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/* MPEG audio packet decoder.
* Written by Shaun Jackman <sjackman@gmail.com>.
* Copyright 2007 Shaun Jackman
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/asn1.h>
#include <wsutil/mpeg-audio.h>
#include "packet-per.h"
#include "packet-mpeg-audio-hf.c"
#include "packet-mpeg-audio-ett.c"
#include "packet-mpeg-audio-fn.c"
void proto_register_mpeg_audio(void);
void proto_reg_handoff_mpeg_audio(void);
dissector_handle_t mpeg_audio_handle;
static int proto_mpeg_audio = -1;
static dissector_handle_t id3v2_handle;
static int hf_mpeg_audio_header = -1;
static int hf_mpeg_audio_data = -1;
static int hf_mpeg_audio_padbytes = -1;
static int hf_id3v1 = -1;
static int ett_mpeg_audio = -1;
static gboolean
test_mpeg_audio(tvbuff_t *tvb, int offset)
{
guint32 hdr;
struct mpa mpa;
if (!tvb_bytes_exist(tvb, offset, 4))
return FALSE;
if (tvb_strneql(tvb, offset, "TAG", 3) == 0)
return TRUE;
if (tvb_strneql(tvb, offset, "ID3", 3) == 0)
return TRUE;
hdr = tvb_get_guint32(tvb, offset, ENC_BIG_ENDIAN);
MPA_UNMARSHAL(&mpa, hdr);
return MPA_VALID(&mpa);
}
static int
mpeg_resync(tvbuff_t *tvb, int offset)
{
guint32 hdr;
struct mpa mpa;
/* This only looks to resync on another frame; it doesn't
* look for an ID3 tag.
*/
offset = tvb_find_guint8(tvb, offset, -1, '\xff');
while (offset != -1 && tvb_bytes_exist(tvb, offset, 4)) {
hdr = tvb_get_guint32(tvb, offset, ENC_BIG_ENDIAN);
MPA_UNMARSHAL(&mpa, hdr);
if (MPA_VALID(&mpa)) {
return offset;
}
offset = tvb_find_guint8(tvb, offset + 1, -1, '\xff');
}
return tvb_reported_length(tvb);
}
static int
dissect_mpeg_audio_frame(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
guint32 h;
struct mpa mpa;
int data_size = 0;
asn1_ctx_t asn1_ctx;
int offset = 0;
static const char *version_names[] = { "1", "2", "2.5" };
if (!tvb_bytes_exist(tvb, 0, 4))
return 0;
h = tvb_get_ntohl(tvb, 0);
MPA_UNMARSHAL(&mpa, h);
if (!MPA_SYNC_VALID(&mpa) || !MPA_VERSION_VALID(&mpa) || !MPA_LAYER_VALID(&mpa)) {
return 0;
}
col_add_fstr(pinfo->cinfo, COL_PROTOCOL,
"MPEG-%s", version_names[mpa_version(&mpa)]);
col_add_fstr(pinfo->cinfo, COL_INFO,
"Audio Layer %d", mpa_layer(&mpa) + 1);
if (MPA_BITRATE_VALID(&mpa) && MPA_FREQUENCY_VALID(&mpa)) {
data_size = (int)(MPA_DATA_BYTES(&mpa) - sizeof mpa);
col_append_fstr(pinfo->cinfo, COL_INFO,
", %d kb/s, %g kHz",
mpa_bitrate(&mpa) / 1000,
mpa_frequency(&mpa) / (float)1000);
}
asn1_ctx_init(&asn1_ctx, ASN1_ENC_PER, TRUE, pinfo);
offset = dissect_mpeg_audio_Audio(tvb, offset, &asn1_ctx,
tree, hf_mpeg_audio_header);
if (data_size > 0) {
unsigned int padding;
proto_tree_add_item(tree, hf_mpeg_audio_data, tvb,
offset / 8, data_size, ENC_NA);
offset += data_size * 8;
padding = mpa_padding(&mpa);
if (padding > 0) {
proto_tree_add_item(tree, hf_mpeg_audio_padbytes, tvb,
offset / 8, padding, ENC_NA);
offset += padding * 8;
}
}
