oma: support for encrypted files

Signed-off-by: David Goldwich <david.goldwich@gmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

1 files changed, 255 insertions, 14 deletions

diff --git a/libavformat/oma.c b/libavformat/oma.c
index 7675841792..5ffe8fa9f0 100644
--- a/libavformat/oma.c
+++ b/libavformat/oma.c
@@ -3,6 +3,7 @@
  *
  * Copyright (c) 2008 Maxim Poliakovski
  *               2008 Benjamin Larsson
+ *               2011 David Goldwich
  *
  * This file is part of Libav.
  *
@@ -36,20 +37,19 @@
  * - Sound data organized in packets follow the EA3 header
  *   (can be encrypted using the Sony DRM!).
  *
- * LIMITATIONS: This version supports only plain (unencrypted) OMA files.
- * If any DRM-protected (encrypted) file is encountered you will get the
- * corresponding error message. Try to remove the encryption using any
- * Sony software (for example SonicStage).
  * CODEC SUPPORT: Only ATRAC3 codec is currently supported!
  */
 
 #include "avformat.h"
 #include "libavutil/intreadwrite.h"
+#include "libavutil/des.h"
 #include "pcm.h"
 #include "riff.h"
 #include "id3v2.h"
 
 #define EA3_HEADER_SIZE 96
+#define ID3v2_EA3_MAGIC "ea3"
+#define OMA_ENC_HEADER_SIZE 16
 
 enum {
     OMA_CODECID_ATRAC3  = 0,
@@ -65,7 +65,211 @@ static const AVCodecTag codec_oma_tags[] = {
     { CODEC_ID_MP3,     OMA_CODECID_MP3 },
 };
 
