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aadec.c
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1 /*
2  * Audible AA demuxer
3  * Copyright (c) 2015 Vesselin Bontchev
4  *
5  * Header parsing is borrowed from https://github.com/jteeuwen/audible project.
6  * Copyright (c) 2001-2014, Jim Teeuwen
7  *
8  * Redistribution and use in source and binary forms, with or without modification,
9  * are permitted provided that the following conditions are met:
10  *
11  * 1. Redistributions of source code must retain the above copyright notice, this
12  * list of conditions and the following disclaimer.
13  *
14  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
15  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
16  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
17  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
18  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
19  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
20  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
21  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
23  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24  */
25 
26 #include "avformat.h"
27 #include "internal.h"
28 #include "libavutil/intreadwrite.h"
29 #include "libavutil/tea.h"
30 #include "libavutil/opt.h"
31 
32 #define AA_MAGIC 1469084982 /* this identifies an audible .aa file */
33 #define MAX_CODEC_SECOND_SIZE 3982
34 #define MAX_TOC_ENTRIES 16
35 #define MAX_DICTIONARY_ENTRIES 128
36 #define TEA_BLOCK_SIZE 8
37 
38 typedef struct AADemuxContext {
39  AVClass *class;
45  struct AVTEA *tea_ctx;
49 
50 static int get_second_size(char *codec_name)
51 {
52  int result = -1;
53 
54  if (!strcmp(codec_name, "mp332")) {
55  result = 3982;
56  } else if (!strcmp(codec_name, "acelp16")) {
57  result = 2000;
58  } else if (!strcmp(codec_name, "acelp85")) {
59  result = 1045;
60  }
61 
62  return result;
63 }
64 
66 {
67  int i, j, idx, largest_idx = -1;
68  uint32_t nkey, nval, toc_size, npairs, header_seed = 0, start;
69  char key[128], val[128], codec_name[64] = {0};
70  uint8_t output[24], dst[8], src[8];
71  int64_t largest_size = -1, current_size = -1;
72  struct toc_entry {
73  uint32_t offset;
74  uint32_t size;
75  } TOC[MAX_TOC_ENTRIES];
76  uint32_t header_key_part[4];
77  uint8_t header_key[16] = {0};
79  AVIOContext *pb = s->pb;
80  AVStream *st;
81 
82  /* parse .aa header */
83  avio_skip(pb, 4); // file size
84  avio_skip(pb, 4); // magic string
85  toc_size = avio_rb32(pb); // TOC size
86  avio_skip(pb, 4); // unidentified integer
87  if (toc_size > MAX_TOC_ENTRIES)
88  return AVERROR_INVALIDDATA;
89  for (i = 0; i < toc_size; i++) { // read TOC
90  avio_skip(pb, 4); // TOC entry index
91  TOC[i].offset = avio_rb32(pb); // block offset
92  TOC[i].size = avio_rb32(pb); // block size
93  }
94  avio_skip(pb, 24); // header termination block (ignored)
95  npairs = avio_rb32(pb); // read dictionary entries
96  if (npairs > MAX_DICTIONARY_ENTRIES)
97  return AVERROR_INVALIDDATA;
98  for (i = 0; i < npairs; i++) {
99  memset(val, 0, sizeof(val));
100  memset(key, 0, sizeof(key));
101  avio_skip(pb, 1); // unidentified integer
102  nkey = avio_rb32(pb); // key string length
103  nval = avio_rb32(pb); // value string length
104  if (nkey > sizeof(key)) {
105  avio_skip(pb, nkey);
106  } else {
107  avio_read(pb, key, nkey); // key string
108  }
109  if (nval > sizeof(val)) {
110  avio_skip(pb, nval);
111  } else {
112  avio_read(pb, val, nval); // value string
113  }
114  if (!strcmp(key, "codec")) {
115  av_log(s, AV_LOG_DEBUG, "Codec is <%s>\n", val);
116  strncpy(codec_name, val, sizeof(codec_name) - 1);
117  }
118  if (!strcmp(key, "HeaderSeed")) {
119  av_log(s, AV_LOG_DEBUG, "HeaderSeed is <%s>\n", val);
120  header_seed = atoi(val);
121  }
122  if (!strcmp(key, "HeaderKey")) { // this looks like "1234567890 1234567890 1234567890 1234567890"
123  av_log(s, AV_LOG_DEBUG, "HeaderKey is <%s>\n", val);
124  sscanf(val, "%u%u%u%u", &header_key_part[0], &header_key_part[1], &header_key_part[2], &header_key_part[3]);
