1 /*
2 * Apple HTTP Live Streaming Sample Encryption/Decryption
3 *
4 * Copyright (c) 2021 Nachiket Tarate
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 /**
24 * @file
25 * Apple HTTP Live Streaming Sample Encryption
26 * https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/HLS_Sample_Encryption
27 */
28
29 #include "libavutil/aes.h"
30 #include "libavutil/channel_layout.h"
31
32 #include "hls_sample_encryption.h"
33
34 #include "libavcodec/adts_header.h"
35 #include "libavcodec/adts_parser.h"
36 #include "libavcodec/ac3tab.h"
37 #include "libavcodec/ac3_parser_internal.h"
38
39
40 typedef struct NALUnit {
41 uint8_t *data;
42 int type;
43 int length;
44 int start_code_length;
45 } NALUnit;
46
47 typedef struct AudioFrame {
48 uint8_t *data;
49 int length;
50 int header_length;
51 } AudioFrame;
52
53 typedef struct CodecParserContext {
54 const uint8_t *buf_ptr;
55 const uint8_t *buf_end;
56 } CodecParserContext;
57
58 static const int eac3_sample_rate_tab[] = { 48000, 44100, 32000, 0 };
59
ff_hls_senc_read_audio_setup_info(HLSAudioSetupInfo *info, const uint8_t *buf, size_t size)60 void ff_hls_senc_read_audio_setup_info(HLSAudioSetupInfo *info, const uint8_t *buf, size_t size)
61 {
62 if (size < 8)
63 return;
64
65 info->codec_tag = AV_RL32(buf);
66
67 if (info->codec_tag == MKTAG('z','a','a','c'))
68 info->codec_id = AV_CODEC_ID_AAC;
69 else if (info->codec_tag == MKTAG('z','a','c','3'))
70 info->codec_id = AV_CODEC_ID_AC3;
71 else if (info->codec_tag == MKTAG('z','e','c','3'))
72 info->codec_id = AV_CODEC_ID_EAC3;
73 else
74 info->codec_id = AV_CODEC_ID_NONE;
75
76 buf += 4;
77 info->priming = AV_RL16(buf);
78 buf += 2;
79 info->version = *buf++;
80 info->setup_data_length = *buf++;
81
82 if (info->setup_data_length > size - 8)
83 info->setup_data_length = size - 8;
84
85 if (info->setup_data_length > HLS_MAX_AUDIO_SETUP_DATA_LEN)
86 return;
87
88 memcpy(info->setup_data, buf, info->setup_data_length);
89 }
90
ff_hls_senc_parse_audio_setup_info(AVStream *st, HLSAudioSetupInfo *info)91 int ff_hls_senc_parse_audio_setup_info(AVStream *st, HLSAudioSetupInfo *info)
92 {
93 int ret = 0;
94
95 st->codecpar->codec_tag = info->codec_tag;
96
97 if (st->codecpar->codec_id == AV_CODEC_ID_AAC)
98 return 0;
99
100 if (st->codecpar->codec_id != AV_CODEC_ID_AC3 && st->codecpar->codec_id != AV_CODEC_ID_EAC3)
101 return AVERROR_INVALIDDATA;
102
103 if (st->codecpar->codec_id == AV_CODEC_ID_AC3) {
104 AC3HeaderInfo *ac3hdr = NULL;
105
106 ret = avpriv_ac3_parse_header(&ac3hdr, info->setup_data, info->setup_data_length);
107 if (ret < 0) {
108 if (ret != AVERROR(ENOMEM))
109 av_free(ac3hdr);
110 return ret;
111 }
112
113 st->codecpar->sample_rate = ac3hdr->sample_rate;
114 av_channel_layout_uninit(&st->codecpar->ch_layout);
115 av_channel_layout_from_mask(&st->codecpar->ch_layout, ac3hdr->channel_layout);
116 st->codecpar->bit_rate = ac3hdr->bit_rate;
117
118 av_free(ac3hdr);
119 } else { /* Parse 'dec3' EC3SpecificBox */
120 GetBitContext gb;
121 uint64_t mask;
122 int data_rate, fscod, acmod, lfeon;
123
124 ret = init_get_bits8(&gb, info->setup_data, info->setup_data_length);
125 if (ret < 0)
126 return AVERROR_INVALIDDATA;
127
128 data_rate = get_bits(&gb, 13);
129 skip_bits(&gb, 3);
130 fscod = get_bits(&gb, 2);
131 skip_bits(&gb, 10);
132 acmod = get_bits(&gb, 3);
133 lfeon = get_bits(&gb, 1);
134
135 st->codecpar->sample_rate = eac3_sample_rate_tab[fscod];
136
137 mask = ff_ac3_channel_layout_tab[acmod];
138 if (lfeon)
139 mask |= AV_CH_LOW_FREQUENCY;
140
141 av_channel_layout_uninit(&st->codecpar->ch_layout);
142 av_channel_layout_from_mask(&st->codecpar->ch_layout, mask);
143
