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 #define MAX_BUFFER_BLOCKS 150
32 typedef struct CryptoContext {
35 uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
36 outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
38 int indata, indata_used, outdata;
52 struct AVAES *aes_decrypt;
53 struct AVAES *aes_encrypt;
55 uint8_t pad[BLOCKSIZE];
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 },
73 static const AVClass crypto_class = {
74 .class_name = "crypto",
75 .item_name = av_default_item_name,
77 .version = LIBAVUTIL_VERSION_INT,
80 static int set_aes_arg(CryptoContext *c, uint8_t **buf, int *buf_len,
81 uint8_t *default_buf, int default_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) {
89 av_log(c, AV_LOG_ERROR,
90 "invalid %s size (%d bytes, block size is %d)\n",
91 desc, default_buf_len, BLOCKSIZE);
92 return AVERROR(EINVAL);
94 *buf = av_memdup(default_buf, default_buf_len);
96 return AVERROR(ENOMEM);
97 *buf_len = default_buf_len;
98 } else if (*buf_len != BLOCKSIZE) {
99 av_log(c, AV_LOG_ERROR,
100 "invalid %s size (%d bytes, block size is %d)\n",
101 desc, *buf_len, BLOCKSIZE);
102 return AVERROR(EINVAL);
107 static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
109 const char *nested_url;
111 CryptoContext *c = h->priv_data;
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);
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)
124 if ((ret = set_aes_arg(c, &c->decrypt_iv, &c->decrypt_ivlen,
125 c->iv, c->ivlen, "decryption IV")) < 0)
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)
134 if ((ret = set_aes_arg(c, &c->encrypt_iv, &c->encrypt_ivlen,
135 c->iv, c->ivlen, "encryption IV")) < 0)
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);
145 if (flags & AVIO_FLAG_READ) {
146 c->aes_decrypt = av_aes_alloc();
147 if (!c->aes_decrypt) {
148 ret = AVERROR(ENOMEM);
151 ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE*8, 1);
156 if (flags & AVIO_FLAG_WRITE) {
157 c->aes_encrypt = av_aes_alloc();
158 if (!c->aes_encrypt) {
159 ret = AVERROR(ENOMEM);
162 ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE*8, 0);
175 static int crypto_read(URLContext *h, uint8_t *buf, int size)
177 CryptoContext *c = h->priv_data;
180 if (c->outdata > 0) {
181 size = FFMIN(size, c->outdata);
182 memcpy(buf, c->outptr, size);
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
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);
200 blocks = (c->indata - c->indata_used) / BLOCKSIZE;
205 av_aes_crypt(c->aes_decrypt, c->outbuffer, c->inbuffer + c->indata_used,
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;
217 // Remove PKCS7 padding at the end
218 int padding = c->outbuffer[c->outdata - 1];
219 c->outdata -= padding;
224 static int crypto_write(URLContext *h, const unsigned char *buf, int size)
226 CryptoContext *c = h->priv_data;
227 int total_size, blocks, pad_len, out_size;
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;
237 out_buf = av_malloc(out_size);
239 return AVERROR(ENOMEM);
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);
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);
251 ret = ffurl_write(c->hd, out_buf, out_size);
256 memcpy(c->pad, &buf[size - pad_len], pad_len);
258 memcpy(&c->pad[c->pad_len], buf, size);
260 c->pad_len = pad_len;
265 static int crypto_close(URLContext *h)
267 CryptoContext *c = h->priv_data;
268 uint8_t out_buf[BLOCKSIZE];
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)
281 av_freep(&c->aes_decrypt);
282 av_freep(&c->aes_encrypt);
286 URLProtocol ff_crypto_protocol = {
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,
294 .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME,