libavformat/hls: add support for decryption of HLS media segments encrypted using SAMPLE-AES encryption method
Apple HTTP Live Streaming Sample Encryption: https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/HLS_Sample_Encryption Signed-off-by: Nachiket Tarate <nachiket.programmer@gmail.com> Signed-off-by: Steven Liu <lq@chinaffmpeg.org>
This commit is contained in:
Nachiket Tarate
committed by
Steven Liu
Steven Liu
parent
ef0f5d1be6
commit
ff958b3846
389
libavformat/hls_sample_encryption.c
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389
libavformat/hls_sample_encryption.c
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/*
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* Apple HTTP Live Streaming Sample Encryption/Decryption
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*
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* Copyright (c) 2021 Nachiket Tarate
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* Apple HTTP Live Streaming Sample Encryption
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* https://developer.apple.com/library/ios/documentation/AudioVideo/Conceptual/HLS_Sample_Encryption
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*/
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#include "hls_sample_encryption.h"
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#include "libavcodec/adts_header.h"
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#include "libavcodec/adts_parser.h"
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#include "libavcodec/ac3_parser_internal.h"
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typedef struct NALUnit {
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uint8_t *data;
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int type;
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int length;
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int start_code_length;
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} NALUnit;
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typedef struct AudioFrame {
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uint8_t *data;
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int length;
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int header_length;
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} AudioFrame;
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typedef struct CodecParserContext {
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const uint8_t *buf_ptr;
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const uint8_t *buf_end;
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} CodecParserContext;
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static const int eac3_sample_rate_tab[] = { 48000, 44100, 32000, 0 };
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void ff_hls_senc_read_audio_setup_info(HLSAudioSetupInfo *info, const uint8_t *buf, size_t size)
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{
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if (size < 8)
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return;
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info->codec_tag = AV_RL32(buf);
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if (info->codec_tag == MKTAG('z','a','a','c'))
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info->codec_id = AV_CODEC_ID_AAC;
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else if (info->codec_tag == MKTAG('z','a','c','3'))
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info->codec_id = AV_CODEC_ID_AC3;
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else if (info->codec_tag == MKTAG('z','e','c','3'))
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info->codec_id = AV_CODEC_ID_EAC3;
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else
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info->codec_id = AV_CODEC_ID_NONE;
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buf += 4;
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info->priming = AV_RL16(buf);
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buf += 2;
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info->version = *buf++;
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info->setup_data_length = *buf++;
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if (info->setup_data_length > size - 8)
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info->setup_data_length = size - 8;
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if (info->setup_data_length > HLS_MAX_AUDIO_SETUP_DATA_LEN)
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return;
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memcpy(info->setup_data, buf, info->setup_data_length);
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}
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int ff_hls_senc_parse_audio_setup_info(AVStream *st, HLSAudioSetupInfo *info)
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{
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int ret = 0;
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st->codecpar->codec_tag = info->codec_tag;
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if (st->codecpar->codec_id == AV_CODEC_ID_AAC)
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return 0;
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if (st->codecpar->codec_id != AV_CODEC_ID_AC3 && st->codecpar->codec_id != AV_CODEC_ID_EAC3)
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return AVERROR_INVALIDDATA;
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if (st->codecpar->codec_id == AV_CODEC_ID_AC3) {
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AC3HeaderInfo *ac3hdr = NULL;
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ret = avpriv_ac3_parse_header(&ac3hdr, info->setup_data, info->setup_data_length);
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if (ret < 0) {
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if (ret != AVERROR(ENOMEM))
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av_free(ac3hdr);
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return ret;
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}
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st->codecpar->sample_rate = ac3hdr->sample_rate;
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st->codecpar->channels = ac3hdr->channels;
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st->codecpar->channel_layout = ac3hdr->channel_layout;
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st->codecpar->bit_rate = ac3hdr->bit_rate;
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av_free(ac3hdr);
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} else { /* Parse 'dec3' EC3SpecificBox */
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GetBitContext gb;
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int data_rate, fscod, acmod, lfeon;
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ret = init_get_bits8(&gb, info->setup_data, info->setup_data_length);
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if (ret < 0)
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return AVERROR_INVALIDDATA;
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data_rate = get_bits(&gb, 13);
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skip_bits(&gb, 3);
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fscod = get_bits(&gb, 2);
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skip_bits(&gb, 10);
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acmod = get_bits(&gb, 3);
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lfeon = get_bits(&gb, 1);
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st->codecpar->sample_rate = eac3_sample_rate_tab[fscod];
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st->codecpar->channel_layout = avpriv_ac3_channel_layout_tab[acmod];
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if (lfeon)
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st->codecpar->channel_layout |= AV_CH_LOW_FREQUENCY;