144 st->codecpar->bit_rate = data_rate*1000;
145 }
146
147 return 0;
148 }
149
150 /*
151 * Remove start code emulation prevention 0x03 bytes
152 */
remove_scep_3_bytes(NALUnit *nalu)153 static void remove_scep_3_bytes(NALUnit *nalu)
154 {
155 int i = 0;
156 int j = 0;
157
158 uint8_t *data = nalu->data;
159
160 while (i < nalu->length) {
161 if (nalu->length - i > 3 && AV_RB24(&data[i]) == 0x000003) {
162 data[j++] = data[i++];
163 data[j++] = data[i++];
164 i++;
165 } else {
166 data[j++] = data[i++];
167 }
168 }
169
170 nalu->length = j;
171 }
172
get_next_nal_unit(CodecParserContext *ctx, NALUnit *nalu)173 static int get_next_nal_unit(CodecParserContext *ctx, NALUnit *nalu)
174 {
175 const uint8_t *nalu_start = ctx->buf_ptr;
176
177 if (ctx->buf_end - ctx->buf_ptr >= 4 && AV_RB32(ctx->buf_ptr) == 0x00000001)
178 nalu->start_code_length = 4;
179 else if (ctx->buf_end - ctx->buf_ptr >= 3 && AV_RB24(ctx->buf_ptr) == 0x000001)
180 nalu->start_code_length = 3;
181 else /* No start code at the beginning of the NAL unit */
182 return -1;
183
184 ctx->buf_ptr += nalu->start_code_length;
185
186 while (ctx->buf_ptr < ctx->buf_end) {
187 if (ctx->buf_end - ctx->buf_ptr >= 4 && AV_RB32(ctx->buf_ptr) == 0x00000001)
188 break;
189 else if (ctx->buf_end - ctx->buf_ptr >= 3 && AV_RB24(ctx->buf_ptr) == 0x000001)
190 break;
191 ctx->buf_ptr++;
192 }
193
194 nalu->data = (uint8_t *)nalu_start + nalu->start_code_length;
195 nalu->length = ctx->buf_ptr - nalu->data;
196 nalu->type = *nalu->data & 0x1F;
197
198 return 0;
199 }
200
decrypt_nal_unit(HLSCryptoContext *crypto_ctx, NALUnit *nalu)201 static int decrypt_nal_unit(HLSCryptoContext *crypto_ctx, NALUnit *nalu)
202 {
203 int ret = 0;
204 int rem_bytes;
205 uint8_t *data;
206 uint8_t iv[16];
207
208 ret = av_aes_init(crypto_ctx->aes_ctx, crypto_ctx->key, 16 * 8, 1);
209 if (ret < 0)
210 return ret;
211
212 /* Remove start code emulation prevention 0x03 bytes */
213 remove_scep_3_bytes(nalu);
214
215 data = nalu->data + 32;
216 rem_bytes = nalu->length - 32;
217
218 memcpy(iv, crypto_ctx->iv, 16);
219
220 while (rem_bytes > 0) {
221 if (rem_bytes > 16) {
222 av_aes_crypt(crypto_ctx->aes_ctx, data, data, 1, iv, 1);
223 data += 16;
224 rem_bytes -= 16;
225 }
226 data += FFMIN(144, rem_bytes);
227 rem_bytes -= FFMIN(144, rem_bytes);
228 }
229
230 return 0;
231 }
232
decrypt_video_frame(HLSCryptoContext *crypto_ctx, AVPacket *pkt)233 static int decrypt_video_frame(HLSCryptoContext *crypto_ctx, AVPacket *pkt)
234 {
235 int ret = 0;
236 CodecParserContext ctx;
237 NALUnit nalu;
238 uint8_t *data_ptr;
239 int move_nalu = 0;
240
241 memset(&ctx, 0, sizeof(ctx));
242 ctx.buf_ptr = pkt->data;
243 ctx.buf_end = pkt->data + pkt->size;
244
245 data_ptr = pkt->data;
246
247 while (ctx.buf_ptr < ctx.buf_end) {
248 memset(&nalu, 0, sizeof(nalu));
249 ret = get_next_nal_unit(&ctx, &nalu);
250 if (ret < 0)
251 return ret;
252 if ((nalu.type == 0x01 || nalu.type == 0x05) && nalu.length > 48) {
253 int encrypted_nalu_length = nalu.length;
254 ret = decrypt_nal_unit(crypto_ctx, &nalu);
255 if (ret < 0)
256 return ret;
257 move_nalu = nalu.length != encrypted_nalu_length;
258 }
259 if (move_nalu)
260 memmove(data_ptr, nalu.data - nalu.start_code_length, nalu.start_code_length + nalu.length);
261 data_ptr += nalu.start_code_length + nalu.length;
262 }
263
264 av_shrink_packet(pkt, data_ptr - pkt->data);
265
266 return 0;
267 }
268
get_next_adts_frame(CodecParserContext *ctx, AudioFrame *frame)269 static int get_next_adts_frame(CodecParserContext *ctx, AudioFrame *frame)
270 {
271 int ret = 0;
272
273 AACADTSHeaderInfo *adts_hdr = NULL;
274
275 /* Find next sync word 0xFFF */
