2 * Decryption protocol handler
3 * Copyright (c) 2011 Martin Storsjo
5 * This file is part of FFmpeg.
7 * FFmpeg 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.
12 * FFmpeg 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.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
23 #include "libavutil/aes.h"
24 #include "libavutil/avstring.h"
25 #include "libavutil/opt.h"
29 // encourage reads of 4096 bytes - 1 block is always retained.
30 #define MAX_BUFFER_BLOCKS 257
33 typedef struct CryptoContext {
36 uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
37 outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
39 int indata, indata_used, outdata;
40 int64_t position; // position in file - used in seek
55 struct AVAES *aes_decrypt;
56 struct AVAES *aes_encrypt;
58 uint8_t pad[BLOCKSIZE];
63 #define OFFSET(x) offsetof(CryptoContext, x)
64 #define D AV_OPT_FLAG_DECODING_PARAM
65 #define E AV_OPT_FLAG_ENCODING_PARAM
66 static const AVOption options[] = {
67 {"key", "AES encryption/decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D|E },
68 {"iv", "AES encryption/decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D|E },
69 {"decryption_key", "AES decryption key", OFFSET(decrypt_key), AV_OPT_TYPE_BINARY, .flags = D },
70 {"decryption_iv", "AES decryption initialization vector", OFFSET(decrypt_iv), AV_OPT_TYPE_BINARY, .flags = D },
71 {"encryption_key", "AES encryption key", OFFSET(encrypt_key), AV_OPT_TYPE_BINARY, .flags = E },
72 {"encryption_iv", "AES encryption initialization vector", OFFSET(encrypt_iv), AV_OPT_TYPE_BINARY, .flags = E },
76 static const AVClass crypto_class = {
77 .class_name = "crypto",
78 .item_name = av_default_item_name,
80 .version = LIBAVUTIL_VERSION_INT,
83 static int set_aes_arg(CryptoContext *c, uint8_t **buf, int *buf_len,
84 uint8_t *default_buf, int default_buf_len,
88 if (!default_buf_len) {
89 av_log(c, AV_LOG_ERROR, "%s not set\n", desc);
90 return AVERROR(EINVAL);
91 } else if (default_buf_len != BLOCKSIZE) {
92 av_log(c, AV_LOG_ERROR,
93 "invalid %s size (%d bytes, block size is %d)\n",
94 desc, default_buf_len, BLOCKSIZE);
95 return AVERROR(EINVAL);
97 *buf = av_memdup(default_buf, default_buf_len);
99 return AVERROR(ENOMEM);
100 *buf_len = default_buf_len;
101 } else if (*buf_len != BLOCKSIZE) {
102 av_log(c, AV_LOG_ERROR,
103 "invalid %s size (%d bytes, block size is %d)\n",
104 desc, *buf_len, BLOCKSIZE);
105 return AVERROR(EINVAL);
110 static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
112 const char *nested_url;
114 CryptoContext *c = h->priv_data;
117 if (!av_strstart(uri, "crypto+", &nested_url) &&
118 !av_strstart(uri, "crypto:", &nested_url)) {
119 av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
120 ret = AVERROR(EINVAL);
126 if (flags & AVIO_FLAG_READ) {
127 if ((ret = set_aes_arg(c, &c->decrypt_key, &c->decrypt_keylen,
128 c->key, c->keylen, "decryption key")) < 0)
130 if ((ret = set_aes_arg(c, &c->decrypt_iv, &c->decrypt_ivlen,
131 c->iv, c->ivlen, "decryption IV")) < 0)
135 if (flags & AVIO_FLAG_WRITE) {
136 if ((ret = set_aes_arg(c, &c->encrypt_key, &c->encrypt_keylen,
137 c->key, c->keylen, "encryption key")) < 0)
140 if ((ret = set_aes_arg(c, &c->encrypt_iv, &c->encrypt_ivlen,
141 c->iv, c->ivlen, "encryption IV")) < 0)
145 if ((ret = ffurl_open_whitelist(&c->hd, nested_url, flags,
146 &h->interrupt_callback, options,
147 h->protocol_whitelist, h->protocol_blacklist, h)) < 0) {
148 av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", nested_url);
152 if (flags & AVIO_FLAG_READ) {
153 c->aes_decrypt = av_aes_alloc();
154 if (!c->aes_decrypt) {
155 ret = AVERROR(ENOMEM);
158 ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE*8, 1);
162 // pass back information about the context we openned
163 if (c->hd->is_streamed)
164 h->is_streamed = c->hd->is_streamed;
167 if (flags & AVIO_FLAG_WRITE) {
168 c->aes_encrypt = av_aes_alloc();
169 if (!c->aes_encrypt) {
170 ret = AVERROR(ENOMEM);
173 ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE*8, 0);
176 // for write, we must be streamed
177 // - linear write only for crytpo aes-128-cbc
187 static int crypto_read(URLContext *h, uint8_t *buf, int size)
189 CryptoContext *c = h->priv_data;
192 if (c->outdata > 0) {
193 size = FFMIN(size, c->outdata);
194 memcpy(buf, c->outptr, size);
197 c->position = c->position + size;
200 // We avoid using the last block until we've found EOF,
201 // since we'll remove PKCS7 padding at the end. So make
202 // sure we've got at least 2 blocks, so we can decrypt
204 while (c->indata - c->indata_used < 2*BLOCKSIZE) {
205 int n = ffurl_read(c->hd, c->inbuffer + c->indata,
206 sizeof(c->inbuffer) - c->indata);
213 blocks = (c->indata - c->indata_used) / BLOCKSIZE;
218 av_aes_crypt(c->aes_decrypt, c->outbuffer, c->inbuffer + c->indata_used,
219 blocks, c->decrypt_iv, 1);
220 c->outdata = BLOCKSIZE * blocks;
221 c->outptr = c->outbuffer;
222 c->indata_used += BLOCKSIZE * blocks;
223 if (c->indata_used >= sizeof(c->inbuffer)/2) {
224 memmove(c->inbuffer, c->inbuffer + c->indata_used,
225 c->indata - c->indata_used);
226 c->indata -= c->indata_used;
230 // Remove PKCS7 padding at the end
231 int padding = c->outbuffer[c->outdata - 1];
232 c->outdata -= padding;
237 static int64_t crypto_seek(URLContext *h, int64_t pos, int whence)
239 CryptoContext *c = h->priv_data;
243 if (c->flags & AVIO_FLAG_WRITE) {
244 av_log(h, AV_LOG_ERROR,
245 "Crypto: seek not supported for write\r\n");
246 /* seems the most appropriate error to return */
247 return AVERROR(ESPIPE);
250 // reset eof, else we won't read it correctly if we already hit eof.
