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mpv/demux/ebml.c
wm4 ac7f67b3f2 demux_mkv, stream: attempt to improve behavior in unseekable streams 
stream_skip() semantics were kind of bad, especially after the recent
change to the stream code. Forward stream_skip() calls could still
trigger a seek and fail, even if it was supposed to actually skip data.
(Maybe the idea that stream_skip() should try to seek is worthless in
the first place.)

Rename it to stream_seek_skip() (takes absolute position now because I
think that's better), and make it always skip if the stream is marked as
forward.

While we're at it, make EOF detection more robust. I guess s->eof
shouldn't exist at all, since it's valid only "sometimes". It should be
removed... but not today. A 1-byte stream_read_peek() call is good to
get the s->eof flag set to a correct value.
2019-11-14 12:59:14 +01:00

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/*
* native ebml reader for the Matroska demuxer
* new parser copyright (c) 2010 Uoti Urpala
* copyright (c) 2004 Aurelien Jacobs <aurel@gnuage.org>
* based on the one written by Ronald Bultje for gstreamer
*
* This file is part of mpv.
*
* mpv is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* mpv is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with mpv. If not, see <http://www.gnu.org/licenses/>.
*/
#include "config.h"
#include <stdlib.h>
#include <stdbool.h>
#include <inttypes.h>
#include <stddef.h>
#include <assert.h>
#include <libavutil/intfloat.h>
#include <libavutil/common.h>
#include "mpv_talloc.h"
#include "ebml.h"
#include "stream/stream.h"
#include "common/msg.h"
// Whether the id is a known Matroska level 1 element (allowed as element on
// global file level, after the level 0 MATROSKA_ID_SEGMENT).
// This (intentionally) doesn't include "global" elements.
bool ebml_is_mkv_level1_id(uint32_t id)
{
switch (id) {
case MATROSKA_ID_SEEKHEAD:
case MATROSKA_ID_INFO:
case MATROSKA_ID_CLUSTER:
case MATROSKA_ID_TRACKS:
case MATROSKA_ID_CUES:
case MATROSKA_ID_ATTACHMENTS:
case MATROSKA_ID_CHAPTERS:
case MATROSKA_ID_TAGS:
return true;
default:
return false;
}
}
/*
* Read: the element content data ID.
* Return: the ID.
*/
uint32_t ebml_read_id(stream_t *s)
{
int i, len_mask = 0x80;
uint32_t id;
for (i = 0, id = stream_read_char(s); i < 4 && !(id & len_mask); i++)
len_mask >>= 1;
if (i >= 4)
return EBML_ID_INVALID;
while (i--)
id = (id << 8) | stream_read_char(s);
return id;
}
/*
* Read: element content length.
*/
uint64_t ebml_read_length(stream_t *s)
{
int i, j, num_ffs = 0, len_mask = 0x80;
uint64_t len;
for (i = 0, len = stream_read_char(s); i < 8 && !(len & len_mask); i++)
len_mask >>= 1;
if (i >= 8)
return EBML_UINT_INVALID;
j = i + 1;
if ((int) (len &= (len_mask - 1)) == len_mask - 1)
num_ffs++;
while (i--) {
len = (len << 8) | stream_read_char(s);
if ((len & 0xFF) == 0xFF)
num_ffs++;
}
if (j == num_ffs)
return EBML_UINT_INVALID;
if (len >= 1ULL<<63) // Can happen if stream_read_char returns EOF
return EBML_UINT_INVALID;
return len;
}
/*
* Read a variable length signed int.
*/
int64_t ebml_read_signed_length(stream_t *s)
{
uint64_t unum;
int l;
/* read as unsigned number first */
uint64_t offset = stream_tell(s);
unum = ebml_read_length(s);
if (unum == EBML_UINT_INVALID)
return EBML_INT_INVALID;
l = stream_tell(s) - offset;
return unum - ((1LL << ((7 * l) - 1)) - 1);
}
/*
* Read the next element as an unsigned int.
