summaryrefslogtreecommitdiff
path: root/libavformat/crypto.c
blob: fecc2c961c2434d4239ea0533462eef18d7b7d1e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
/*
 * Decryption protocol handler
 * Copyright (c) 2011 Martin Storsjo
 *
 * This file is part of Libav.
 *
 * Libav is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * Libav is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with Libav; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include "avformat.h"
#include "libavutil/aes.h"
#include "libavutil/avstring.h"
#include "libavutil/opt.h"
#include "internal.h"
#include "url.h"

#define MAX_BUFFER_BLOCKS 150
#define BLOCKSIZE 16

typedef struct {
    const AVClass *class;
    URLContext *hd;
    uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
            outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
    uint8_t *outptr;
    int indata, indata_used, outdata;
    int eof;
    uint8_t *key;
    int keylen;
    uint8_t *iv;
    int ivlen;
    struct AVAES *aes;
} CryptoContext;

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

static const AVClass crypto_class = {
    "crypto", av_default_item_name, options, LIBAVUTIL_VERSION_INT
};

static int crypto_open(URLContext *h, const char *uri, int flags)
{
    const char *nested_url;
    int ret;
    CryptoContext *c = h->priv_data;

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

    if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) {
        av_log(h, AV_LOG_ERROR, "Key or IV not set\n");
        ret = AVERROR(EINVAL);
        goto err;
    }
    if (flags & AVIO_FLAG_WRITE) {
        av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n");
        ret = AVERROR(ENOSYS);
        goto err;
    }
    if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ)) < 0) {
        av_log(h, AV_LOG_ERROR, "Unable to open input\n");
        goto err;
    }
    c->aes = av_mallocz(av_aes_size);
    if (!c->aes) {
        ret = AVERROR(ENOMEM);
        goto err;
    }

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

    h->is_streamed = 1;

    return 0;
err:
    av_free(c->key);
    av_free(c->iv);
    return ret;
}

static int crypto_read(URLContext *h, uint8_t *buf, int size)
{
    CryptoContext *c = h->priv_data;
    int blocks;
retry:
    if (c->outdata > 0) {
        size = FFMIN(size, c->outdata);
        memcpy(buf, c->outptr, size);
        c->outptr  += size;
        c->outdata -= size;
        return size;
    }
    // We avoid using the last block until we've found EOF,
    // since we'll remove PKCS7 padding at the end. So make
    // sure we've got at least 2 blocks, so we can decrypt
    // at least one.
    while (c->indata - c->indata_used < 2*BLOCKSIZE) {
        int n = ffurl_read(c->hd, c->inbuffer + c->indata,
                           sizeof(c->inbuffer) - c->indata);
        if (n <= 0) {
            c->eof = 1;
            break;
        }
        c->indata += n;
    }
    blocks = (c->indata - c->indata_used) / BLOCKSIZE;
    if (!blocks)
        return AVERROR_EOF;
    if (!c->eof)
        blocks--;
    av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks,
                 c->iv, 1);
    c->outdata      = BLOCKSIZE * blocks;
    c->outptr       = c->outbuffer;
    c->indata_used += BLOCKSIZE * blocks;
    if (c->indata_used >= sizeof(c->inbuffer)/2) {
        memmove(c->inbuffer, c->inbuffer + c->indata_used,
                c->indata - c->indata_used);
        c->indata     -= c->indata_used;
        c->indata_used = 0;
    }
    if (c->eof) {
        // Remove PKCS7 padding at the end
        int padding = c->outbuffer[c->outdata - 1];
        c->outdata -= padding;
    }
    goto retry;
}

static int crypto_close(URLContext *h)
{
    CryptoContext *c = h->priv_data;
    if (c->hd)
        ffurl_close(c->hd);
    av_freep(&c->aes);
    av_freep(&c->key);
    av_freep(&c->iv);
    return 0;
}

URLProtocol ff_crypto_protocol = {
    .name            = "crypto",
    .url_open        = crypto_open,
    .url_read        = crypto_read,
    .url_close       = crypto_close,
    .priv_data_size  = sizeof(CryptoContext),
    .priv_data_class = &crypto_class,
    .flags           = URL_PROTOCOL_FLAG_NESTED_SCHEME,
};