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![Hendrik Leppkes](/assets/img/avatar_default.png)
* commit '10de408738d28ab17aa5c1fdccd809b0637c12d5': lavf: Update to the new crypto API Merged-by: Hendrik Leppkes <h.leppkes@gmail.com>
196 lines
5.5 KiB
C
196 lines
5.5 KiB
C
/*
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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 "libavutil/bswap.h"
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#include "libavutil/common.h"
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#include "libavutil/des.h"
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#include "libavutil/intreadwrite.h"
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#include "libavutil/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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{
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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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{
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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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{
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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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{
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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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{
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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],
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uint64_t key, uint64_t data)
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{
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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],
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uint64_t key, uint64_t data)
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{
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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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{
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struct AVDES *des;
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struct AVRC4 *rc4;
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int num_qwords = len >> 3;
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uint8_t *qwords = data;
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uint64_t rc4buff[8] = { 0 };
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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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des = av_des_alloc();
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rc4 = av_rc4_alloc();
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if (!des || !rc4) {
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av_freep(&des);
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av_freep(&rc4);
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return;
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}
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av_rc4_init(rc4, key, 12 * 8, 1);
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av_rc4_crypt(rc4, (uint8_t *)rc4buff, NULL, sizeof(rc4buff), NULL, 1);
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multiswap_init((uint8_t *)rc4buff, ms_keys);
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packetkey = AV_RN64(&qwords[num_qwords * 8 - 8]);
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packetkey ^= rc4buff[7];
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av_des_init(des, key + 12, 64, 1);
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av_des_crypt(des, (uint8_t *)&packetkey, (uint8_t *)&packetkey, 1, NULL, 1);
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packetkey ^= rc4buff[6];
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av_rc4_init(rc4, (uint8_t *)&packetkey, 64, 1);
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av_rc4_crypt(rc4, data, data, len, NULL, 1);
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ms_state = 0;
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for (i = 0; i < num_qwords - 1; i++, qwords += 8)
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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 = av_le2ne64(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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av_free(rc4);
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av_free(des);
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}
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