*/
uint64_t ebml_read_uint(stream_t *s)
{
uint64_t len, value = 0;
len = ebml_read_length(s);
if (len == EBML_UINT_INVALID || len > 8)
return EBML_UINT_INVALID;
while (len--)
value = (value << 8) | stream_read_char(s);
return value;
}
/*
* Read the next element as a signed int.
*/
int64_t ebml_read_int(stream_t *s)
{
uint64_t value = 0;
uint64_t len;
int l;
len = ebml_read_length(s);
if (len == EBML_UINT_INVALID || len > 8)
return EBML_INT_INVALID;
if (!len)
return 0;
len--;
l = stream_read_char(s);
if (l & 0x80)
value = -1;
value = (value << 8) | l;
while (len--)
value = (value << 8) | stream_read_char(s);
return (int64_t)value; // assume complement of 2
}
/*
* Skip the current element.
* end: the end of the parent element or -1 (for robust error handling)
*/
int ebml_read_skip(struct mp_log *log, int64_t end, stream_t *s)
{
uint64_t len;
int64_t pos = stream_tell(s);
len = ebml_read_length(s);
if (len == EBML_UINT_INVALID)
goto invalid;
int64_t pos2 = stream_tell(s);
if (len >= INT64_MAX - pos2 || (end > 0 && pos2 + len > end))
goto invalid;
if (!stream_seek_skip(s, pos2 + len))
goto invalid;
return 0;
invalid:
mp_err(log, "Invalid EBML length at position %"PRId64"\n", pos);
stream_seek_skip(s, pos);
return 1;
}
/*
* Skip to (probable) next cluster (MATROSKA_ID_CLUSTER) element start position.
*/
int ebml_resync_cluster(struct mp_log *log, stream_t *s)
{
int64_t pos = stream_tell(s);
uint32_t last_4_bytes = 0;
stream_read_peek(s, &(char){0}, 1);
if (!s->eof) {
mp_err(log, "Corrupt file detected. "
"Trying to resync starting from position %"PRId64"...\n", pos);
}
while (!s->eof) {
// Assumes MATROSKA_ID_CLUSTER is 4 bytes, with no 0 bytes.
if (last_4_bytes == MATROSKA_ID_CLUSTER) {
mp_err(log, "Cluster found at %"PRId64".\n", pos - 4);
stream_seek(s, pos - 4);
return 0;
}
last_4_bytes = (last_4_bytes << 8) | stream_read_char(s);
pos++;
}
return -1;
}
#define EVALARGS(F, ...) F(__VA_ARGS__)
#define E(str, N, type) const struct ebml_elem_desc ebml_ ## N ## _desc = { str, type };
#define E_SN(str, count, N) const struct ebml_elem_desc ebml_ ## N ## _desc = { str, EBML_TYPE_SUBELEMENTS, sizeof(struct ebml_ ## N), count, (const struct ebml_field_desc[]){
#define E_S(str, count) EVALARGS(E_SN, str, count, N)
#define FN(id, name, multiple, N) { id, multiple, offsetof(struct ebml_ ## N, name), offsetof(struct ebml_ ## N, n_ ## name), &ebml_##name##_desc},
#define F(id, name, multiple) EVALARGS(FN, id, name, multiple, N)
#include "ebml_defs.c"
#undef EVALARGS
#undef SN
#undef S
#undef FN
#undef F
// Used to read/write pointers to different struct types
struct generic;
#define generic_struct struct generic
static uint32_t ebml_parse_id(uint8_t *data, size_t data_len, int *length)
{
*length = -1;
uint8_t *end = data + data_len;
if (data == end)
return EBML_ID_INVALID;
int len = 1;
uint32_t id = *data++;
for (int len_mask = 0x80; !(id & len_mask); len_mask >>= 1) {
len++;
if (len > 4)
return EBML_ID_INVALID;
}
*length = len;
while (--len && data < end)