-#define ID3v2_EA3_MAGIC "ea3"
+static const uint64_t leaf_table[] = {
+    0xd79e8283acea4620, 0x7a9762f445afd0d8,
+    0x354d60a60b8c79f1, 0x584e1cde00b07aee,
+    0x1573cd93da7df623, 0x47f98d79620dd535
+};
+
+typedef struct OMAContext {
+    uint64_t content_start;
+    int encrypted;
+    uint16_t k_size;
+    uint16_t e_size;
+    uint16_t i_size;
+    uint16_t s_size;
+    uint32_t rid;
+    uint8_t r_val[24];
+    uint8_t n_val[24];
+    uint8_t m_val[8];
+    uint8_t s_val[8];
+    uint8_t sm_val[8];
+    uint8_t e_val[8];
+    uint8_t iv[8];
+    struct AVDES av_des;
+} OMAContext;
+
+static void hex_log(AVFormatContext *s, int level, const char *name, const uint8_t *value, int len)
+{
+    char buf[33];
+    len = FFMIN(len, 16);
+    if (av_log_get_level() < level)
+        return;
+    ff_data_to_hex(buf, value, len, 1);
+    buf[len<<1] = '\0';
+    av_log(s, level, "%s: %s\n", name, buf);
+}
+
+static int kset(AVFormatContext *s, const uint8_t *r_val, const uint8_t *n_val, int len)
+{
+    OMAContext *oc = s->priv_data;
+
+    if (!r_val && !n_val)
+        return -1;
+
+    len = FFMIN(len, 16);
+
+    /* use first 64 bits in the third round again */
+    if (r_val) {
+        if (r_val != oc->r_val) {
+            memset(oc->r_val, 0, 24);
+            memcpy(oc->r_val, r_val, len);
+        }
+        memcpy(&oc->r_val[16], r_val, 8);
+    }
+    if (n_val) {
+        if (n_val != oc->n_val) {
+            memset(oc->n_val, 0, 24);
+            memcpy(oc->n_val, n_val, len);
+        }
+        memcpy(&oc->n_val[16], n_val, 8);
+    }
+
+    return 0;
+}
+
+static int rprobe(AVFormatContext *s, uint8_t *enc_header, const uint8_t *r_val)
+{
+    OMAContext *oc = s->priv_data;
+    unsigned int pos;
+    struct AVDES av_des;
+
+    if (!enc_header || !r_val)
+        return -1;
+
+    /* m_val */
+    av_des_init(&av_des, r_val, 192, 1);
+    av_des_crypt(&av_des, oc->m_val, &enc_header[48], 1, NULL, 1);
+
+    /* s_val */
+    av_des_init(&av_des, oc->m_val, 64, 0);
+    av_des_crypt(&av_des, oc->s_val, NULL, 1, NULL, 0);
+
+    /* sm_val */
+    pos = OMA_ENC_HEADER_SIZE + oc->k_size + oc->e_size;
+    av_des_init(&av_des, oc->s_val, 64, 0);
+    av_des_mac(&av_des, oc->sm_val, &enc_header[pos], (oc->i_size >> 3));
+
+    pos += oc->i_size;
+
+    return memcmp(&enc_header[pos], oc->sm_val, 8) ? -1 : 0;
+}
+
+static int nprobe(AVFormatContext *s, uint8_t *enc_header, const uint8_t *n_val)
+{
+    OMAContext *oc = s->priv_data;
+    uint32_t pos, taglen, datalen;
+    struct AVDES av_des;
+
+    if (!enc_header || !n_val)
+        return -1;
+
+    pos = OMA_ENC_HEADER_SIZE + oc->k_size;
+    if (!memcmp(&enc_header[pos], "EKB ", 4))
+        pos += 32;
+
+    if (AV_RB32(&enc_header[pos]) != oc->rid)
+        av_log(s, AV_LOG_DEBUG, "Mismatching RID\n");
+
+    taglen = AV_RB32(&enc_header[pos+32]);
+    datalen = AV_RB32(&enc_header[pos+36]) >> 4;
+
+    pos += 44 + taglen;
+
+    av_des_init(&av_des, n_val, 192, 1);
+    while (datalen-- > 0) {
+        av_des_crypt(&av_des, oc->r_val, &enc_header[pos], 2, NULL, 1);
+        kset(s, oc->r_val, NULL, 16);
+        if (!rprobe(s, enc_header, oc->r_val))
+            return 0;
+        pos += 16;
+    }
+
+    return -1;
+}
+
+static int decrypt_init(AVFormatContext *s, ID3v2ExtraMeta *em, uint8_t *header)
+{
+    OMAContext *oc = s->priv_data;
+    ID3v2ExtraMetaGEOB *geob = NULL;
+    uint8_t *gdata;
+
+    oc->encrypted = 1;
+    av_log(s, AV_LOG_INFO, "File is encrypted\n");
+
+    /* find GEOB metadata */
+    while (em) {
+        if (!strcmp(em->tag, "GEOB") &&
+            (geob = em->data) &&
+            !strcmp(geob->description, "OMG_LSI") ||
+            !strcmp(geob->description, "OMG_BKLSI")) {
+            break;
+        }
+        em = em->next;
+    }
+    if (!em) {
+        av_log(s, AV_LOG_ERROR, "No encryption header found\n");
+        return -1;
+    }
+
+    if (geob->datasize < 64) {
+        av_log(s, AV_LOG_ERROR, "Invalid GEOB data size: %u\n", geob->datasize);
+        return -1;
+    }
+
+    gdata = geob->data;
+
+    if (AV_RB16(gdata) != 1)
+        av_log(s, AV_LOG_WARNING, "Unknown version in encryption header\n");
+
+    oc->k_size = AV_RB16(&gdata[2]);
+    oc->e_size = AV_RB16(&gdata[4]);
+    oc->i_size = AV_RB16(&gdata[6]);
+    oc->s_size = AV_RB16(&gdata[8]);
+
+    if (memcmp(&gdata[OMA_ENC_HEADER_SIZE], "KEYRING     ", 12)) {
+        av_log(s, AV_LOG_ERROR, "Invalid encryption header\n");
+        return -1;
+    }
+    oc->rid = AV_RB32(&gdata[OMA_ENC_HEADER_SIZE + 28]);
+    av_log(s, AV_LOG_DEBUG, "RID: %.8x\n", oc->rid);
+
+    memcpy(oc->iv, &header[0x58], 8);
+    hex_log(s, AV_LOG_DEBUG, "IV", oc->iv, 8);
+
+    hex_log(s, AV_LOG_DEBUG, "CBC-MAC", &gdata[OMA_ENC_HEADER_SIZE+oc->k_size+oc->e_size+oc->i_size], 8);
+
+    if (s->keylen > 0) {
+        kset(s, s->key, s->key, s->keylen);
+    }
+    if (!memcmp(oc->r_val, (const uint8_t[8]){0}, 8) ||
+        rprobe(s, gdata, oc->r_val) < 0 &&
+        nprobe(s, gdata, oc->n_val) < 0) {
+        int i;
+        for (i = 0; i < sizeof(leaf_table); i += 2) {
+            uint8_t buf[16];
+            AV_WL64(buf, leaf_table[i]);
+            AV_WL64(&buf[8], leaf_table[i+1]);
+            kset(s, buf, buf, 16);
+            if (!rprobe(s, gdata, oc->r_val) || !nprobe(s, gdata, oc->n_val))
+                break;
+        }
+        if (i >= sizeof(leaf_table)) {
+            av_log(s, AV_LOG_ERROR, "Invalid key\n");
+            return -1;
+        }
+    }
+
+    /* e_val */
+    av_des_init(&oc->av_des, oc->m_val, 64, 0);
+    av_des_crypt(&oc->av_des, oc->e_val, &gdata[OMA_ENC_HEADER_SIZE + 40], 1, NULL, 0);
+    hex_log(s, AV_LOG_DEBUG, "EK", oc->e_val, 8);
+
+    /* init e_val */
+    av_des_init(&oc->av_des, oc->e_val, 64, 1);
+
+    return 0;
+}
 
