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ffmpeg/libavformat/srtp.c
Andreas Rheinhardt 790f793844 avutil/common: Don't auto-include mem.h 
There are lots of files that don't need it: The number of object
files that actually need it went down from 2011 to 884 here.

Keep it for external users in order to not cause breakages.

Also improve the other headers a bit while just at it.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
2024-03-31 00:08:43 +01:00

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/*
* SRTP encryption/decryption
* Copyright (c) 2012 Martin Storsjo
*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/base64.h"
#include "libavutil/aes.h"
#include "libavutil/hmac.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "libavutil/mem.h"
#include "rtp.h"
#include "rtpdec.h"
#include "srtp.h"
void ff_srtp_free(struct SRTPContext *s)
{
if (!s)
return;
av_freep(&s->aes);
if (s->hmac)
av_hmac_free(s->hmac);
s->hmac = NULL;
}
static void encrypt_counter(struct AVAES *aes, uint8_t *iv, uint8_t *outbuf,
int outlen)
{
int i, j, outpos;
for (i = 0, outpos = 0; outpos < outlen; i++) {
uint8_t keystream[16];
AV_WB16(&iv[14], i);
av_aes_crypt(aes, keystream, iv, 1, NULL, 0);
for (j = 0; j < 16 && outpos < outlen; j++, outpos++)
outbuf[outpos] ^= keystream[j];
}
}
static void derive_key(struct AVAES *aes, const uint8_t *salt, int label,
uint8_t *out, int outlen)
{
uint8_t input[16] = { 0 };
memcpy(input, salt, 14);
// Key derivation rate assumed to be zero
input[14 - 7] ^= label;
memset(out, 0, outlen);
encrypt_counter(aes, input, out, outlen);
}
int ff_srtp_set_crypto(struct SRTPContext *s, const char *suite,
const char *params)
{
uint8_t buf[30];
ff_srtp_free(s);
// RFC 4568
if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80") ||
!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_80")) {
s->rtp_hmac_size = s->rtcp_hmac_size = 10;
} else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
s->rtp_hmac_size = s->rtcp_hmac_size = 4;
} else if (!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_32")) {
// RFC 5764 section 4.1.2
s->rtp_hmac_size = 4;
s->rtcp_hmac_size = 10;
} else {
av_log(NULL, AV_LOG_WARNING, "SRTP Crypto suite %s not supported\n",
suite);
return AVERROR(EINVAL);
}
if (av_base64_decode(buf, params, sizeof(buf)) != sizeof(buf)) {
av_log(NULL, AV_LOG_WARNING, "Incorrect amount of SRTP params\n");
return AVERROR(EINVAL);
}
// MKI and lifetime not handled yet
s->aes = av_aes_alloc();
s->hmac = av_hmac_alloc(AV_HMAC_SHA1);
if (!s->aes || !s->hmac)
return AVERROR(ENOMEM);
memcpy(s->master_key, buf, 16);
memcpy(s->master_salt, buf + 16, 14);
// RFC 3711
av_aes_init(s->aes, s->master_key, 128, 0);
derive_key(s->aes, s->master_salt, 0x00, s->rtp_key, sizeof(s->rtp_key));
derive_key(s->aes, s->master_salt, 0x02, s->rtp_salt, sizeof(s->rtp_salt));
derive_key(s->aes, s->master_salt, 0x01, s->rtp_auth, sizeof(s->rtp_auth));
derive_key(s->aes, s->master_salt, 0x03, s->rtcp_key, sizeof(s->rtcp_key));
derive_key(s->aes, s->master_salt, 0x05, s->rtcp_salt, sizeof(s->rtcp_salt));
derive_key(s->aes, s->master_salt, 0x04, s->rtcp_auth, sizeof(s->rtcp_auth));
return 0;
}
static void create_iv(uint8_t *iv, const uint8_t *salt, uint64_t index,
uint32_t ssrc)
{
uint8_t indexbuf[8];
int i;
memset(iv, 0, 16);
AV_WB32(&iv[4], ssrc);
AV_WB64(indexbuf, index);
for (i = 0; i < 8; i++) // index << 16
iv[6 + i] ^= indexbuf[i];
for (i = 0; i < 14; i++)
iv[i] ^= salt[i];
}
int ff_srtp_decrypt(struct SRTPContext *s, uint8_t *buf, int *lenptr)
{
uint8_t iv[16] = { 0 }, hmac[20];
int len = *lenptr;
