Statistics
| Branch: | Revision:

ffmpeg / libavformat / crypto.c @ ac9cf2e5

History | View | Annotate | Download (4.82 KB)

1
/*
2
 * Decryption protocol handler
3
 * Copyright (c) 2011 Martin Storsjo
4
 *
5
 * This file is part of Libav.
6
 *
7
 * Libav 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
 * Libav 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 Libav; 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;
34
    URLContext *hd;
35
    uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
36
            outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
37
    uint8_t *outptr;
38
    int indata, indata_used, outdata;
39
    int eof;
40
    uint8_t *key;
41
    int keylen;
42
    uint8_t *iv;
43
    int ivlen;
44
    struct AVAES *aes;
45
} CryptoContext;
46

    
47
#define OFFSET(x) offsetof(CryptoContext, x)
48
static const AVOption options[] = {
49
    {"key", "AES decryption key", OFFSET(key), FF_OPT_TYPE_BINARY },
50
    {"iv",  "AES decryption initialization vector", OFFSET(iv),  FF_OPT_TYPE_BINARY },
51
    { NULL }
52
};
53

    
54
static const AVClass crypto_class = {
55
    "crypto", av_default_item_name, options, LIBAVUTIL_VERSION_INT
56
};
57

    
58
static int crypto_open(URLContext *h, const char *uri, int flags)
59
{
60
    const char *nested_url;
61
    int ret;
62
    CryptoContext *c = h->priv_data;
63

    
64
    if (!av_strstart(uri, "crypto+", &nested_url) &&
65
        !av_strstart(uri, "crypto:", &nested_url)) {
66
        av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
67
        ret = AVERROR(EINVAL);
68
        goto err;
69
    }
70

    
71
    if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) {
72
        av_log(h, AV_LOG_ERROR, "Key or IV not set\n");
73
        ret = AVERROR(EINVAL);
74
        goto err;
75
    }
76
    if (flags & AVIO_FLAG_WRITE) {
77
        av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n");
78
        ret = AVERROR(ENOSYS);
79
        goto err;
80
    }
81
    if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ)) < 0) {
82
        av_log(h, AV_LOG_ERROR, "Unable to open input\n");
83
        goto err;
84
    }
85
    c->aes = av_mallocz(av_aes_size);
86
    if (!c->aes) {
87
        ret = AVERROR(ENOMEM);
88
        goto err;
89
    }
90

    
91
    av_aes_init(c->aes, c->key, 128, 1);
92

    
93
    h->is_streamed = 1;
94

    
95
    return 0;
96
err:
97
    av_free(c->key);
98
    av_free(c->iv);
99
    return ret;
100
}
101

    
102
static int crypto_read(URLContext *h, uint8_t *buf, int size)
103
{
104
    CryptoContext *c = h->priv_data;
105
    int blocks;
106
retry:
107
    if (c->outdata > 0) {
108
        size = FFMIN(size, c->outdata);
109
        memcpy(buf, c->outptr, size);
110
        c->outptr  += size;
111
        c->outdata -= size;
112
        return size;
113
    }
114
    // We avoid using the last block until we've found EOF,
115
    // since we'll remove PKCS7 padding at the end. So make
116
    // sure we've got at least 2 blocks, so we can decrypt
117
    // at least one.
118
    while (c->indata - c->indata_used < 2*BLOCKSIZE) {
119
        int n = ffurl_read(c->hd, c->inbuffer + c->indata,
120
                           sizeof(c->inbuffer) - c->indata);
121
        if (n <= 0) {
122
            c->eof = 1;
123
            break;
124
        }
125
        c->indata += n;
126
    }
127
    blocks = (c->indata - c->indata_used) / BLOCKSIZE;
128
    if (!blocks)
129
        return AVERROR_EOF;
130
    if (!c->eof)
131
        blocks--;
132
    av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks,
133
                 c->iv, 1);
134
    c->outdata      = BLOCKSIZE * blocks;
135
    c->outptr       = c->outbuffer;
136
    c->indata_used += BLOCKSIZE * blocks;
137
    if (c->indata_used >= sizeof(c->inbuffer)/2) {
138
        memmove(c->inbuffer, c->inbuffer + c->indata_used,
139
                c->indata - c->indata_used);
140
        c->indata     -= c->indata_used;
141
        c->indata_used = 0;
142
    }
143
    if (c->eof) {
144
        // Remove PKCS7 padding at the end
145
        int padding = c->outbuffer[c->outdata - 1];
146
        c->outdata -= padding;
147
    }
148
    goto retry;
149
}
150

    
151
static int crypto_close(URLContext *h)
152
{
153
    CryptoContext *c = h->priv_data;
154
    if (c->hd)
155
        ffurl_close(c->hd);
156
    av_freep(&c->aes);
157
    av_freep(&c->key);
158
    av_freep(&c->iv);
159
    return 0;
160
}
161

    
162
URLProtocol ff_crypto_protocol = {
163
    .name            = "crypto",
164
    .url_open        = crypto_open,
165
    .url_read        = crypto_read,
166
    .url_close       = crypto_close,
167
    .priv_data_size  = sizeof(CryptoContext),
168
    .priv_data_class = &crypto_class,
169
    .flags           = URL_PROTOCOL_FLAG_NESTED_SCHEME,
170
};