| /* |
| * 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, |
| }; |