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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 #define MAX_BUFFER_BLOCKS 150
30 #define BLOCKSIZE 16
31 
32 typedef struct {
33  const AVClass *class;
36  outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
38  int indata, indata_used, outdata;
39  int eof;
41  int keylen;
43  int ivlen;
52  struct AVAES *aes_decrypt;
53  struct AVAES *aes_encrypt;
54 
56  int pad_len;
57 
59 
60 #define OFFSET(x) offsetof(CryptoContext, x)
61 #define D AV_OPT_FLAG_DECODING_PARAM
62 #define E AV_OPT_FLAG_ENCODING_PARAM
63 static const AVOption options[] = {
64  {"key", "AES encryption/decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D|E },
65  {"iv", "AES encryption/decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D|E },
66  {"decryption_key", "AES decryption key", OFFSET(decrypt_key), AV_OPT_TYPE_BINARY, .flags = D },
67  {"decryption_iv", "AES decryption initialization vector", OFFSET(decrypt_iv), AV_OPT_TYPE_BINARY, .flags = D },
68  {"encryption_key", "AES encryption key", OFFSET(encrypt_key), AV_OPT_TYPE_BINARY, .flags = E },
69  {"encryption_iv", "AES encryption initialization vector", OFFSET(encrypt_iv), AV_OPT_TYPE_BINARY, .flags = E },
70  { NULL }
71 };
72 
73 static const AVClass crypto_class = {
74  .class_name = "crypto",
75  .item_name = av_default_item_name,
76  .option = options,
77  .version = LIBAVUTIL_VERSION_INT,
78 };
79 
80 static int set_aes_arg(CryptoContext *c, uint8_t **buf, int *buf_len,
81  uint8_t *default_buf, int default_buf_len,
82  const char *desc)
83 {
84  if (!*buf_len) {
85  if (!default_buf_len) {
86  av_log(c, AV_LOG_ERROR, "%s not set\n", desc);
87  return AVERROR(EINVAL);
88  } else if (default_buf_len != BLOCKSIZE) {
90  "invalid %s size (%d bytes, block size is %d)\n",
91  desc, default_buf_len, BLOCKSIZE);
92  return AVERROR(EINVAL);
93  }
94  *buf = av_memdup(default_buf, default_buf_len);
95  if (!*buf)
96  return AVERROR(ENOMEM);
97  *buf_len = default_buf_len;
98  } else if (*buf_len != BLOCKSIZE) {
100  "invalid %s size (%d bytes, block size is %d)\n",
101  desc, *buf_len, BLOCKSIZE);
102  return AVERROR(EINVAL);
103  }
104  return 0;
105 }
106 
107 static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
108 {
109  const char *nested_url;
110  int ret = 0;
111  CryptoContext *c = h->priv_data;
112 
113  if (!av_strstart(uri, "crypto+", &nested_url) &&
114  !av_strstart(uri, "crypto:", &nested_url)) {
115  av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
116  ret = AVERROR(EINVAL);
117  goto err;
118  }
119 
120  if (flags & AVIO_FLAG_READ) {
121  if ((ret = set_aes_arg(c, &c->decrypt_key, &c->decrypt_keylen,
122  c->key, c->keylen, "decryption key")) < 0)
123  goto err;
124  if ((ret = set_aes_arg(c, &c->decrypt_iv, &c->decrypt_ivlen,
125  c->iv, c->ivlen, "decryption IV")) < 0)
126  goto err;
127  }
128 
129  if (flags & AVIO_FLAG_WRITE) {
130  if ((ret = set_aes_arg(c, &c->encrypt_key, &c->encrypt_keylen,
131  c->key, c->keylen, "encryption key")) < 0)
132  if (ret < 0)
133  goto err;
134  if ((ret = set_aes_arg(c, &c->encrypt_iv, &c->encrypt_ivlen,
135  c->iv, c->ivlen, "encryption IV")) < 0)
136  goto err;
137  }
138 
139  if ((ret = ffurl_open(&c->hd, nested_url, flags,
140  &h->interrupt_callback, options)) < 0) {
141  av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", nested_url);
142  goto err;
143  }
144 
145  if (flags & AVIO_FLAG_READ) {
146  c->aes_decrypt = av_aes_alloc();
147  if (!c->aes_decrypt) {
148  ret = AVERROR(ENOMEM);
149  goto err;
150  }
151  ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE*8, 1);
152  if (ret < 0)
153  goto err;
154  }
155 
156  if (flags & AVIO_FLAG_WRITE) {
157  c->aes_encrypt = av_aes_alloc();
158  if (!c->aes_encrypt) {
159  ret = AVERROR(ENOMEM);
160  goto err;
161  }
162  ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE*8, 0);
163  if (ret < 0)
164  goto err;
165  }
166 
167  c->pad_len = 0;
168 
169  h->is_streamed = 1;
170 
171 err:
172  return ret;
173 }
174 
175 static int crypto_read(URLContext *h, uint8_t *buf, int size)
176 {
177  CryptoContext *c = h->priv_data;
178  int blocks;
179 retry:
180  if (c->outdata > 0) {
181  size = FFMIN(size, c->outdata);
182  memcpy(buf, c->outptr, size);
183  c->outptr += size;
184  c->outdata -= size;
185  return size;
186  }
187  // We avoid using the last block until we've found EOF,
188  // since we'll remove PKCS7 padding at the end. So make
189  // sure we've got at least 2 blocks, so we can decrypt
190  // at least one.
