/usr/man/cat.3/SSL_CTX_set_msg_callback.3

SSL_CTX_set_msg_callback(3)  OpenSSL  SSL_CTX_set_msg_callback(3)

NAME

     SSL_CTX_set_msg_callback, SSL_CTX_set_msg_callback_arg,
     SSL_set_msg_callback, SSL_get_msg_callback_arg - install
     callback for observing protocol messages

SYNOPSIS

      #include <openssl/ssl.h>

      void SSL_CTX_set_msg_callback(SSL_CTX *ctx, void (*cb)(int write_p, int version, int content_type, const void *buf, size_t len, SSL *ssl, void *arg));
      void SSL_CTX_set_msg_callback_arg(SSL_CTX *ctx, void *arg);

      void SSL_set_msg_callback(SSL *ssl, void (*cb)(int write_p, int version, int content_type, const void *buf, size_t len, SSL *ssl, void *arg));
      void SSL_set_msg_callback_arg(SSL *ssl, void *arg);

DESCRIPTION

     SSL_CTX_set_msg_callback() or SSL_set_msg_callback() can be
     used to define a message callback function cb for observing
     all SSL/TLS protocol messages (such as handshake messages)
     that are received or sent.  SSL_CTX_set_msg_callback_arg()
     and SSL_set_msg_callback_arg() can be used to set argument
     arg to the callback function, which is available for
     arbitrary application use.

     SSL_CTX_set_msg_callback() and
     SSL_CTX_set_msg_callback_arg() specify default settings that
     will be copied to new SSL objects by SSL_new(3).
     SSL_set_msg_callback() and SSL_set_msg_callback_arg() modify
     the actual settings of an SSL object. Using a 0 pointer for
     cb disables the message callback.

     When cb is called by the SSL/TLS library for a protocol
     message, the function arguments have the following meaning:

     write_p
         This flag is 0 when a protocol message has been received
         and 1 when a protocol message has been sent.

     version
         The protocol version according to which the protocol
         message is interpreted by the library. Currently, this
         is one of SSL2_VERSION, SSL3_VERSION and TLS1_VERSION
         (for SSL 2.0, SSL 3.0 and TLS 1.0, respectively).

     content_type
         In the case of SSL 2.0, this is always 0.  In the case
         of SSL 3.0 or TLS 1.0, this is one of the ContentType
         values defined in the protocol specification
         (change_cipher_spec(20), alert(21), handshake(22); but
         never application_data(23) because the callback will
         only be called for protocol messages).

     buf, len

1.0.2t               Last change: 2019-09-10                    1

SSL_CTX_set_msg_callback(3)  OpenSSL  SSL_CTX_set_msg_callback(3)

         buf points to a buffer containing the protocol message,
         which consists of len bytes. The buffer is no longer
         valid after the callback function has returned.

     ssl The SSL object that received or sent the message.

     arg The user-defined argument optionally defined by
         SSL_CTX_set_msg_callback_arg() or
         SSL_set_msg_callback_arg().

NOTES

     Protocol messages are passed to the callback function after
     decryption and fragment collection where applicable. (Thus
     record boundaries are not visible.)

     If processing a received protocol message results in an
     error, the callback function may not be called.  For
     example, the callback function will never see messages that
     are considered too large to be processed.

     Due to automatic protocol version negotiation, version is
     not necessarily the protocol version used by the sender of
     the message: If a TLS 1.0 ClientHello message is received by
     an SSL 3.0-only server, version will be SSL3_VERSION.

SEE ALSO

     ssl(3), SSL_new(3)

HISTORY

     SSL_CTX_set_msg_callback(), SSL_CTX_set_msg_callback_arg(),
     SSL_set_msg_callback() and SSL_get_msg_callback_arg() were
     added in OpenSSL 0.9.7.

1.0.2t               Last change: 2019-09-10                    2

See also SSL_CTX_set_msg_callback_arg(3)
See also SSL_get_msg_callback_arg(3)
See also SSL_set_msg_callback(3)