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st->codecpar->channels = av_get_channel_layout_nb_channels(st->codecpar->channel_layout);
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st->codecpar->bit_rate = data_rate*1000;
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}
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return 0;
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}
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/*
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* Remove start code emulation prevention 0x03 bytes
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*/
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static void remove_scep_3_bytes(NALUnit *nalu)
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{
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int i = 0;
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int j = 0;
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uint8_t *data = nalu->data;
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while (i < nalu->length) {
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if (nalu->length - i > 3 && AV_RB24(&data[i]) == 0x000003) {
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data[j++] = data[i++];
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data[j++] = data[i++];
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i++;
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} else {
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data[j++] = data[i++];
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}
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}
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nalu->length = j;
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}
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static int get_next_nal_unit(CodecParserContext *ctx, NALUnit *nalu)
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{
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const uint8_t *nalu_start = ctx->buf_ptr;
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if (ctx->buf_end - ctx->buf_ptr >= 4 && AV_RB32(ctx->buf_ptr) == 0x00000001)
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nalu->start_code_length = 4;
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else if (ctx->buf_end - ctx->buf_ptr >= 3 && AV_RB24(ctx->buf_ptr) == 0x000001)
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nalu->start_code_length = 3;
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else /* No start code at the beginning of the NAL unit */
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return -1;
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ctx->buf_ptr += nalu->start_code_length;
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while (ctx->buf_ptr < ctx->buf_end) {
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if (ctx->buf_end - ctx->buf_ptr >= 4 && AV_RB32(ctx->buf_ptr) == 0x00000001)
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break;
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else if (ctx->buf_end - ctx->buf_ptr >= 3 && AV_RB24(ctx->buf_ptr) == 0x000001)
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break;
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ctx->buf_ptr++;
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}
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nalu->data = (uint8_t *)nalu_start + nalu->start_code_length;
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nalu->length = ctx->buf_ptr - nalu->data;
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nalu->type = *nalu->data & 0x1F;
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return 0;
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}
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static int decrypt_nal_unit(HLSCryptoContext *crypto_ctx, NALUnit *nalu)
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{
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int ret = 0;
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int rem_bytes;
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uint8_t *data;
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uint8_t iv[16];
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ret = av_aes_init(crypto_ctx->aes_ctx, crypto_ctx->key, 16 * 8, 1);
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if (ret < 0)
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return ret;
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/* Remove start code emulation prevention 0x03 bytes */
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remove_scep_3_bytes(nalu);
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data = nalu->data + 32;
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rem_bytes = nalu->length - 32;
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memcpy(iv, crypto_ctx->iv, 16);
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while (rem_bytes > 0) {
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if (rem_bytes > 16) {
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av_aes_crypt(crypto_ctx->aes_ctx, data, data, 1, iv, 1);
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data += 16;
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rem_bytes -= 16;
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}
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data += FFMIN(144, rem_bytes);
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rem_bytes -= FFMIN(144, rem_bytes);
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}
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return 0;
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}
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static int decrypt_video_frame(HLSCryptoContext *crypto_ctx, AVPacket *pkt)
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{
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int ret = 0;
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CodecParserContext ctx;
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NALUnit nalu;
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uint8_t *data_ptr;
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int move_nalu = 0;
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memset(&ctx, 0, sizeof(ctx));
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ctx.buf_ptr = pkt->data;
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ctx.buf_end = pkt->data + pkt->size;
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data_ptr = pkt->data;
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while (ctx.buf_ptr < ctx.buf_end) {
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memset(&nalu, 0, sizeof(nalu));
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ret = get_next_nal_unit(&ctx, &nalu);
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if (ret < 0)
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return ret;
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if ((nalu.type == 0x01 || nalu.type == 0x05) && nalu.length > 48) {
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int encrypted_nalu_length = nalu.length;
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ret = decrypt_nal_unit(crypto_ctx, &nalu);
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if (ret < 0)
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return ret;
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move_nalu = nalu.length != encrypted_nalu_length;
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}
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if (move_nalu)
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memmove(data_ptr, nalu.data - nalu.start_code_length, nalu.start_code_length + nalu.length);
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data_ptr += nalu.start_code_length + nalu.length;
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}
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av_shrink_packet(pkt, data_ptr - pkt->data);
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return 0;
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}
