aboutsummaryrefslogtreecommitdiff
path: root/plugins/rtp/src/srtp.c
diff options
context:
space:
mode:
authorMarvin W <git@larma.de>2021-03-23 20:04:28 +0100
committerMarvin W <git@larma.de>2021-03-23 20:04:28 +0100
commit4b230808b9566322fae8d1ef0d1a5cb3e8027d3b (patch)
tree0243fa93129ece9cfc1f92430ccc6659ee1259aa /plugins/rtp/src/srtp.c
parent97ab7de7ab4f958eb7d273e524151007d44ea1d7 (diff)
downloaddino-4b230808b9566322fae8d1ef0d1a5cb3e8027d3b.tar.gz
dino-4b230808b9566322fae8d1ef0d1a5cb3e8027d3b.zip
Move SRTP implementation into crypto library for reuse
Diffstat (limited to 'plugins/rtp/src/srtp.c')
-rw-r--r--plugins/rtp/src/srtp.c836
1 files changed, 0 insertions, 836 deletions
diff --git a/plugins/rtp/src/srtp.c b/plugins/rtp/src/srtp.c
deleted file mode 100644
index 708244d9..00000000
--- a/plugins/rtp/src/srtp.c
+++ /dev/null
@@ -1,836 +0,0 @@
-/*
- * Secure RTP with libgcrypt
- * Copyright (C) 2007 RĂ©mi Denis-Courmont
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; either
- * version 2.1 of the License, or (at your option) any later version.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * 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 <config.h>
-#endif
-
-#include <stdint.h>
-#include <stddef.h>
-
-#include "srtp.h"
-
-#include <stdbool.h>
-#include <stdlib.h>
-#include <assert.h>
-#include <errno.h>
-
-#include <gcrypt.h>
-
-#ifdef _WIN32
-# include <winsock2.h>
-#else
-# include <netinet/in.h>
-#endif
-
-#define debug( ... ) (void)0
-
-typedef struct srtp_proto_t
-{
- gcry_cipher_hd_t cipher;
- gcry_md_hd_t mac;
- uint64_t window;
- uint32_t salt[4];
-} srtp_proto_t;
-
-struct srtp_session_t
-{
- srtp_proto_t rtp;
- srtp_proto_t rtcp;
- unsigned flags;
- unsigned kdr;
- uint32_t rtcp_index;
- uint32_t rtp_roc;
- uint16_t rtp_seq;
- uint16_t rtp_rcc;
- uint8_t tag_len;
-};
-
-enum
-{
- SRTP_CRYPT,
- SRTP_AUTH,
- SRTP_SALT,
- SRTCP_CRYPT,
- SRTCP_AUTH,
- SRTCP_SALT
-};
-
-
-static inline unsigned rcc_mode (const srtp_session_t *s)
-{
- return (s->flags >> 4) & 3;
-}
-
-
-static void proto_destroy (srtp_proto_t *p)
-{
- gcry_md_close (p->mac);
- gcry_cipher_close (p->cipher);
-}
-
-
-/**
- * Releases all resources associated with a Secure RTP session.
- */
-void srtp_destroy (srtp_session_t *s)
-{
- assert (s != NULL);
-
- proto_destroy (&s->rtcp);
- proto_destroy (&s->rtp);
- free (s);
-}
-
-
-static int proto_create (srtp_proto_t *p, int gcipher, int gmd)
-{
- if (gcry_cipher_open (&p->cipher, gcipher, GCRY_CIPHER_MODE_CTR, 0) == 0)
- {
- if (gcry_md_open (&p->mac, gmd, GCRY_MD_FLAG_HMAC) == 0)
- return 0;
- gcry_cipher_close (p->cipher);
- }
- return -1;
-}
-
-
-/**
- * Allocates a Secure RTP one-way session.
- * The same session cannot be used both ways because this would confuse
- * internal cryptographic counters; it is however of course feasible to open
- * multiple simultaneous sessions with the same master key.
- *
- * @param encr encryption algorithm number
- * @param auth authentication algortihm number
- * @param tag_len authentication tag byte length (NOT including RCC)
- * @param flags OR'ed optional flags.
