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srtp.c
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1 /*
2  * SRTP encryption/decryption
3  * Copyright (c) 2012 Martin Storsjo
4  *
5  * This file is part of FFmpeg.
6  *
7  * FFmpeg is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU Lesser General Public
9  * License as published by the Free Software Foundation; either
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #include "libavutil/base64.h"
23 #include "libavutil/aes.h"
24 #include "libavutil/hmac.h"
25 #include "libavutil/intreadwrite.h"
26 #include "libavutil/log.h"
27 #include "rtp.h"
28 #include "rtpdec.h"
29 #include "srtp.h"
30 
31 void ff_srtp_free(struct SRTPContext *s)
32 {
33  if (!s)
34  return;
35  av_freep(&s->aes);
36  if (s->hmac)
37  av_hmac_free(s->hmac);
38  s->hmac = NULL;
39 }
40 
41 static void encrypt_counter(struct AVAES *aes, uint8_t *iv, uint8_t *outbuf,
42  int outlen)
43 {
44  int i, j, outpos;
45  for (i = 0, outpos = 0; outpos < outlen; i++) {
46  uint8_t keystream[16];
47  AV_WB16(&iv[14], i);
48  av_aes_crypt(aes, keystream, iv, 1, NULL, 0);
49  for (j = 0; j < 16 && outpos < outlen; j++, outpos++)
50  outbuf[outpos] ^= keystream[j];
51  }
52 }
53 
54 static void derive_key(struct AVAES *aes, const uint8_t *salt, int label,
55  uint8_t *out, int outlen)
56 {
57  uint8_t input[16] = { 0 };
58  memcpy(input, salt, 14);
59  // Key derivation rate assumed to be zero
60  input[14 - 7] ^= label;
61  memset(out, 0, outlen);
62  encrypt_counter(aes, input, out, outlen);
63 }
64 
65 int ff_srtp_set_crypto(struct SRTPContext *s, const char *suite,
66  const char *params)
67 {
68  uint8_t buf[30];
69 
70  ff_srtp_free(s);
71 
72  // RFC 4568
73  if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80") ||
74  !strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_80")) {
75  s->rtp_hmac_size = s->rtcp_hmac_size = 10;
76  } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
77  s->rtp_hmac_size = s->rtcp_hmac_size = 4;
78  } else if (!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_32")) {
79  // RFC 5764 section 4.1.2
80  s->rtp_hmac_size = 4;
81  s->rtcp_hmac_size = 10;
82  } else {
83  av_log(NULL, AV_LOG_WARNING, "SRTP Crypto suite %s not supported\n",
84  suite);
85  return AVERROR(EINVAL);
86  }
87  if (av_base64_decode(buf, params, sizeof(buf)) != sizeof(buf)) {
88  av_log(NULL, AV_LOG_WARNING, "Incorrect amount of SRTP params\n");
89  return AVERROR(EINVAL);
90  }
91  // MKI and lifetime not handled yet
92  s->aes = av_aes_alloc();
94  if (!s->aes || !s->hmac)
95  return AVERROR(ENOMEM);
96  memcpy(s->master_key, buf, 16);
97  memcpy(s->master_salt, buf + 16, 14);
98 
99  // RFC 3711
100  av_aes_init(s->aes, s->master_key, 128, 0);
101 
102  derive_key(s->aes, s->master_salt, 0x00, s->rtp_key, sizeof(s->rtp_key));
103  derive_key(s->aes, s->master_salt, 0x02, s->rtp_salt, sizeof(s->rtp_salt));
104  derive_key(s->aes, s->master_salt, 0x01, s->rtp_auth, sizeof(s->rtp_auth));
105 
