diff options
Diffstat (limited to 'libavformat/crypto.c')
| -rw-r--r-- | libavformat/crypto.c | 170 |
1 files changed, 170 insertions, 0 deletions
diff --git a/libavformat/crypto.c b/libavformat/crypto.c new file mode 100644 index 0000000000..ea6012ad09 --- /dev/null +++ b/libavformat/crypto.c @@ -0,0 +1,170 @@ +/* + * Decryption protocol handler + * Copyright (c) 2011 Martin Storsjo + * + * This file is part of Libav. + * + * Libav 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. + * + * Libav 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 Libav; 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) +static const AVOption options[] = { + {"key", "AES decryption key", OFFSET(key), FF_OPT_TYPE_BINARY }, + {"iv", "AES decryption initialization vector", OFFSET(iv), FF_OPT_TYPE_BINARY }, + { NULL } +}; + +static const AVClass crypto_class = { + "crypto", av_default_item_name, options, LIBAVUTIL_VERSION_INT +}; + +static int crypto_open(URLContext *h, const char *uri, int flags) +{ + const char *nested_url; + int ret; + 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)) < 0) { + av_log(h, AV_LOG_ERROR, "Unable to open input\n"); + goto err; + } + c->aes = av_mallocz(av_aes_size); + if (!c->aes) { + ret = AVERROR(ENOMEM); + goto err; + } + + av_aes_init(c->aes, c->key, 128, 1); + + h->is_streamed = 1; + + return 0; +err: + av_free(c->key); + av_free(c->iv); + 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_free(c->aes); + av_free(c->key); + av_free(c->iv); + return 0; +} + +URLProtocol ff_crypto_protocol = { + .name = "crypto", + .url_open = crypto_open, + .url_read = crypto_read, + .url_close = crypto_close, + .priv_data_size = sizeof(CryptoContext), + .priv_data_class = &crypto_class, + .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME, +}; |