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crypto.c
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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 
33 typedef struct CryptoContext {
34  const AVClass *class;
40  int64_t position; // position in file - used in seek
41  int flags;
42  int eof;
44  int keylen;
46  int ivlen;
55  struct AVAES *aes_decrypt;
56  struct AVAES *aes_encrypt;
58  unsigned int write_buf_size;
60  int pad_len;
62 
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 },
73  { NULL }
74 };
75 
76 static 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 
83 static 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) {
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 
110 static 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 
179 err:
180  return ret;
181 }
182 
183 static int crypto_read(URLContext *h, uint8_t *buf, int size)
184 {
185  CryptoContext *c = h->priv_data;
186  int blocks;
187 retry:
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--;
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 
233 static 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 
333 static 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 
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 
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 
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,
406 };
static int crypto_close(URLContext *h)
Definition: crypto.c:374
#define NULL
Definition: coverity.c:32
int ffurl_open_whitelist(URLContext **puc, const char *filename, int flags, const AVIOInterruptCB *int_cb, AVDictionary **options, const char *whitelist, const char *blacklist, URLContext *parent)
Create an URLContext for accessing to the resource indicated by url, and open it. ...
Definition: avio.c:309
uint8_t * iv
Definition: crypto.c:45
AVOption.
Definition: opt.h:246
int ivlen
Definition: crypto.c:46
#define LIBAVUTIL_VERSION_INT
Definition: version.h:85
int ffurl_write(URLContext *h, const unsigned char *buf, int size)
Write size bytes from buf to the resource accessed by h.
Definition: avio.c:421
const char * desc
Definition: nvenc.c:60
int is_streamed
true if streamed (no seek possible), default = false
Definition: url.h:45
int decrypt_ivlen
Definition: crypto.c:50
int64_t position
Definition: crypto.c:40
AVIOInterruptCB interrupt_callback
Definition: url.h:47
static int crypto_read(URLContext *h, uint8_t *buf, int size)
Definition: crypto.c:183
#define AVIO_FLAG_READ
read-only
Definition: avio.h:622
void av_aes_crypt(AVAES *a, uint8_t *dst, const uint8_t *src, int count, uint8_t *iv, int decrypt)
Encrypt or decrypt a buffer using a previously initialized context.
Definition: aes.c:163
#define AVIO_FLAG_WRITE
write-only
Definition: avio.h:623
int decrypt_keylen
Definition: crypto.c:48
int out_size
Definition: movenc.c:55
int encrypt_ivlen
Definition: crypto.c:54
static const AVOption options[]
Definition: crypto.c:66
unsigned int write_buf_size
Definition: crypto.c:58
uint8_t inbuffer[BLOCKSIZE *MAX_BUFFER_BLOCKS]
Definition: crypto.c:36
uint8_t * outptr
Definition: crypto.c:38
uint8_t * encrypt_key
Definition: crypto.c:51
static int set_aes_arg(URLContext *h, uint8_t **buf, int *buf_len, uint8_t *default_buf, int default_buf_len, const char *desc)
Definition: crypto.c:83
#define E
Definition: crypto.c:65
uint8_t outbuffer[BLOCKSIZE *MAX_BUFFER_BLOCKS]
Definition: crypto.c:36
static int16_t block[64]
Definition: dct.c:115
const char * class_name
The name of the class; usually it is the same name as the context structure type to which the AVClass...
Definition: log.h:72
int keylen
Definition: crypto.c:44
uint8_t
AVOptions.
static int flags
Definition: log.c:57
#define AVERROR_EOF
End of file.
Definition: error.h:55
ptrdiff_t size
Definition: opengl_enc.c:101
#define av_log(a,...)
static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
Definition: crypto.c:110
#define MAX_BUFFER_BLOCKS
Definition: crypto.c:30
#define BLOCKSIZE
Definition: crypto.c:31
#define AV_LOG_ERROR
Something went wrong and cannot losslessly be recovered.
Definition: log.h:176
struct AVAES * aes_decrypt
Definition: crypto.c:55
uint8_t * decrypt_key
Definition: crypto.c:47
int indata_used
Definition: crypto.c:39
const char * protocol_whitelist
Definition: url.h:49
av_default_item_name
#define AVERROR(e)
Definition: error.h:43
uint8_t pad[BLOCKSIZE]
Definition: crypto.c:59
#define URL_PROTOCOL_FLAG_NESTED_SCHEME
Definition: url.h:33
int pad_len
Definition: crypto.c:60
int outdata
Definition: crypto.c:39
struct AVAES * av_aes_alloc(void)
Allocate an AVAES context.
Definition: aes.c:31
struct AVAES * aes_encrypt
Definition: crypto.c:56
uint8_t * encrypt_iv
Definition: crypto.c:53
void * av_memdup(const void *p, size_t size)
Duplicate a buffer with av_malloc().
Definition: mem.c:269
#define D
Definition: crypto.c:64
void av_fast_malloc(void *ptr, unsigned int *size, size_t min_size)
Allocate a buffer, reusing the given one if large enough.
Definition: mem.c:469
uint8_t * key
Definition: crypto.c:43
#define FFMIN(a, b)
Definition: common.h:96
static const AVClass crypto_class
Definition: crypto.c:76
URLContext * hd
Definition: crypto.c:35
uint8_t * write_buf
Definition: crypto.c:57
int n
Definition: avisynth_c.h:684
int indata
Definition: crypto.c:39
offset must point to a pointer immediately followed by an int for the length
Definition: opt.h:229
int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
Initialize an AVAES context.
Definition: aes.c:195
const char * protocol_blacklist
Definition: url.h:50
const URLProtocol ff_crypto_protocol
Definition: crypto.c:396
static int64_t crypto_seek(URLContext *h, int64_t pos, int whence)
Definition: crypto.c:233
uint8_t * decrypt_iv
Definition: crypto.c:49
void * buf
Definition: avisynth_c.h:690
Definition: url.h:38
Describe the class of an AVClass context structure.
Definition: log.h:67
void * priv_data
Definition: url.h:41
static int crypto_write(URLContext *h, const unsigned char *buf, int size)
Definition: crypto.c:333
const char * name
Definition: url.h:54
int ffurl_close(URLContext *h)
Definition: avio.c:467
int av_strerror(int errnum, char *errbuf, size_t errbuf_size)
Put a description of the AVERROR code errnum in errbuf.
Definition: error.c:105
int av_strstart(const char *str, const char *pfx, const char **ptr)
Return non-zero if pfx is a prefix of str.
Definition: avstring.c:34
Main libavformat public API header.
int64_t ffurl_seek(URLContext *h, int64_t pos, int whence)
Change the position that will be used by the next read/write operation on the resource accessed by h...
Definition: avio.c:434
static double c[64]
#define AVSEEK_SIZE
ORing this as the "whence" parameter to a seek function causes it to return the filesize without seek...
Definition: avio.h:501
int len
#define OFFSET(x)
Definition: crypto.c:63
int flags
Definition: crypto.c:41
#define av_freep(p)
unbuffered private I/O API
int encrypt_keylen
Definition: crypto.c:52
int ffurl_read(URLContext *h, unsigned char *buf, int size)
Read up to size bytes from the resource accessed by h, and store the read bytes in buf...
Definition: avio.c:407