106  derive_key(s->aes, s->master_salt, 0x03, s->rtcp_key, sizeof(s->rtcp_key));
107  derive_key(s->aes, s->master_salt, 0x05, s->rtcp_salt, sizeof(s->rtcp_salt));
108  derive_key(s->aes, s->master_salt, 0x04, s->rtcp_auth, sizeof(s->rtcp_auth));
109  return 0;
110 }
111 
112 static void create_iv(uint8_t *iv, const uint8_t *salt, uint64_t index,
113  uint32_t ssrc)
114 {
115  uint8_t indexbuf[8];
116  int i;
117  memset(iv, 0, 16);
118  AV_WB32(&iv[4], ssrc);
119  AV_WB64(indexbuf, index);
120  for (i = 0; i < 8; i++) // index << 16
121  iv[6 + i] ^= indexbuf[i];
122  for (i = 0; i < 14; i++)
123  iv[i] ^= salt[i];
124 }
125 
126 int ff_srtp_decrypt(struct SRTPContext *s, uint8_t *buf, int *lenptr)
127 {
128  uint8_t iv[16] = { 0 }, hmac[20];
129  int len = *lenptr;
130  int av_uninit(seq_largest);
131  uint32_t ssrc, av_uninit(roc);
132  uint64_t index;
133  int rtcp, hmac_size;
134 
135  // TODO: Missing replay protection
136 
137  if (len < 2)
138  return AVERROR_INVALIDDATA;
139 
140  rtcp = RTP_PT_IS_RTCP(buf[1]);
141  hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;
142 
143  if (len < hmac_size)
144  return AVERROR_INVALIDDATA;
145 
146  // Authentication HMAC
147  av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
148  // If MKI is used, this should exclude the MKI as well
149  av_hmac_update(s->hmac, buf, len - hmac_size);
150 
151  if (!rtcp) {
152  int seq = AV_RB16(buf + 2);
153  uint32_t v;
154  uint8_t rocbuf[4];
155 
156  // RFC 3711 section 3.3.1, appendix A
157  seq_largest = s->seq_initialized ? s->seq_largest : seq;
158  v = roc = s->roc;
159  if (seq_largest < 32768) {
160  if (seq - seq_largest > 32768)
161  v = roc - 1;
162  } else {
163  if (seq_largest - 32768 > seq)
164  v = roc + 1;
165  }
166  if (v == roc) {
167  seq_largest = FFMAX(seq_largest, seq);
168  } else if (v == roc + 1) {
169  seq_largest = seq;
170  roc = v;
171  }
172  index = seq + (((uint64_t)v) << 16);
173 
174  AV_WB32(rocbuf, roc);
175  av_hmac_update(s->hmac, rocbuf, 4);
176  }
177 
178  av_hmac_final(s->hmac, hmac, sizeof(hmac));
179  if (memcmp(hmac, buf + len - hmac_size, hmac_size)) {
180  av_log(NULL, AV_LOG_WARNING, "HMAC mismatch\n");
181  return AVERROR_INVALIDDATA;
182  }
183 
184  len -= hmac_size;
185  *lenptr = len;
186 
187  if (len < 12)
188  return AVERROR_INVALIDDATA;
189 
190  if (rtcp) {
191  uint32_t srtcp_index = AV_RB32(buf + len - 4);
192  len -= 4;
193  *lenptr = len;
194 
195  ssrc = AV_RB32(buf + 4);
196  index = srtcp_index & 0x7fffffff;
197 
198  buf += 8;
199  len -= 8;
200  if (!(srtcp_index & 0x80000000))
201  return 0;
202  } else {
203  int ext, csrc;
204  s->seq_initialized = 1;
206  s->roc = roc;
207 
208  csrc = buf[0] & 0x0f;
209  ext = buf[0] & 0x10;
210  ssrc = AV_RB32(buf + 8);
211 
212  buf += 12;
213  len -= 12;
214 
215  buf += 4 * csrc;
216  len -= 4 * csrc;
217  if (len < 0)
218  return AVERROR_INVALIDDATA;
219 
220  if (ext) {
221  if (len < 4)
222  return AVERROR_INVALIDDATA;
223  ext = (AV_RB16(buf + 2) + 1) * 4;
224  if (len < ext)
225  return AVERROR_INVALIDDATA;