- *
- * @return NULL in case of error
- */
-srtp_session_t *
-srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags)
-{
- if ((flags & ~SRTP_FLAGS_MASK))
- return NULL;
-
- int cipher, md;
- switch (encr)
- {
- case SRTP_ENCR_NULL:
- cipher = GCRY_CIPHER_NONE;
- break;
-
- case SRTP_ENCR_AES_CM:
- cipher = GCRY_CIPHER_AES;
- break;
-
- default:
- return NULL;
- }
-
- switch (auth)
- {
- case SRTP_AUTH_NULL:
- md = GCRY_MD_NONE;
- break;
-
- case SRTP_AUTH_HMAC_SHA1:
- md = GCRY_MD_SHA1;
- break;
-
- default:
- return NULL;
- }
-
- if (tag_len > gcry_md_get_algo_dlen (md))
- return NULL;
-
- if (prf != SRTP_PRF_AES_CM)
- return NULL;
-
- srtp_session_t *s = malloc (sizeof (*s));
- if (s == NULL)
- return NULL;
-
- 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)
- {
- if (proto_create (&s->rtcp, cipher, md) == 0)
- return s;
- proto_destroy (&s->rtp);
- }
-
- error:
- free (s);
- return NULL;
-}
-
-
-/**
- * Counter Mode encryption/decryption (ctr length = 16 bytes)
- * with non-padded (truncated) text
- */
-static int
-do_ctr_crypt (gcry_cipher_hd_t hd, const void *ctr, uint8_t *data, size_t len)
-{
- const size_t ctrlen = 16;
- div_t d = div (len, ctrlen);
-
- if (gcry_cipher_setctr (hd, ctr, ctrlen)
- || gcry_cipher_encrypt (hd, data, d.quot * ctrlen, NULL, 0))
- return -1;
-
- if (d.rem)
- {
- /* Truncated last block */
- uint8_t dummy[ctrlen];
- data += d.quot * ctrlen;
- memcpy (dummy, data, d.rem);
- memset (dummy + d.rem, 0, ctrlen - d.rem);
-
- if (gcry_cipher_encrypt (hd, dummy, ctrlen, data, ctrlen))
- return -1;
- memcpy (data, dummy, d.rem);
- }
-
- return 0;
-}
-
-
-/**
- * AES-CM key derivation (saltlen = 14 bytes)
- */
-static int
-do_derive (gcry_cipher_hd_t prf, const void *salt,
- const uint8_t *r, size_t rlen, uint8_t label,
- void *out, size_t outlen)
-{
- uint8_t iv[16];
-
- memcpy (iv, salt, 14);
- iv[14] = iv[15] = 0;
-
- assert (rlen < 14);
- iv[13 - rlen] ^= label;
- for (size_t i = 0; i < rlen; i++)
- iv[sizeof (iv) - rlen + i] ^= r[i];
-
- memset (out, 0, outlen);
- return do_ctr_crypt (prf, iv, out, outlen);
-}
-
-
-/**
- * Sets (or resets) the master key and master salt for a SRTP session.
- * This must be done at least once before using srtp_send(), srtp_recv(),
- * srtcp_send() or srtcp_recv(). Also, rekeying is required every
- * 2^48 RTP packets or 2^31 RTCP packets (whichever comes first),
- * otherwise the protocol security might be broken.
