SSL_CTX_SET_MSG_CALLB... BSD Library Functions Manual SSL_CTX_SET_MSG_CALLB...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);
DESCRIPTIONSSL_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 NULL pointer for cb disables the mes‐
sage 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 The buffer is no longer valid after the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 call‐
back 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 ALSOssl(3), SSL_new(3)HISTORYSSL_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.
BSD April 25, 2024 BSD
