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// Copyright 2005-2019 The Mumble Developers. All rights reserved.
// Use of this source code is governed by a BSD-style license
// that can be found in the LICENSE file at the root of the
// Mumble source tree or at <https://www.mumble.info/LICENSE>.
/*
* This code implements OCB-AES128.
* In the US, OCB is covered by patents. The inventor has given a license
* to all programs distributed under the GPL.
* Mumble is BSD (revised) licensed, meaning you can use the code in a
* closed-source program. If you do, you'll have to either replace
* OCB with something else or get yourself a license.
*/
#include "CryptState.h"
#include "ByteSwap.h"
CryptState::CryptState() {
for (int i=0;i<0x100;i++)
decrypt_history[i] = 0;
bInit = false;
memset(raw_key, 0, AES_KEY_SIZE_BYTES);
memset(encrypt_iv, 0, AES_BLOCK_SIZE);
memset(decrypt_iv, 0, AES_BLOCK_SIZE);
uiGood=uiLate=uiLost=uiResync=0;
uiRemoteGood=uiRemoteLate=uiRemoteLost=uiRemoteResync=0;
}
bool CryptState::isValid() const {
return bInit;
}
void CryptState::genKey() {
RAND_bytes(raw_key, AES_KEY_SIZE_BYTES);
RAND_bytes(encrypt_iv, AES_BLOCK_SIZE);
RAND_bytes(decrypt_iv, AES_BLOCK_SIZE);
AES_set_encrypt_key(raw_key, AES_KEY_SIZE_BITS, &encrypt_key);
AES_set_decrypt_key(raw_key, AES_KEY_SIZE_BITS, &decrypt_key);
bInit = true;
}
void CryptState::setKey(const unsigned char *rkey, const unsigned char *eiv, const unsigned char *div) {
memcpy(raw_key, rkey, AES_KEY_SIZE_BYTES);
memcpy(encrypt_iv, eiv, AES_BLOCK_SIZE);
memcpy(decrypt_iv, div, AES_BLOCK_SIZE);
AES_set_encrypt_key(raw_key, AES_KEY_SIZE_BITS, &encrypt_key);
AES_set_decrypt_key(raw_key, AES_KEY_SIZE_BITS, &decrypt_key);
bInit = true;
}
void CryptState::setDecryptIV(const unsigned char *iv) {
memcpy(decrypt_iv, iv, AES_BLOCK_SIZE);
}
void CryptState::encrypt(const unsigned char *source, unsigned char *dst, unsigned int plain_length) {
unsigned char tag[AES_BLOCK_SIZE];
// First, increase our IV.
for (int i=0;i<AES_BLOCK_SIZE;i++)
if (++encrypt_iv[i])
break;
ocb_encrypt(source, dst+4, plain_length, encrypt_iv, tag);
dst[0] = encrypt_iv[0];
dst[1] = tag[0];
dst[2] = tag[1];
dst[3] = tag[2];
}
bool CryptState::decrypt(const unsigned char *source, unsigned char *dst, unsigned int crypted_length) {
if (crypted_length < 4)
return false;
unsigned int plain_length = crypted_length - 4;
unsigned char saveiv[AES_BLOCK_SIZE];
unsigned char ivbyte = source[0];
bool restore = false;
unsigned char tag[AES_BLOCK_SIZE];
int lost = 0;
int late = 0;
memcpy(saveiv, decrypt_iv, AES_BLOCK_SIZE);
if (((decrypt_iv[0] + 1) & 0xFF) == ivbyte) {
// In order as expected.
if (ivbyte > decrypt_iv[0]) {
decrypt_iv[0] = ivbyte;
} else if (ivbyte < decrypt_iv[0]) {
decrypt_iv[0] = ivbyte;
for (int i=1;i<AES_BLOCK_SIZE;i++)
if (++decrypt_iv[i])
break;
} else {
return false;
}
} else {
// This is either out of order or a repeat.
int diff = ivbyte - decrypt_iv[0];
if (diff > 128)
diff = diff-256;
else if (diff < -128)
diff = diff+256;
if ((ivbyte < decrypt_iv[0]) && (diff > -30) && (diff < 0)) {
// Late packet, but no wraparound.
late = 1;
lost = -1;
decrypt_iv[0] = ivbyte;
restore = true;
} else if ((ivbyte > decrypt_iv[0]) && (diff > -30) && (diff < 0)) {
// Last was 0x02, here comes 0xff from last round
late = 1;
lost = -1;
decrypt_iv[0] = ivbyte;
for (int i=1;i<AES_BLOCK_SIZE;i++)
if (decrypt_iv[i]--)
break;
restore = true;
} else if ((ivbyte > decrypt_iv[0]) && (diff > 0)) {
// Lost a few packets, but beyond that we're good.