- *
- * @return 0 on success, in case of error:
- * EINVAL invalid or unsupported key/salt sizes combination
- */
-int
-srtp_setkey (srtp_session_t *s, const void *key, size_t keylen,
- const void *salt, size_t saltlen)
-{
- /* SRTP/SRTCP cipher/salt/MAC keys derivation */
- gcry_cipher_hd_t prf;
- uint8_t r[6], keybuf[20];
-
- if (saltlen != 14)
- return EINVAL;
-
- if (gcry_cipher_open (&prf, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, 0)
- || gcry_cipher_setkey (prf, key, keylen))
- return EINVAL;
-
- /* SRTP key derivation */
-#if 0
- if (s->kdr != 0)
- {
- uint64_t index = (((uint64_t)s->rtp_roc) << 16) | s->rtp_seq;
- index /= s->kdr;
-
- for (int i = sizeof (r) - 1; i >= 0; i--)
- {
- r[i] = index & 0xff;
- index = index >> 8;
- }
- }
- else
-#endif
- memset (r, 0, sizeof (r));
- if (do_derive (prf, salt, r, 6, SRTP_CRYPT, keybuf, 16)
- || gcry_cipher_setkey (s->rtp.cipher, keybuf, 16)
- || do_derive (prf, salt, r, 6, SRTP_AUTH, keybuf, 20)
- || gcry_md_setkey (s->rtp.mac, keybuf, 20)
- || do_derive (prf, salt, r, 6, SRTP_SALT, s->rtp.salt, 14))
- return -1;
-
- /* SRTCP key derivation */
- memcpy (r, &(uint32_t){ htonl (s->rtcp_index) }, 4);
- if (do_derive (prf, salt, r, 4, SRTCP_CRYPT, keybuf, 16)
- || gcry_cipher_setkey (s->rtcp.cipher, keybuf, 16)
- || do_derive (prf, salt, r, 4, SRTCP_AUTH, keybuf, 20)
- || gcry_md_setkey (s->rtcp.mac, keybuf, 20)
- || do_derive (prf, salt, r, 4, SRTCP_SALT, s->rtcp.salt, 14))
- return -1;
-
- (void)gcry_cipher_close (prf);
- return 0;
-}
-
-static int hexdigit (char c)
-{
- if ((c >= '0') && (c <= '9'))
- return c - '0';
- if ((c >= 'A') && (c <= 'F'))
- return c - 'A' + 0xA;
- if ((c >= 'a') && (c <= 'f'))
- return c - 'a' + 0xa;
- return -1;
-}
-
-static ssize_t hexstring (const char *in, uint8_t *out, size_t outlen)
-{
- size_t inlen = strlen (in);
-
- if ((inlen > (2 * outlen)) || (inlen & 1))
- return -1;
-
- for (size_t i = 0; i < inlen; i += 2)
- {
- int a = hexdigit (in[i]), b = hexdigit (in[i + 1]);
- if ((a == -1) || (b == -1))
- return -1;
- out[i / 2] = (a << 4) | b;
- }
- return inlen / 2;
-}
-
-/**
- * Sets (or resets) the master key and master salt for a SRTP session
- * from hexadecimal strings. See also srtp_setkey().
- *
- * @return 0 on success, in case of error:
- * EINVAL invalid or unsupported key/salt sizes combination
- */
-int
-srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt)
-{
- uint8_t bkey[16]; /* TODO/NOTE: hard-coded for AES */
- uint8_t bsalt[14]; /* TODO/NOTE: hard-coded for the PRF-AES-CM */
- ssize_t bkeylen = hexstring (key, bkey, sizeof (bkey));
- ssize_t bsaltlen = hexstring (salt, bsalt, sizeof (bsalt));
-
- if ((bkeylen == -1) || (bsaltlen == -1))
- return EINVAL;
- return srtp_setkey (s, bkey, bkeylen, bsalt, bsaltlen) ? EINVAL : 0;
-}
-
-/**
- * Sets Roll-over-Counter Carry (RCC) rate for the SRTP session. If not
- * specified (through this function), the default rate of ONE is assumed
- * (i.e. every RTP packets will carry the RoC). RCC rate is ignored if none
- * of the RCC mode has been selected.
- *
- * The RCC mode is selected through one of these flags for srtp_create():
- * SRTP_RCC_MODE1: integrity protection only for RoC carrying packets
- * SRTP_RCC_MODE2: integrity protection for all packets
- * SRTP_RCC_MODE3: no integrity protection
- *
- * RCC mode 3 is insecure. Compared to plain RTP, it provides confidentiality
- * (through encryption) but is much more prone to DoS. It can only be used if
- * anti-spoofing protection is provided by lower network layers (e.g. IPsec,
- * or trusted routers and proper source address filtering).
- *
- * If RCC rate is 1, RCC mode 1 and 2 are functionally identical.