id = (id << 8) | *data++;
return id;
}
static uint64_t ebml_parse_length(uint8_t *data, size_t data_len, int *length)
{
*length = -1;
uint8_t *end = data + data_len;
if (data == end)
return -1;
uint64_t r = *data++;
int len = 1;
int len_mask;
for (len_mask = 0x80; !(r & len_mask); len_mask >>= 1) {
len++;
if (len > 8)
return -1;
}
r &= len_mask - 1;
int num_allones = 0;
if (r == len_mask - 1)
num_allones++;
for (int i = 1; i < len; i++) {
if (data == end)
return -1;
if (*data == 255)
num_allones++;
r = (r << 8) | *data++;
}
// According to Matroska specs this means "unknown length"
// Could be supported if there are any actual files using it
if (num_allones == len)
return -1;
*length = len;
return r;
}
static uint64_t ebml_parse_uint(uint8_t *data, int length)
{
assert(length >= 0 && length <= 8);
uint64_t r = 0;
while (length--)
r = (r << 8) + *data++;
return r;
}
static int64_t ebml_parse_sint(uint8_t *data, int length)
{
assert(length >= 0 && length <= 8);
if (!length)
return 0;
uint64_t r = 0;
if (*data & 0x80)
r = -1;
while (length--)
r = (r << 8) | *data++;
return (int64_t)r; // assume complement of 2
}
static double ebml_parse_float(uint8_t *data, int length)
{
assert(length == 0 || length == 4 || length == 8);
uint64_t i = ebml_parse_uint(data, length);
if (length == 4)
return av_int2float(i);
else
return av_int2double(i);
}
// target must be initialized to zero
static void ebml_parse_element(struct ebml_parse_ctx *ctx, void *target,
uint8_t *data, int size,
const struct ebml_elem_desc *type, int level)
{
assert(type->type == EBML_TYPE_SUBELEMENTS);
assert(level < 8);
MP_TRACE(ctx, "%.*sParsing element %s\n", level, " ", type->name);
char *s = target;
uint8_t *end = data + size;
uint8_t *p = data;
int num_elems[MAX_EBML_SUBELEMENTS] = {0};
while (p < end) {
uint8_t *startp = p;
int len;
uint32_t id = ebml_parse_id(p, end - p, &len);
if (len > end - p)
goto past_end_error;
if (len < 0) {
MP_ERR(ctx, "Error parsing subelement id\n");
goto other_error;
}
p += len;
uint64_t length = ebml_parse_length(p, end - p, &len);
if (len > end - p)
goto past_end_error;
if (len < 0) {
MP_ERR(ctx, "Error parsing subelement length\n");
goto other_error;
}
p += len;
int field_idx = -1;
for (int i = 0; i < type->field_count; i++)
if (type->fields[i].id == id) {
field_idx = i;
num_elems[i]++;
if (num_elems[i] >= 0x70000000) {
MP_ERR(ctx, "Too many EBML subelements.\n");
goto other_error;
}
break;
}
if (length > end - p) {
if (field_idx >= 0 && type->fields[field_idx].desc->type
!= EBML_TYPE_SUBELEMENTS) {
MP_ERR(ctx, "Subelement content goes "
"past end of containing element\n");
goto other_error;
}
// Try to parse what is possible from inside this partial element
ctx->has_errors = true;
length = end - p;
}
p += length;
continue;
past_end_error:
MP_ERR(ctx, "Subelement headers go past end of containing element\n");
other_error:
ctx->has_errors = true;
end = startp;
break;
}
for (int i = 0; i < type->field_count; i++) {
