| /* |
| * Decryption protocol handler |
| * Copyright (c) 2011 Martin Storsjo |
| * |
| * This file is part of FFmpeg. |
| * |
| * FFmpeg 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. |
| * |
| * FFmpeg 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 FFmpeg; 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" |
| |
| // encourage reads of 4096 bytes - 1 block is always retained. |
| #define MAX_BUFFER_BLOCKS 257 |
| #define BLOCKSIZE 16 |
| |
| typedef struct CryptoContext { |
| 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; |
| int64_t position; // position in file - used in seek |
| int flags; |
| int eof; |
| uint8_t *key; |
| int keylen; |
| uint8_t *iv; |
| int ivlen; |
| uint8_t *decrypt_key; |
| int decrypt_keylen; |
| uint8_t *decrypt_iv; |
| int decrypt_ivlen; |
| uint8_t *encrypt_key; |
| int encrypt_keylen; |
| uint8_t *encrypt_iv; |
| int encrypt_ivlen; |
| struct AVAES *aes_decrypt; |
| struct AVAES *aes_encrypt; |
| uint8_t *write_buf; |
| unsigned int write_buf_size; |
| uint8_t pad[BLOCKSIZE]; |
| int pad_len; |
| } CryptoContext; |
| |
| #define OFFSET(x) offsetof(CryptoContext, x) |
| #define D AV_OPT_FLAG_DECODING_PARAM |
| #define E AV_OPT_FLAG_ENCODING_PARAM |
| static const AVOption options[] = { |
| {"key", "AES encryption/decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D|E }, |
| {"iv", "AES encryption/decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D|E }, |
| {"decryption_key", "AES decryption key", OFFSET(decrypt_key), AV_OPT_TYPE_BINARY, .flags = D }, |
| {"decryption_iv", "AES decryption initialization vector", OFFSET(decrypt_iv), AV_OPT_TYPE_BINARY, .flags = D }, |
| {"encryption_key", "AES encryption key", OFFSET(encrypt_key), AV_OPT_TYPE_BINARY, .flags = E }, |
| {"encryption_iv", "AES encryption initialization vector", OFFSET(encrypt_iv), AV_OPT_TYPE_BINARY, .flags = E }, |
| { NULL } |
| }; |
| |
| static const AVClass crypto_class = { |
| .class_name = "crypto", |
| .item_name = av_default_item_name, |
| .option = options, |
| .version = LIBAVUTIL_VERSION_INT, |
| }; |
| |
| static int set_aes_arg(URLContext *h, uint8_t **buf, int *buf_len, |
| uint8_t *default_buf, int default_buf_len, |
| const char *desc) |
| { |
| if (!*buf_len) { |
| if (!default_buf_len) { |
| av_log(h, AV_LOG_ERROR, "%s not set\n", desc); |
| return AVERROR(EINVAL); |
| } else if (default_buf_len != BLOCKSIZE) { |
| av_log(h, AV_LOG_ERROR, |
| "invalid %s size (%d bytes, block size is %d)\n", |
| desc, default_buf_len, BLOCKSIZE); |
| return AVERROR(EINVAL); |
| } |
| *buf = av_memdup(default_buf, default_buf_len); |
| if (!*buf) |
| return AVERROR(ENOMEM); |
| *buf_len = default_buf_len; |
| } else if (*buf_len != BLOCKSIZE) { |
| av_log(h, AV_LOG_ERROR, |
| "invalid %s size (%d bytes, block size is %d)\n", |
| desc, *buf_len, BLOCKSIZE); |
| return AVERROR(EINVAL); |
| } |
| return 0; |
| } |
| |
| static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options) |
| { |
| const char *nested_url; |
| int ret = 0; |
| CryptoContext *c = h->priv_data; |
| c->flags = flags; |
| |
| 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 (flags & AVIO_FLAG_READ) { |
| if ((ret = set_aes_arg(h, &c->decrypt_key, &c->decrypt_keylen, |