- *
- * @param rate RoC Carry rate (MUST NOT be zero)
- */
-void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate)
-{
- assert (rate != 0);
- s->rtp_rcc = rate;
-}
-
-
-/** AES-CM for RTP (salt = 14 bytes + 2 nul bytes) */
-static int
-rtp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t roc, uint16_t seq,
- const uint32_t *salt, uint8_t *data, size_t len)
-{
- /* Determines cryptographic counter (IV) */
- uint32_t counter[4];
- counter[0] = salt[0];
- counter[1] = salt[1] ^ ssrc;
- counter[2] = salt[2] ^ htonl (roc);
- counter[3] = salt[3] ^ htonl (seq << 16);
-
- /* Encryption */
- return do_ctr_crypt (hd, counter, data, len);
-}
-
-
-/** Determines SRTP Roll-Over-Counter (in host-byte order) */
-static uint32_t
-srtp_compute_roc (const srtp_session_t *s, uint16_t seq)
-{
- uint32_t roc = s->rtp_roc;
-
- if (((seq - s->rtp_seq) & 0xffff) < 0x8000)
- {
- /* Sequence is ahead, good */
- if (seq < s->rtp_seq)
- roc++; /* Sequence number wrap */
- }
- else
- {
- /* Sequence is late, bad */
- if (seq > s->rtp_seq)
- roc--; /* Wrap back */
- }
- return roc;
-}
-
-
-/** Returns RTP sequence (in host-byte order) */
-static inline uint16_t rtp_seq (const uint8_t *buf)
-{
- return (buf[2] << 8) | buf[3];
-}
-
-
-/** Message Authentication and Integrity for RTP */
-static const uint8_t *
-rtp_digest (gcry_md_hd_t md, const uint8_t *data, size_t len,
- uint32_t roc)
-{
- gcry_md_reset (md);
- gcry_md_write (md, data, len);
- gcry_md_write (md, &(uint32_t){ htonl (roc) }, 4);
- return gcry_md_read (md, 0);
-}
-
-
-/**
- * Encrypts/decrypts a RTP packet and updates SRTP context
- * (CTR block cypher mode of operation has identical encryption and
- * decryption function).
- *
- * @param buf RTP packet to be en-/decrypted
- * @param len RTP packet length
- *
- * @return 0 on success, in case of error:
- * EINVAL malformatted RTP packet
- * EACCES replayed packet or out-of-window or sync lost
- */
-static int srtp_crypt (srtp_session_t *s, uint8_t *buf, size_t len)
-{
- assert (s != NULL);
- assert (len >= 12u);
-
- if ((buf[0] >> 6) != 2)
- return EINVAL;
-
- /* Computes encryption offset */
- uint16_t offset = 12;
- offset += (buf[0] & 0xf) * 4; // skips CSRC
-
- if (buf[0] & 0x10)
- {
- uint16_t extlen;
-
- offset += 4;
- if (len < offset)
- return EINVAL;
-
- memcpy (&extlen, buf + offset - 2, 2);
- offset += htons (extlen); // skips RTP extension header
- }
-
- if (len < offset)
- return EINVAL;
-
- /* Determines RTP 48-bits counter and SSRC */
- uint16_t seq = rtp_seq (buf);
- uint32_t roc = srtp_compute_roc (s, seq), ssrc;
- memcpy (&ssrc, buf + 8, 4);
-
- /* Updates ROC and sequence (it's safe now) */
- int16_t diff = seq - s->rtp_seq;
- if (diff > 0)
- {
- /* Sequence in the future, good */
- s->rtp.window = s->rtp.window << diff;
- s->rtp.window |= UINT64_C(1);
- s->rtp_seq = seq, s->rtp_roc = roc;
- }
- else
- {
- /* Sequence in the past/present, bad */
- diff = -diff;
- if ((diff >= 64) || ((s->rtp.window >> diff) & 1))
- return EACCES; /* Replay attack */
- s->rtp.window |= UINT64_C(1) << diff;
- }
-
- /* Encrypt/Decrypt */
- if (s->flags & SRTP_UNENCRYPTED)
- return 0;
-
- if (rtp_crypt (s->rtp.cipher, ssrc, roc, seq, s->rtp.salt,
- buf + offset, len - offset))
- return EINVAL;
-
- return 0;
-}
-
-
-/**
- * Turns a RTP packet into a SRTP packet: encrypt it, then computes
- * the authentication tag and appends it.
