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path: root/libavformat/crypto.c (plain)
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1/*
2 * Decryption protocol handler
3 * Copyright (c) 2011 Martin Storsjo
4 *
5 * This file is part of FFmpeg.
6 *
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.
11 *
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.
16 *
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
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// encourage reads of 4096 bytes - 1 block is always retained.
30#define MAX_BUFFER_BLOCKS 257
31#define BLOCKSIZE 16
32
33typedef struct CryptoContext {
34 const AVClass *class;
35 URLContext *hd;
36 uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
37 outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
38 uint8_t *outptr;
39 int indata, indata_used, outdata;
40 int64_t position; // position in file - used in seek
41 int flags;
42 int eof;
43 uint8_t *key;
44 int keylen;
45 uint8_t *iv;
46 int ivlen;
47 uint8_t *decrypt_key;
48 int decrypt_keylen;
49 uint8_t *decrypt_iv;
50 int decrypt_ivlen;
51 uint8_t *encrypt_key;
52 int encrypt_keylen;
53 uint8_t *encrypt_iv;
54 int encrypt_ivlen;
55 struct AVAES *aes_decrypt;
56 struct AVAES *aes_encrypt;
57 uint8_t *write_buf;
58 unsigned int write_buf_size;
59 uint8_t pad[BLOCKSIZE];
60 int pad_len;
61} CryptoContext;
62
63#define OFFSET(x) offsetof(CryptoContext, x)
64#define D AV_OPT_FLAG_DECODING_PARAM
65#define E AV_OPT_FLAG_ENCODING_PARAM
66static 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 },
73 { NULL }
74};
75
76static const AVClass crypto_class = {
77 .class_name = "crypto",
78 .item_name = av_default_item_name,
79 .option = options,
80 .version = LIBAVUTIL_VERSION_INT,
81};
82
83static int set_aes_arg(URLContext *h, uint8_t **buf, int *buf_len,
84 uint8_t *default_buf, int default_buf_len,
85 const char *desc)
86{
87 if (!*buf_len) {
88 if (!default_buf_len) {
89 av_log(h, AV_LOG_ERROR, "%s not set\n", desc);
90 return AVERROR(EINVAL);
91 } else if (default_buf_len != BLOCKSIZE) {
92 av_log(h, AV_LOG_ERROR,
93 "invalid %s size (%d bytes, block size is %d)\n",
94 desc, default_buf_len, BLOCKSIZE);
95 return AVERROR(EINVAL);
96 }
97 *buf = av_memdup(default_buf, default_buf_len);
98 if (!*buf)
99 return AVERROR(ENOMEM);
100 *buf_len = default_buf_len;
101 } else if (*buf_len != BLOCKSIZE) {
102 av_log(h, AV_LOG_ERROR,
103 "invalid %s size (%d bytes, block size is %d)\n",
104 desc, *buf_len, BLOCKSIZE);
105 return AVERROR(EINVAL);
106 }
107 return 0;
108}
109
110static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
111{
112 const char *nested_url;
113 int ret = 0;
114 CryptoContext *c = h->priv_data;
115 c->flags = flags;
116
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);
121 goto err;
122 }
123
124 if (flags & AVIO_FLAG_READ) {
125 if ((ret = set_aes_arg(h, &c->decrypt_key, &c->decrypt_keylen,
126 c->key, c->keylen, "decryption key")) < 0)
127 goto err;
128 if ((ret = set_aes_arg(h, &c->decrypt_iv, &c->decrypt_ivlen,
129 c->iv, c->ivlen, "decryption IV")) < 0)
130 goto err;
131 }
132
133 if (flags & AVIO_FLAG_WRITE) {
134 if ((ret = set_aes_arg(h, &c->encrypt_key, &c->encrypt_keylen,
135 c->key, c->keylen, "encryption key")) < 0)
136 if (ret < 0)
137 goto err;
138 if ((ret = set_aes_arg(h, &c->encrypt_iv, &c->encrypt_ivlen,
139 c->iv, c->ivlen, "encryption IV")) < 0)
140 goto err;
141 }
142
143 if ((ret = ffurl_open_whitelist(&c->hd, nested_url, flags,
144 &h->interrupt_callback, options,
145 h->protocol_whitelist, h->protocol_blacklist, h)) < 0) {
146 av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", nested_url);
147 goto err;
148 }
149
150 if (flags & AVIO_FLAG_READ) {
151 c->aes_decrypt = av_aes_alloc();
152 if (!c->aes_decrypt) {