125  for (idx = 0; idx < 4; idx++) {
126  AV_WB32(&header_key[idx * 4], header_key_part[idx]); // convert each part to BE!
127  }
128  av_log(s, AV_LOG_DEBUG, "Processed HeaderKey is ");
129  for (i = 0; i < 16; i++)
130  av_log(s, AV_LOG_DEBUG, "%02x", header_key[i]);
131  av_log(s, AV_LOG_DEBUG, "\n");
132  }
133  }
134 
135  /* verify fixed key */
136  if (c->aa_fixed_key_len != 16) {
137  av_log(s, AV_LOG_ERROR, "aa_fixed_key value needs to be 16 bytes!\n");
138  return AVERROR(EINVAL);
139  }
140 
141  /* verify codec */
142  if ((c->codec_second_size = get_second_size(codec_name)) == -1) {
143  av_log(s, AV_LOG_ERROR, "unknown codec <%s>!\n", codec_name);
144  return AVERROR(EINVAL);
145  }
146 
147  /* decryption key derivation */
148  c->tea_ctx = av_tea_alloc();
149  if (!c->tea_ctx)
150  return AVERROR(ENOMEM);
151  av_tea_init(c->tea_ctx, c->aa_fixed_key, 16);
152  output[0] = output[1] = 0; // purely for padding purposes
153  memcpy(output + 2, header_key, 16);
154  idx = 0;
155  for (i = 0; i < 3; i++) { // TEA CBC with weird mixed endianness
156  AV_WB32(src, header_seed);
157  AV_WB32(src + 4, header_seed + 1);
158  header_seed += 2;
159  av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 0); // TEA ECB encrypt
160  for (j = 0; j < TEA_BLOCK_SIZE && idx < 18; j+=1, idx+=1) {
161  output[idx] = output[idx] ^ dst[j];
162  }
163  }
164  memcpy(c->file_key, output + 2, 16); // skip first 2 bytes of output
165  av_log(s, AV_LOG_DEBUG, "File key is ");
166  for (i = 0; i < 16; i++)
167  av_log(s, AV_LOG_DEBUG, "%02x", c->file_key[i]);
168  av_log(s, AV_LOG_DEBUG, "\n");
169 
170  /* decoder setup */
171  st = avformat_new_stream(s, NULL);
172  if (!st) {
173  av_freep(&c->tea_ctx);
174  return AVERROR(ENOMEM);
175  }
177  if (!strcmp(codec_name, "mp332")) {
179  st->codecpar->sample_rate = 22050;
181  st->start_time = 0;
182  } else if (!strcmp(codec_name, "acelp85")) {
184  st->codecpar->block_align = 19;
185  st->codecpar->channels = 1;
186  st->codecpar->sample_rate = 8500;
187  } else if (!strcmp(codec_name, "acelp16")) {
189  st->codecpar->block_align = 20;
190  st->codecpar->channels = 1;
191  st->codecpar->sample_rate = 16000;
192  }
193 
194  /* determine, and jump to audio start offset */
195  for (i = 1; i < toc_size; i++) { // skip the first entry!
196  current_size = TOC[i].size;
197  if (current_size > largest_size) {
198  largest_idx = i;
199  largest_size = current_size;
200  }
201  }
202  start = TOC[largest_idx].offset;
203  avio_seek(pb, start, SEEK_SET);
204  c->current_chapter_size = 0;
205 
206  return 0;
207 }
208 
210 {
211  uint8_t dst[TEA_BLOCK_SIZE];
213  int i;
214  int trailing_bytes;
215  int blocks;
217  int written = 0;
218  int ret;
219  AADemuxContext *c = s->priv_data;
220 
221  // are we at the start of a chapter?
222  if (c->current_chapter_size == 0) {
224  if (c->current_chapter_size == 0) {
225  return AVERROR_EOF;
226  }
227  av_log(s, AV_LOG_DEBUG, "Chapter %d (%" PRId64 " bytes)\n", c->chapter_idx, c->current_chapter_size);
228  c->chapter_idx = c->chapter_idx + 1;
229  avio_skip(s->pb, 4); // data start offset
231  }
232 
233  // is this the last block in this chapter?