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static int get_next_adts_frame(CodecParserContext *ctx, AudioFrame *frame)
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{
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int ret = 0;
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AACADTSHeaderInfo *adts_hdr = NULL;
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/* Find next sync word 0xFFF */
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while (ctx->buf_ptr < ctx->buf_end - 1) {
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if (*ctx->buf_ptr == 0xFF && *(ctx->buf_ptr + 1) & 0xF0 == 0xF0)
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break;
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ctx->buf_ptr++;
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}
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if (ctx->buf_ptr >= ctx->buf_end - 1)
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return -1;
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frame->data = (uint8_t*)ctx->buf_ptr;
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ret = avpriv_adts_header_parse (&adts_hdr, frame->data, ctx->buf_end - frame->data);
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if (ret < 0)
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return ret;
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frame->header_length = adts_hdr->crc_absent ? AV_AAC_ADTS_HEADER_SIZE : AV_AAC_ADTS_HEADER_SIZE + 2;
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frame->length = adts_hdr->frame_length;
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av_free(adts_hdr);
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return 0;
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}
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static int get_next_ac3_eac3_sync_frame(CodecParserContext *ctx, AudioFrame *frame)
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{
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int ret = 0;
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AC3HeaderInfo *hdr = NULL;
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/* Find next sync word 0x0B77 */
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while (ctx->buf_ptr < ctx->buf_end - 1) {
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if (*ctx->buf_ptr == 0x0B && *(ctx->buf_ptr + 1) == 0x77)
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break;
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ctx->buf_ptr++;
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}
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if (ctx->buf_ptr >= ctx->buf_end - 1)
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return -1;
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frame->data = (uint8_t*)ctx->buf_ptr;
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frame->header_length = 0;
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ret = avpriv_ac3_parse_header(&hdr, frame->data, ctx->buf_end - frame->data);
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if (ret < 0) {
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if (ret != AVERROR(ENOMEM))
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av_free(hdr);
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return ret;
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}
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frame->length = hdr->frame_size;
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av_free(hdr);
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return 0;
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}
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static int get_next_sync_frame(enum AVCodecID codec_id, CodecParserContext *ctx, AudioFrame *frame)
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{
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if (codec_id == AV_CODEC_ID_AAC)
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return get_next_adts_frame(ctx, frame);
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else if (codec_id == AV_CODEC_ID_AC3 || codec_id == AV_CODEC_ID_EAC3)
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return get_next_ac3_eac3_sync_frame(ctx, frame);
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else
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return AVERROR_INVALIDDATA;
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}
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static int decrypt_sync_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AudioFrame *frame)
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{
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int ret = 0;
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uint8_t *data;
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int num_of_encrypted_blocks;
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ret = av_aes_init(crypto_ctx->aes_ctx, crypto_ctx->key, 16 * 8, 1);
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if (ret < 0)
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return ret;
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data = frame->data + frame->header_length + 16;
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num_of_encrypted_blocks = (frame->length - frame->header_length - 16)/16;
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av_aes_crypt(crypto_ctx->aes_ctx, data, data, num_of_encrypted_blocks, crypto_ctx->iv, 1);
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return 0;
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}
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static int decrypt_audio_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)
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{
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int ret = 0;
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CodecParserContext ctx;
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AudioFrame frame;
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memset(&ctx, 0, sizeof(ctx));
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ctx.buf_ptr = pkt->data;
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ctx.buf_end = pkt->data + pkt->size;
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while (ctx.buf_ptr < ctx.buf_end) {
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memset(&frame, 0, sizeof(frame));
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ret = get_next_sync_frame(codec_id, &ctx, &frame);
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if (ret < 0)
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return ret;
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if (frame.length - frame.header_length > 31) {
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ret = decrypt_sync_frame(codec_id, crypto_ctx, &frame);
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if (ret < 0)
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return ret;
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}
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ctx.buf_ptr += frame.length;
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}
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return 0;
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}
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int ff_hls_senc_decrypt_frame(enum AVCodecID codec_id, HLSCryptoContext *crypto_ctx, AVPacket *pkt)
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{
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if (codec_id == AV_CODEC_ID_H264)
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return decrypt_video_frame(crypto_ctx, pkt);
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else if (codec_id == AV_CODEC_ID_AAC || codec_id == AV_CODEC_ID_AC3 || codec_id == AV_CODEC_ID_EAC3)
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return decrypt_audio_frame(codec_id, crypto_ctx, pkt);
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return AVERROR_INVALIDDATA;
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}
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