if (num_elems[i] && type->fields[i].multiple) {
char *ptr = s + type->fields[i].offset;
switch (type->fields[i].desc->type) {
case EBML_TYPE_SUBELEMENTS: {
size_t max = 1000000000 / type->fields[i].desc->size;
if (num_elems[i] > max) {
MP_ERR(ctx, "Too many subelements.\n");
num_elems[i] = max;
}
int sz = num_elems[i] * type->fields[i].desc->size;
*(generic_struct **) ptr = talloc_zero_size(ctx->talloc_ctx, sz);
break;
}
case EBML_TYPE_UINT:
*(uint64_t **) ptr = talloc_zero_array(ctx->talloc_ctx,
uint64_t, num_elems[i]);
break;
case EBML_TYPE_SINT:
*(int64_t **) ptr = talloc_zero_array(ctx->talloc_ctx,
int64_t, num_elems[i]);
break;
case EBML_TYPE_FLOAT:
*(double **) ptr = talloc_zero_array(ctx->talloc_ctx,
double, num_elems[i]);
break;
case EBML_TYPE_STR:
*(char ***) ptr = talloc_zero_array(ctx->talloc_ctx,
char *, num_elems[i]);
break;
case EBML_TYPE_BINARY:
*(struct bstr **) ptr = talloc_zero_array(ctx->talloc_ctx,
struct bstr,
num_elems[i]);
break;
case EBML_TYPE_EBML_ID:
*(int32_t **) ptr = talloc_zero_array(ctx->talloc_ctx,
uint32_t, num_elems[i]);
break;
default:
abort();
}
}
}
while (data < end) {
int len;
uint32_t id = ebml_parse_id(data, end - data, &len);
if (len < 0 || len > end - data) {
MP_ERR(ctx, "Error parsing subelement\n");
break;
}
data += len;
uint64_t length = ebml_parse_length(data, end - data, &len);
if (len < 0 || len > end - data) {
MP_ERR(ctx, "Error parsing subelement length\n");
break;
}
data += len;
if (length > end - data) {
// Try to parse what is possible from inside this partial element
length = end - data;
MP_ERR(ctx, "Next subelement content goes "
"past end of containing element, will be truncated\n");
}
int field_idx = -1;
for (int i = 0; i < type->field_count; i++)
if (type->fields[i].id == id) {
field_idx = i;
break;
}
if (field_idx < 0) {
if (id == 0xec) {
MP_TRACE(ctx, "%.*sIgnoring Void element "
"size: %"PRIu64"\n", level+1, " ", length);
} else if (id == 0xbf) {
MP_TRACE(ctx, "%.*sIgnoring CRC-32 "
"element size: %"PRIu64"\n", level+1, " ",
length);
} else {
MP_DBG(ctx, "Ignoring unrecognized "
"subelement. ID: %x size: %"PRIu64"\n", id, length);
}
data += length;
continue;
}
const struct ebml_field_desc *fd = &type->fields[field_idx];
const struct ebml_elem_desc *ed = fd->desc;
bool multiple = fd->multiple;
int *countptr = (int *) (s + fd->count_offset);
if (*countptr >= num_elems[field_idx]) {
// Shouldn't happen on any sane file without bugs
MP_ERR(ctx, "Too many subelements.\n");
ctx->has_errors = true;
data += length;
continue;
}
if (*countptr > 0 && !multiple) {
MP_WARN(ctx, "Another subelement of type "
"%x %s (size: %"PRIu64"). Only one allowed. Ignoring.\n",
id, ed->name, length);
ctx->has_errors = true;
data += length;
continue;
}
MP_TRACE(ctx, "%.*sParsing %x %s size: %"PRIu64
" value: ", level+1, " ", id, ed->name, length);
char *fieldptr = s + fd->offset;
switch (ed->type) {
case EBML_TYPE_SUBELEMENTS:
MP_TRACE(ctx, "subelements\n");
char *subelptr;
if (multiple) {
char *array_start = (char *) *(generic_struct **) fieldptr;