236  }
237 
238  // decrypt c->current_codec_second_size bytes
240  for (i = 0; i < blocks; i++) {
241  avio_read(s->pb, src, TEA_BLOCK_SIZE);
242  av_tea_init(c->tea_ctx, c->file_key, 16);
243  av_tea_crypt(c->tea_ctx, dst, src, 1, NULL, 1);
244  memcpy(buf + written, dst, TEA_BLOCK_SIZE);
245  written = written + TEA_BLOCK_SIZE;
246  }
247  trailing_bytes = c->current_codec_second_size % TEA_BLOCK_SIZE;
248  if (trailing_bytes != 0) { // trailing bytes are left unencrypted!
249  avio_read(s->pb, src, trailing_bytes);
250  memcpy(buf + written, src, trailing_bytes);
251  written = written + trailing_bytes;
252  }
253 
254  // update state
256  if (c->current_chapter_size <= 0)
257  c->current_chapter_size = 0;
258 
259  ret = av_new_packet(pkt, written);
260  if (ret < 0)
261  return ret;
262  memcpy(pkt->data, buf, written);
263 
264  return 0;
265 }
266 
267 static int aa_probe(AVProbeData *p)
268 {
269  uint8_t *buf = p->buf;
270 
271  // first 4 bytes are file size, next 4 bytes are the magic
272  if (AV_RB32(buf+4) != AA_MAGIC)
273  return 0;
274 
275  return AVPROBE_SCORE_MAX / 2;
276 }
277 
279 {
280  AADemuxContext *c = s->priv_data;
281 
282  av_freep(&c->tea_ctx);
283 
284  return 0;
285 }
286 
287 #define OFFSET(x) offsetof(AADemuxContext, x)
288 static const AVOption aa_options[] = {
289  { "aa_fixed_key", // extracted from libAAX_SDK.so and AAXSDKWin.dll files!
290  "Fixed key used for handling Audible AA files", OFFSET(aa_fixed_key),
291  AV_OPT_TYPE_BINARY, {.str="77214d4b196a87cd520045fd2a51d673"},
292  .flags = AV_OPT_FLAG_DECODING_PARAM },
293  { NULL },
294 };
295 
296 static const AVClass aa_class = {
297  .class_name = "aa",
298  .item_name = av_default_item_name,
299  .option = aa_options,
300  .version = LIBAVUTIL_VERSION_INT,
301 };
302 
304  .name = "aa",
305  .long_name = NULL_IF_CONFIG_SMALL("Audible AA format files"),
306  .priv_class = &aa_class,
307  .priv_data_size = sizeof(AADemuxContext),
308  .extensions = "aa",
309  .read_probe = aa_probe,
314 };
#define NULL
Definition: coverity.c:32
const char const char void * val
Definition: avisynth_c.h:771
const char * s
Definition: avisynth_c.h:768
Bytestream IO Context.
Definition: avio.h:147
#define AVERROR_INVALIDDATA
Invalid data found when processing input.
Definition: error.h:59
AVOption.
Definition: opt.h:245
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
uint8_t file_key[16]
Definition: aadec.c:46
#define AA_MAGIC
Definition: aadec.c:32
static int aa_read_packet(AVFormatContext *s, AVPacket *pkt)
Definition: aadec.c:209
enum AVCodecID codec_id
Specific type of the encoded data (the codec used).
Definition: avcodec.h:3980
int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
fseek() equivalent for AVIOContext.
Definition: aviobuf.c:230
int current_codec_second_size
Definition: aadec.c:43
int64_t avio_skip(AVIOContext *s, int64_t offset)
Skip given number of bytes forward.
Definition: aviobuf.c:304
static AVPacket pkt
struct AVTEA * av_tea_alloc(void)
Allocate an AVTEA context To free the struct: av_free(ptr)
Definition: tea.c:35
Format I/O context.
Definition: avformat.h:1338
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:72
uint8_t
static int aa_probe(AVProbeData *p)
Definition: aadec.c:267
AVOptions.
#define MAX_CODEC_SECOND_SIZE
Definition: aadec.c:33
unsigned int avio_rb32(AVIOContext *s)
Definition: aviobuf.c:757
static const AVOption aa_options[]
Definition: aadec.c:288
enum AVStreamParseType need_parsing
Definition: avformat.h:1076
AVStream * avformat_new_stream(AVFormatContext *s, const AVCodec *c)
Add a new stream to a media file.
Definition: utils.c:4193
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
Definition: tea.c:30
uint8_t * data
Definition: avcodec.h:1601
#define AVERROR_EOF
End of file.
