406 lines
13 KiB
C
406 lines
13 KiB
C
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/*
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* Decryption protocol handler
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* Copyright (c) 2011 Martin Storsjo
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avformat.h"
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#include "libavutil/aes.h"
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#include "libavutil/avstring.h"
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#include "libavutil/opt.h"
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#include "internal.h"
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#include "url.h"
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// encourage reads of 4096 bytes - 1 block is always retained.
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#define MAX_BUFFER_BLOCKS 257
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#define BLOCKSIZE 16
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typedef struct CryptoContext {
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const AVClass *class;
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URLContext *hd;
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uint8_t inbuffer [BLOCKSIZE*MAX_BUFFER_BLOCKS],
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outbuffer[BLOCKSIZE*MAX_BUFFER_BLOCKS];
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uint8_t *outptr;
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int indata, indata_used, outdata;
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int64_t position; // position in file - used in seek
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int flags;
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int eof;
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uint8_t *key;
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int keylen;
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uint8_t *iv;
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int ivlen;
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uint8_t *decrypt_key;
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int decrypt_keylen;
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uint8_t *decrypt_iv;
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int decrypt_ivlen;
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uint8_t *encrypt_key;
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int encrypt_keylen;
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uint8_t *encrypt_iv;
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int encrypt_ivlen;
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struct AVAES *aes_decrypt;
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struct AVAES *aes_encrypt;
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uint8_t *write_buf;
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unsigned int write_buf_size;
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uint8_t pad[BLOCKSIZE];
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int pad_len;
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} CryptoContext;
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#define OFFSET(x) offsetof(CryptoContext, x)
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#define D AV_OPT_FLAG_DECODING_PARAM
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#define E AV_OPT_FLAG_ENCODING_PARAM
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static const AVOption options[] = {
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{"key", "AES encryption/decryption key", OFFSET(key), AV_OPT_TYPE_BINARY, .flags = D|E },
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{"iv", "AES encryption/decryption initialization vector", OFFSET(iv), AV_OPT_TYPE_BINARY, .flags = D|E },
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{"decryption_key", "AES decryption key", OFFSET(decrypt_key), AV_OPT_TYPE_BINARY, .flags = D },
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{"decryption_iv", "AES decryption initialization vector", OFFSET(decrypt_iv), AV_OPT_TYPE_BINARY, .flags = D },
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{"encryption_key", "AES encryption key", OFFSET(encrypt_key), AV_OPT_TYPE_BINARY, .flags = E },
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{"encryption_iv", "AES encryption initialization vector", OFFSET(encrypt_iv), AV_OPT_TYPE_BINARY, .flags = E },
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{ NULL }
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};
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static const AVClass crypto_class = {
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.class_name = "crypto",
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.item_name = av_default_item_name,
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.option = options,
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.version = LIBAVUTIL_VERSION_INT,
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};
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static int set_aes_arg(URLContext *h, uint8_t **buf, int *buf_len,
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uint8_t *default_buf, int default_buf_len,
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const char *desc)
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{
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if (!*buf_len) {
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if (!default_buf_len) {
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av_log(h, AV_LOG_ERROR, "%s not set\n", desc);
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return AVERROR(EINVAL);
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} else if (default_buf_len != BLOCKSIZE) {
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av_log(h, AV_LOG_ERROR,
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"invalid %s size (%d bytes, block size is %d)\n",
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desc, default_buf_len, BLOCKSIZE);
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return AVERROR(EINVAL);
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}
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*buf = av_memdup(default_buf, default_buf_len);
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if (!*buf)
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return AVERROR(ENOMEM);
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*buf_len = default_buf_len;
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} else if (*buf_len != BLOCKSIZE) {
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av_log(h, AV_LOG_ERROR,
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"invalid %s size (%d bytes, block size is %d)\n",
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desc, *buf_len, BLOCKSIZE);
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return AVERROR(EINVAL);
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}
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return 0;
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}
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static int crypto_open2(URLContext *h, const char *uri, int flags, AVDictionary **options)
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{
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const char *nested_url;
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int ret = 0;
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CryptoContext *c = h->priv_data;
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c->flags = flags;
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if (!av_strstart(uri, "crypto+", &nested_url) &&
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!av_strstart(uri, "crypto:", &nested_url)) {
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av_log(h, AV_LOG_ERROR, "Unsupported url %s\n", uri);
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ret = AVERROR(EINVAL);
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goto err;
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}
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if (flags & AVIO_FLAG_READ) {
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if ((ret = set_aes_arg(h, &c->decrypt_key, &c->decrypt_keylen,
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c->key, c->keylen, "decryption key")) < 0)
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goto err;
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if ((ret = set_aes_arg(h, &c->decrypt_iv, &c->decrypt_ivlen,
