yading@11: /*
yading@11:  * Decryption protocol handler
yading@11:  * Copyright (c) 2011 Martin Storsjo
yading@11:  *
yading@11:  * This file is part of Libav.
yading@11:  *
yading@11:  * Libav is free software; you can redistribute it and/or
yading@11:  * modify it under the terms of the GNU Lesser General Public
yading@11:  * License as published by the Free Software Foundation; either
yading@11:  * version 2.1 of the License, or (at your option) any later version.
yading@11:  *
yading@11:  * Libav is distributed in the hope that it will be useful,
yading@11:  * but WITHOUT ANY WARRANTY; without even the implied warranty of
yading@11:  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
yading@11:  * Lesser General Public License for more details.
yading@11:  *
yading@11:  * You should have received a copy of the GNU Lesser General Public
yading@11:  * License along with Libav; if not, write to the Free Software
yading@11:  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
yading@11:  */
yading@11: 
yading@11: #include "avformat.h"
yading@11: #include "libavutil/aes.h"
yading@11: #include "libavutil/avstring.h"
yading@11: #include "libavutil/opt.h"
yading@11: #include "internal.h"
yading@11: #include "url.h"
yading@11: 
yading@11: #define MAX_BUFFER_BLOCKS 150
yading@11: #define BLOCKSIZE 16
yading@11: 
yading@11: typedef struct {
yading@11:     const AVClass *class;
yading@11:     URLContext *hd;
yading@11:     uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
yading@11:             outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
yading@11:     uint8_t *outptr;
yading@11:     int indata, indata_used, outdata;
yading@11:     int eof;
yading@11:     uint8_t *key;
yading@11:     int keylen;
yading@11:     uint8_t *iv;
yading@11:     int ivlen;
yading@11:     struct AVAES *aes;
yading@11: } CryptoContext;
yading@11: 
yading@11: #define OFFSET(x) offsetof(CryptoContext, x)
yading@11: #define D AV_OPT_FLAG_DECODING_PARAM
yading@11: static const AVOption options[] = {
yading@11:     {"key", "AES decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D },
yading@11:     {"iv",  "AES decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D },
yading@11:     { NULL }
yading@11: };
yading@11: 
yading@11: static const AVClass crypto_class = {
yading@11:     .class_name     = "crypto",
yading@11:     .item_name      = av_default_item_name,
yading@11:     .option         = options,
yading@11:     .version        = LIBAVUTIL_VERSION_INT,
yading@11: };
yading@11: 
yading@11: static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
yading@11: {
yading@11:     const char *nested_url;
yading@11:     int ret = 0;
yading@11:     CryptoContext *c = h->priv_data;
yading@11: 
yading@11:     if (!av_strstart(uri, "crypto+", &nested_url) &&
yading@11:         !av_strstart(uri, "crypto:", &nested_url)) {
yading@11:         av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
yading@11:         ret = AVERROR(EINVAL);
yading@11:         goto err;
yading@11:     }
yading@11: 
yading@11:     if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) {
yading@11:         av_log(h, AV_LOG_ERROR, "Key or IV not set\n");
yading@11:         ret = AVERROR(EINVAL);
yading@11:         goto err;
yading@11:     }
yading@11:     if (flags & AVIO_FLAG_WRITE) {
yading@11:         av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n");
yading@11:         ret = AVERROR(ENOSYS);
yading@11:         goto err;
yading@11:     }
yading@11:     if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ,
yading@11:                           &h->interrupt_callback, options)) < 0) {
yading@11:         av_log(h, AV_LOG_ERROR, "Unable to open input\n");
yading@11:         goto err;
yading@11:     }
yading@11:     c->aes = av_aes_alloc();
yading@11:     if (!c->aes) {
yading@11:         ret = AVERROR(ENOMEM);
yading@11:         goto err;
yading@11:     }
yading@11: 
yading@11:     av_aes_init(c->aes, c->key, 128, 1);
yading@11: 
yading@11:     h->is_streamed = 1;
yading@11: 
yading@11: err:
yading@11:     return ret;
yading@11: }
yading@11: 
yading@11: static int crypto_read(URLContext *h, uint8_t *buf, int size)
yading@11: {
yading@11:     CryptoContext *c = h->priv_data;
yading@11:     int blocks;
yading@11: retry:
yading@11:     if (c->outdata > 0) {
yading@11:         size = FFMIN(size, c->outdata);
yading@11:         memcpy(buf, c->outptr, size);
yading@11:         c->outptr  += size;
yading@11:         c->outdata -= size;
yading@11:         return size;
yading@11:     }
yading@11:     // We avoid using the last block until we've found EOF,
yading@11:     // since we'll remove PKCS7 padding at the end. So make
yading@11:     // sure we've got at least 2 blocks, so we can decrypt
yading@11:     // at least one.
yading@11:     while (c->indata - c->indata_used < 2*BLOCKSIZE) {
yading@11:         int n = ffurl_read(c->hd, c->inbuffer + c->indata,
yading@11:                            sizeof(c->inbuffer) - c->indata);
yading@11:         if (n <= 0) {
yading@11:             c->eof = 1;
yading@11:             break;
yading@11:         }
yading@11:         c->indata += n;
yading@11:     }
yading@11:     blocks = (c->indata - c->indata_used) / BLOCKSIZE;
yading@11:     if (!blocks)
yading@11:         return AVERROR_EOF;
yading@11:     if (!c->eof)
yading@11:         blocks--;
yading@11:     av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks,
yading@11:                  c->iv, 1);
yading@11:     c->outdata      = BLOCKSIZE * blocks;
yading@11:     c->outptr       = c->outbuffer;
yading@11:     c->indata_used += BLOCKSIZE * blocks;
yading@11:     if (c->indata_used >= sizeof(c->inbuffer)/2) {
yading@11:         memmove(c->inbuffer, c->inbuffer + c->indata_used,
yading@11:                 c->indata - c->indata_used);
yading@11:         c->indata     -= c->indata_used;
yading@11:         c->indata_used = 0;
yading@11:     }
yading@11:     if (c->eof) {
yading@11:         // Remove PKCS7 padding at the end
yading@11:         int padding = c->outbuffer[c->outdata - 1];
yading@11:         c->outdata -= padding;
yading@11:     }
yading@11:     goto retry;
yading@11: }
yading@11: 
yading@11: static int crypto_close(URLContext *h)
yading@11: {
yading@11:     CryptoContext *c = h->priv_data;
yading@11:     if (c->hd)
yading@11:         ffurl_close(c->hd);
yading@11:     av_freep(&c->aes);
yading@11:     return 0;
yading@11: }
yading@11: 
yading@11: URLProtocol ff_crypto_protocol = {
yading@11:     .name            = "crypto",
yading@11:     .url_open2       = crypto_open2,
yading@11:     .url_read        = crypto_read,
yading@11:     .url_close       = crypto_close,
yading@11:     .priv_data_size  = sizeof(CryptoContext),
yading@11:     .priv_data_class = &crypto_class,
yading@11:     .flags           = URL_PROTOCOL_FLAG_NESTED_SCHEME,
yading@11: };