subelptr = array_start + *countptr * ed->size;
} else
subelptr = fieldptr;
ebml_parse_element(ctx, subelptr, data, length, ed, level + 1);
break;
case EBML_TYPE_UINT:;
uint64_t *uintptr;
#define GETPTR(subelptr, fieldtype) \
if (multiple) \
subelptr = *(fieldtype **) fieldptr + *countptr; \
else \
subelptr = (fieldtype *) fieldptr
GETPTR(uintptr, uint64_t);
if (length < 1 || length > 8) {
MP_ERR(ctx, "uint invalid length %"PRIu64"\n", length);
goto error;
}
*uintptr = ebml_parse_uint(data, length);
MP_TRACE(ctx, "uint %"PRIu64"\n", *uintptr);
break;
case EBML_TYPE_SINT:;
int64_t *sintptr;
GETPTR(sintptr, int64_t);
if (length > 8) {
MP_ERR(ctx, "sint invalid length %"PRIu64"\n", length);
goto error;
}
*sintptr = ebml_parse_sint(data, length);
MP_TRACE(ctx, "sint %"PRId64"\n", *sintptr);
break;
case EBML_TYPE_FLOAT:;
double *floatptr;
GETPTR(floatptr, double);
if (length != 0 && length != 4 && length != 8) {
MP_ERR(ctx, "float invalid length %"PRIu64"\n", length);
goto error;
}
*floatptr = ebml_parse_float(data, length);
MP_DBG(ctx, "float %f\n", *floatptr);
break;
case EBML_TYPE_STR:
if (length > 1024 * 1024) {
MP_ERR(ctx, "Not reading overly long string element.\n");
break;
}
char **strptr;
GETPTR(strptr, char *);
*strptr = talloc_strndup(ctx->talloc_ctx, data, length);
MP_TRACE(ctx, "string \"%s\"\n", *strptr);
break;
case EBML_TYPE_BINARY:;
if (length > 0x80000000) {
MP_ERR(ctx, "Not reading overly long EBML element.\n");
break;
}
struct bstr *binptr;
GETPTR(binptr, struct bstr);
binptr->start = data;
binptr->len = length;
MP_TRACE(ctx, "binary %zd bytes\n", binptr->len);
break;
case EBML_TYPE_EBML_ID:;
uint32_t *idptr;
GETPTR(idptr, uint32_t);
*idptr = ebml_parse_id(data, end - data, &len);
if (len != length) {
MP_ERR(ctx, "ebml_id broken value\n");
goto error;
}
MP_TRACE(ctx, "ebml_id %x\n", (unsigned)*idptr);
break;
default:
abort();
}
*countptr += 1;
error:
data += length;
}
}
// target must be initialized to zero
int ebml_read_element(struct stream *s, struct ebml_parse_ctx *ctx,
void *target, const struct ebml_elem_desc *desc)
{
ctx->has_errors = false;
int msglevel = ctx->no_error_messages ? MSGL_DEBUG : MSGL_WARN;
uint64_t length = ebml_read_length(s);
if (s->eof) {
MP_MSG(ctx, msglevel, "Unexpected end of file "
"- partial or corrupt file?\n");
return -1;
}
if (length == EBML_UINT_INVALID) {
MP_MSG(ctx, msglevel, "EBML element with unknown length - unsupported\n");
return -1;
}
if (length > 1000000000) {
MP_MSG(ctx, msglevel, "Refusing to read element over 100 MB in size\n");
return -1;
}
ctx->talloc_ctx = talloc_size(NULL, length);
int read_len = stream_read(s, ctx->talloc_ctx, length);
if (read_len < length)
MP_MSG(ctx, msglevel, "Unexpected end of file - partial or corrupt file?\n");
ebml_parse_element(ctx, target, ctx->talloc_ctx, read_len, desc, 0);
if (ctx->has_errors)
MP_MSG(ctx, msglevel, "Error parsing element %s\n", desc->name);
return 0;
}
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