return offset / 8;
}
static int
dissect_id3v1(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
asn1_ctx_t asn1_ctx;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "ID3v1");
col_clear(pinfo->cinfo, COL_INFO);
asn1_ctx_init(&asn1_ctx, ASN1_ENC_PER, TRUE, pinfo);
return dissect_mpeg_audio_ID3v1(tvb, 0, &asn1_ctx,
tree, hf_id3v1);
}
static int
dissect_mpeg_audio(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data _U_)
{
proto_item *ti;
proto_tree *mpeg_audio_tree;
int magic, offset = 0;
guint32 frame_len;
tvbuff_t *next_tvb;
ti = proto_tree_add_item(tree, proto_mpeg_audio, tvb, offset, -1, ENC_NA);
mpeg_audio_tree = proto_item_add_subtree(ti, ett_mpeg_audio);
while (tvb_reported_length_remaining(tvb, offset) >= 4) {
next_tvb = tvb_new_subset_remaining(tvb, offset);
magic = tvb_get_ntoh24(next_tvb, 0);
switch (magic) {
case 0x544147: /* TAG */
offset += dissect_id3v1(next_tvb, pinfo, mpeg_audio_tree);
break;
case 0x494433: /* ID3 */
offset += call_dissector(id3v2_handle, tvb, pinfo, mpeg_audio_tree);
break;
default:
frame_len = dissect_mpeg_audio_frame(next_tvb, pinfo, mpeg_audio_tree);
if (frame_len == 0) {
frame_len = mpeg_resync(next_tvb, 0);
}
offset += frame_len;
}
}
return tvb_reported_length(tvb);
}
static gboolean
dissect_mpeg_audio_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
if (!test_mpeg_audio(tvb, 0)) {
return FALSE;
}
dissect_mpeg_audio(tvb, pinfo, tree, data);
return TRUE;
}
void
proto_register_mpeg_audio(void)
{
static hf_register_info hf[] = {
#include "packet-mpeg-audio-hfarr.c"
{ &hf_mpeg_audio_header,
{ "Frame Header", "mpeg-audio.header",
FT_NONE, BASE_NONE, NULL, 0, NULL, HFILL }},
{ &hf_mpeg_audio_data,
{ "Data", "mpeg-audio.data",
FT_BYTES, BASE_NONE, NULL, 0, NULL, HFILL }},
{ &hf_mpeg_audio_padbytes,
{ "Padding", "mpeg-audio.padbytes",
FT_BYTES, BASE_NONE, NULL, 0, NULL, HFILL }},
{ &hf_id3v1,
{ "ID3v1", "mpeg-audio.id3v1",
FT_NONE, BASE_NONE, NULL, 0, NULL, HFILL }},
};
static gint *ett[] = {
&ett_mpeg_audio,
#include "packet-mpeg-audio-ettarr.c"
};
proto_mpeg_audio = proto_register_protocol("Moving Picture Experts Group Audio", "MPEG Audio", "mpeg-audio");
proto_register_field_array(proto_mpeg_audio, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
mpeg_audio_handle = register_dissector("mpeg-audio", dissect_mpeg_audio, proto_mpeg_audio);
}
void
proto_reg_handoff_mpeg_audio(void)
{
dissector_add_string("media_type", "audio/mpeg", mpeg_audio_handle);
/* "audio/mp3" used by Chrome before 2020 */
/* https://chromium.googlesource.com/chromium/src/+/842f46a95f49e24534ad35c7a71e5c425d426550 */
dissector_add_string("media_type", "audio/mp3", mpeg_audio_handle);
heur_dissector_add("mpeg", dissect_mpeg_audio_heur, "MPEG Audio", "mpeg_audio", proto_mpeg_audio, HEURISTIC_ENABLE);
id3v2_handle = find_dissector("id3v2");
}
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