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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_CTX *ctx, 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_CTX *ctx, 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
           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.



0.9.8                                            2009-04-03                      SSL_CTX_set_msg_callback(3)