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FFmpeg/libavcodec/cbs_mpeg2.c
Andreas Rheinhardt cda3e8ca04 avcodec/cbs: Fix potential overflow 
The number of bits in a PutBitContext must fit into an int, yet nothing
guaranteed the size argument cbs_write_unit_data() uses in init_put_bits()
to be in the range 0..INT_MAX / 8. This has been changed.

Furthermore, the check 8 * data_size > data_bit_start that there is
data beyond the initial padding when writing mpeg2 or H.264/5 slices
could also overflow, so divide it by 8 to get an equivalent check
without this problem.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
2019-11-17 23:31:45 +00:00

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/*
* This file is part of FFmpeg.
*
* FFmpeg 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.
*
* FFmpeg 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 FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "libavutil/avassert.h"
#include "cbs.h"
#include "cbs_internal.h"
#include "cbs_mpeg2.h"
#include "internal.h"
#define HEADER(name) do { \
ff_cbs_trace_header(ctx, name); \
} while (0)
#define CHECK(call) do { \
err = (call); \
if (err < 0) \
return err; \
} while (0)
#define FUNC_NAME(rw, codec, name) cbs_ ## codec ## _ ## rw ## _ ## name
#define FUNC_MPEG2(rw, name) FUNC_NAME(rw, mpeg2, name)
#define FUNC(name) FUNC_MPEG2(READWRITE, name)
#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)
#define ui(width, name) \
xui(width, name, current->name, 0, MAX_UINT_BITS(width), 0)
#define uir(width, name) \
xui(width, name, current->name, 1, MAX_UINT_BITS(width), 0)
#define uis(width, name, subs, ...) \
xui(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define uirs(width, name, subs, ...) \
xui(width, name, current->name, 1, MAX_UINT_BITS(width), subs, __VA_ARGS__)
#define xui(width, name, var, range_min, range_max, subs, ...) \
xuia(width, #name, var, range_min, range_max, subs, __VA_ARGS__)
#define sis(width, name, subs, ...) \
xsi(width, name, current->name, subs, __VA_ARGS__)
#define marker_bit() \
bit("marker_bit", 1)
#define bit(string, value) do { \
av_unused uint32_t bit = value; \
xuia(1, string, bit, value, value, 0); \
} while (0)
#define READ
#define READWRITE read
#define RWContext GetBitContext
#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
uint32_t value; \
CHECK(ff_cbs_read_unsigned(ctx, rw, width, string, \
SUBSCRIPTS(subs, __VA_ARGS__), \
&value, range_min, range_max)); \
var = value; \
} while (0)
#define xsi(width, name, var, subs, ...) do { \
int32_t value; \
CHECK(ff_cbs_read_signed(ctx, rw, width, #name, \
SUBSCRIPTS(subs, __VA_ARGS__), &value, \
MIN_INT_BITS(width), \
MAX_INT_BITS(width))); \
var = value; \
} while (0)
#define nextbits(width, compare, var) \
(get_bits_left(rw) >= width && \
(var = show_bits(rw, width)) == (compare))
#define infer(name, value) do { \
current->name = value; \
} while (0)
#include "cbs_mpeg2_syntax_template.c"
#undef READ
#undef READWRITE
#undef RWContext
#undef xuia
#undef xsi
#undef nextbits
#undef infer
#define WRITE
#define READWRITE write
#define RWContext PutBitContext
#define xuia(width, string, var, range_min, range_max, subs, ...) do { \
CHECK(ff_cbs_write_unsigned(ctx, rw, width, string, \
SUBSCRIPTS(subs, __VA_ARGS__), \
var, range_min, range_max)); \
} while (0)
#define xsi(width, name, var, subs, ...) do { \
CHECK(ff_cbs_write_signed(ctx, rw, width, #name, \
SUBSCRIPTS(subs, __VA_ARGS__), var, \
MIN_INT_BITS(width), \
MAX_INT_BITS(width))); \
} while (0)
#define nextbits(width, compare, var) (var)
#define infer(name, value) do { \
if (current->name != (value)) { \
av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
"%s does not match inferred value: " \
