FFmpeg/libavutil/encryption_info.c

/**
 * 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 "encryption_info.h"
#include "mem.h"
#include "intreadwrite.h"

#define FF_ENCRYPTION_INFO_EXTRA 24

// The format of the AVEncryptionInfo side data:
// u32be scheme
// u32be crypt_byte_block
// u32be skip_byte_block
// u32be key_id_size
// u32be iv_size
// u32be subsample_count
// u8[key_id_size] key_id
// u8[iv_size] iv
// {
//   u32be bytes_of_clear_data
//   u32be bytes_of_protected_data
// }[subsample_count]

AVEncryptionInfo *av_encryption_info_alloc(uint32_t subsample_count, uint32_t key_id_size, uint32_t iv_size)
{
    AVEncryptionInfo *info;

    info = av_mallocz(sizeof(*info));
    if (!info)
        return NULL;

    info->key_id = av_mallocz(key_id_size);
    info->key_id_size = key_id_size;
    info->iv = av_mallocz(iv_size);
    info->iv_size = iv_size;
    info->subsamples = av_mallocz_array(subsample_count, sizeof(*info->subsamples));
    info->subsample_count = subsample_count;

    // Allow info->subsamples to be NULL if there are no subsamples.
    if (!info->key_id || !info->iv || (!info->subsamples && subsample_count)) {
        av_encryption_info_free(info);
        return NULL;
    }

    return info;
}

AVEncryptionInfo *av_encryption_info_clone(const AVEncryptionInfo *info)
{
    AVEncryptionInfo *ret;

    ret = av_encryption_info_alloc(info->subsample_count, info->key_id_size, info->iv_size);
    if (!ret)
        return NULL;

    ret->scheme = info->scheme;
    ret->crypt_byte_block = info->crypt_byte_block;
    ret->skip_byte_block = info->skip_byte_block;
    memcpy(ret->iv, info->iv, info->iv_size);
    memcpy(ret->key_id, info->key_id, info->key_id_size);
    memcpy(ret->subsamples, info->subsamples, sizeof(*info->subsamples) * info->subsample_count);
    return ret;
}

void av_encryption_info_free(AVEncryptionInfo *info)
{
    if (info) {
        av_free(info->key_id);
        av_free(info->iv);
        av_free(info->subsamples);
        av_free(info);
    }
}

AVEncryptionInfo *av_encryption_info_get_side_data(const uint8_t* buffer, size_t size)
{
    AVEncryptionInfo *info;
    uint64_t key_id_size, iv_size, subsample_count, i;

    if (!buffer || size < FF_ENCRYPTION_INFO_EXTRA)
        return NULL;

    key_id_size = AV_RB32(buffer + 12);
    iv_size = AV_RB32(buffer + 16);
    subsample_count = AV_RB32(buffer + 20);

    if (size < FF_ENCRYPTION_INFO_EXTRA + key_id_size + iv_size + subsample_count * 8)
        return NULL;

    info = av_encryption_info_alloc(subsample_count, key_id_size, iv_size);
    if (!info)
        return NULL;

    info->scheme = AV_RB32(buffer);
    info->crypt_byte_block = AV_RB32(buffer + 4);
    info->skip_byte_block = AV_RB32(buffer + 8);
    memcpy(info->key_id, buffer + 24, key_id_size);
    memcpy(info->iv, buffer + key_id_size + 24, iv_size);

    buffer += key_id_size + iv_size + 24;
    for (i = 0; i < subsample_count; i++) {
        info->subsamples[i].bytes_of_clear_data = AV_RB32(buffer);
        info->subsamples[i].bytes_of_protected_data = AV_RB32(buffer + 4);
        buffer += 8;
    }

    return info;
}

uint8_t *av_encryption_info_add_side_data(const AVEncryptionInfo *info, size_t *size)
{
    uint8_t *buffer, *cur_buffer;
    uint32_t i;

    if (UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA < info->key_id_size ||
        UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA - info->key_id_size < info->iv_size ||
        (UINT32_MAX - FF_ENCRYPTION_INFO_EXTRA - info->key_id_size - info->iv_size) / 8 < info->subsample_count) {
        return NULL;
    }

    *size = FF_ENCRYPTION_INFO_EXTRA + info->key_id_size + info->iv_size +
            (info->subsample_count * 8);
    cur_buffer = buffer = av_malloc(*size);
    if (!buffer)
        return NULL;

    AV_WB32(cur_buffer,      info->scheme);
    AV_WB32(cur_buffer +  4, info->crypt_byte_block);
    AV_WB32(cur_buffer +  8, info->skip_byte_block);
    AV_WB32(cur_buffer + 12, info->key_id_size);
    AV_WB32(cur_buffer + 16, info->iv_size);
    AV_WB32(cur_buffer + 20, info->subsample_count);
    cur_buffer += 24;
    memcpy(cur_buffer, info->key_id, info->key_id_size);
    cur_buffer += info->key_id_size;
    memcpy(cur_buffer, info->iv, info->iv_size);
    cur_buffer += info->iv_size;
    for (i = 0; i < info->subsample_count; i++) {
        AV_WB32(cur_buffer, info->subsamples[i].bytes_of_clear_data);
        AV_WB32(cur_buffer + 4, info->subsamples[i].bytes_of_protected_data);
        cur_buffer += 8;
    }

    return buffer;
}

// The format of the AVEncryptionInitInfo side data:
// u32be system_id_size
// u32be num_key_ids
// u32be key_id_size
// u32be data_size
// u8[system_id_size] system_id
// u8[key_id_size][num_key_id] key_ids
// u8[data_size] data