191  while (c->indata - c->indata_used < 2*BLOCKSIZE) {
192  int n = ffurl_read(c->hd, c->inbuffer + c->indata,
193  sizeof(c->inbuffer) - c->indata);
194  if (n <= 0) {
195  c->eof = 1;
196  break;
197  }
198  c->indata += n;
199  }
200  blocks = (c->indata - c->indata_used) / BLOCKSIZE;
201  if (!blocks)
202  return AVERROR_EOF;
203  if (!c->eof)
204  blocks--;
206  blocks, c->decrypt_iv, 1);
207  c->outdata = BLOCKSIZE * blocks;
208  c->outptr = c->outbuffer;
209  c->indata_used += BLOCKSIZE * blocks;
210  if (c->indata_used >= sizeof(c->inbuffer)/2) {
211  memmove(c->inbuffer, c->inbuffer + c->indata_used,
212  c->indata - c->indata_used);
213  c->indata -= c->indata_used;
214  c->indata_used = 0;
215  }
216  if (c->eof) {
217  // Remove PKCS7 padding at the end
218  int padding = c->outbuffer[c->outdata - 1];
219  c->outdata -= padding;
220  }
221  goto retry;
222 }
223 
224 static int crypto_write(URLContext *h, const unsigned char *buf, int size)
225 {
226  CryptoContext *c = h->priv_data;
227  int total_size, blocks, pad_len, out_size;
228  uint8_t *out_buf;
229  int ret = 0;
230 
231  total_size = size + c->pad_len;
232  pad_len = total_size % BLOCKSIZE;
233  out_size = total_size - pad_len;
234  blocks = out_size / BLOCKSIZE;
235 
236  if (out_size) {
237  out_buf = av_malloc(out_size);
238  if (!out_buf)
239  return AVERROR(ENOMEM);
240 
241  if (c->pad_len) {
242  memcpy(&c->pad[c->pad_len], buf, BLOCKSIZE - c->pad_len);
243  av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0);
244  blocks--;
245  }
246 
247  av_aes_crypt(c->aes_encrypt, &out_buf[c->pad_len ? BLOCKSIZE : 0],
248  &buf[c->pad_len ? BLOCKSIZE - c->pad_len: 0],
249  blocks, c->encrypt_iv, 0);
250 
251  ret = ffurl_write(c->hd, out_buf, out_size);
252  av_free(out_buf);
253  if (ret < 0)
254  return ret;
255 
256  memcpy(c->pad, &buf[size - pad_len], pad_len);
257  } else
258  memcpy(&c->pad[c->pad_len], buf, size);
259 
260  c->pad_len = pad_len;
261 
262  return size;
263 }
264 
265 static int crypto_close(URLContext *h)
266 {
267  CryptoContext *c = h->priv_data;
268  uint8_t out_buf[BLOCKSIZE];
269  int ret, pad;
270 
271  if (c->aes_encrypt) {
272  pad = BLOCKSIZE - c->pad_len;
273  memset(&c->pad[c->pad_len], pad, pad);
274  av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0);
275  if ((ret = ffurl_write(c->hd, out_buf, BLOCKSIZE)) < 0)
276  return ret;
277  }
278 
279  if (c->hd)
280  ffurl_close(c->hd);
281  av_freep(&c->aes_decrypt);
282  av_freep(&c->aes_encrypt);
283  return 0;
284 }
285 
287  .name = "crypto",
288  .url_open2 = crypto_open2,
289  .url_read = crypto_read,
290  .url_write = crypto_write,
291  .url_close = crypto_close,
292  .priv_data_size = sizeof(CryptoContext),
293  .priv_data_class = &crypto_class,
295 };