forked from KolibriOS/kolibrios
315 lines
11 KiB
C
315 lines
11 KiB
C
/*
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* Audible AA demuxer
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* Copyright (c) 2015 Vesselin Bontchev
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*
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* Header parsing is borrowed from https://github.com/jteeuwen/audible project.
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* Copyright (c) 2001-2014, Jim Teeuwen
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*
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* Redistribution and use in source and binary forms, with or without modification,
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* are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
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* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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* ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "avformat.h"
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#include "internal.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/tea.h"
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#include "libavutil/opt.h"
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#define AA_MAGIC 1469084982 /* this identifies an audible .aa file */
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#define MAX_CODEC_SECOND_SIZE 3982
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#define MAX_TOC_ENTRIES 16
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#define MAX_DICTIONARY_ENTRIES 128
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#define TEA_BLOCK_SIZE 8
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typedef struct AADemuxContext {
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AVClass *class;
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uint8_t *aa_fixed_key;
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int aa_fixed_key_len;
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int codec_second_size;
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int current_codec_second_size;
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int chapter_idx;
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struct AVTEA *tea_ctx;
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uint8_t file_key[16];
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int64_t current_chapter_size;
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} AADemuxContext;
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static int get_second_size(char *codec_name)
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{
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int result = -1;
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if (!strcmp(codec_name, "mp332")) {
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result = 3982;
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} else if (!strcmp(codec_name, "acelp16")) {
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result = 2000;
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} else if (!strcmp(codec_name, "acelp85")) {
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result = 1045;
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}
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return result;
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}
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static int aa_read_header(AVFormatContext *s)
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{
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int i, j, idx, largest_idx = -1;
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uint32_t nkey, nval, toc_size, npairs, header_seed, start;
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char key[128], val[128], codec_name[64] = {0};
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uint8_t output[24], dst[8], src[8];
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int64_t largest_size = -1, current_size = -1;
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struct toc_entry {
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uint32_t offset;
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uint32_t size;
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} TOC[MAX_TOC_ENTRIES];
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uint32_t header_key_part[4];
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uint8_t header_key[16];
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AADemuxContext *c = s->priv_data;
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AVIOContext *pb = s->pb;
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AVStream *st;
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/* parse .aa header */
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avio_skip(pb, 4); // file size
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avio_skip(pb, 4); // magic string
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toc_size = avio_rb32(pb); // TOC size
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avio_skip(pb, 4); // unidentified integer
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if (toc_size > MAX_TOC_ENTRIES)
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return AVERROR_INVALIDDATA;
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for (i = 0; i < toc_size; i++) { // read TOC
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avio_skip(pb, 4); // TOC entry index
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TOC[i].offset = avio_rb32(pb); // block offset
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TOC[i].size = avio_rb32(pb); // block size
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}
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avio_skip(pb, 24); // header termination block (ignored)
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npairs = avio_rb32(pb); // read dictionary entries
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if (npairs > MAX_DICTIONARY_ENTRIES)
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return AVERROR_INVALIDDATA;
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for (i = 0; i < npairs; i++) {
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memset(val, 0, sizeof(val));
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memset(key, 0, sizeof(key));
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avio_skip(pb, 1); // unidentified integer
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nkey = avio_rb32(pb); // key string length
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nval = avio_rb32(pb); // value string length
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if (nkey > sizeof(key)) {
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avio_skip(pb, nkey);
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} else {
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avio_read(pb, key, nkey); // key string
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}
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if (nval > sizeof(val)) {
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avio_skip(pb, nval);
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} else {
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avio_read(pb, val, nval); // value string
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}
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if (!strcmp(key, "codec")) {
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av_log(s, AV_LOG_DEBUG, "Codec is <%s>\n", val);
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strncpy(codec_name, val, sizeof(codec_name) - 1);
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}
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if (!strcmp(key, "HeaderSeed")) {
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av_log(s, AV_LOG_DEBUG, "HeaderSeed is <%s>\n", val);
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header_seed = atoi(val);
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}
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if (!strcmp(key, "HeaderKey")) { // this looks like "1234567890 1234567890 1234567890 1234567890"
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av_log(s, AV_LOG_DEBUG, "HeaderKey is <%s>\n", val);
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sscanf(val, "%u%u%u%u", &header_key_part[0], &header_key_part[1], &header_key_part[2], &header_key_part[3]);
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for (idx = 0; idx < 4; idx++) {
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AV_WB32(&header_key[idx * 4], header_key_part[idx]); // convert each part to BE!