Definition: error.h:55
static av_cold int read_close(AVFormatContext *ctx)
Definition: libcdio.c:145
ptrdiff_t size
Definition: opengl_enc.c:101
AVInputFormat ff_aa_demuxer
Definition: aadec.c:303
full parsing and repack with timestamp and position generation by parser for raw this assumes that ea...
Definition: avformat.h:814
#define av_log(a,...)
int avio_read(AVIOContext *s, unsigned char *buf, int size)
Read size bytes from AVIOContext into buf.
Definition: aviobuf.c:604
int av_new_packet(AVPacket *pkt, int size)
Allocate the payload of a packet and initialize its fields with default values.
Definition: avpacket.c:86
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
av_default_item_name
#define AVERROR(e)
Definition: error.h:43
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:176
#define AV_LOG_DEBUG
Stuff which is only useful for libav* developers.
Definition: log.h:197
preferred ID for decoding MPEG audio layer 1, 2 or 3
Definition: avcodec.h:517
enum AVMediaType codec_type
General type of the encoded data.
Definition: avcodec.h:3976
static int aa_read_header(AVFormatContext *s)
Definition: aadec.c:65
uint8_t * aa_fixed_key
Definition: aadec.c:40
static const uint8_t offset[127][2]
Definition: vf_spp.c:92
unsigned char * buf
Buffer must have AVPROBE_PADDING_SIZE of extra allocated bytes filled with zero.
Definition: avformat.h:463
int64_t current_chapter_size
Definition: aadec.c:47
int block_align
Audio only.
Definition: avcodec.h:4097
static int read_probe(AVProbeData *pd)
Definition: jvdec.c:55
Public header for libavutil TEA algorithm.
void av_tea_crypt(AVTEA *ctx, 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: tea.c:95
struct AVTEA * tea_ctx
Definition: aadec.c:45
#define MAX_DICTIONARY_ENTRIES
Definition: aadec.c:35
#define OFFSET(x)
Definition: aadec.c:287
#define src
Definition: vp9dsp.c:530
offset must point to a pointer immediately followed by an int for the length
Definition: opt.h:229
static int read_header(FFV1Context *f)
Definition: ffv1dec.c:514
static int aa_read_close(AVFormatContext *s)
Definition: aadec.c:278
Stream structure.
Definition: avformat.h:889
static int read_packet(void *opaque, uint8_t *buf, int buf_size)
Definition: avio_reading.c:42
AVIOContext * pb
I/O context.
Definition: avformat.h:1380
#define MAX_TOC_ENTRIES
Definition: aadec.c:34
void * buf
Definition: avisynth_c.h:690
Describe the class of an AVClass context structure.
Definition: log.h:67
#define AV_WB32(p, v)
Definition: intreadwrite.h:419
#define AVFMT_GENERIC_INDEX
Use generic index building code.
Definition: avformat.h:487
#define AV_OPT_FLAG_DECODING_PARAM
a generic parameter which can be set by the user for demuxing or decoding
Definition: opt.h:276
static int get_second_size(char *codec_name)
Definition: aadec.c:50
static const AVClass aa_class
Definition: aadec.c:296
This structure contains the data a format has to probe a file.
Definition: avformat.h:461
int chapter_idx
Definition: aadec.c:44
static int flags
Definition: cpu.c:47
int sample_rate
Audio only.
Definition: avcodec.h:4090
#define AVPROBE_SCORE_MAX
maximum score
Definition: avformat.h:473
Main libavformat public API header.
void av_tea_init(AVTEA *ctx, const uint8_t key[16], int rounds)
Initialize an AVTEA context.
Definition: tea.c:42
int64_t start_time
Decoding: pts of the first frame of the stream in presentation order, in stream time base...
Definition: avformat.h:936
static double c[64]
#define TEA_BLOCK_SIZE
Definition: aadec.c:36
int codec_second_size
Definition: aadec.c:42
uint32_t key[16]
Definition: tea.c:31
int aa_fixed_key_len
Definition: aadec.c:41
void * priv_data
Format private data.
Definition: avformat.h:1366
int channels
Audio only.
Definition: avcodec.h:4086
#define av_freep(p)
void INT64 start
Definition: avisynth_c.h:690
const char * name
A comma separated list of short names for the format.
Definition: avformat.h:664
AVCodecParameters * codecpar
Definition: avformat.h:1241
This structure stores compressed data.
Definition: avcodec.h:1578