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Add ssl_set_dtls_badmac_limit()

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Manuel Pégourié-Gonnard 2014-10-14 18:30:36 +02:00 committed by Paul Bakker
parent 9b35f18f66
commit b0643d152d
4 changed files with 66 additions and 2 deletions
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5
include/polarssl/check_config.h
View file

@ -277,6 +277,11 @@
#error "POLARSSL_SSL_DTLS_ANTI_REPLAY defined, but not all prerequisites"
#endif
#if defined(POLARSSL_SSL_DTLS_BADMAC_LIMIT) && \
( !defined(POLARSSL_SSL_TLS_C) || !defined(POLARSSL_SSL_PROTO_DTLS) )
#error "POLARSSL_SSL_DTLS_BADMAC_LIMIT defined, but not all prerequisites"
#endif
#if defined(POLARSSL_SSL_SESSION_TICKETS) && defined(POLARSSL_SSL_TLS_C) && \
( !defined(POLARSSL_AES_C) || !defined(POLARSSL_SHA256_C) || \
!defined(POLARSSL_CIPHER_MODE_CBC) )

15
include/polarssl/config.h
View file

@ -929,7 +929,7 @@
* Enable support for the anti-replay mechanism in DTLS.
*
* Requires: POLARSSL_SSL_TLS_C
* POLARSSL_POLARSSL_PROTO_DTLS
* POLARSSL_SSL_PROTO_DTLS
*
* \warning Disabling this is often a security risk!
* See ssl_set_dtls_anti_replay() for details.
@ -951,12 +951,23 @@
* \warning Disabling this can ba a security risk! (see above)
*
* Requires: POLARSSL_SSL_SRV_C
* POLARSSL_POLARSSL_PROTO_DTLS
* POLARSSL_SSL_PROTO_DTLS
*
* Comment this to disable support for HelloVerifyRequest.
*/
#define POLARSSL_SSL_DTLS_HELLO_VERIFY
/**
* \def POLARSSL_SSL_DTLS_BADMAC_LIMIT
*
* Enable support for a limit of records with bad MAC.
*
* See ssl_set_dtls_badmac_limit().
*
* Requires: POLARSSL_SSL_PROTO_DTLS
*/
#define POLARSSL_SSL_DTLS_BADMAC_LIMIT
/**
* \def POLARSSL_SSL_SESSION_TICKETS
*

32
include/polarssl/ssl.h
View file

@ -772,6 +772,11 @@ struct _ssl_context
uint32_t read_timeout; /*!< timeout for ssl_read in milliseconds */
#if defined(POLARSSL_SSL_DTLS_BADMAC_LIMIT)
unsigned badmac_limit; /*!< limit of records with a bad MAC */
unsigned badmac_seen; /*!< records with a bad MAC received */
#endif
/*
* Callbacks (RNG, debug, I/O, verification)
*/
@ -1294,6 +1299,33 @@ void ssl_set_dtls_cookies( ssl_context *ssl,
void ssl_set_dtls_anti_replay( ssl_context *ssl, char mode );
#endif /* POLARSSL_SSL_DTLS_ANTI_REPLAY */
#if defined(POLARSSL_SSL_DTLS_BADMAC_LIMIT)
/**
* \brief Set a limit on the number of records with a bad MAC
* before terminating the connection.
* (DTLS only, no effect on TLS.)
* Default: 0 (disabled).
*
* \param ssl SSL context
* \param limit Limit, or 0 to disable.
*
* \note If the limit is N, then the connection is terminated when
* the Nth non-authentic record is seen.
*
* \note Records with an invalid header are not counted, only the
* ones going through the authentication-decryption phase.
*
* \note This is a security trade-off related to the fact that it's
* often relatively easy for an active attacker ot inject UDP
* datagrams. On one hand, setting a low limit here makes it
* easier for such an attacker to forcibly terminated a
* connection. On the other hand, a high limit or no limit
* might make us waste resources checking authentication on
* many bogus packets.
*/
void ssl_set_dtls_badmac_limit( ssl_context *ssl, unsigned limit );
#endif /* POLARSSL_DTLS_BADMAC_LIMIT */
#if defined(POLARSSL_SSL_PROTO_DTLS)
/**
* \brief Set retransmit timeout values for the DTLS handshale.

16
library/ssl_tls.c
View file

@ -3238,6 +3238,15 @@ read_record_header:
if( ret == POLARSSL_ERR_SSL_INVALID_RECORD ||
ret == POLARSSL_ERR_SSL_INVALID_MAC )
{
#if defined(POLARSSL_SSL_DTLS_BADMAC_LIMIT)
if( ssl->badmac_limit != 0 &&
++ssl->badmac_seen >= ssl->badmac_limit )
{
SSL_DEBUG_MSG( 1, ( "too many records with bad MAC" ) );
return( POLARSSL_ERR_SSL_INVALID_MAC );
}
#endif
SSL_DEBUG_MSG( 1, ( "discarding invalid record" ) );
goto read_record_header;
}
@ -4923,6 +4932,13 @@ void ssl_set_dtls_anti_replay( ssl_context *ssl, char mode )
}
#endif
#if defined(POLARSSL_SSL_DTLS_BADMAC_LIMIT)
void ssl_set_dtls_badmac_limit( ssl_context *ssl, unsigned limit )
{
ssl->badmac_limit = limit;
}
#endif
#if defined(POLARSSL_SSL_PROTO_DTLS)
void ssl_set_handshake_timeout( ssl_context *ssl, uint32_t min, uint32_t max )
{