153 ret = AVERROR(ENOMEM);
154 goto err;
155 }
156 ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE * 8, 1);
157 if (ret < 0)
158 goto err;
159
160 // pass back information about the context we openned
161 if (c->hd->is_streamed)
162 h->is_streamed = c->hd->is_streamed;
163 }
164
165 if (flags & AVIO_FLAG_WRITE) {
166 c->aes_encrypt = av_aes_alloc();
167 if (!c->aes_encrypt) {
168 ret = AVERROR(ENOMEM);
169 goto err;
170 }
171 ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE * 8, 0);
172 if (ret < 0)
173 goto err;
174 // for write, we must be streamed
175 // - linear write only for crytpo aes-128-cbc
176 h->is_streamed = 1;
177 }
178
179err:
180 return ret;
181}
182
183static int crypto_read(URLContext *h, uint8_t *buf, int size)
184{
185 CryptoContext *c = h->priv_data;
186 int blocks;
187retry:
188 if (c->outdata > 0) {
189 size = FFMIN(size, c->outdata);
190 memcpy(buf, c->outptr, size);
191 c->outptr += size;
192 c->outdata -= size;
193 c->position = c->position + size;
194 return size;
195 }
196 // We avoid using the last block until we've found EOF,
197 // since we'll remove PKCS7 padding at the end. So make
198 // sure we've got at least 2 blocks, so we can decrypt
199 // at least one.
200 while (c->indata - c->indata_used < 2*BLOCKSIZE) {
201 int n = ffurl_read(c->hd, c->inbuffer + c->indata,
202 sizeof(c->inbuffer) - c->indata);
203 if (n <= 0) {
204 c->eof = 1;
205 break;
206 }
207 c->indata += n;
208 }
209 blocks = (c->indata - c->indata_used) / BLOCKSIZE;
210 if (!blocks)
211 return AVERROR_EOF;
212 if (!c->eof)
213 blocks--;
214 av_aes_crypt(c->aes_decrypt, c->outbuffer, c->inbuffer + c->indata_used,
215 blocks, c->decrypt_iv, 1);
216 c->outdata = BLOCKSIZE * blocks;
217 c->outptr = c->outbuffer;
218 c->indata_used += BLOCKSIZE * blocks;
219 if (c->indata_used >= sizeof(c->inbuffer)/2) {
220 memmove(c->inbuffer, c->inbuffer + c->indata_used,
221 c->indata - c->indata_used);
222 c->indata -= c->indata_used;
223 c->indata_used = 0;
224 }
225 if (c->eof) {
226 // Remove PKCS7 padding at the end
227 int padding = c->outbuffer[c->outdata - 1];
228 c->outdata -= padding;
229 }
230 goto retry;
231}
232
233static int64_t crypto_seek(URLContext *h, int64_t pos, int whence)
234{
235 CryptoContext *c = h->priv_data;
236 int64_t block;
237 int64_t newpos;
238
239 if (c->flags & AVIO_FLAG_WRITE) {
240 av_log(h, AV_LOG_ERROR,
241 "Crypto: seek not supported for write\r\n");
242 /* seems the most appropriate error to return */
243 return AVERROR(ESPIPE);
244 }
245
246 // reset eof, else we won't read it correctly if we already hit eof.
247 c->eof = 0;
248
249 switch (whence) {
250 case SEEK_SET:
251 break;
252 case SEEK_CUR:
253 pos = pos + c->position;
254 break;
255 case SEEK_END: {
256 int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
257 if (newpos < 0) {
258 av_log(h, AV_LOG_ERROR,
259 "Crypto: seek_end - can't get file size (pos=%lld)\r\n", (long long int)pos);
260 return newpos;
261 }
262 pos = newpos - pos;
263 }
264 break;
265 case AVSEEK_SIZE: {
266 int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
267 return newpos;
268 }
269 break;
270 default:
271 av_log(h, AV_LOG_ERROR,
272 "Crypto: no support for seek where 'whence' is %d\r\n", whence);
273 return AVERROR(EINVAL);
274 }
275
276 c->outdata = 0;
277 c->indata = 0;
278 c->indata_used = 0;
279 c->outptr = c->outbuffer;
280
281 // identify the block containing the IV for the
282 // next block we will decrypt
283 block = pos/BLOCKSIZE;
284 if (block == 0) {
285 // restore the iv to the seed one - this is the iv for the FIRST block
286 memcpy( c->decrypt_iv, c->iv, c->ivlen );
287 c->position = 0;
288 } else {
289 // else, go back one block - we will get av_cyrpt to read this block
290 // which it will then store use as the iv.
