Thanks for all the feedback, and help.
Vesselin
From 1ed235454a61fe1f8d993d09d3d6398e7609c624 Mon Sep 17 00:00:00 2001
From: Vesselin Bontchev <vesselin.bontc...@yandex.com>
Date: Sat, 11 Jul 2015 18:02:47 +0000
Subject: [PATCH] Add support for Audible AAX (and AAX+) files
---
libavformat/isom.h | 5 ++
libavformat/mov.c | 138 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 143 insertions(+)
diff --git a/libavformat/isom.h b/libavformat/isom.h
index 5d48989..9fa02e7 100644
--- a/libavformat/isom.h
+++ b/libavformat/isom.h
@@ -198,6 +198,11 @@ typedef struct MOVContext {
MOVFragmentIndex** fragment_index_data;
unsigned fragment_index_count;
int atom_depth;
+ unsigned int aax_mode; ///< 'aax' file has been detected
+ unsigned char file_key[20];
+ unsigned char file_iv[20];
+ void *activation_bytes;
+ int activation_bytes_size;
} MOVContext;
int ff_mp4_read_descr_len(AVIOContext *pb);
diff --git a/libavformat/mov.c b/libavformat/mov.c
index d1b29a2..6f9bf50 100644
--- a/libavformat/mov.c
+++ b/libavformat/mov.c
@@ -26,6 +26,7 @@
#include <inttypes.h>
#include <limits.h>
#include <stdint.h>
+#include <ctype.h>
#include "libavutil/attributes.h"
#include "libavutil/channel_layout.h"
@@ -37,6 +38,8 @@
#include "libavutil/dict.h"
#include "libavutil/display.h"
#include "libavutil/opt.h"
+#include "libavutil/aes.h"
+#include "libavutil/sha.h"
#include "libavutil/timecode.h"
#include "libavcodec/ac3tab.h"
#include "avformat.h"
@@ -807,6 +810,109 @@ static int mov_read_mdat(MOVContext *c, AVIOContext *pb, MOVAtom atom)
return 0; /* now go for moov */
}
+static void hex_encode(unsigned char *s, int len, unsigned char *o)
+{
+ char itoa16_private[16] = "0123456789abcdef";
+ int i;
+ for (i = 0; i < len; ++i) {
+ o[0] = itoa16_private[s[i] >> 4];
+ o[1] = itoa16_private[s[i] & 15];
+ o += 2;
+ }
+}
+
+#define DRM_BLOB_SIZE 56
+
+static int mov_read_adrm(MOVContext *c, AVIOContext *pb, MOVAtom atom)
+{
+ // extracted from libAAX_SDK.so and AAXSDKWin.dll files!
+ unsigned char fixed_key[] = { 0x77, 0x21, 0x4d, 0x4b, 0x19, 0x6a, 0x87, 0xcd,
+ 0x52, 0x00, 0x45, 0xfd, 0x20, 0xa5, 0x1d, 0x67 };
+ unsigned char intermediate_key[20] = {0};
+ unsigned char intermediate_iv[20] = {0};
+ unsigned char input[64] = {0};
+ unsigned char output[64] = {0};
+ unsigned char file_checksum[20] = {0};
+ unsigned char file_checksum_encoded[41] = {0};
+ unsigned char file_key_encoded[41] = {0};
+ unsigned char file_iv_encoded[41] = {0};
+ unsigned char calculated_checksum[20];
+ struct AVSHA *ctx;
+ struct AVAES *aes_decrypt;
+ int i;
+ unsigned char *activation_bytes = (unsigned char*) c->activation_bytes;
+
+ av_log(c->fc, AV_LOG_DEBUG, "[aax] aax file detected!\n");
+ c->aax_mode = 1;
+
+ ctx = av_sha_alloc();
+ aes_decrypt = av_aes_alloc();
+ if (!aes_decrypt) {
+ return AVERROR(ENOMEM);
+ }
+
+ /* drm blob processing */
+ ffio_read_size(pb, output, 8); // go to offset 8, absolute postion 0x251
+ ffio_read_size(pb, input, DRM_BLOB_SIZE);
+ ffio_read_size(pb, output, 4); // go to offset 4, absolute postion 0x28d
+ ffio_read_size(pb, file_checksum, 20);
+ hex_encode(file_checksum, 20, file_checksum_encoded);
+ av_log(c->fc, AV_LOG_DEBUG, "[aax] file checksum == %s\n", file_checksum_encoded);
+
+ /* verify activation data */
+ if (!activation_bytes || c->activation_bytes_size != 4) {
+ av_log(c->fc, AV_LOG_FATAL, "[aax] activation_bytes option is missing!\n");
+ return AVERROR_INVALIDDATA;
+ }
+ if (c->activation_bytes_size != 4) {
+ av_log(c->fc, AV_LOG_FATAL, "[aax] activation_bytes value needs to be 4 bytes!\n");
+ return AVERROR_INVALIDDATA;
+ }
+