 static int oma_read_header(AVFormatContext *s,
                            AVFormatParameters *ap)
@@ -77,8 +281,10 @@ static int oma_read_header(AVFormatContext *s,
     uint8_t buf[EA3_HEADER_SIZE];
     uint8_t *edata;
     AVStream *st;
+    ID3v2ExtraMeta *extra_meta = NULL;
+    OMAContext *oc = s->priv_data;
 
-    ff_id3v2_read(s, ID3v2_EA3_MAGIC);
+    ff_id3v2_read_all(s, ID3v2_EA3_MAGIC, &extra_meta);
     ret = avio_read(s->pb, buf, EA3_HEADER_SIZE);
     if (ret < EA3_HEADER_SIZE)
         return -1;
@@ -88,12 +294,17 @@ static int oma_read_header(AVFormatContext *s,
         return -1;
     }
 
+    oc->content_start = avio_tell(s->pb);
+
+    /* encrypted file */
     eid = AV_RB16(&buf[6]);
-    if (eid != -1 && eid != -128) {
-        av_log(s, AV_LOG_ERROR, "Encrypted file! Eid: %d\n", eid);
+    if (eid != -1 && eid != -128 && decrypt_init(s, extra_meta, buf) < 0) {
+        ff_id3v2_free_extra_meta(&extra_meta);
         return -1;
     }
 
+    ff_id3v2_free_extra_meta(&extra_meta);
+
     codec_params = AV_RB24(&buf[33]);
 
     st = av_new_stream(s, 0);
@@ -159,12 +370,20 @@ static int oma_read_header(AVFormatContext *s,
 
 static int oma_read_packet(AVFormatContext *s, AVPacket *pkt)
 {
-    int ret = av_get_packet(s->pb, pkt, s->streams[0]->codec->block_align);
+    OMAContext *oc = s->priv_data;
+    int packet_size = s->streams[0]->codec->block_align;
+    int ret = av_get_packet(s->pb, pkt, packet_size);
 
-    pkt->stream_index = 0;
     if (ret <= 0)
         return AVERROR(EIO);
 
+    pkt->stream_index = 0;
+
+    if (oc->encrypted) {
+        /* previous unencrypted block saved in IV for the next packet (CBC mode) */
+        av_des_crypt(&oc->av_des, pkt->data, pkt->data, (packet_size >> 3), oc->iv, 1);
+    }
+
     return ret;
 }
 
@@ -190,16 +409,38 @@ static int oma_read_probe(AVProbeData *p)
         return 0;
 }
 
+static int oma_read_seek(struct AVFormatContext *s, int stream_index, int64_t timestamp, int flags)
+{
+    OMAContext *oc = s->priv_data;
+
+    pcm_read_seek(s, stream_index, timestamp, flags);
+
+    if (oc->encrypted) {
+        /* readjust IV for CBC */
+        int64_t pos = avio_tell(s->pb);
+        if (pos < oc->content_start)
+            memset(oc->iv, 0, 8);
+        else {
+            if (avio_seek(s->pb, -8, SEEK_CUR) < 0 || avio_read(s->pb, oc->iv, 8) < 8) {
+                memset(oc->iv, 0, 8);
+                return -1;
+            }
+        }
+    }
+
+    return 0;
+}
 
 AVInputFormat ff_oma_demuxer = {
     .name           = "oma",
     .long_name      = NULL_IF_CONFIG_SMALL("Sony OpenMG audio"),
+    .priv_data_size = sizeof(OMAContext),
     .read_probe     = oma_read_probe,
     .read_header    = oma_read_header,
     .read_packet    = oma_read_packet,
-    .read_seek      = pcm_read_seek,
-    .flags= AVFMT_GENERIC_INDEX,
-    .extensions = "oma,aa3",
-    .codec_tag= (const AVCodecTag* const []){codec_oma_tags, 0},
+    .read_seek      = oma_read_seek,
+    .flags          = AVFMT_GENERIC_INDEX,
+    .extensions     = "oma,omg,aa3",
+    .codec_tag      = (const AVCodecTag* const []){codec_oma_tags, 0},
 };