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}
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av_log(s, AV_LOG_DEBUG, "Processed HeaderKey is ");
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for (i = 0; i < 16; i++)
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av_log(s, AV_LOG_DEBUG, "%02x", header_key[i]);
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av_log(s, AV_LOG_DEBUG, "\n");
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}
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}
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/* verify fixed key */
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if (c->aa_fixed_key_len != 16) {
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av_log(s, AV_LOG_ERROR, "aa_fixed_key value needs to be 16 bytes!\n");
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return AVERROR(EINVAL);
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}
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/* verify codec */
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if ((c->codec_second_size = get_second_size(codec_name)) == -1) {
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av_log(s, AV_LOG_ERROR, "unknown codec <%s>!\n", codec_name);
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return AVERROR(EINVAL);
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}
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/* decryption key derivation */
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c->tea_ctx = av_tea_alloc();
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if (!c->tea_ctx)
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return AVERROR(ENOMEM);
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av_tea_init(c->tea_ctx, c->aa_fixed_key, 16);
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output[0] = output[1] = 0; // purely for padding purposes
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memcpy(output + 2, header_key, 16);
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idx = 0;
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for (i = 0; i < 3; i++) { // TEA CBC with weird mixed endianness
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AV_WB32(src, header_seed);
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AV_WB32(src + 4, header_seed + 1);
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header_seed += 2;
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av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 0); // TEA ECB encrypt
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for (j = 0; j < TEA_BLOCK_SIZE && idx < 18; j+=1, idx+=1) {
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output[idx] = output[idx] ^ dst[j];
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}
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}
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memcpy(c->file_key, output + 2, 16); // skip first 2 bytes of output
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av_log(s, AV_LOG_DEBUG, "File key is ");
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for (i = 0; i < 16; i++)
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av_log(s, AV_LOG_DEBUG, "%02x", c->file_key[i]);
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av_log(s, AV_LOG_DEBUG, "\n");
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/* decoder setup */
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st = avformat_new_stream(s, NULL);
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if (!st) {
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av_freep(&c->tea_ctx);
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return AVERROR(ENOMEM);
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}
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st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
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if (!strcmp(codec_name, "mp332")) {
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st->codec->codec_id = AV_CODEC_ID_MP3;
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st->codec->sample_rate = 22050;
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st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
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st->start_time = 0;
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} else if (!strcmp(codec_name, "acelp85")) {
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st->codec->codec_id = AV_CODEC_ID_SIPR;
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st->codec->block_align = 19;
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st->codec->channels = 1;
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st->codec->sample_rate = 8500;
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} else if (!strcmp(codec_name, "acelp16")) {
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st->codec->codec_id = AV_CODEC_ID_SIPR;
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st->codec->block_align = 20;
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st->codec->channels = 1;
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st->codec->sample_rate = 16000;
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}
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/* determine, and jump to audio start offset */
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for (i = 1; i < toc_size; i++) { // skip the first entry!
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current_size = TOC[i].size;
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if (current_size > largest_size) {
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largest_idx = i;
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largest_size = current_size;
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}
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}
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start = TOC[largest_idx].offset;
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avio_seek(pb, start, SEEK_SET);
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c->current_chapter_size = 0;
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return 0;
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}
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static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
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{
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uint8_t dst[TEA_BLOCK_SIZE];
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uint8_t src[TEA_BLOCK_SIZE];
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int i;
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int trailing_bytes;
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int blocks;
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uint8_t buf[MAX_CODEC_SECOND_SIZE * 2];
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int written = 0;
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int ret;
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AADemuxContext *c = s->priv_data;
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// are we at the start of a chapter?
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if (c->current_chapter_size == 0) {
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c->current_chapter_size = avio_rb32(s->pb);
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if (c->current_chapter_size == 0) {
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return AVERROR_EOF;
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}
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av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size);
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c->chapter_idx = c->chapter_idx + 1;
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avio_skip(s->pb, 4); // data start offset
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c->current_codec_second_size = c->codec_second_size;
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}
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// is this the last block in this chapter?
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if (c->current_chapter_size / c->current_codec_second_size == 0) {
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c->current_codec_second_size = c->current_chapter_size % c->current_codec_second_size;
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}
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// decrypt c->current_codec_second_size bytes
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blocks = c->current_codec_second_size / TEA_BLOCK_SIZE;
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for (i = 0; i < blocks; i++) {
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avio_read(s->pb, src, TEA_BLOCK_SIZE);
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av_tea_init(c->tea_ctx, c->file_key, 16);
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av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 1);
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memcpy(buf + written, dst, TEA_BLOCK_SIZE);
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written = written + TEA_BLOCK_SIZE;
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}
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trailing_bytes = c->current_codec_second_size % TEA_BLOCK_SIZE;
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if (trailing_bytes != 0) { // trailing bytes are left unencrypted!
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avio_read(s->pb, src, trailing_bytes);
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memcpy(buf + written, src, trailing_bytes);
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written = written + trailing_bytes;
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}
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// update state
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c->current_chapter_size = c->current_chapter_size - c->current_codec_second_size;
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if (c->current_chapter_size <= 0)
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c->current_chapter_size = 0;
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ret = av_new_packet(pkt, written);
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if (ret < 0)
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return ret;
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memcpy(pkt->data, buf, written);
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return 0;
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}
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static int aa_probe(AVProbeData *p)
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{
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uint8_t *buf = p->buf;
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// first 4 bytes are file size, next 4 bytes are the magic
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if (AV_RB32(buf+4) != AA_MAGIC)
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return 0;
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return AVPROBE_SCORE_MAX / 2;
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}
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static int aa_read_close(AVFormatContext *s)
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{
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AADemuxContext *c = s->priv_data;
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av_freep(&c->tea_ctx);
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return 0;
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}
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#define OFFSET(x) offsetof(AADemuxContext, x)
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static const AVOption aa_options[] = {
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{ "aa_fixed_key", // extracted from libAAX_SDK.so and AAXSDKWin.dll files!
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"Fixed key used for handling Audible AA files", OFFSET(aa_fixed_key),
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AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd2a51d673"},
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.flags = AV_OPT_FLAG_DECODING_PARAM },
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{ NULL },
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};
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static const AVClass aa_class = {
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.class_name = "aa",
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.item_name = av_default_item_name,
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.option = aa_options,
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.version = LIBAVUTIL_VERSION_INT,
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};
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AVInputFormat ff_aa_demuxer = {
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.name = "aa",
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.long_name = NULL_IF_CONFIG_SMALL("Audible AA format files"),
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.priv_class = &aa_class,
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.priv_data_size = sizeof(AADemuxContext),
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.extensions = "aa",
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.read_probe = aa_probe,
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.read_header = aa_read_header,
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.read_packet = aa_read_packet,
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.read_close = aa_read_close,
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.flags = AVFMT_GENERIC_INDEX,
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};
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