+ /* AAX (and AAX+) key derivation */
+ av_sha_init(ctx, 160);
+ av_sha_update(ctx, fixed_key, 16);
+ av_sha_update(ctx, activation_bytes, 4);
+ av_sha_final(ctx, intermediate_key);
+ av_sha_init(ctx, 160);
+ av_sha_update(ctx, fixed_key, 16);
+ av_sha_update(ctx, intermediate_key, 20);
+ av_sha_update(ctx, activation_bytes, 4);
+ av_sha_final(ctx, intermediate_iv);
+ av_sha_init(ctx, 160);
+ av_sha_update(ctx, intermediate_key, 16);
+ av_sha_update(ctx, intermediate_iv, 16);
+ av_sha_final(ctx, calculated_checksum);
+ if (memcmp(calculated_checksum, file_checksum, 20)) {
+ av_log(c->fc, AV_LOG_ERROR, "[aax] mismatch in checksums!\n");
+ return AVERROR_INVALIDDATA;
+ }
+ av_aes_init(aes_decrypt, intermediate_key, 128, 1);
+ av_aes_crypt(aes_decrypt, output, input, DRM_BLOB_SIZE >> 4, intermediate_iv, 1);
+ for (i = 0; i < 4; i++) {
+ if (activation_bytes[i] != output[3 - i]) {
+ av_log(c->fc, AV_LOG_ERROR, "[aax] error in drm blob decryption!\n");
+ return AVERROR_INVALIDDATA;
+ }
+ }
+ memcpy(c->file_key, output + 8, 16);
+ memcpy(input, output + 26, 16);
+ av_sha_init(ctx, 160);
+ av_sha_update(ctx, input, 16);
+ av_sha_update(ctx, c->file_key, 16);
+ av_sha_update(ctx, fixed_key, 16);
+ av_sha_final(ctx, c->file_iv);
+ hex_encode(c->file_key, 16, file_key_encoded);
+ av_log(c->fc, AV_LOG_DEBUG, "[aax] file key == %s\n", file_key_encoded);
+ hex_encode(c->file_iv, 16, file_iv_encoded);
+ av_log(c->fc, AV_LOG_DEBUG, "[aax] file iv == %s\n", file_iv_encoded);
+
+ av_free(aes_decrypt);
+ av_free(ctx);
+
+ return 0;
+}
+
/* read major brand, minor version and compatible brands and store them as metadata */
static int mov_read_ftyp(MOVContext *c, AVIOContext *pb, MOVAtom atom)
{
@@ -3594,6 +3700,7 @@ static const MOVParseTableEntry mov_default_parse_table[] = {
{ MKTAG('e','l','s','t'), mov_read_elst },
{ MKTAG('e','n','d','a'), mov_read_enda },
{ MKTAG('f','i','e','l'), mov_read_fiel },
+{ MKTAG('a','d','r','m'), mov_read_adrm },
{ MKTAG('f','t','y','p'), mov_read_ftyp },
{ MKTAG('g','l','b','l'), mov_read_glbl },
{ MKTAG('h','d','l','r'), mov_read_hdlr },
@@ -4337,6 +4444,32 @@ static int should_retry(AVIOContext *pb, int error_code) {
return 1;
}
+/* Audible AAX (and AAX+) bytestream decryption
+ *
+ * ffmpeg -activation_bytes 00112233 -i test.aax -vn -codec copy -v debug output.mp4
+ *
+ */
+static int aax_filter(uint8_t *input, int size, MOVContext *c)
+{
+ int blocks = 0;
+ unsigned char iv[16];
+ struct AVAES *aes_decrypt;
+
+ aes_decrypt = av_aes_alloc();
+ if (!aes_decrypt) {
+ return AVERROR(ENOMEM);
+ }
+
+ memcpy(iv, c->file_iv, 16); // iv is overwritten
+ blocks = size >> 4;
+ av_aes_init(aes_decrypt, c->file_key, 128, 1);
+ av_aes_crypt(aes_decrypt, input, input, blocks, iv, 1);
+
+ av_free(aes_decrypt);
+
+ return 0;
+}
+
static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
{
MOVContext *mov = s->priv_data;
@@ -4431,6 +4564,9 @@ static int mov_read_packet(AVFormatContext *s, AVPacket *pkt)
pkt->flags |= sample->flags & AVINDEX_KEYFRAME ? AV_PKT_FLAG_KEY : 0;
pkt->pos = sample->pos;
+ if (mov->aax_mode)
+ aax_filter(pkt->data, pkt->size, mov);
+
return 0;
}
@@ -4544,6 +4680,8 @@ static const AVOption mov_options[] = {
AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, .flags = FLAGS },
{ "export_xmp", "Export full XMP metadata", OFFSET(export_xmp),
AV_OPT_TYPE_INT, { .i64 = 0 }, 0, 1, .flags = FLAGS },
+ { "activation_bytes", "Secret bytes for Audible AAX files", OFFSET(activation_bytes),
+ AV_OPT_TYPE_BINARY, .flags = AV_OPT_FLAG_DECODING_PARAM },
{ NULL },
};
--
1.7.10.4
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