| 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; |
| 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 | #define D AV_OPT_FLAG_DECODING_PARAM |
| 49 | static const AVOption options[] = { |
| 50 | {"key", "AES decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D }, |
| 51 | {"iv", "AES decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D }, |
| 52 | { NULL } |
| 53 | }; |
| 54 | |
| 55 | static const AVClass crypto_class = { |
| 56 | .class_name = "crypto", |
| 57 | .item_name = av_default_item_name, |
| 58 | .option = options, |
| 59 | .version = LIBAVUTIL_VERSION_INT, |
| 60 | }; |
| 61 | |
| 62 | static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options) |
| 63 | { |
| 64 | const char *nested_url; |
| 65 | int ret = 0; |
| 66 | CryptoContext *c = h->priv_data; |
| 67 | |
| 68 | if (!av_strstart(uri, "crypto+", &nested_url) && |
| 69 | !av_strstart(uri, "crypto:", &nested_url)) { |
| 70 | av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri); |
| 71 | ret = AVERROR(EINVAL); |
| 72 | goto err; |
| 73 | } |
| 74 | |
| 75 | if (c->keylen < BLOCKSIZE || c->ivlen < BLOCKSIZE) { |
| 76 | av_log(h, AV_LOG_ERROR, "Key or IV not set\n"); |
| 77 | ret = AVERROR(EINVAL); |
| 78 | goto err; |
| 79 | } |
| 80 | if (flags & AVIO_FLAG_WRITE) { |
| 81 | av_log(h, AV_LOG_ERROR, "Only decryption is supported currently\n"); |
| 82 | ret = AVERROR(ENOSYS); |
| 83 | goto err; |
| 84 | } |
| 85 | if ((ret = ffurl_open(&c->hd, nested_url, AVIO_FLAG_READ, |
| 86 | &h->interrupt_callback, options)) < 0) { |
| 87 | av_log(h, AV_LOG_ERROR, "Unable to open input\n"); |
| 88 | goto err; |
| 89 | } |
| 90 | c->aes = av_aes_alloc(); |
| 91 | if (!c->aes) { |
| 92 | ret = AVERROR(ENOMEM); |
| 93 | goto err; |
| 94 | } |
| 95 | |
| 96 | av_aes_init(c->aes, c->key, 128, 1); |
| 97 | |
| 98 | h->is_streamed = 1; |
| 99 | |
| 100 | err: |
| 101 | return ret; |
| 102 | } |
| 103 | |
| 104 | static int crypto_read(URLContext *h, uint8_t *buf, int size) |
| 105 | { |
| 106 | CryptoContext *c = h->priv_data; |
| 107 | int blocks; |
| 108 | retry: |
| 109 | if (c->outdata > 0) { |
| 110 | size = FFMIN(size, c->outdata); |
| 111 | memcpy(buf, c->outptr, size); |
| 112 | c->outptr += size; |
| 113 | c->outdata -= size; |
| 114 | return size; |
| 115 | } |
| 116 | // We avoid using the last block until we've found EOF, |
| 117 | // since we'll remove PKCS7 padding at the end. So make |
| 118 | // sure we've got at least 2 blocks, so we can decrypt |
| 119 | // at least one. |
| 120 | while (c->indata - c->indata_used < 2*BLOCKSIZE) { |
| 121 | int n = ffurl_read(c->hd, c->inbuffer + c->indata, |
| 122 | sizeof(c->inbuffer) - c->indata); |
| 123 | if (n <= 0) { |
| 124 | c->eof = 1; |
| 125 | break; |
| 126 | } |
| 127 | c->indata += n; |
| 128 | } |
| 129 | blocks = (c->indata - c->indata_used) / BLOCKSIZE; |
| 130 | if (!blocks) |
| 131 | return AVERROR_EOF; |
| 132 | if (!c->eof) |
| 133 | blocks--; |
| 134 | av_aes_crypt(c->aes, c->outbuffer, c->inbuffer + c->indata_used, blocks, |
| 135 | c->iv, 1); |
| 136 | c->outdata = BLOCKSIZE * blocks; |
| 137 | c->outptr = c->outbuffer; |
| 138 | c->indata_used += BLOCKSIZE * blocks; |
| 139 | if (c->indata_used >= sizeof(c->inbuffer)/2) { |
| 140 | memmove(c->inbuffer, c->inbuffer + c->indata_used, |
| 141 | c->indata - c->indata_used); |
| 142 | c->indata -= c->indata_used; |
| 143 | c->indata_used = 0; |
| 144 | } |
| 145 | if (c->eof) { |
| 146 | // Remove PKCS7 padding at the end |
| 147 | int padding = c->outbuffer[c->outdata - 1]; |
| 148 | c->outdata -= padding; |
| 149 | } |
| 150 | goto retry; |
| 151 | } |
| 152 | |
| 153 | static int crypto_close(URLContext *h) |
| 154 | { |
| 155 | CryptoContext *c = h->priv_data; |
| 156 | if (c->hd) |
| 157 | ffurl_close(c->hd); |
| 158 | av_freep(&c->aes); |
| 159 | return 0; |
| 160 | } |
| 161 | |
| 162 | URLProtocol ff_crypto_protocol = { |
| 163 | .name = "crypto", |
| 164 | .url_open2 = crypto_open2, |
| 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 | }; |