276 while (ctx->buf_ptr < ctx->buf_end - 1) {
277 if (*ctx->buf_ptr == 0xFF && (*(ctx->buf_ptr + 1) & 0xF0) == 0xF0)
278 break;
279 ctx->buf_ptr++;
280 }
281
282 if (ctx->buf_ptr >= ctx->buf_end - 1)
283 return -1;
284
285 frame->data = (uint8_t*)ctx->buf_ptr;
286
287 ret = avpriv_adts_header_parse (&adts_hdr, frame->data, ctx->buf_end - frame->data);
288 if (ret < 0)
289 return ret;
290
291 frame->header_length = adts_hdr->crc_absent ? AV_AAC_ADTS_HEADER_SIZE : AV_AAC_ADTS_HEADER_SIZE + 2;
292 frame->length = adts_hdr->frame_length;
293
294 av_free(adts_hdr);
295
296 return 0;
297 }
298
get_next_ac3_eac3_sync_frame(CodecParserContext *ctx, AudioFrame *frame)299 static int get_next_ac3_eac3_sync_frame(CodecParserContext *ctx, AudioFrame *frame)
300 {
301 int ret = 0;
302
303 AC3HeaderInfo *hdr = NULL;
304
305 /* Find next sync word 0x0B77 */
306 while (ctx->buf_ptr < ctx->buf_end - 1) {
307 if (*ctx->buf_ptr == 0x0B && *(ctx->buf_ptr + 1) == 0x77)
308 break;
309 ctx->buf_ptr++;
310 }
311
312 if (ctx->buf_ptr >= ctx->buf_end - 1)
313 return -1;
314
315 frame->data = (uint8_t*)ctx->buf_ptr;
316 frame->header_length = 0;
317
318 ret = avpriv_ac3_parse_header(&hdr, frame->data, ctx->buf_end - frame->data);
319 if (ret < 0) {
320 if (ret != AVERROR(ENOMEM))
321 av_free(hdr);
322 return ret;
323 }
324
325 frame->length = hdr->frame_size;
326
327 av_free(hdr);
328
329 return 0;
330 }
331
get_next_sync_frame(enum AVCodecID codec_id, CodecParserContext *ctx, AudioFrame *frame)332 static int get_next_sync_frame(enum AVCodecID codec_id, CodecParserContext *ctx, AudioFrame *frame)
333 {
334 if (codec_id == AV_CODEC_ID_AAC)
335 return get_next_adts_frame(ctx, frame);
336 else if (codec_id == AV_CODEC_ID_AC3 || codec_id == AV_CODEC_ID_EAC3)
337 return get_next_ac3_eac3_sync_frame(ctx, frame);
338 else
339 return AVERROR_INVALIDDATA;
340 }
341
decrypt_sync_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AudioFrame *frame)342 static int decrypt_sync_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AudioFrame *frame)
343 {
344 int ret = 0;
345 uint8_t *data;
346 int num_of_encrypted_blocks;
347
348 ret = av_aes_init(crypto_ctx->aes_ctx, crypto_ctx->key, 16 * 8, 1);
349 if (ret < 0)
350 return ret;
351
352 data = frame->data + frame->header_length + 16;
353
354 num_of_encrypted_blocks = (frame->length - frame->header_length - 16)/16;
355
356 av_aes_crypt(crypto_ctx->aes_ctx, data, data, num_of_encrypted_blocks, crypto_ctx->iv, 1);
357
358 return 0;
359 }
360
decrypt_audio_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)361 static int decrypt_audio_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)
362 {
363 int ret = 0;
364 CodecParserContext ctx;
365 AudioFrame frame;
366
367 memset(&ctx, 0, sizeof(ctx));
368 ctx.buf_ptr = pkt->data;
369 ctx.buf_end = pkt->data + pkt->size;
370
371 while (ctx.buf_ptr < ctx.buf_end) {
372 memset(&frame, 0, sizeof(frame));
373 ret = get_next_sync_frame(codec_id, &ctx, &frame);
374 if (ret < 0)
375 return ret;
376 if (frame.length - frame.header_length > 31) {
377 ret = decrypt_sync_frame(codec_id, crypto_ctx, &frame);
378 if (ret < 0)
379 return ret;
380 }
381 ctx.buf_ptr += frame.length;
382 }
383
384 return 0;
385 }
386
ff_hls_senc_decrypt_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)387 int ff_hls_senc_decrypt_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)
388 {
389 if (codec_id == AV_CODEC_ID_H264)
390 return decrypt_video_frame(crypto_ctx, pkt);
391 else if (codec_id == AV_CODEC_ID_AAC || codec_id == AV_CODEC_ID_AC3 || codec_id == AV_CODEC_ID_EAC3)
392 return decrypt_audio_frame(codec_id, crypto_ctx, pkt);
393
394 return AVERROR_INVALIDDATA;
395 }
396