can be set to disable this behaviour. In other words, when this flag is set an .Vt SSL .Vt BIO using a blocking transport will never request a retry. .Pp Since unknown .Xr BIO_ctrl 3 operations are sent through filter .Vt BIO Ns s , the server name and port can be set using .Xr BIO_set_conn_hostname 3 and .Xr BIO_set_conn_port 3 on the .Vt BIO returned by .Fn BIO_new_ssl_connect without having to locate the connect .Vt BIO first. .Pp Applications do not have to call .Fn BIO_do_handshake but may wish to do so to separate the handshake process from other I/O processing. .Pp .Fn BIO_set_ssl , .Fn BIO_get_ssl , .Fn BIO_set_ssl_mode , .Fn BIO_set_ssl_renegotiate_bytes , .Fn BIO_set_ssl_renegotiate_timeout , .Fn BIO_get_num_renegotiates , and .Fn BIO_do_handshake are implemented as macros. .Sh RETURN VALUES .Fn BIO_f_ssl returns a pointer to a static .Vt BIO_METHOD structure. .Pp When called on an SSL BIO object, .Xr BIO_method_type 3 returns the constant .Dv BIO_TYPE_SSL and .Xr BIO_method_name 3 returns a pointer to the static string .Qq ssl . .Pp .Fn BIO_set_ssl , .Fn BIO_get_ssl , .Fn BIO_set_ssl_mode , .Fn BIO_set_ssl_renegotiate_bytes , .Fn BIO_set_ssl_renegotiate_timeout , and .Fn BIO_get_num_renegotiates return 1 on success or a value less than or equal to 0 if an error occurred. .Pp .Fn BIO_new_ssl , .Fn BIO_new_ssl_connect , and .Fn BIO_new_buffer_ssl_connect returns a pointer to a newly allocated .Vt BIO chain or .Dv NULL if an error occurred. .Pp .Fn BIO_ssl_copy_session_id returns 1 on success or 0 on error. .Pp .Fn BIO_do_handshake returns 1 if the connection was established successfully or a value less than or equal to 0 otherwise. .Sh 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 .Xr BIO_s_connect 3 . .Bd -literal BIO *sbio, *out; int len; char tmpbuf[1024]; SSL_CTX *ctx; SSL *ssl; ERR_load_crypto_strings(); ERR_load_SSL_strings(); OpenSSL_add_all_algorithms(); /* * We would seed the PRNG here if the platform didn't do it automatically */ ctx = SSL_CTX_new(SSLv23_client_method()); /* * We'd normally set some stuff like the verify paths and mode here because * as things stand this will connect to any server whose certificate is * signed by any CA. */ sbio = BIO_new_ssl_connect(ctx); BIO_get_ssl(sbio, &ssl); if (!ssl) { fprintf(stderr, "Can't locate SSL pointer\en"); /* whatever ... */ } /* Don't want any retries */ SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); /* We might want to do other things with ssl here */ BIO_set_conn_hostname(sbio, "localhost:https"); out = BIO_new_fp(stdout, BIO_NOCLOSE); if (BIO_do_connect(sbio) <= 0) { fprintf(stderr, "Error connecting to server\en"); ERR_print_errors_fp(stderr); /* whatever ... */ } if (BIO_do_handshake(sbio) <= 0) { fprintf(stderr, "Error establishing SSL connection\en"); ERR_print_errors_fp(stderr); /* whatever ... */ } /* Could examine ssl here to get connection info */ BIO_puts(sbio, "GET / HTTP/1.0\en\en"); for (;;) { len = BIO_read(sbio, tmpbuf, 1024); if(len <= 0) break; BIO_write(out, tmpbuf, len); } BIO_free_all(sbio); BIO_free(out); .Ed .Pp Here is a simple server example. It makes use of a buffering .Vt BIO to allow lines to be read from the .Vt SSL .Vt BIO using .Xr BIO_gets 3 . It creates a pseudo web page containing the actual request from a client and also echoes the request to standard output. .Bd -literal BIO *sbio, *bbio, *acpt, *out; int len; char tmpbuf[1024]; SSL_CTX *ctx; SSL *ssl; ctx = SSL_CTX_new(SSLv23_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\en"); ERR_print_errors_fp(stderr); return 0; } /* * Might do other things here like setting verify locations and DH and/or * RSA temporary key callbacks */ /* New SSL BIO setup as server */ sbio = BIO_new_ssl(ctx,0); BIO_get_ssl(sbio, &ssl); if (!ssl) { fprintf(stderr, "Can't locate SSL pointer\en"); /* whatever ... */ } /* Don't want any retries */ SSL_set_mode(ssl, SSL_MODE_AUTO_RETRY); /* Create the buffering BIO */ bbio = BIO_new(BIO_f_buffer()); /* Add to chain */ 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); /* Wait for incoming connection */ if (BIO_do_accept(acpt) <= 0) { fprintf(stderr, "Error setting up accept BIO\en"); ERR_print_errors_fp(stderr); return 0; } /* 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\en"); ERR_print_errors_fp(stderr); return 0; } BIO_puts(sbio, "HTTP/1.0 200 OK\er\enContent-type: text/plain\er\en\er\en"); BIO_puts(sbio, "\er\enConnection Established\er\enRequest headers:\er\en"); BIO_puts(sbio, "--------------------------------------------------\er\en"); 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] == '\er') || (tmpbuf[0] == '\en')) break; } BIO_puts(sbio, "--------------------------------------------------\er\en"); BIO_puts(sbio, "\er\en"); /* Since there is a buffering BIO present we had better flush it */ BIO_flush(sbio); BIO_free_all(sbio); .Ed .Sh SEE ALSO .Xr BIO_new 3 , .Xr ssl 3 .Sh HISTORY .Fn BIO_f_ssl , .Fn BIO_set_ssl , and .Fn BIO_get_ssl first appeared in SSLeay 0.6.0. .Fn BIO_set_ssl_mode , .Fn BIO_new_ssl , and .Fn BIO_ssl_copy_session_id first appeared in SSLeay 0.8.0. .Fn BIO_ssl_shutdown and .Fn BIO_do_handshake first appeared in SSLeay 0.8.1. .Fn BIO_set_ssl_renegotiate_bytes , .Fn BIO_get_num_renegotiates , .Fn BIO_set_ssl_renegotiate_timeout , .Fn BIO_new_ssl_connect , and .Fn BIO_new_buffer_ssl_connect first appeared in SSLeay 0.9.0. All these functions have been available since .Ox 2.4 .