1/* 2 * Decryption protocol handler 3 * Copyright (c) 2011 Martin Storsjo 4 * 5 * This file is part of Libav. 6 * 7 * Libav is free software; you can redistribute it and/or 8 * modify it under the terms of the GNU Lesser General Public 9 * License as published by the Free Software Foundation; either 10 * version 2.1 of the License, or (at your option) any later version. 11 * 12 * Libav is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15 * Lesser General Public License for more details. 16 * 17 * You should have received a copy of the GNU Lesser General Public 18 * License along with Libav; if not, write to the Free Software 19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 20 */ 21 22#include "avformat.h" 23#include "libavutil/aes.h" 24#include "libavutil/avstring.h" 25#include "libavutil/opt.h" 26#include "internal.h" 27#include "url.h" 28 29#define MAX_BUFFER_BLOCKS 150 30#define BLOCKSIZE 16 31 32typedef struct { 33 const AVClass *class; 34 URLContext *hd; 35 uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS], 36 outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS]; 37 uint8_t *outptr; 38 int indata, indata_used, outdata; 39 int eof; 40 uint8_t *key; 41 int keylen; 42 uint8_t *iv; 43 int ivlen; 44 struct AVAES *aes; 45} CryptoContext; 46 47#define OFFSET(x) offsetof(CryptoContext, x) 48#define D AV_OPT_FLAG_DECODING_PARAM 49static const AVOption options[] = { 50 {"key", "AES decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D }, 51 {"iv", "AES decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D }, 52 { NULL } 53}; 54 55static const AVClass crypto_class = { 56 .class_name = "crypto", 57 .item_name = av_default_item_name, 58 .option = options, 59 .version = LIBAVUTIL_VERSION_INT, 60}; 61 62static int crypto_open(URLContext *h, const char *uri, int flags) 63{ 64 const char *nested_url; 65 int ret = 0; 66 CryptoContext *c = h->priv_data; 67 68 if (!av_strstart(uri, "crypto+", &nested_url) && 69 !av_strstart(uri, "crypto:", &nested_url)) { 70 av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri); 71 ret = AVERROR(EINVAL); 72 goto err; 73 } 74 75 if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) { 76 av_log(h, AV_LOG_ERROR, "Key or IV not set\n"); 77 ret = AVERROR(EINVAL); 78 goto err; 79 } 80 if (flags & AVIO_FLAG_WRITE) { 81 av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n"); 82 ret = AVERROR(ENOSYS); 83 goto err; 84 } 85 if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ, 86 &h->interrupt_callback, NULL)) < 0) { 87 av_log(h, AV_LOG_ERROR, "Unable to open input\n"); 88 goto err; 89 } 90 c->aes = av_mallocz(av_aes_size); 91 if (!c->aes) { 92 ret = AVERROR(ENOMEM); 93 goto err; 94 } 95 96 av_aes_init(c->aes, c->key, 128, 1); 97 98 h->is_streamed = 1; 99 100err: 101 return ret; 102} 103 104static int crypto_read(URLContext *h, uint8_t *buf, int size) 105{ 106 CryptoContext *c = h->priv_data; 107 int blocks; 108retry: 109 if (c->outdata > 0) { 110 size = FFMIN(size, c->outdata); 111 memcpy(buf, c->outptr, size); 112 c->outptr += size; 113 c->outdata -= size; 114 return size; 115 } 116 // We avoid using the last block until we've found EOF, 117 // since we'll remove PKCS7 padding at the end. So make 118 // sure we've got at least 2 blocks, so we can decrypt 119 // at least one. 120 while (c->indata - c->indata_used < 2*BLOCKSIZE) { 121 int n = ffurl_read(c->hd, c->inbuffer + c->indata, 122 sizeof(c->inbuffer) - c->indata); 123 if (n <= 0) { 124 c->eof = 1; 125 break; 126 } 127 c->indata += n; 128 } 129 blocks = (c->indata - c->indata_used) / BLOCKSIZE; 130 if (!blocks) 131 return AVERROR_EOF; 132 if (!c->eof) 133 blocks--; 134 av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks, 135 c->iv, 1); 136 c->outdata = BLOCKSIZE * blocks; 137 c->outptr = c->outbuffer; 138 c->indata_used += BLOCKSIZE * blocks; 139 if (c->indata_used >= sizeof(c->inbuffer)/2) { 140 memmove(c->inbuffer, c->inbuffer + c->indata_used, 141 c->indata - c->indata_used); 142 c->indata -= c->indata_used; 143 c->indata_used = 0; 144 } 145 if (c->eof) { 146 // Remove PKCS7 padding at the end 147 int padding = c->outbuffer[c->outdata - 1]; 148 c->outdata -= padding; 149 } 150 goto retry; 151} 152 153static int crypto_close(URLContext *h) 154{ 155 CryptoContext *c = h->priv_data; 156 if (c->hd) 157 ffurl_close(c->hd); 158 av_freep(&c->aes); 159 return 0; 160} 161 162URLProtocol ff_crypto_protocol = { 163 .name = "crypto", 164 .url_open = crypto_open, 165 .url_read = crypto_read, 166 .url_close = crypto_close, 167 .priv_data_size = sizeof(CryptoContext), 168 .priv_data_class = &crypto_class, 169 .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME, 170}; 171