- * Note that you can encrypt packet in disorder.
- *
- * @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 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
- * (<lenp> will hold the required byte size)
- * EACCES packet would trigger a replay error on receiver
- */
-int
-srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize)
-{
- size_t len = *lenp;
- size_t tag_len;
- size_t roc_len = 0;
-
- /* Compute required buffer size */
- if (len < 12u)
- return EINVAL;
-
- if (!(s->flags & SRTP_UNAUTHENTICATED))
- {
- tag_len = s->tag_len;
-
- if (rcc_mode (s))
- {
- assert (tag_len >= 4);
- assert (s->rtp_rcc != 0);
- if ((rtp_seq (buf) % s->rtp_rcc) == 0)
- {
- roc_len = 4;
- if (rcc_mode (s) == 3)
- tag_len = 0; /* RCC mode 3 -> no auth*/
- else
- tag_len -= 4; /* RCC mode 1 or 2 -> auth*/
- }
- else
- {
- if (rcc_mode (s) & 1)
- tag_len = 0; /* RCC mode 1 or 3 -> no auth */
- }
- }
-
- *lenp = len + roc_len + tag_len;
- }
- else
- tag_len = 0;
-
- if (bufsize < *lenp)
- return ENOSPC;
-
- /* Encrypt payload */
- int val = srtp_crypt (s, buf, len);
- if (val)
- return val;
-
- /* Authenticate payload */
- if (!(s->flags & SRTP_UNAUTHENTICATED))
- {
- uint32_t roc = srtp_compute_roc (s, rtp_seq (buf));
- const uint8_t *tag = rtp_digest (s->rtp.mac, buf, len, roc);
-
- if (roc_len)
- {
- memcpy (buf + len, &(uint32_t){ htonl (s->rtp_roc) }, 4);
- len += 4;
- }
- memcpy (buf + len, tag, tag_len);
-#if 0
- printf ("Sent : 0x");
- for (unsigned i = 0; i < tag_len; i++)
- printf ("%02x", tag[i]);
- puts ("");
-#endif
- }
-
- return 0;
-}
-
-
-/**
- * Turns a SRTP packet into a RTP packet: authenticates the packet,
- * then decrypts it.
- *
- * @param buf RTP packet to be digested/decrypted
- * @param lenp pointer to the SRTP packet length on entry,
- * set to the RTP length on exit (undefined in case of error)
- *
- * @return 0 on success, in case of error:
- * EINVAL malformatted SRTP packet
- * EACCES authentication failed (spoofed packet or out-of-sync)
- */
-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))
- {
- 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 -= roc_len + 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->rtp.mac, buf, len, rcc);
-#if 0
- printf ("Computed: 0x");
- for (unsigned i = 0; i < tag_len; i++)
- printf ("%02x", tag[i]);
- printf ("\nReceived: 0x");
- for (unsigned i = 0; i < tag_len; i++)
- printf ("%02x", buf[len + roc_len + i]);
- puts ("");
-#endif
- if (memcmp (buf + len + roc_len, tag, 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;
- }
-
- return srtp_crypt (s, buf, len);
-}
-
-
-/** AES-CM for RTCP (salt = 14 bytes + 2 nul bytes) */
-static int
-rtcp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t index,
- const uint32_t *salt, uint8_t *data, size_t len)
-{
- return rtp_crypt (hd, ssrc, index >> 16, index & 0xffff, salt, data, len);
-}
-
-
-/** Message Authentication and Integrity for RTCP */
-static const uint8_t *
-rtcp_digest (gcry_md_hd_t md, const void *data, size_t len)
-{
- gcry_md_reset (md);
- gcry_md_write (md, data, len);
- return gcry_md_read (md, 0);
-}
-
-
-/**
- * Encrypts/decrypts a RTCP packet and updates SRTCP context
- * (CTR block cypher mode of operation has identical encryption and
- * decryption function).