#define FF_ENCRYPTION_INIT_INFO_EXTRA 16

AVEncryptionInitInfo *av_encryption_init_info_alloc(
    uint32_t system_id_size, uint32_t num_key_ids, uint32_t key_id_size, uint32_t data_size)
{
    AVEncryptionInitInfo *info;
    uint32_t i;

    info = av_mallocz(sizeof(*info));
    if (!info)
        return NULL;

    info->system_id = av_mallocz(system_id_size);
    info->system_id_size = system_id_size;
    info->key_ids = key_id_size ? av_mallocz_array(num_key_ids, sizeof(*info->key_ids)) : NULL;
    info->num_key_ids = num_key_ids;
    info->key_id_size = key_id_size;
    info->data = av_mallocz(data_size);
    info->data_size = data_size;

    // Allow pointers to be NULL if the size is 0.
    if ((!info->system_id && system_id_size) || (!info->data && data_size) ||
        (!info->key_ids && num_key_ids && key_id_size)) {
        av_encryption_init_info_free(info);
        return NULL;
    }

    if (key_id_size) {
        for (i = 0; i < num_key_ids; i++) {
            info->key_ids[i] = av_mallocz(key_id_size);
            if (!info->key_ids[i]) {
                av_encryption_init_info_free(info);
                return NULL;
            }
        }
    }

    return info;
}

void av_encryption_init_info_free(AVEncryptionInitInfo *info)
{
    uint32_t i;
    if (info) {
        for (i = 0; i < info->num_key_ids; i++) {
            av_free(info->key_ids[i]);
        }
        av_free(info->system_id);
        av_free(info->key_ids);
        av_free(info->data);
        av_free(info);
    }
}

AVEncryptionInitInfo *av_encryption_init_info_get_side_data(
    const uint8_t *side_data, size_t side_data_size)
{
    AVEncryptionInitInfo *info;
    uint64_t system_id_size, num_key_ids, key_id_size, data_size, i;

    if (!side_data || side_data_size < FF_ENCRYPTION_INIT_INFO_EXTRA)
        return NULL;

    system_id_size = AV_RB32(side_data);
    num_key_ids = AV_RB32(side_data + 4);
    key_id_size = AV_RB32(side_data + 8);
    data_size = AV_RB32(side_data + 12);

    // UINT32_MAX + UINT32_MAX + UINT32_MAX * UINT32_MAX == UINT64_MAX
    if (side_data_size - FF_ENCRYPTION_INIT_INFO_EXTRA < system_id_size + data_size + num_key_ids * key_id_size)
        return NULL;

    info = av_encryption_init_info_alloc(system_id_size, num_key_ids, key_id_size, data_size);
    if (!info)
        return NULL;

    memcpy(info->system_id, side_data + 16, system_id_size);
    side_data += system_id_size + 16;
    for (i = 0; i < num_key_ids; i++) {
      memcpy(info->key_ids[i], side_data, key_id_size);
      side_data += key_id_size;
    }
    memcpy(info->data, side_data, data_size);

    return info;
}

uint8_t *av_encryption_init_info_add_side_data(const AVEncryptionInitInfo *info, size_t *side_data_size)
{
    uint8_t *buffer, *cur_buffer;
    uint32_t i, max_size;

    if (UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA < info->system_id_size ||
        UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA - info->system_id_size < info->data_size) {
        return NULL;
    }

    if (info->num_key_ids) {
        max_size = UINT32_MAX - FF_ENCRYPTION_INIT_INFO_EXTRA - info->system_id_size - info->data_size;
        if (max_size / info->num_key_ids < info->key_id_size)
            return NULL;
    }

    *side_data_size = FF_ENCRYPTION_INIT_INFO_EXTRA + info->system_id_size +
                      info->data_size + (info->num_key_ids * info->key_id_size);
    cur_buffer = buffer = av_malloc(*side_data_size);
    if (!buffer)
        return NULL;

    AV_WB32(cur_buffer,      info->system_id_size);
    AV_WB32(cur_buffer +  4, info->num_key_ids);
    AV_WB32(cur_buffer +  8, info->key_id_size);
    AV_WB32(cur_buffer + 12, info->data_size);
    cur_buffer += 16;

    memcpy(cur_buffer, info->system_id, info->system_id_size);
    cur_buffer += info->system_id_size;
    for (i = 0; i < info->num_key_ids; i++) {
        memcpy(cur_buffer, info->key_ids[i], info->key_id_size);
        cur_buffer += info->key_id_size;
    }
    memcpy(cur_buffer, info->data, info->data_size);

    return buffer;
}