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c->iv, c->ivlen, "decryption IV")) < 0)
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goto err;
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}
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if (flags & AVIO_FLAG_WRITE) {
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if ((ret = set_aes_arg(h, &c->encrypt_key, &c->encrypt_keylen,
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c->key, c->keylen, "encryption key")) < 0)
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if (ret < 0)
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goto err;
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if ((ret = set_aes_arg(h, &c->encrypt_iv, &c->encrypt_ivlen,
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c->iv, c->ivlen, "encryption IV")) < 0)
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goto err;
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}
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if ((ret = ffurl_open_whitelist(&c->hd, nested_url, flags,
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&h->interrupt_callback, options,
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h->protocol_whitelist, h->protocol_blacklist, h)) < 0) {
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av_log(h, AV_LOG_ERROR, "Unable to open resource: %s\n", nested_url);
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goto err;
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}
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if (flags & AVIO_FLAG_READ) {
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c->aes_decrypt = av_aes_alloc();
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if (!c->aes_decrypt) {
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ret = AVERROR(ENOMEM);
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goto err;
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}
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ret = av_aes_init(c->aes_decrypt, c->decrypt_key, BLOCKSIZE * 8, 1);
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if (ret < 0)
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goto err;
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// pass back information about the context we openned
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if (c->hd->is_streamed)
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h->is_streamed = c->hd->is_streamed;
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}
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if (flags & AVIO_FLAG_WRITE) {
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c->aes_encrypt = av_aes_alloc();
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if (!c->aes_encrypt) {
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ret = AVERROR(ENOMEM);
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goto err;
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}
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ret = av_aes_init(c->aes_encrypt, c->encrypt_key, BLOCKSIZE * 8, 0);
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if (ret < 0)
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goto err;
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// for write, we must be streamed
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// - linear write only for crytpo aes-128-cbc
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h->is_streamed = 1;
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}
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err:
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return ret;
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}
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static int crypto_read(URLContext *h, uint8_t *buf, int size)
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{
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CryptoContext *c = h->priv_data;
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int blocks;
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retry:
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if (c->outdata > 0) {
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size = FFMIN(size, c->outdata);
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memcpy(buf, c->outptr, size);
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c->outptr += size;
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c->outdata -= size;
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c->position = c->position + size;
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return size;
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}
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// We avoid using the last block until we've found EOF,
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// since we'll remove PKCS7 padding at the end. So make
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// sure we've got at least 2 blocks, so we can decrypt
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// at least one.
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while (c->indata - c->indata_used < 2*BLOCKSIZE) {
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int n = ffurl_read(c->hd, c->inbuffer + c->indata,
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sizeof(c->inbuffer) - c->indata);
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if (n <= 0) {
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c->eof = 1;
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break;
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}
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c->indata += n;
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}
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blocks = (c->indata - c->indata_used) / BLOCKSIZE;
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if (!blocks)
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return AVERROR_EOF;
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if (!c->eof)
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blocks--;
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av_aes_crypt(c->aes_decrypt, c->outbuffer, c->inbuffer + c->indata_used,
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blocks, c->decrypt_iv, 1);
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c->outdata = BLOCKSIZE * blocks;
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c->outptr = c->outbuffer;
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c->indata_used += BLOCKSIZE * blocks;
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if (c->indata_used >= sizeof(c->inbuffer)/2) {
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memmove(c->inbuffer, c->inbuffer + c->indata_used,
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c->indata - c->indata_used);
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c->indata -= c->indata_used;
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c->indata_used = 0;
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}
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if (c->eof) {
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// Remove PKCS7 padding at the end
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int padding = c->outbuffer[c->outdata - 1];
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c->outdata -= padding;
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}
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goto retry;
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}
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static int64_t crypto_seek(URLContext *h, int64_t pos, int whence)
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{
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CryptoContext *c = h->priv_data;
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int64_t block;
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int64_t newpos;
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if (c->flags & AVIO_FLAG_WRITE) {
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av_log(h, AV_LOG_ERROR,
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"Crypto: seek not supported for write\r\n");
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/* seems the most appropriate error to return */
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return AVERROR(ESPIPE);
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}
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// reset eof, else we won't read it correctly if we already hit eof.