- *
- * @param buf RTCP packet to be en-/decrypted
- * @param len RTCP packet length
- *
- * @return 0 on success, in case of error:
- * EINVAL malformatted RTCP packet
- */
-static int srtcp_crypt (srtp_session_t *s, uint8_t *buf, size_t len)
-{
- assert (s != NULL);
-
- /* 8-bytes unencrypted header, and 4-bytes unencrypted footer */
- if ((len < 12) || ((buf[0] >> 6) != 2))
- return EINVAL;
-
- uint32_t index;
- memcpy (&index, buf + len, 4);
- index = ntohl (index);
- if (((index >> 31) != 0) != ((s->flags & SRTCP_UNENCRYPTED) == 0))
- return EINVAL; // E-bit mismatch
-
- index &= ~(1 << 31); // clear E-bit for counter
-
- /* Updates SRTCP index (safe here) */
- int32_t diff = index - s->rtcp_index;
- if (diff > 0)
- {
- /* Packet in the future, good */
- s->rtcp.window = s->rtcp.window << diff;
- s->rtcp.window |= UINT64_C(1);
- s->rtcp_index = index;
- }
- else
- {
- /* Packet in the past/present, bad */
- diff = -diff;
- if ((diff >= 64) || ((s->rtcp.window >> diff) & 1))
- return EACCES; // replay attack!
- s->rtp.window |= UINT64_C(1) << diff;
- }
-
- /* Crypts SRTCP */
- if (s->flags & SRTCP_UNENCRYPTED)
- return 0;
-
- uint32_t ssrc;
- memcpy (&ssrc, buf + 4, 4);
-
- if (rtcp_crypt (s->rtcp.cipher, ssrc, index, s->rtp.salt,
- buf + 8, len - 8))
- return EINVAL;
- return 0;
-}
-
-
-/**
- * Turns a RTCP packet into a SRTCP packet: encrypt it, then computes
- * the authentication tag and appends it.
- *
- * @param buf RTCP packet to be encrypted/digested
- * @param lenp pointer to the RTCP packet length on entry,
- * set to the SRTCP length on exit (undefined in case of error)
- * @param bufsize size (bytes) of the packet buffer
- *
- * @return 0 on success, in case of error:
- * EINVAL malformatted RTCP packet or internal error
- * ENOSPC bufsize is too small (to add index and authentication tag)
- */
-int
-srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize)
-{
- size_t len = *lenp;
- if (bufsize < (len + 4 + s->tag_len))
- return ENOSPC;
-
- uint32_t index = ++s->rtcp_index;
- if (index >> 31)
- s->rtcp_index = index = 0; /* 31-bit wrap */
-
- if ((s->flags & SRTCP_UNENCRYPTED) == 0)
- index |= 0x80000000; /* Set Encrypted bit */
- memcpy (buf + len, &(uint32_t){ htonl (index) }, 4);
-
- int val = srtcp_crypt (s, buf, len);
- if (val)
- return val;
-
- len += 4; /* Digests SRTCP index too */
-
- const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len);
- memcpy (buf + len, tag, s->tag_len);
- *lenp = len + s->tag_len;
- return 0;
-}
-
-
-/**
- * Turns a SRTCP packet into a RTCP packet: authenticates the packet,
- * then decrypts it.
- *
- * @param buf RTCP packet to be digested/decrypted
- * @param lenp pointer to the SRTCP packet length on entry,
- * set to the RTCP length on exit (undefined in case of error)
- *
- * @return 0 on success, in case of error:
- * EINVAL malformatted SRTCP packet
- * EACCES authentication failed (spoofed packet or out-of-sync)
- */
-int
-srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp)
-{
- size_t len = *lenp;
-
- if (len < (4u + s->tag_len))
- return EINVAL;
- len -= s->tag_len;
-
- const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len);
- if (memcmp (buf + len, tag, s->tag_len))
- return EACCES;
-
- len -= 4; /* Remove SRTCP index before decryption */
- *lenp = len;
- return srtcp_crypt (s, buf, len);
-} \ No newline at end of file