"%"PRId64", but should be %"PRId64".\n", \
#name, (int64_t)current->name, (int64_t)(value)); \
} \
} while (0)
#include "cbs_mpeg2_syntax_template.c"
#undef WRITE
#undef READWRITE
#undef RWContext
#undef xuia
#undef xsi
#undef nextbits
#undef infer
static void cbs_mpeg2_free_picture_header(void *opaque, uint8_t *content)
{
MPEG2RawPictureHeader *picture = (MPEG2RawPictureHeader*)content;
av_buffer_unref(&picture->extra_information_picture.extra_information_ref);
av_freep(&content);
}
static void cbs_mpeg2_free_user_data(void *opaque, uint8_t *content)
{
MPEG2RawUserData *user = (MPEG2RawUserData*)content;
av_buffer_unref(&user->user_data_ref);
av_freep(&content);
}
static void cbs_mpeg2_free_slice(void *opaque, uint8_t *content)
{
MPEG2RawSlice *slice = (MPEG2RawSlice*)content;
av_buffer_unref(&slice->header.extra_information_slice.extra_information_ref);
av_buffer_unref(&slice->data_ref);
av_freep(&content);
}
static int cbs_mpeg2_split_fragment(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag,
int header)
{
const uint8_t *start, *end;
CodedBitstreamUnitType unit_type;
uint32_t start_code = -1;
size_t unit_size;
int err, i, final = 0;
start = avpriv_find_start_code(frag->data, frag->data + frag->data_size,
&start_code);
if (start_code >> 8 != 0x000001) {
// No start code found.
return AVERROR_INVALIDDATA;
}
for (i = 0;; i++) {
unit_type = start_code & 0xff;
if (start == frag->data + frag->data_size) {
// The last four bytes form a start code which constitutes
// a unit of its own. In this situation avpriv_find_start_code
// won't modify start_code at all so modify start_code so that
// the next unit will be treated as the last unit.
start_code = 0;
}
end = avpriv_find_start_code(start--, frag->data + frag->data_size,
&start_code);
// start points to the byte containing the start_code_identifier
// (may be the last byte of fragment->data); end points to the byte
// following the byte containing the start code identifier (or to
// the end of fragment->data).
if (start_code >> 8 == 0x000001) {
// Unit runs from start to the beginning of the start code
// pointed to by end (including any padding zeroes).
unit_size = (end - 4) - start;
} else {
// We didn't find a start code, so this is the final unit.
unit_size = end - start;
final = 1;
}
err = ff_cbs_insert_unit_data(ctx, frag, i, unit_type, (uint8_t*)start,
unit_size, frag->data_ref);
if (err < 0)
return err;
if (final)
break;
start = end;
}
return 0;
}
static int cbs_mpeg2_read_unit(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit)
{
GetBitContext gbc;
int err;
err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
if (err < 0)
return err;
if (MPEG2_START_IS_SLICE(unit->type)) {
MPEG2RawSlice *slice;
int pos, len;
err = ff_cbs_alloc_unit_content(ctx, unit, sizeof(*slice),
&cbs_mpeg2_free_slice);
if (err < 0)
return err;
slice = unit->content;
err = cbs_mpeg2_read_slice_header(ctx, &gbc, &slice->header);
if (err < 0)
return err;
pos = get_bits_count(&gbc);
len = unit->data_size;
slice->data_size = len - pos / 8;
slice->data_ref = av_buffer_ref(unit->data_ref);
if (!slice->data_ref)
return AVERROR(ENOMEM);
slice->data = unit->data + pos / 8;
slice->data_bit_start = pos % 8;
} else {
switch (unit->type) {
#define START(start_code, type, read_func, free_func) \
case start_code: \
{ \
type *header; \
err = ff_cbs_alloc_unit_content(ctx, unit, \
sizeof(*header), free_func); \
if (err < 0) \
return err; \
header = unit->content; \
err = cbs_mpeg2_read_ ## read_func(ctx, &gbc, header); \
if (err < 0) \
return err; \
} \
break;
START(MPEG2_START_PICTURE, MPEG2RawPictureHeader,
picture_header, &cbs_mpeg2_free_picture_header);
START(MPEG2_START_USER_DATA, MPEG2RawUserData,
user_data, &cbs_mpeg2_free_user_data);
