ffmpeg / libavformat / crypto.c @ ac9cf2e5
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/*
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* Decryption protocol handler
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* Copyright (c) 2011 Martin Storsjo
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avformat.h" |
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#include "libavutil/aes.h" |
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#include "libavutil/avstring.h" |
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#include "libavutil/opt.h" |
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#include "internal.h" |
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#include "url.h" |
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#define MAX_BUFFER_BLOCKS 150 |
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#define BLOCKSIZE 16 |
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typedef struct { |
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const AVClass *class;
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URLContext *hd; |
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uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS], |
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outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS]; |
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uint8_t *outptr; |
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int indata, indata_used, outdata;
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int eof;
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uint8_t *key; |
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int keylen;
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uint8_t *iv; |
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int ivlen;
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struct AVAES *aes;
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} CryptoContext; |
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#define OFFSET(x) offsetof(CryptoContext, x)
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static const AVOption options[] = { |
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{"key", "AES decryption key", OFFSET(key), FF_OPT_TYPE_BINARY }, |
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{"iv", "AES decryption initialization vector", OFFSET(iv), FF_OPT_TYPE_BINARY }, |
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{ NULL }
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}; |
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static const AVClass crypto_class = { |
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"crypto", av_default_item_name, options, LIBAVUTIL_VERSION_INT
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}; |
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static int crypto_open(URLContext *h, const char *uri, int flags) |
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{ |
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const char *nested_url; |
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int ret;
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CryptoContext *c = h->priv_data; |
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if (!av_strstart(uri, "crypto+", &nested_url) && |
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!av_strstart(uri, "crypto:", &nested_url)) {
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av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
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ret = AVERROR(EINVAL); |
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goto err;
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} |
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if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) {
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av_log(h, AV_LOG_ERROR, "Key or IV not set\n");
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ret = AVERROR(EINVAL); |
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goto err;
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} |
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if (flags & AVIO_FLAG_WRITE) {
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av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n");
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ret = AVERROR(ENOSYS); |
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goto err;
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} |
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if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ)) < 0) { |
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av_log(h, AV_LOG_ERROR, "Unable to open input\n");
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goto err;
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} |
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c->aes = av_mallocz(av_aes_size); |
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if (!c->aes) {
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ret = AVERROR(ENOMEM); |
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goto err;
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} |
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av_aes_init(c->aes, c->key, 128, 1); |
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h->is_streamed = 1;
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return 0; |
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err:
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av_free(c->key); |
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av_free(c->iv); |
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return ret;
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} |
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static int crypto_read(URLContext *h, uint8_t *buf, int size) |
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{ |
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CryptoContext *c = h->priv_data; |
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int blocks;
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retry:
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if (c->outdata > 0) { |
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size = FFMIN(size, c->outdata); |
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memcpy(buf, c->outptr, size); |
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c->outptr += size; |
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c->outdata -= size; |
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return size;
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} |
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// We avoid using the last block until we've found EOF,
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// since we'll remove PKCS7 padding at the end. So make
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// sure we've got at least 2 blocks, so we can decrypt
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// at least one.
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while (c->indata - c->indata_used < 2*BLOCKSIZE) { |
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int n = ffurl_read(c->hd, c->inbuffer + c->indata,
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sizeof(c->inbuffer) - c->indata);
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if (n <= 0) { |
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c->eof = 1;
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break;
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} |
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c->indata += n; |
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} |
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blocks = (c->indata - c->indata_used) / BLOCKSIZE; |
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if (!blocks)
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return AVERROR_EOF;
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if (!c->eof)
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blocks--; |
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av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks, |
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c->iv, 1);
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c->outdata = BLOCKSIZE * blocks; |
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c->outptr = c->outbuffer; |
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c->indata_used += BLOCKSIZE * blocks; |
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if (c->indata_used >= sizeof(c->inbuffer)/2) { |
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memmove(c->inbuffer, c->inbuffer + c->indata_used, |
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c->indata - c->indata_used); |
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c->indata -= c->indata_used; |
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c->indata_used = 0;
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} |
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if (c->eof) {
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// Remove PKCS7 padding at the end
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int padding = c->outbuffer[c->outdata - 1]; |
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c->outdata -= padding; |
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} |
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goto retry;
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} |
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static int crypto_close(URLContext *h) |
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{ |
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CryptoContext *c = h->priv_data; |
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if (c->hd)
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ffurl_close(c->hd); |
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av_freep(&c->aes); |
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av_freep(&c->key); |
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av_freep(&c->iv); |
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return 0; |
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} |
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URLProtocol ff_crypto_protocol = { |
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.name = "crypto",
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.url_open = crypto_open, |
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.url_read = crypto_read, |
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.url_close = crypto_close, |
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.priv_data_size = sizeof(CryptoContext),
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.priv_data_class = &crypto_class, |
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.flags = URL_PROTOCOL_FLAG_NESTED_SCHEME, |
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}; |