From: Rémi Denis-Courmont Date: Sun, 11 Mar 2007 18:53:53 +0000 (+0000) Subject: Untested support for RFC4771: X-Git-Tag: 0.9.0-test0~8150 X-Git-Url: https://git.sesse.net/?p=vlc;a=commitdiff_plain;h=7bdd4ba5b1c58233b656c75e4abd9017f7ef02ee Untested support for RFC4771: Integrity Transform Carrying Roll-Over Counter for SRTP Once debugged, it should provide a simple way to synchronize live (multicast...) secure streams. --- diff --git a/libs/srtp/srtp.c b/libs/srtp/srtp.c index a3accb5698..daf0e18d20 100644 --- a/libs/srtp/srtp.c +++ b/libs/srtp/srtp.c @@ -17,6 +17,12 @@ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */ +/* TODO: + * Useless stuff (because nothing depends on it): + * - non-nul key derivation rate + * - MKI payload + */ + #ifdef HAVE_CONFIG_H # include #endif @@ -33,16 +39,15 @@ #include -#define debug( ... ) (void)0 +#ifdef WIN32 +# include +#else +# include +# include +GCRY_THREAD_OPTION_PTHREAD_IMPL; +#endif -/* TODO: - * Useful stuff: - * - ROC profile thingy (multicast really needs this) - * - * Useless stuff (because nothing depends on it): - * - non-nul key derivation rate - * - MKI payload - */ +#define debug( ... ) (void)0 typedef struct srtp_proto_t { @@ -76,13 +81,10 @@ enum }; -#ifdef WIN32 -# include -#else -# include -# include -GCRY_THREAD_OPTION_PTHREAD_IMPL; -#endif +static inline unsigned rcc_mode (const srtp_session_t *s) +{ + return (s->flags >> 4) & 3; +} static bool libgcrypt_usable = false; @@ -216,6 +218,12 @@ srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags) memset (s, 0, sizeof (*s)); s->flags = flags; s->tag_len = tag_len; + s->rtp_rcc = 1; /* Default RCC rate */ + if (rcc_mode (s)) + { + if (tag_len < 4) + goto error; + } if (proto_create (&s->rtp, cipher, md) == 0) { @@ -224,6 +232,7 @@ srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags) proto_destroy (&s->rtp); } +error: free (s); return NULL; } @@ -440,14 +449,14 @@ static inline uint16_t rtp_seq (const uint8_t *buf) /** Message Authentication and Integrity for RTP */ static const uint8_t * -rtp_digest (srtp_session_t *s, const uint8_t *data, size_t len) +rtp_digest (srtp_session_t *s, const uint8_t *data, size_t len, + uint32_t roc) { const gcry_md_hd_t md = s->rtp.mac; - uint32_t roc = htonl (srtp_compute_roc (s, rtp_seq (data))); gcry_md_reset (md); gcry_md_write (md, data, len); - gcry_md_write (md, &roc, 4); + gcry_md_write (md, &(uint32_t){ htonl (roc) }, 4); return gcry_md_read (md, 0); } @@ -532,12 +541,13 @@ static int srtp_crypt (srtp_session_t *s, uint8_t *buf, size_t len) * * @param buf RTP packet to be encrypted/digested * @param lenp pointer to the RTP packet length on entry, - * set to the SRTP length on exit (undefined in case of error) + * set to the SRTP length on exit (undefined on non-ENOSPC error) * @param bufsize size (bytes) of the packet buffer * * @return 0 on success, in case of error: * EINVAL malformatted RTP packet or internal error - * ENOSPC bufsize is too small (to add authentication tag) + * ENOSPC bufsize is too small to add authentication tag + * ( will hold the required byte size) * EACCES packet would trigger a replay error on receiver */ int @@ -550,12 +560,32 @@ srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize) if (!(s->flags & SRTP_UNAUTHENTICATED)) { - if (bufsize < (len + s->tag_len)) + size_t tag_len = s->tag_len; + *lenp = len + tag_len; + if (bufsize < (len + tag_len)) return ENOSPC; - const uint8_t *tag = rtp_digest (s, buf, len); - memcpy (buf + len, tag, s->tag_len); - *lenp = len + s->tag_len; + uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)); + const uint8_t *tag = rtp_digest (s, buf, len, roc); + if (rcc_mode (s)) + { + assert (s->rtp_rcc); + if ((rtp_seq (buf) % s->rtp_rcc) == 0) + { + memcpy (buf + len, &(uint32_t){ htonl (s->rtp_roc) }, 4); + len += 4; + if (rcc_mode (s) == 3) + tag_len = 0; + else + tag_len -= 4; + } + else + { + if (rcc_mode (s) & 1) + tag_len = 0; + } + } + memcpy (buf + len, tag, tag_len); } return 0; @@ -578,17 +608,53 @@ int srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp) { size_t len = *lenp; + if (len < 12u) + return EINVAL; if (!(s->flags & SRTP_UNAUTHENTICATED)) { - if (len < (12u + s->tag_len)) + size_t tag_len = s->tag_len, roc_len = 0; + if (rcc_mode (s)) + { + if ((rtp_seq (buf) % s->rtp_rcc) == 0) + { + roc_len = 4; + if (rcc_mode (s) == 3) + tag_len = 0; + else + tag_len -= 4; + } + else + { + if (rcc_mode (s) & 1) + tag_len = 0; // RCC mode 1 or 3: no auth + } + } + + if (len < (12u + roc_len + tag_len)) return EINVAL; - len -= s->tag_len; + len -= roc_len + tag_len; - const uint8_t *tag = rtp_digest (s, buf, len); - if (memcmp (buf + len, tag, s->tag_len)) + uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)), rcc; + if (roc_len) + { + assert (roc_len == 4); + memcpy (&rcc, buf + len, 4); + rcc = ntohl (rcc); + } + else + rcc = roc; + + const uint8_t *tag = rtp_digest (s, buf, len, rcc); + if (memcmp (buf + len + roc_len, tag, s->tag_len)) return EACCES; + if (roc_len) + { + /* Authenticated packet carried a Roll-Over-Counter */ + s->rtp_roc += rcc - roc; + assert (srtp_compute_roc (s, rtp_seq (buf)) == rcc); + } *lenp = len; }