98 lines
3.4 KiB
Text
98 lines
3.4 KiB
Text
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=pod
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=head1 NAME
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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
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=head1 SYNOPSIS
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#include <openssl/ssl.h>
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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));
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void SSL_CTX_set_msg_callback_arg(SSL_CTX *ctx, void *arg);
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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));
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void SSL_set_msg_callback_arg(SSL_CTX *ctx, void *arg);
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=head1 DESCRIPTION
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SSL_CTX_set_msg_callback() or SSL_set_msg_callback() can be used to
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define a message callback function I<cb> for observing all SSL/TLS
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protocol messages (such as handshake messages) that are received or
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sent. SSL_CTX_set_msg_callback_arg() and SSL_set_msg_callback_arg()
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can be used to set argument I<arg> to the callback function, which is
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available for arbitrary application use.
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SSL_CTX_set_msg_callback() and SSL_CTX_set_msg_callback_arg() specify
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default settings that will be copied to new B<SSL> objects by
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L<SSL_new(3)|SSL_new(3)>. SSL_set_msg_callback() and
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SSL_set_msg_callback_arg() modify the actual settings of an B<SSL>
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object. Using a B<0> pointer for I<cb> disables the message callback.
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When I<cb> is called by the SSL/TLS library for a protocol message,
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the function arguments have the following meaning:
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=over 4
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=item I<write_p>
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This flag is B<0> when a protocol message has been received and B<1>
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when a protocol message has been sent.
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=item I<version>
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The protocol version according to which the protocol message is
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interpreted by the library. Currently, this is one of
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B<SSL2_VERSION>, B<SSL3_VERSION> and B<TLS1_VERSION> (for SSL 2.0, SSL
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3.0 and TLS 1.0, respectively).
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=item I<content_type>
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In the case of SSL 2.0, this is always B<0>. In the case of SSL 3.0
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or TLS 1.0, this is one of the B<ContentType> values defined in the
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protocol specification (B<change_cipher_spec(20)>, B<alert(21)>,
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B<handshake(22)>; but never B<application_data(23)> because the
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callback will only be called for protocol messages).
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=item I<buf>, I<len>
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I<buf> points to a buffer containing the protocol message, which
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consists of I<len> bytes. The buffer is no longer valid after the
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callback function has returned.
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=item I<ssl>
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The B<SSL> object that received or sent the message.
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=item I<arg>
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The user-defined argument optionally defined by
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SSL_CTX_set_msg_callback_arg() or SSL_set_msg_callback_arg().
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=head1 NOTES
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Protocol messages are passed to the callback function after decryption
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and fragment collection where applicable. (Thus record boundaries are
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not visible.)
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If processing a received protocol message results in an error,
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the callback function may not be called. For example, the callback
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function will never see messages that are considered too large to be
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processed.
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Due to automatic protocol version negotiation, I<version> is not
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necessarily the protocol version used by the sender of the message: If
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a TLS 1.0 ClientHello message is received by an SSL 3.0-only server,
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I<version> will be B<SSL3_VERSION>.
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=head1 SEE ALSO
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L<ssl(3)|ssl(3)>, L<SSL_new(3)|SSL_new(3)>
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=head1 HISTORY
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SSL_CTX_set_msg_callback(), SSL_CTX_set_msg_callback_arg(),
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SSL_set_msg_callback() and SSL_get_msg_callback_arg() were added in OpenSSL 0.9.7.
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=cut
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