lost = ivbyte - decrypt_iv[0] - 1;
decrypt_iv[0] = ivbyte;
} else if ((ivbyte < decrypt_iv[0]) && (diff > 0)) {
// Lost a few packets, and wrapped around
lost = 256 - decrypt_iv[0] + ivbyte - 1;
decrypt_iv[0] = ivbyte;
for (int i=1;i<AES_BLOCK_SIZE;i++)
if (++decrypt_iv[i])
break;
} else {
return false;
}
if (decrypt_history[decrypt_iv[0]] == decrypt_iv[1]) {
memcpy(decrypt_iv, saveiv, AES_BLOCK_SIZE);
return false;
}
}
ocb_decrypt(source+4, dst, plain_length, decrypt_iv, tag);
if (memcmp(tag, source+1, 3) != 0) {
memcpy(decrypt_iv, saveiv, AES_BLOCK_SIZE);
return false;
}
decrypt_history[decrypt_iv[0]] = decrypt_iv[1];
if (restore)
memcpy(decrypt_iv, saveiv, AES_BLOCK_SIZE);
uiGood++;
uiLate += late;
uiLost += lost;
tLastGood.restart();
return true;
}
#if defined(__LP64__)
#define BLOCKSIZE 2
#define SHIFTBITS 63
typedef quint64 subblock;
#define SWAPPED(x) SWAP64(x)
#else
#define BLOCKSIZE 4
#define SHIFTBITS 31
typedef quint32 subblock;
#define SWAPPED(x) htonl(x)
#endif
typedef subblock keyblock[BLOCKSIZE];
#define HIGHBIT (1<<SHIFTBITS);
static void inline XOR(subblock *dst, const subblock *a, const subblock *b) {
for (int i=0;i<BLOCKSIZE;i++) {
dst[i] = a[i] ^ b[i];
}
}
static void inline S2(subblock *block) {
subblock carry = SWAPPED(block[0]) >> SHIFTBITS;
for (int i=0;i<BLOCKSIZE-1;i++)
block[i] = SWAPPED((SWAPPED(block[i]) << 1) | (SWAPPED(block[i+1]) >> SHIFTBITS));
block[BLOCKSIZE-1] = SWAPPED((SWAPPED(block[BLOCKSIZE-1]) << 1) ^(carry * 0x87));
}
static void inline S3(subblock *block) {
subblock carry = SWAPPED(block[0]) >> SHIFTBITS;
for (int i=0;i<BLOCKSIZE-1;i++)
block[i] ^= SWAPPED((SWAPPED(block[i]) << 1) | (SWAPPED(block[i+1]) >> SHIFTBITS));
block[BLOCKSIZE-1] ^= SWAPPED((SWAPPED(block[BLOCKSIZE-1]) << 1) ^(carry * 0x87));
}
static void inline ZERO(keyblock &block) {
for (int i=0;i<BLOCKSIZE;i++)
block[i]=0;
}
#define AESencrypt(src,dst,key) AES_encrypt(reinterpret_cast<const unsigned char *>(src),reinterpret_cast<unsigned char *>(dst), key);
#define AESdecrypt(src,dst,key) AES_decrypt(reinterpret_cast<const unsigned char *>(src),reinterpret_cast<unsigned char *>(dst), key);
void CryptState::ocb_encrypt(const unsigned char *plain, unsigned char *encrypted, unsigned int len, const unsigned char *nonce, unsigned char *tag) {
keyblock checksum, delta, tmp, pad;
// Initialize
AESencrypt(nonce, delta, &encrypt_key);
ZERO(checksum);
while (len > AES_BLOCK_SIZE) {
S2(delta);
XOR(tmp, delta, reinterpret_cast<const subblock *>(plain));
AESencrypt(tmp, tmp, &encrypt_key);
XOR(reinterpret_cast<subblock *>(encrypted), delta, tmp);
XOR(checksum, checksum, reinterpret_cast<const subblock *>(plain));
len -= AES_BLOCK_SIZE;
plain += AES_BLOCK_SIZE;
encrypted += AES_BLOCK_SIZE;
}
S2(delta);
ZERO(tmp);
tmp[BLOCKSIZE - 1] = SWAPPED(len * 8);
XOR(tmp, tmp, delta);
AESencrypt(tmp, pad, &encrypt_key);
memcpy(tmp, plain, len);
memcpy(reinterpret_cast<unsigned char *>(tmp)+len, reinterpret_cast<const unsigned char *>(pad)+len, AES_BLOCK_SIZE - len);
XOR(checksum, checksum, tmp);
XOR(tmp, pad, tmp);
memcpy(encrypted, tmp, len);
S3(delta);
XOR(tmp, delta, checksum);
AESencrypt(tmp, tag, &encrypt_key);
}
void CryptState::ocb_decrypt(const unsigned char *encrypted, unsigned char *plain, unsigned int len, const unsigned char *nonce, unsigned char *tag) {
keyblock checksum, delta, tmp, pad;
// Initialize
AESencrypt(nonce, delta, &encrypt_key);
ZERO(checksum);
while (len > AES_BLOCK_SIZE) {
S2(delta);
XOR(tmp, delta, reinterpret_cast<const subblock *>(encrypted));
AESdecrypt(tmp, tmp, &decrypt_key);
XOR(reinterpret_cast<subblock *>(plain), delta, tmp);
XOR(checksum, checksum, reinterpret_cast<const subblock *>(plain));
len -= AES_BLOCK_SIZE;
plain += AES_BLOCK_SIZE;
encrypted += AES_BLOCK_SIZE;
}
S2(delta);
ZERO(tmp);
tmp[BLOCKSIZE - 1] = SWAPPED(len * 8);
XOR(tmp, tmp, delta);
AESencrypt(tmp, pad, &encrypt_key);
memset(tmp, 0, AES_BLOCK_SIZE);
memcpy(tmp, encrypted, len);
XOR(tmp, tmp, pad);
XOR(checksum, checksum, tmp);
memcpy(plain, tmp, len);
S3(delta);
XOR(tmp, delta, checksum);
AESencrypt(tmp, tag, &encrypt_key);
}
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