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Add support for decrypting asf files
Originally committed as revision 10821 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
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aa237f4535
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@ -21,7 +21,7 @@ OBJS-$(CONFIG_AMR_DEMUXER) += amr.o
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OBJS-$(CONFIG_AMR_MUXER) += amr.o
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OBJS-$(CONFIG_APC_DEMUXER) += apc.o
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OBJS-$(CONFIG_APE_DEMUXER) += ape.o
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OBJS-$(CONFIG_ASF_DEMUXER) += asf.o riff.o
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OBJS-$(CONFIG_ASF_DEMUXER) += asf.o asfcrypt.o riff.o
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OBJS-$(CONFIG_ASF_MUXER) += asf-enc.o riff.o
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OBJS-$(CONFIG_ASF_STREAM_MUXER) += asf-enc.o riff.o
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OBJS-$(CONFIG_AU_DEMUXER) += au.o raw.o
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@ -23,6 +23,7 @@
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#include "mpegaudio.h"
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#include "asf.h"
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#include "common.h"
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#include "asfcrypt.h"
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#undef NDEBUG
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#include <assert.h>
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@ -823,6 +824,9 @@ static int asf_read_packet(AVFormatContext *s, AVPacket *pkt)
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get_buffer(pb, asf_st->pkt.data + asf->packet_frag_offset,
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asf->packet_frag_size);
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if (s->key && s->keylen == 20)
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ff_asfcrypt_dec(s->key, asf_st->pkt.data + asf->packet_frag_offset,
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asf->packet_frag_size);
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asf_st->frag_offset += asf->packet_frag_size;
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/* test if whole packet is read */
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if (asf_st->frag_offset == asf_st->pkt.size) {
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172
libavformat/asfcrypt.c
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172
libavformat/asfcrypt.c
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@ -0,0 +1,172 @@
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/*
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* ASF decryption
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* Copyright (c) 2007 Reimar Doeffinger
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* This is a rewrite of code contained in freeme/freeme2
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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 "common.h"
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#include "intreadwrite.h"
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#include "bswap.h"
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#include "des.h"
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#include "rc4.h"
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#include "asfcrypt.h"
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/**
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* \brief find multiplicative inverse modulo 2 ^ 32
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* \param v number to invert, must be odd!
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* \return number so that result * v = 1 (mod 2^32)
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*/
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static uint32_t inverse(uint32_t v) {
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// v ^ 3 gives the inverse (mod 16), could also be implemented
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// as table etc. (only lowest 4 bits matter!)
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uint32_t inverse = v * v * v;
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// uses a fixpoint-iteration that doubles the number
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// of correct lowest bits each time
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inverse *= 2 - v * inverse;
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inverse *= 2 - v * inverse;
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inverse *= 2 - v * inverse;
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return inverse;
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}
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/**
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* \brief read keys from keybuf into keys
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* \param keybuf buffer containing the keys
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* \param keys output key array containing the keys for encryption in
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* native endianness
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*/
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static void multiswap_init(const uint8_t keybuf[48], uint32_t keys[12]) {
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int i;
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for (i = 0; i < 12; i++)
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keys[i] = AV_RL32(keybuf + (i << 2)) | 1;
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}
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/**
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* \brief invert the keys so that encryption become decryption keys and
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* the other way round.
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* \param keys key array of ints to invert
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*/
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static void multiswap_invert_keys(uint32_t keys[12]) {
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int i;
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for (i = 0; i < 5; i++)
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keys[i] = inverse(keys[i]);
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for (i = 6; i < 11; i++)
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keys[i] = inverse(keys[i]);
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}
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static uint32_t multiswap_step(const uint32_t keys[12], uint32_t v) {
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int i;
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v *= keys[0];
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for (i = 1; i < 5; i++) {
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v = (v >> 16) | (v << 16);
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v *= keys[i];
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}
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v += keys[5];
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return v;
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}
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static uint32_t multiswap_inv_step(const uint32_t keys[12], uint32_t v) {
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int i;
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v -= keys[5];
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for (i = 4; i > 0; i--) {
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v *= keys[i];
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v = (v >> 16) | (v << 16);
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}
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v *= keys[0];
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return v;
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}
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/**
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* \brief "MultiSwap" encryption
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* \param keys 32 bit numbers in machine endianness,
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* 0-4 and 6-10 must be inverted from decryption
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* \param key another key, this one must be the same for the decryption
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* \param data data to encrypt
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* \return encrypted data
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*/
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static uint64_t multiswap_enc(const uint32_t keys[12], uint64_t key, uint64_t data) {
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uint32_t a = data;
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uint32_t b = data >> 32;
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uint32_t c;
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uint32_t tmp;
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a += key;
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tmp = multiswap_step(keys , a);
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b += tmp;
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c = (key >> 32) + tmp;
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tmp = multiswap_step(keys + 6, b);
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c += tmp;
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return ((uint64_t)c << 32) | tmp;
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}
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/**
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* \brief "MultiSwap" decryption
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* \param keys 32 bit numbers in machine endianness,
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* 0-4 and 6-10 must be inverted from encryption
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* \param key another key, this one must be the same as for the encryption
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* \param data data to decrypt
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* \return decrypted data
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*/
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static uint64_t multiswap_dec(const uint32_t keys[12], uint64_t key, uint64_t data) {
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uint32_t a;
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uint32_t b;
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uint32_t c = data >> 32;
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uint32_t tmp = data;
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c -= tmp;
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b = multiswap_inv_step(keys + 6, tmp);
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tmp = c - (key >> 32);
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b -= tmp;
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a = multiswap_inv_step(keys , tmp);
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a -= key;
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return ((uint64_t)b << 32) | a;
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}
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void ff_asfcrypt_dec(const uint8_t key[20], uint8_t *data, int len) {
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int num_qwords = len >> 3;
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uint64_t *qwords = (uint64_t *)data;
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uint64_t rc4buff[8];
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uint64_t packetkey;
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uint32_t ms_keys[12];
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uint64_t ms_state;
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int i;
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if (len < 16) {
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for (i = 0; i < len; i++)
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data[i] ^= key[i];
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return;
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}
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memset(rc4buff, 0, sizeof(rc4buff));
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ff_rc4_enc(key, 12, (uint8_t *)rc4buff, sizeof(rc4buff));
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multiswap_init((uint8_t *)rc4buff, ms_keys);
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packetkey = qwords[num_qwords - 1];
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packetkey ^= rc4buff[7];
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packetkey = be2me_64(packetkey);
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packetkey = ff_des_encdec(packetkey, AV_RB64(key + 12), 1);
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packetkey = be2me_64(packetkey);
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packetkey ^= rc4buff[6];
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ff_rc4_enc((uint8_t *)&packetkey, 8, data, len);
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ms_state = 0;
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for (i = 0; i < num_qwords - 1; i++, qwords++)
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ms_state = multiswap_enc(ms_keys, ms_state, AV_RL64(qwords));
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multiswap_invert_keys(ms_keys);
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packetkey = (packetkey << 32) | (packetkey >> 32);
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packetkey = le2me_64(packetkey);
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packetkey = multiswap_dec(ms_keys, ms_state, packetkey);
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AV_WL64(qwords, packetkey);
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}
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27
libavformat/asfcrypt.h
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27
libavformat/asfcrypt.h
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@ -0,0 +1,27 @@
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/*
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* ASF decryption
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* Copyright (c) 2007 Reimar Doeffinger
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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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#ifndef FFMPEG_ASFCRYPT_H
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#define FFMPEG_ASFCRYPT_H
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void ff_asfcrypt_dec(const uint8_t key[20], uint8_t *data, int len);
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#endif
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