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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 *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
           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.

1.0.2k                            2017-01-26       SSL_CTX_set_msg_callback(3)