226  len -= ext;
227  buf += ext;
228  }
229  }
230 
231  create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
232  av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
233  encrypt_counter(s->aes, iv, buf, len);
234 
235  return 0;
236 }
237 
238 int ff_srtp_encrypt(struct SRTPContext *s, const uint8_t *in, int len,
239  uint8_t *out, int outlen)
240 {
241  uint8_t iv[16] = { 0 }, hmac[20];
242  uint64_t index;
243  uint32_t ssrc;
244  int rtcp, hmac_size, padding;
245  uint8_t *buf;
246 
247  if (len < 8)
248  return AVERROR_INVALIDDATA;
249 
250  rtcp = RTP_PT_IS_RTCP(in[1]);
251  hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;
252  padding = hmac_size;
253  if (rtcp)
254  padding += 4; // For the RTCP index
255 
256  if (len + padding > outlen)
257  return 0;
258 
259  memcpy(out, in, len);
260  buf = out;
261 
262  if (rtcp) {
263  ssrc = AV_RB32(buf + 4);
264  index = s->rtcp_index++;
265 
266  buf += 8;
267  len -= 8;
268  } else {
269  int ext, csrc;
270  int seq = AV_RB16(buf + 2);
271 
272  if (len < 12)
273  return AVERROR_INVALIDDATA;
274 
275  ssrc = AV_RB32(buf + 8);
276 
277  if (seq < s->seq_largest)
278  s->roc++;
279  s->seq_largest = seq;
280  index = seq + (((uint64_t)s->roc) << 16);
281 
282  csrc = buf[0] & 0x0f;
283  ext = buf[0] & 0x10;
284 
285  buf += 12;
286  len -= 12;
287 
288  buf += 4 * csrc;
289  len -= 4 * csrc;
290  if (len < 0)
291  return AVERROR_INVALIDDATA;
292 
293  if (ext) {
294  if (len < 4)
295  return AVERROR_INVALIDDATA;
296  ext = (AV_RB16(buf + 2) + 1) * 4;
297  if (len < ext)
298  return AVERROR_INVALIDDATA;
299  len -= ext;
300  buf += ext;
301  }
302  }
303 
304  create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
305  av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
306  encrypt_counter(s->aes, iv, buf, len);
307 
308  if (rtcp) {
309  AV_WB32(buf + len, 0x80000000 | index);
310  len += 4;
311  }
312 
313  av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
314  av_hmac_update(s->hmac, out, buf + len - out);
315  if (!rtcp) {
316  uint8_t rocbuf[4];
317  AV_WB32(rocbuf, s->roc);
318  av_hmac_update(s->hmac, rocbuf, 4);
319  }
320  av_hmac_final(s->hmac, hmac, sizeof(hmac));
321 
322  memcpy(buf + len, hmac, hmac_size);
323  len += hmac_size;
324  return buf + len - out;
325 }
int rtp_hmac_size
Definition: srtp.h:33
#define NULL
Definition: coverity.c:32
const char * s
Definition: avisynth_c.h:631
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
int ff_srtp_encrypt(struct SRTPContext *s, const uint8_t *in, int len, uint8_t *out, int outlen)
Definition: srtp.c:238
AVHMAC * av_hmac_alloc(enum AVHMACType type)
Allocate an AVHMAC context.
Definition: hmac.c:61
#define AV_LOG_WARNING
Something somehow does not look correct.
Definition: log.h:182
static void encrypt_counter(struct AVAES *aes, uint8_t *iv, uint8_t *outbuf, int outlen)
Definition: srtp.c:41
void av_aes_crypt(AVAES *a, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt)
Encrypt or decrypt a buffer using a previously initialized context.