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c->eof = 0;
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switch (whence) {
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case SEEK_SET:
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break;
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case SEEK_CUR:
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pos = pos + c->position;
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break;
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case SEEK_END: {
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int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
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if (newpos < 0) {
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av_log(h, AV_LOG_ERROR,
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"Crypto: seek_end - can't get file size (pos=%lld)\r\n", (long long int)pos);
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return newpos;
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}
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pos = newpos - pos;
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}
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break;
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case AVSEEK_SIZE: {
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int64_t newpos = ffurl_seek( c->hd, pos, AVSEEK_SIZE );
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return newpos;
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}
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break;
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default:
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av_log(h, AV_LOG_ERROR,
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"Crypto: no support for seek where 'whence' is %d\r\n", whence);
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return AVERROR(EINVAL);
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}
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c->outdata = 0;
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c->indata = 0;
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c->indata_used = 0;
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c->outptr = c->outbuffer;
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// identify the block containing the IV for the
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// next block we will decrypt
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block = pos/BLOCKSIZE;
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if (block == 0) {
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// restore the iv to the seed one - this is the iv for the FIRST block
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memcpy( c->decrypt_iv, c->iv, c->ivlen );
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c->position = 0;
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} else {
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// else, go back one block - we will get av_cyrpt to read this block
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// which it will then store use as the iv.
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// note that the DECRYPTED result will not be correct,
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// but will be discarded
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block--;
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c->position = (block * BLOCKSIZE);
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}
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newpos = ffurl_seek( c->hd, c->position, SEEK_SET );
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if (newpos < 0) {
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av_log(h, AV_LOG_ERROR,
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"Crypto: nested protocol no support for seek or seek failed\n");
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return newpos;
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}
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// read and discard from here up to required position
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// (which will set the iv correctly to it).
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if (pos - c->position) {
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uint8_t buff[BLOCKSIZE*2]; // maximum size of pos-c->position
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int len = pos - c->position;
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int res;
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while (len > 0) {
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// note: this may not return all the bytes first time
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res = crypto_read(h, buff, len);
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if (res < 0)
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break;
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len -= res;
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}
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// if we did not get all the bytes
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if (len != 0) {
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char errbuf[100] = "unknown error";
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av_strerror(res, errbuf, sizeof(errbuf));
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av_log(h, AV_LOG_ERROR,
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"Crypto: discard read did not get all the bytes (%d remain) - read returned (%d)-%s\n",
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len, res, errbuf);
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return AVERROR(EINVAL);
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}
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}
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return c->position;
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}
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static int crypto_write(URLContext *h, const unsigned char *buf, int size)
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{
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CryptoContext *c = h->priv_data;
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int total_size, blocks, pad_len, out_size;
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int ret = 0;
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total_size = size + c->pad_len;
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pad_len = total_size % BLOCKSIZE;
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out_size = total_size - pad_len;
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blocks = out_size / BLOCKSIZE;
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if (out_size) {
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av_fast_malloc(&c->write_buf, &c->write_buf_size, out_size);
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if (!c->write_buf)
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return AVERROR(ENOMEM);
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if (c->pad_len) {
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memcpy(&c->pad[c->pad_len], buf, BLOCKSIZE - c->pad_len);
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av_aes_crypt(c->aes_encrypt, c->write_buf, c->pad, 1, c->encrypt_iv, 0);
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blocks--;
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}
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av_aes_crypt(c->aes_encrypt,
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&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,
|
||
|
|
};
|