257 pos = pos + c->position;
260 int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
262 av_log(h, AV_LOG_ERROR,
263 "Crypto: seek_end - can't get file size (pos=%lld)\r\n", (long long int)pos);
270 int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
275 av_log(h, AV_LOG_ERROR,
276 "Crypto: no support for seek where 'whence' is %d\r\n", whence);
277 return AVERROR(EINVAL);
283 c->outptr = c->outbuffer;
285 // identify the block containing the IV for the
286 // next block we will decrypt
287 block = pos/BLOCKSIZE;
289 // restore the iv to the seed one - this is the iv for the FIRST block
290 memcpy( c->decrypt_iv, c->iv, c->ivlen );
293 // else, go back one block - we will get av_cyrpt to read this block
294 // which it will then store use as the iv.
295 // note that the DECRYPTED result will not be correct,
296 // but will be discarded
298 c->position = (block * BLOCKSIZE);
301 newpos = ffurl_seek( c->hd, c->position, SEEK_SET );
303 av_log(h, AV_LOG_ERROR,
304 "Crypto: nested protocol no support for seek or seek failed\n");
308 // read and discard from here up to required position
309 // (which will set the iv correctly to it).
310 if (pos - c->position) {
311 uint8_t buff[BLOCKSIZE*2]; // maximum size of pos-c->position
312 int len = pos - c->position;
316 // note: this may not return all the bytes first time
317 res = crypto_read(h, buff, len);
323 // if we did not get all the bytes
325 char errbuf[100] = "unknown error";
326 av_strerror(res, errbuf, sizeof(errbuf));
327 av_log(h, AV_LOG_ERROR,
328 "Crypto: discard read did not get all the bytes (%d remain) - read returned (%d)-%s\n",
330 return AVERROR(EINVAL);
337 static int crypto_write(URLContext *h, const unsigned char *buf, int size)
339 CryptoContext *c = h->priv_data;
340 int total_size, blocks, pad_len, out_size;
344 total_size = size + c->pad_len;
345 pad_len = total_size % BLOCKSIZE;
346 out_size = total_size - pad_len;
347 blocks = out_size / BLOCKSIZE;
350 out_buf = av_malloc(out_size);
352 return AVERROR(ENOMEM);
355 memcpy(&c->pad[c->pad_len], buf, BLOCKSIZE - c->pad_len);
356 av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0);
360 av_aes_crypt(c->aes_encrypt, &out_buf[c->pad_len ? BLOCKSIZE : 0],
361 &buf[c->pad_len ? BLOCKSIZE - c->pad_len: 0],
362 blocks, c->encrypt_iv, 0);
364 ret = ffurl_write(c->hd, out_buf, out_size);
369 memcpy(c->pad, &buf[size - pad_len], pad_len);
371 memcpy(&c->pad[c->pad_len], buf, size);
373 c->pad_len = pad_len;
378 static int crypto_close(URLContext *h)
380 CryptoContext *c = h->priv_data;
381 uint8_t out_buf[BLOCKSIZE];
384 if (c->aes_encrypt) {
385 pad = BLOCKSIZE - c->pad_len;
386 memset(&c->pad[c->pad_len], pad, pad);
387 av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0);
388 if ((ret = ffurl_write(c->hd, out_buf, BLOCKSIZE)) < 0)
394 av_freep(&c->aes_decrypt);
395 av_freep(&c->aes_encrypt);
399 const URLProtocol ff_crypto_protocol = {
401 .url_open2 = crypto_open2,
402 .url_seek = crypto_seek,
403 .url_read = crypto_read,
404 .url_write = crypto_write,
405 .url_close = crypto_close,
406 .priv_data_size = sizeof(CryptoContext),
407 .priv_data_class = &crypto_class,
408 .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME,