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https://github.com/Mbed-TLS/mbedtls.git
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Introduce helper for handling of post-handshake handshake messages
Handling the receipt of a handshake record after the initial handshake requires non-trivial logic depending on the protocol version and the endpoint. This logic is currently embedded in mbedtls_ssl_read(). With the introduction of support for [D]TLS 1.3, the logic will become even more complex, since [D]TLS 1.3 drops support for renegotiation -- which in [D]TLS 1.2 is the main purpose of post-handshake handshake messages -- but instead introduces numerous other post-handshake handshake messages. In order to pave the way for those changes, this commit improves readability and maintainability of mbedtls_ssl_read() by moving the TLS <=1.2 logic for handling post-handshake handshake messages into a separate helper function ssl_handle_hs_message_post_handshake(). The logic of the code is entirely unchanged. Signed-off-by: Hanno Becker <hanno.becker@arm.com>
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Hanno Becker
parent
59d97a16d6
commit
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@ -5112,6 +5112,120 @@ static int ssl_check_ctr_renegotiate( mbedtls_ssl_context *ssl )
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}
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#endif /* MBEDTLS_SSL_RENEGOTIATION */
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/* This function is called from mbedtls_ssl_read() when a handshake message is
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* received after the initial handshake. In this context, handshake messages
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* may only be sent for the purpose of initiating renegotiations.
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*
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* This function is introduced as a separate helper since the handling
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* of post-handshake handshake messages changes significantly in TLS 1.3,
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* and having a helper function allows to distinguish between TLS <= 1.2 and
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* TLS 1.3 in the future without bloating the logic of mbedtls_ssl_read().
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*/
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int ssl_handle_hs_message_post_handshake( mbedtls_ssl_context *ssl )
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{
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int ret;
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/*
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* - For client-side, expect SERVER_HELLO_REQUEST.
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* - For server-side, expect CLIENT_HELLO.
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* - Fail (TLS) or silently drop record (DTLS) in other cases.
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*/
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#if defined(MBEDTLS_SSL_CLI_C)
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if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT &&
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( ssl->in_msg[0] != MBEDTLS_SSL_HS_HELLO_REQUEST ||
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ssl->in_hslen != mbedtls_ssl_hs_hdr_len( ssl ) ) )
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not HelloRequest)" ) );
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/* With DTLS, drop the packet (probably from last handshake) */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
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{
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return( 0 );
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}
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#endif
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return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
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}
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#endif /* MBEDTLS_SSL_CLI_C */
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#if defined(MBEDTLS_SSL_SRV_C)
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if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
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ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO )
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not ClientHello)" ) );
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/* With DTLS, drop the packet (probably from last handshake) */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
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{
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return( 0 );
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}
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#endif
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return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
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}
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#endif /* MBEDTLS_SSL_SRV_C */
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#if defined(MBEDTLS_SSL_RENEGOTIATION)
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/* Determine whether renegotiation attempt should be accepted */
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if( ! ( ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED ||
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( ssl->secure_renegotiation == MBEDTLS_SSL_LEGACY_RENEGOTIATION &&
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ssl->conf->allow_legacy_renegotiation ==
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MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION ) ) )
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{
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/*
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* Accept renegotiation request
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*/
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/* DTLS clients need to know renego is server-initiated */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
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ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT )
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{
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ssl->renego_status = MBEDTLS_SSL_RENEGOTIATION_PENDING;
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}
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#endif
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ret = mbedtls_ssl_start_renegotiation( ssl );
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if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO &&
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ret != 0 )
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{
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MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_start_renegotiation",
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ret );
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return( ret );
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}
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}
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else
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#endif /* MBEDTLS_SSL_RENEGOTIATION */
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{
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/*
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* Refuse renegotiation
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*/
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "refusing renegotiation, sending alert" ) );
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#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
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defined(MBEDTLS_SSL_PROTO_TLS1_2)
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if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
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{
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if( ( ret = mbedtls_ssl_send_alert_message( ssl,
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MBEDTLS_SSL_ALERT_LEVEL_WARNING,
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MBEDTLS_SSL_ALERT_MSG_NO_RENEGOTIATION ) ) != 0 )
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{
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return( ret );
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}
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}
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else
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#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 ||
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MBEDTLS_SSL_PROTO_TLS1_2 */
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
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return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
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}
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}
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return( 0 );
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}
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/*
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* Receive application data decrypted from the SSL layer
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*/
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@ -5210,124 +5324,15 @@ int mbedtls_ssl_read( mbedtls_ssl_context *ssl, unsigned char *buf, size_t len )
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if( ssl->in_msgtype == MBEDTLS_SSL_MSG_HANDSHAKE )
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "received handshake message" ) );
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/*
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* - For client-side, expect SERVER_HELLO_REQUEST.
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* - For server-side, expect CLIENT_HELLO.
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* - Fail (TLS) or silently drop record (DTLS) in other cases.