int av_uninit(seq_largest);
uint32_t ssrc, av_uninit(roc);
uint64_t index;
int rtcp, hmac_size;
// TODO: Missing replay protection
if (len < 2)
return AVERROR_INVALIDDATA;
rtcp = RTP_PT_IS_RTCP(buf[1]);
hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;
if (len < hmac_size)
return AVERROR_INVALIDDATA;
// Authentication HMAC
av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
// If MKI is used, this should exclude the MKI as well
av_hmac_update(s->hmac, buf, len - hmac_size);
if (!rtcp) {
int seq = AV_RB16(buf + 2);
uint32_t v;
uint8_t rocbuf[4];
// RFC 3711 section 3.3.1, appendix A
seq_largest = s->seq_initialized ? s->seq_largest : seq;
v = roc = s->roc;
if (seq_largest < 32768) {
if (seq - seq_largest > 32768)
v = roc - 1;
} else {
if (seq_largest - 32768 > seq)
v = roc + 1;
}
if (v == roc) {
seq_largest = FFMAX(seq_largest, seq);
} else if (v == roc + 1) {
seq_largest = seq;
roc = v;
}
index = seq + (((uint64_t)v) << 16);
AV_WB32(rocbuf, roc);
av_hmac_update(s->hmac, rocbuf, 4);
}
av_hmac_final(s->hmac, hmac, sizeof(hmac));
if (memcmp(hmac, buf + len - hmac_size, hmac_size)) {
av_log(NULL, AV_LOG_WARNING, "HMAC mismatch\n");
return AVERROR_INVALIDDATA;
}
len -= hmac_size;
*lenptr = len;
if (len < 12)
return AVERROR_INVALIDDATA;
if (rtcp) {
uint32_t srtcp_index = AV_RB32(buf + len - 4);
len -= 4;
*lenptr = len;
ssrc = AV_RB32(buf + 4);
index = srtcp_index & 0x7fffffff;
buf += 8;
len -= 8;
if (!(srtcp_index & 0x80000000))
return 0;
} else {
int ext, csrc;
s->seq_initialized = 1;
s->seq_largest = seq_largest;
s->roc = roc;
csrc = buf[0] & 0x0f;
ext = buf[0] & 0x10;
ssrc = AV_RB32(buf + 8);
buf += 12;
len -= 12;
buf += 4 * csrc;
len -= 4 * csrc;
if (len < 0)
return AVERROR_INVALIDDATA;
if (ext) {
if (len < 4)
return AVERROR_INVALIDDATA;
ext = (AV_RB16(buf + 2) + 1) * 4;
if (len < ext)
return AVERROR_INVALIDDATA;
len -= ext;
buf += ext;
}
}
create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
encrypt_counter(s->aes, iv, buf, len);
return 0;
}
int ff_srtp_encrypt(struct SRTPContext *s, const uint8_t *in, int len,
uint8_t *out, int outlen)
{
uint8_t iv[16] = { 0 }, hmac[20];
uint64_t index;
uint32_t ssrc;
int rtcp, hmac_size, padding;
uint8_t *buf;
if (len < 8)
return AVERROR_INVALIDDATA;
rtcp = RTP_PT_IS_RTCP(in[1]);
hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;
padding = hmac_size;
if (rtcp)
padding += 4; // For the RTCP index
if (len + padding > outlen)
return 0;
memcpy(out, in, len);
buf = out;
if (rtcp) {
ssrc = AV_RB32(buf + 4);
index = s->rtcp_index++;
buf += 8;
len -= 8;
} else {
int ext, csrc;
int seq = AV_RB16(buf + 2);
if (len < 12)
return AVERROR_INVALIDDATA;
ssrc = AV_RB32(buf + 8);
if (seq < s->seq_largest)
s->roc++;
s->seq_largest = seq;
index = seq + (((uint64_t)s->roc) << 16);
csrc = buf[0] & 0x0f;
ext = buf[0] & 0x10;
buf += 12;
len -= 12;
buf += 4 * csrc;
len -= 4 * csrc;
if (len < 0)
return AVERROR_INVALIDDATA;
if (ext) {
if (len < 4)
return AVERROR_INVALIDDATA;
ext = (AV_RB16(buf + 2) + 1) * 4;
if (len < ext)
return AVERROR_INVALIDDATA;
len -= ext;
buf += ext;
}
}
create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
encrypt_counter(s->aes, iv, buf, len);
if (rtcp) {
AV_WB32(buf + len, 0x80000000 | index);
len += 4;
}
av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
av_hmac_update(s->hmac, out, buf + len - out);
if (!rtcp) {
uint8_t rocbuf[4];
AV_WB32(rocbuf, s->roc);
av_hmac_update(s->hmac, rocbuf, 4);
}
av_hmac_final(s->hmac, hmac, sizeof(hmac));
memcpy(buf + len, hmac, hmac_size);
len += hmac_size;
return buf + len - out;
}
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