man > ssl(7ssl)

SSL(7SSL)                                      OpenSSL                                     SSL(7SSL)

NAME
       ssl - OpenSSL SSL/TLS library

SYNOPSIS
       See the individual manual pages for details.

DESCRIPTION
       The OpenSSL ssl library implements several versions of the Secure Sockets Layer, Transport
       Layer Security, and Datagram Transport Layer Security protocols.  This page gives a brief
       overview of the extensive API and data types provided by the library.

       An SSL_CTX object is created as a framework to establish TLS/SSL enabled connections (see
       SSL_CTX_new(3)).  Various options regarding certificates, algorithms etc. can be set in this
       object.

       When a network connection has been created, it can be assigned to an SSL object. After the
       SSL object has been created using SSL_new(3), SSL_set_fd(3) or SSL_set_bio(3) can be used to
       associate the network connection with the object.

       When the TLS/SSL handshake is performed using SSL_accept(3) or SSL_connect(3) respectively.
       SSL_read_ex(3), SSL_read(3), SSL_write_ex(3) and SSL_write(3) are used to read and write data
       on the TLS/SSL connection.  SSL_shutdown(3) can be used to shut down the TLS/SSL connection.

DATA STRUCTURES
       Here are some of the main data structures in the library.

       SSL_METHOD (SSL Method)
           This  is a dispatch structure describing the internal ssl library methods/functions which
           implement the various protocol versions (SSLv3 TLSv1, ...).  It's  needed  to  create  an
           SSL_CTX.

       SSL_CIPHER (SSL Cipher)
           This  structure  holds the algorithm information for a particular cipher which are a core
           part of the SSL/TLS protocol. The available ciphers are configured on a SSL_CTX basis and
           the actual ones used are then part of the SSL_SESSION.

       SSL_CTX (SSL Context)
           This is the global context structure which is created by a  server  or  client  once  per
           program  life-time and which holds mainly default values for the SSL structures which are
           later created for the connections.

       SSL_SESSION (SSL Session)
           This is a structure containing the current TLS/SSL  session  details  for  a  connection:
           SSL_CIPHERs, client and server certificates, keys, etc.

       SSL (SSL Connection)
           This is the main SSL/TLS structure which is created by a server or client per established
           connection.  This  actually  is  the  core  structure  in  the  SSL API.  At run-time the
           application usually deals with this  structure  which  has  links  to  mostly  all  other
           structures.

HEADER FILES
       Currently  the  OpenSSL  ssl  library  provides  the  following C header files containing the
       prototypes for the data structures and functions:

       <openssl/ssl.h>
           This is the common header file for the SSL/TLS API.  Include it into your program to make
           the API of the ssl library available.  It  internally  includes  both  more  private  SSL
           headers  and headers from the crypto library.  Whenever you need hard-core details on the
           internals of the SSL API, look inside this header file.   This  file  also  includes  the
           others listed below.

       <openssl/ssl2.h>
           Unused. Present for backwards compatibility only.

       <openssl/ssl3.h>
           This is the sub header file dealing with the SSLv3 protocol only.

       <openssl/tls1.h>
           This is the sub header file dealing with the TLSv1 protocol only.

COPYRIGHT
       Copyright 2000-2018 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 <https://www.openssl.org/source/license.html>.

3.0.13                                       2026-07-29                                    SSL(7SSL)