| c->key, c->keylen, "decryption key")) < 0) |
| goto err; |
| if ((ret = set_aes_arg(h, &c->decrypt_iv, &c->decrypt_ivlen, |
| c->iv, c->ivlen, "decryption IV")) < 0) |
| goto err; |
| } |
| |
| if (flags & AVIO_FLAG_WRITE) { |
| if ((ret = set_aes_arg(h, &c->encrypt_key, &c->encrypt_keylen, |
| c->key, c->keylen, "encryption key")) < 0) |
| if (ret < 0) |
| goto err; |
| if ((ret = set_aes_arg(h, &c->encrypt_iv, &c->encrypt_ivlen, |
| c->iv, c->ivlen, "encryption IV")) < 0) |
| goto err; |
| } |
| |
| if ((ret = ffurl_open_whitelist(&c->hd, nested_url, flags, |
| &h->interrupt_callback, options, |
| h->protocol_whitelist, h->protocol_blacklist, h)) < 0) { |
| av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", nested_url); |
| goto err; |
| } |
| |
| if (flags & AVIO_FLAG_READ) { |
| c->aes_decrypt = av_aes_alloc(); |
| if (!c->aes_decrypt) { |
| ret = AVERROR(ENOMEM); |
| goto err; |
| } |
| ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE * 8, 1); |
| if (ret < 0) |
| goto err; |
| |
| // pass back information about the context we openned |
| if (c->hd->is_streamed) |
| h->is_streamed = c->hd->is_streamed; |
| } |
| |
| if (flags & AVIO_FLAG_WRITE) { |
| c->aes_encrypt = av_aes_alloc(); |
| if (!c->aes_encrypt) { |
| ret = AVERROR(ENOMEM); |
| goto err; |
| } |
| ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE * 8, 0); |
| if (ret < 0) |
| goto err; |
| // for write, we must be streamed |
| // - linear write only for crytpo aes-128-cbc |
| h->is_streamed = 1; |
| } |
| |
| err: |
| 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; |
| c->position = c->position + 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_decrypt, c->outbuffer, c->inbuffer + c->indata_used, |
| blocks, c->decrypt_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 int64_t crypto_seek(URLContext *h, int64_t pos, int whence) |
| { |
| CryptoContext *c = h->priv_data; |
| int64_t block; |
| int64_t newpos; |
| |
| if (c->flags & AVIO_FLAG_WRITE) { |
| av_log(h, AV_LOG_ERROR, |
| "Crypto: seek not supported for write\r\n"); |
| /* seems the most appropriate error to return */ |
| return AVERROR(ESPIPE); |
| } |
| |
| // reset eof, else we won't read it correctly if we already hit eof. |
| c->eof = 0; |
| |
| switch (whence) { |
| case SEEK_SET: |
| break; |
| case SEEK_CUR: |
| pos = pos + c->position; |
| break; |
| case SEEK_END: |
| newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE ); |
| if (newpos < 0) { |
| av_log(h, AV_LOG_ERROR, |
| "Crypto: seek_end - can't get file size (pos=%lld)\r\n", (long long int)pos); |
| return newpos; |
| } |
| pos = newpos - pos; |
| break; |
| case AVSEEK_SIZE: |
| return ffurl_seek( c->hd, pos, AVSEEK_SIZE ); |
| default: |
| av_log(h, AV_LOG_ERROR, |
| "Crypto: no support for seek where 'whence' is %d\r\n", whence); |
| return AVERROR(EINVAL); |
| } |
| |
| c->outdata = 0; |
| c->indata = 0; |
| c->indata_used = 0; |
| c->outptr = c->outbuffer; |
| |
| // identify the block containing the IV for the |
| // next block we will decrypt |
| block = pos/BLOCKSIZE; |
| if (block == 0) { |
| // restore the iv to the seed one - this is the iv for the FIRST block |
| memcpy( c->decrypt_iv, c->iv, c->ivlen ); |
| c->position = 0; |
| } else { |