Definition: aes.c:163
uint8_t rtcp_auth[20]
Definition: srtp.h:38
uint8_t rtp_auth[20]
Definition: srtp.h:38
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_WB32 unsigned int_TMPL AV_WB24 unsigned int_TMPL AV_RB16
Definition: bytestream.h:87
uint8_t rtcp_salt[14]
Definition: srtp.h:37
#define AV_WB64(p, v)
Definition: intreadwrite.h:433
int seq_initialized
Definition: srtp.h:39
static void derive_key(struct AVAES *aes, const uint8_t *salt, int label, uint8_t *out, int outlen)
Definition: srtp.c:54
void ff_srtp_free(struct SRTPContext *s)
Definition: srtp.c:31
uint8_t
uint64_t_TMPL AV_WL64 unsigned int_TMPL AV_WL32 unsigned int_TMPL AV_WL24 unsigned int_TMPL AV_WL16 uint64_t_TMPL AV_WB64 unsigned int_TMPL AV_RB32
Definition: bytestream.h:87
struct AVHMAC * hmac
Definition: srtp.h:32
void av_hmac_update(AVHMAC *c, const uint8_t *data, unsigned int len)
Hash data with the HMAC.
Definition: hmac.c:155
uint8_t master_salt[14]
Definition: srtp.h:35
#define AV_WB16(p, v)
Definition: intreadwrite.h:405
#define av_log(a,...)
struct AVAES * aes
Definition: srtp.h:31
#define AVERROR(e)
Definition: error.h:43
uint8_t rtcp_key[16]
Definition: srtp.h:36
int seq_largest
Definition: srtp.h:39
GLenum GLint * params
Definition: opengl_enc.c:114
struct AVAES * av_aes_alloc(void)
Allocate an AVAES context.
Definition: aes.c:31
#define FFMAX(a, b)
Definition: common.h:94
static void create_iv(uint8_t *iv, const uint8_t *salt, uint64_t index, uint32_t ssrc)
Definition: srtp.c:112
int ff_srtp_decrypt(struct SRTPContext *s, uint8_t *buf, int *lenptr)
Definition: srtp.c:126
void av_hmac_init(AVHMAC *c, const uint8_t *key, unsigned int keylen)
Initialize an AVHMAC context with an authentication key.
Definition: hmac.c:134
uint8_t rtp_key[16]
Definition: srtp.h:36
FILE * out
Definition: movenc-test.c:54
int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
Initialize an AVAES context.
Definition: aes.c:195
uint8_t pi<< 24) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_U8, uint8_t,(*(constuint8_t *) pi-0x80)*(1.0f/(1<< 7))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_U8, uint8_t,(*(constuint8_t *) pi-0x80)*(1.0/(1<< 7))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_S16, int16_t,(*(constint16_t *) pi >>8)+0x80) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_S16, int16_t,*(constint16_t *) pi *(1.0f/(1<< 15))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_S16, int16_t,*(constint16_t *) pi *(1.0/(1<< 15))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_S32, int32_t,(*(constint32_t *) pi >>24)+0x80) CONV_FUNC_GROUP(AV_SAMPLE_FMT_FLT, float, AV_SAMPLE_FMT_S32, int32_t,*(constint32_t *) pi *(1.0f/(1U<< 31))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_DBL, double, AV_SAMPLE_FMT_S32, int32_t,*(constint32_t *) pi *(1.0/(1U<< 31))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_FLT, float, av_clip_uint8(lrintf(*(constfloat *) pi *(1<< 7))+0x80)) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S16, int16_t, AV_SAMPLE_FMT_FLT, float, av_clip_int16(lrintf(*(constfloat *) pi *(1<< 