76 lines
2.4 KiB
Java
76 lines
2.4 KiB
Java
/*
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Copyright 2019-2022 Dmitry Isaenko
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This file is part of libKonogonka.
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libKonogonka is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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libKonogonka 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with libKonogonka. If not, see <https://www.gnu.org/licenses/>.
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*/
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package libKonogonka.ctraes;
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import libKonogonka.Converter;
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import libKonogonka.RainbowDump;
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/**
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* Simplify decryption of the CTR
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*/
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public class AesCtrDecryptSimple {
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private long realMediaOffset;
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private byte[] IVarray;
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private AesCtr aesCtr;
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private final byte[] initialKey;
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private final byte[] initialSectionCTR;
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private final long initialRealMediaOffset;
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public AesCtrDecryptSimple(byte[] key, byte[] sectionCTR, long realMediaOffset) throws Exception{
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this.initialKey = key;
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this.initialSectionCTR = sectionCTR;
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this.initialRealMediaOffset = realMediaOffset;
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reset();
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}
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public void skipNext(){
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realMediaOffset += 0x200;
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}
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public void skipNext(long blocksNum){
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realMediaOffset += blocksNum * 0x200;
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}
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public byte[] decryptNext(byte[] encryptedBlock) throws Exception{
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updateIV();
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byte[] decryptedBlock = aesCtr.decrypt(encryptedBlock, IVarray);
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realMediaOffset += 0x200;
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return decryptedBlock;
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}
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// Populate last 8 bytes calculated. Thanks hactool project!
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private void updateIV(){
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long offset = realMediaOffset >> 4;
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for (int i = 0; i < 0x8; i++){
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IVarray[0x10-i-1] = (byte)(offset & 0xff); // Note: issues could be here
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offset >>= 8;
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}
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}
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public void reset() throws Exception{
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realMediaOffset = initialRealMediaOffset;
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aesCtr = new AesCtr(initialKey);
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// IV for CTR == 16 bytes
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IVarray = new byte[0x10];
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// Populate first 4 bytes taken from Header's section Block CTR (aka SecureValue)
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System.arraycopy(Converter.flip(initialSectionCTR), 0x0, IVarray, 0x0, 0x4);
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}
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}
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