| // else, go back one block - we will get av_cyrpt to read this block |
| // which it will then store use as the iv. |
| // note that the DECRYPTED result will not be correct, |
| // but will be discarded |
| block--; |
| c->position = (block * BLOCKSIZE); |
| } |
| |
| newpos = ffurl_seek( c->hd, c->position, SEEK_SET ); |
| if (newpos < 0) { |
| av_log(h, AV_LOG_ERROR, |
| "Crypto: nested protocol no support for seek or seek failed\n"); |
| return newpos; |
| } |
| |
| // read and discard from here up to required position |
| // (which will set the iv correctly to it). |
| if (pos - c->position) { |
| uint8_t buff[BLOCKSIZE*2]; // maximum size of pos-c->position |
| int len = pos - c->position; |
| int res; |
| |
| while (len > 0) { |
| // note: this may not return all the bytes first time |
| res = crypto_read(h, buff, len); |
| if (res < 0) |
| break; |
| len -= res; |
| } |
| |
| // if we did not get all the bytes |
| if (len != 0) { |
| char errbuf[100] = "unknown error"; |
| av_strerror(res, errbuf, sizeof(errbuf)); |
| av_log(h, AV_LOG_ERROR, |
| "Crypto: discard read did not get all the bytes (%d remain) - read returned (%d)-%s\n", |
| len, res, errbuf); |
| return AVERROR(EINVAL); |
| } |
| } |
| |
| return c->position; |
| } |
| |
| static int crypto_write(URLContext *h, const unsigned char *buf, int size) |
| { |
| CryptoContext *c = h->priv_data; |
| int total_size, blocks, pad_len, out_size; |
| int ret = 0; |
| |
| total_size = size + c->pad_len; |
| pad_len = total_size % BLOCKSIZE; |
| out_size = total_size - pad_len; |
| blocks = out_size / BLOCKSIZE; |
| |
| if (out_size) { |
| av_fast_malloc(&c->write_buf, &c->write_buf_size, out_size); |
| |
| if (!c->write_buf) |
| return AVERROR(ENOMEM); |
| |
| if (c->pad_len) { |
| memcpy(&c->pad[c->pad_len], buf, BLOCKSIZE - c->pad_len); |
| av_aes_crypt(c->aes_encrypt, c->write_buf, c->pad, 1, c->encrypt_iv, 0); |
| blocks--; |
| } |
| |
| av_aes_crypt(c->aes_encrypt, |
| &c->write_buf[c->pad_len ? BLOCKSIZE : 0], |
| &buf[c->pad_len ? BLOCKSIZE - c->pad_len : 0], |
| blocks, c->encrypt_iv, 0); |
| |
| ret = ffurl_write(c->hd, c->write_buf, out_size); |
| if (ret < 0) |
| return ret; |
| |
| memcpy(c->pad, &buf[size - pad_len], pad_len); |
| } else |
| memcpy(&c->pad[c->pad_len], buf, size); |
| |
| c->pad_len = pad_len; |
| |
| return size; |
| } |
| |
| static int crypto_close(URLContext *h) |
| { |
| CryptoContext *c = h->priv_data; |
| int ret = 0; |
| |
| if (c->aes_encrypt) { |
| uint8_t out_buf[BLOCKSIZE]; |
| int pad = BLOCKSIZE - c->pad_len; |
| |
| memset(&c->pad[c->pad_len], pad, pad); |
| av_aes_crypt(c->aes_encrypt, out_buf, c->pad, 1, c->encrypt_iv, 0); |
| ret = ffurl_write(c->hd, out_buf, BLOCKSIZE); |
| } |
| |
| ffurl_closep(&c->hd); |
| av_freep(&c->aes_decrypt); |
| av_freep(&c->aes_encrypt); |
| av_freep(&c->write_buf); |
| return ret; |
| } |
| |
| const URLProtocol ff_crypto_protocol = { |
| .name = "crypto", |
| .url_open2 = crypto_open2, |
| .url_seek = crypto_seek, |
| .url_read = crypto_read, |
| .url_write = crypto_write, |
| .url_close = crypto_close, |
| .priv_data_size = sizeof(CryptoContext), |
| .priv_data_class = &crypto_class, |
| .flags = URL_PROTOCOL_FLAG_NESTED_SCHEME, |
| }; |