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/*
* Decryption protocol handler
* Copyright (c) 2011 Martin Storsjo
*
* 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 "avformat.h"
#include "libavutil/aes.h"
#include "libavutil/avstring.h"
#include "libavutil/opt.h"
#include "internal.h"
#include "url.h"
#define MAX_BUFFER_BLOCKS 150
#define BLOCKSIZE 16
typedef struct {
const AVClass *class;
URLContext *hd;
uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
uint8_t *outptr;
int indata, indata_used, outdata;
int eof;
uint8_t *key;
int keylen;
uint8_t *iv;
int ivlen;
struct AVAES *aes;
} CryptoContext;
#define OFFSET(x) offsetof(CryptoContext, x)
#define D AV_OPT_FLAG_DECODING_PARAM
static const AVOption options[] = {
{"key", "AES decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D },
{"iv", "AES decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D },
{ NULL }
};
static const AVClass crypto_class = {
.class_name = "crypto",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
};
static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
{
const char *nested_url;
int ret = 0;
CryptoContext *c = h->priv_data;
if (!av_strstart(uri, "crypto+", &nested_url) &&
!av_strstart(uri, "crypto:", &nested_url)) {
av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
ret = AVERROR(EINVAL);
goto err;
}
if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) {
av_log(h, AV_LOG_ERROR, "Key or IV not set\n");
ret = AVERROR(EINVAL);
goto err;
}
if (flags & AVIO_FLAG_WRITE) {
av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n");
ret = AVERROR(ENOSYS);
goto err;
}
if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ,
&h->interrupt_callback, options)) < 0) {
av_log(h, AV_LOG_ERROR, "Unable to open input\n");
goto err;
}
c->aes = av_aes_alloc();
if (!c->aes) {
ret = AVERROR(ENOMEM);
goto err;
}
av_aes_init(c->aes, c->key, 128, 1);
h->is_streamed = 1;
err:
return ret;
}
static int crypto_read(URLContext *h, uint8_t *buf, int size)
{
CryptoContext *c = h->priv_data;
int blocks;
retry:
if (c->outdata > 0) {
size = FFMIN(size, c->outdata);
memcpy(buf, c->outptr, size);
c->outptr += size;
c->outdata -= size;
return size;
}
// We avoid using the last block until we've found EOF,
// since we'll remove PKCS7 padding at the end. So make
// sure we've got at least 2 blocks, so we can decrypt
// at least one.
while (c->indata - c->indata_used < 2*BLOCKSIZE) {
int n = ffurl_read(c->hd, c->inbuffer + c->indata,
sizeof(c->inbuffer) - c->indata);
if (n <= 0) {
c->eof = 1;
break;
}
c->indata += n;
}
blocks = (c->indata - c->indata_used) / BLOCKSIZE;
if (!blocks)
return AVERROR_EOF;
if (!c->eof)
blocks--;
av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks,
c->iv, 1);
c->outdata = BLOCKSIZE * blocks;
c->outptr = c->outbuffer;
c->indata_used += BLOCKSIZE * blocks;
if (c->indata_used >= sizeof(c->inbuffer)/2) {
memmove(c->inbuffer, c->inbuffer + c->indata_used,
c->indata - c->indata_used);
c->indata -= c->indata_used;
c->indata_used = 0;
}
if (c->eof) {
// Remove PKCS7 padding at the end
int padding = c->outbuffer[c->outdata - 1];
c->outdata -= padding;
}
goto retry;
}
static int crypto_close(URLContext *h)
{
CryptoContext *c = h->priv_data;
if (c->hd)
ffurl_close(c->hd);
av_freep(&c->aes);
return 0;
}
URLProtocol ff_crypto_protocol = {
.name = "crypto",
.url_open2 = crypto_open2,
.url_read = crypto_read,
.url_close = crypto_close,
.priv_data_size = sizeof(CryptoContext),
.priv_data_class = &crypto_class,
.flags = URL_PROTOCOL_FLAG_NESTED_SCHEME,
};
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