15)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S32, int32_t, AV_SAMPLE_FMT_FLT, float, av_clipl_int32(llrintf(*(constfloat *) pi *(1U<< 31)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_U8, uint8_t, AV_SAMPLE_FMT_DBL, double, av_clip_uint8(lrint(*(constdouble *) pi *(1<< 7))+0x80)) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S16, int16_t, AV_SAMPLE_FMT_DBL, double, av_clip_int16(lrint(*(constdouble *) pi *(1<< 15)))) CONV_FUNC_GROUP(AV_SAMPLE_FMT_S32, int32_t, AV_SAMPLE_FMT_DBL, double, av_clipl_int32(llrint(*(constdouble *) pi *(1U<< 31))))#defineSET_CONV_FUNC_GROUP(ofmt, ifmt) staticvoidset_generic_function(AudioConvert *ac){}voidff_audio_convert_free(AudioConvert **ac){if(!*ac) return;ff_dither_free(&(*ac) ->dc);av_freep(ac);}AudioConvert *ff_audio_convert_alloc(AVAudioResampleContext *avr, enumAVSampleFormatout_fmt, enumAVSampleFormatin_fmt, intchannels, intsample_rate, intapply_map){AudioConvert *ac;intin_planar, out_planar;ac=av_mallocz(sizeof(*ac));if(!ac) returnNULL;ac->avr=avr;ac->out_fmt=out_fmt;ac->in_fmt=in_fmt;ac->channels=channels;ac->apply_map=apply_map;if(avr->dither_method!=AV_RESAMPLE_DITHER_NONE &&av_get_packed_sample_fmt(out_fmt)==AV_SAMPLE_FMT_S16 &&av_get_bytes_per_sample(in_fmt)>2){ac->dc=ff_dither_alloc(avr, out_fmt, in_fmt, channels, sample_rate, apply_map);if(!ac->dc){av_free(ac);returnNULL;}returnac;}in_planar=ff_sample_fmt_is_planar(in_fmt, channels);out_planar=ff_sample_fmt_is_planar(out_fmt, channels);if(in_planar==out_planar){ac->func_type=CONV_FUNC_TYPE_FLAT;ac->planes=in_planar?ac->channels:1;}elseif(in_planar) ac->func_type=CONV_FUNC_TYPE_INTERLEAVE;elseac->func_type=CONV_FUNC_TYPE_DEINTERLEAVE;set_generic_function(ac);if(ARCH_AARCH64) ff_audio_convert_init_aarch64(ac);if(ARCH_ARM) ff_audio_convert_init_arm(ac);if(ARCH_X86) ff_audio_convert_init_x86(ac);returnac;}intff_audio_convert(AudioConvert *ac, AudioData *out, AudioData *in){intuse_generic=1;intlen=in->nb_samples;intp;if(ac->dc){av_log(ac->avr, AV_LOG_TRACE,"%dsamples-audio_convert:%sto%s(dithered)\n", len, av_get_sample_fmt_name(ac->in_fmt), av_get_sample_fmt_name(ac->out_fmt));returnff_convert_dither(ac-> in
void * buf
Definition: avisynth_c.h:553
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
int index
Definition: gxfenc.c:89
uint8_t master_key[16]
Definition: srtp.h:34
int av_hmac_final(AVHMAC *c, uint8_t *out, unsigned int outlen)
Finish hashing and output the HMAC digest.
Definition: hmac.c:160
#define RTP_PT_IS_RTCP(x)
Definition: rtp.h:110
uint32_t rtcp_index
Definition: srtp.h:42
void av_hmac_free(AVHMAC *c)
Free an AVHMAC context.
Definition: hmac.c:126
int len
int ff_srtp_set_crypto(struct SRTPContext *s, const char *suite, const char *params)
Definition: srtp.c:65
int rtcp_hmac_size
Definition: srtp.h:33
int av_base64_decode(uint8_t *out, const char *in_str, int out_size)
Decode a base64-encoded string.
Definition: base64.c:79
uint8_t rtp_salt[14]
Definition: srtp.h:37
#define av_uninit(x)
Definition: attributes.h:149
#define av_freep(p)
uint32_t roc
Definition: srtp.h:40