291 // note that the DECRYPTED result will not be correct,
292 // but will be discarded
293 block--;
294 c->position = (block * BLOCKSIZE);
295 }
296
297 newpos = ffurl_seek( c->hd, c->position, SEEK_SET );
298 if (newpos < 0) {
299 av_log(h, AV_LOG_ERROR,
300 "Crypto: nested protocol no support for seek or seek failed\n");
301 return newpos;
302 }
303
304 // read and discard from here up to required position
305 // (which will set the iv correctly to it).
306 if (pos - c->position) {
307 uint8_t buff[BLOCKSIZE*2]; // maximum size of pos-c->position
308 int len = pos - c->position;
309 int res;
310
311 while (len > 0) {
312 // note: this may not return all the bytes first time
313 res = crypto_read(h, buff, len);
314 if (res < 0)
315 break;
316 len -= res;
317 }
318
319 // if we did not get all the bytes
320 if (len != 0) {
321 char errbuf[100] = "unknown error";
322 av_strerror(res, errbuf, sizeof(errbuf));
323 av_log(h, AV_LOG_ERROR,
324 "Crypto: discard read did not get all the bytes (%d remain) - read returned (%d)-%s\n",
325 len, res, errbuf);
326 return AVERROR(EINVAL);
327 }
328 }
329
330 return c->position;
331}
332
333static int crypto_write(URLContext *h, const unsigned char *buf, int size)
334{
335 CryptoContext *c = h->priv_data;
336 int total_size, blocks, pad_len, out_size;
337 int ret = 0;
338
339 total_size = size + c->pad_len;
340 pad_len = total_size % BLOCKSIZE;
341 out_size = total_size - pad_len;
342 blocks = out_size / BLOCKSIZE;
343
344 if (out_size) {
345 av_fast_malloc(&c->write_buf, &c->write_buf_size, out_size);
346
347 if (!c->write_buf)
348 return AVERROR(ENOMEM);
349
350 if (c->pad_len) {
351 memcpy(&c->pad[c->pad_len], buf, BLOCKSIZE - c->pad_len);
352 av_aes_crypt(c->aes_encrypt, c->write_buf, c->pad, 1, c->encrypt_iv, 0);
353 blocks--;
354 }
355
356 av_aes_crypt(c->aes_encrypt,
357 &c->write_buf[c->pad_len ? BLOCKSIZE : 0],
358 &buf[c->pad_len ? BLOCKSIZE - c->pad_len : 0],
359 blocks, c->encrypt_iv, 0);
360
361 ret = ffurl_write(c->hd, c->write_buf, out_size);
362 if (ret < 0)
363 return ret;
364
365 memcpy(c->pad, &buf[size - pad_len], pad_len);
366 } else
367 memcpy(&c->pad[c->pad_len], buf, size);
368
369 c->pad_len = pad_len;
370
371 return size;
372}
373
374static int crypto_close(URLContext *h)
375{
376 CryptoContext *c = h->priv_data;
377 int ret = 0;
378
379 if (c->aes_encrypt) {
380 uint8_t out_buf[BLOCKSIZE];
381 int pad = BLOCKSIZE - c->pad_len;
382
383 memset(&c->pad[c->pad_len], pad, pad);
384 av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0);
385 ret = ffurl_write(c->hd, out_buf, BLOCKSIZE);
386 }
387
388 if (c->hd)
389 ffurl_close(c->hd);
390 av_freep(&c->aes_decrypt);
391 av_freep(&c->aes_encrypt);
392 av_freep(&c->write_buf);
393 return ret;
394}
395
396const URLProtocol ff_crypto_protocol = {
397 .name = "crypto",
398 .url_open2 = crypto_open2,
399 .url_seek = crypto_seek,
400 .url_read = crypto_read,
401 .url_write = crypto_write,
402 .url_close = crypto_close,
403 .priv_data_size = sizeof(CryptoContext),
404 .priv_data_class = &crypto_class,
405 .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME,
406};
407
generated by cgit at 2024-05-17 06:31:01 (GMT)