START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader,
sequence_header, NULL);
START(MPEG2_START_EXTENSION, MPEG2RawExtensionData,
extension_data, NULL);
START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
group_of_pictures_header, NULL);
START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd,
sequence_end, NULL);
#undef START
default:
return AVERROR(ENOSYS);
}
}
return 0;
}
static int cbs_mpeg2_write_header(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
int err;
switch (unit->type) {
#define START(start_code, type, func) \
case start_code: \
err = cbs_mpeg2_write_ ## func(ctx, pbc, unit->content); \
break;
START(MPEG2_START_PICTURE, MPEG2RawPictureHeader, picture_header);
START(MPEG2_START_USER_DATA, MPEG2RawUserData, user_data);
START(MPEG2_START_SEQUENCE_HEADER, MPEG2RawSequenceHeader, sequence_header);
START(MPEG2_START_EXTENSION, MPEG2RawExtensionData, extension_data);
START(MPEG2_START_GROUP, MPEG2RawGroupOfPicturesHeader,
group_of_pictures_header);
START(MPEG2_START_SEQUENCE_END, MPEG2RawSequenceEnd, sequence_end);
#undef START
default:
av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for start "
"code %02"PRIx32".\n", unit->type);
return AVERROR_PATCHWELCOME;
}
return err;
}
static int cbs_mpeg2_write_slice(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
MPEG2RawSlice *slice = unit->content;
int err;
err = cbs_mpeg2_write_slice_header(ctx, pbc, &slice->header);
if (err < 0)
return err;
if (slice->data) {
size_t rest = slice->data_size - (slice->data_bit_start + 7) / 8;
uint8_t *pos = slice->data + slice->data_bit_start / 8;
av_assert0(slice->data_bit_start >= 0 &&
slice->data_size > slice->data_bit_start / 8);
if (slice->data_size * 8 + 8 > put_bits_left(pbc))
return AVERROR(ENOSPC);
// First copy the remaining bits of the first byte
if (slice->data_bit_start % 8)
put_bits(pbc, 8 - slice->data_bit_start % 8,
*pos++ & MAX_UINT_BITS(8 - slice->data_bit_start % 8));
if (put_bits_count(pbc) % 8 == 0) {
// If the writer is aligned at this point,
// memcpy can be used to improve performance.
// This is the normal case.
flush_put_bits(pbc);
memcpy(put_bits_ptr(pbc), pos, rest);
skip_put_bytes(pbc, rest);
} else {
// If not, we have to copy manually:
for (; rest > 3; rest -= 4, pos += 4)
put_bits32(pbc, AV_RB32(pos));
for (; rest; rest--, pos++)
put_bits(pbc, 8, *pos);
// Align with zeros
put_bits(pbc, 8 - put_bits_count(pbc) % 8, 0);
}
}
return 0;
}
static int cbs_mpeg2_write_unit(CodedBitstreamContext *ctx,
CodedBitstreamUnit *unit,
PutBitContext *pbc)
{
if (MPEG2_START_IS_SLICE(unit->type))
return cbs_mpeg2_write_slice (ctx, unit, pbc);
else
return cbs_mpeg2_write_header(ctx, unit, pbc);
}
static int cbs_mpeg2_assemble_fragment(CodedBitstreamContext *ctx,
CodedBitstreamFragment *frag)
{
uint8_t *data;
size_t size, dp;
int i;
size = 0;
for (i = 0; i < frag->nb_units; i++)
size += 3 + frag->units[i].data_size;
frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
if (!frag->data_ref)
return AVERROR(ENOMEM);
data = frag->data_ref->data;
dp = 0;
for (i = 0; i < frag->nb_units; i++) {
CodedBitstreamUnit *unit = &frag->units[i];
data[dp++] = 0;
data[dp++] = 0;
data[dp++] = 1;
memcpy(data + dp, unit->data, unit->data_size);
dp += unit->data_size;
}
av_assert0(dp == size);
memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
frag->data = data;
frag->data_size = size;
return 0;
}
const CodedBitstreamType ff_cbs_type_mpeg2 = {
.codec_id = AV_CODEC_ID_MPEG2VIDEO,
.priv_data_size = sizeof(CodedBitstreamMPEG2Context),
.split_fragment = &cbs_mpeg2_split_fragment,
.read_unit = &cbs_mpeg2_read_unit,
.write_unit = &cbs_mpeg2_write_unit,
.assemble_fragment = &cbs_mpeg2_assemble_fragment,
};
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