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*/
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#if defined(MBEDTLS_SSL_CLI_C)
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if( ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT &&
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( ssl->in_msg[0] != MBEDTLS_SSL_HS_HELLO_REQUEST ||
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ssl->in_hslen != mbedtls_ssl_hs_hdr_len( ssl ) ) )
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ret = ssl_handle_hs_message_post_handshake( ssl );
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if( ret != 0)
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not HelloRequest)" ) );
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/* With DTLS, drop the packet (probably from last handshake) */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
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{
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continue;
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}
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#endif
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return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
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}
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#endif /* MBEDTLS_SSL_CLI_C */
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#if defined(MBEDTLS_SSL_SRV_C)
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if( ssl->conf->endpoint == MBEDTLS_SSL_IS_SERVER &&
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ssl->in_msg[0] != MBEDTLS_SSL_HS_CLIENT_HELLO )
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "handshake received (not ClientHello)" ) );
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/* With DTLS, drop the packet (probably from last handshake) */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM )
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{
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continue;
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}
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#endif
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return( MBEDTLS_ERR_SSL_UNEXPECTED_MESSAGE );
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}
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#endif /* MBEDTLS_SSL_SRV_C */
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#if defined(MBEDTLS_SSL_RENEGOTIATION)
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/* Determine whether renegotiation attempt should be accepted */
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if( ! ( ssl->conf->disable_renegotiation == MBEDTLS_SSL_RENEGOTIATION_DISABLED ||
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( ssl->secure_renegotiation == MBEDTLS_SSL_LEGACY_RENEGOTIATION &&
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ssl->conf->allow_legacy_renegotiation ==
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MBEDTLS_SSL_LEGACY_NO_RENEGOTIATION ) ) )
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{
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/*
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* Accept renegotiation request
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*/
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/* DTLS clients need to know renego is server-initiated */
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#if defined(MBEDTLS_SSL_PROTO_DTLS)
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if( ssl->conf->transport == MBEDTLS_SSL_TRANSPORT_DATAGRAM &&
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ssl->conf->endpoint == MBEDTLS_SSL_IS_CLIENT )
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{
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ssl->renego_status = MBEDTLS_SSL_RENEGOTIATION_PENDING;
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}
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#endif
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ret = mbedtls_ssl_start_renegotiation( ssl );
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if( ret != MBEDTLS_ERR_SSL_WAITING_SERVER_HELLO_RENEGO &&
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ret != 0 )
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{
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MBEDTLS_SSL_DEBUG_RET( 1, "mbedtls_ssl_start_renegotiation",
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ret );
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return( ret );
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}
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}
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else
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#endif /* MBEDTLS_SSL_RENEGOTIATION */
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{
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/*
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* Refuse renegotiation
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*/
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MBEDTLS_SSL_DEBUG_MSG( 3, ( "refusing renegotiation, sending alert" ) );
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#if defined(MBEDTLS_SSL_PROTO_TLS1) || defined(MBEDTLS_SSL_PROTO_TLS1_1) || \
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defined(MBEDTLS_SSL_PROTO_TLS1_2)
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if( ssl->minor_ver >= MBEDTLS_SSL_MINOR_VERSION_1 )
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{
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if( ( ret = mbedtls_ssl_send_alert_message( ssl,
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MBEDTLS_SSL_ALERT_LEVEL_WARNING,
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MBEDTLS_SSL_ALERT_MSG_NO_RENEGOTIATION ) ) != 0 )
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{
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return( ret );
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}
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}
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else
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#endif /* MBEDTLS_SSL_PROTO_TLS1 || MBEDTLS_SSL_PROTO_TLS1_1 ||
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MBEDTLS_SSL_PROTO_TLS1_2 */
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{
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MBEDTLS_SSL_DEBUG_MSG( 1, ( "should never happen" ) );
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return( MBEDTLS_ERR_SSL_INTERNAL_ERROR );
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}
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MBEDTLS_SSL_DEBUG_RET( 1, "ssl_handle_hs_message_post_handshake",
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ret );
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return( ret );
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}
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/* At this point, we don't know whether the renegotiation has been
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* completed or not. The cases to consider are the following:
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* 1) The renegotiation is complete. In this case, no new record
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* has been read yet.
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* 2) The renegotiation is incomplete because the client received
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* an application data record while awaiting the ServerHello.
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* 3) The renegotiation is incomplete because the client received
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* a non-handshake, non-application data message while awaiting
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* the ServerHello.
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* In each of these case, looping will be the proper action:
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* - For 1), the next iteration will read a new record and check
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* if it's application data.
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* - For 2), the loop condition isn't satisfied as application data
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* is present, hence continue is the same as break
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* - For 3), the loop condition is satisfied and read_record
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* will re-deliver the message that was held back by the client
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* when expecting the ServerHello.
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*/
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/* Post-handshake handshake messages are not passed to the user. */
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continue;
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}
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#if defined(MBEDTLS_SSL_RENEGOTIATION)
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