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/*
* Copyright 2002-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/*
* Copyright (C) 2019-2020 by Sukchan Lee <acetcom@gmail.com>
*
* This file is part of Open5GS.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "ogs-crypt.h"
#if (OGS_AES_BLOCK_SIZE != 16)
#error "Wrong AES block size"
#endif
/* From RFC 4493
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Algorithm Generate_Subkey +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ +
+ Input : K (128-bit key) +
+ Output : K1 (128-bit first subkey) +
+ K2 (128-bit second subkey) +
+-------------------------------------------------------------------+
+ +
+ Constants: const_Zero is 0x00000000000000000000000000000000 +
+ const_Rb is 0x00000000000000000000000000000087 +
+ Variables: L for output of AES-128 applied to 0^128 +
+ +
+ Step 1. L := AES-128(K, const_Zero); +
+ Step 2. if MSB(L) is equal to 0 +
+ then K1 := L << 1; +
+ else K1 := (L << 1) XOR const_Rb; +
+ Step 3. if MSB(K1) is equal to 0 +
+ then K2 := K1 << 1; +
+ else K2 := (K1 << 1) XOR const_Rb; +
+ Step 4. return K1, K2; +
+ +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
static int _generate_subkey(uint8_t *k1, uint8_t *k2,
const uint8_t *key)
{
uint8_t zero[16] = {
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
};
uint8_t rb[16] = {
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x87
};
uint8_t L[16];
uint32_t rk[OGS_AES_RKLENGTH(OGS_AES_MAX_KEY_BITS)];
int i, nrounds;
/* Step 1. L := AES-128(K, const_Zero) */
nrounds = ogs_aes_setup_enc(rk, key, 128);
ogs_aes_encrypt(rk, nrounds, zero, L);
/* Step 2. if MSB(L) is equal to 0 */
if ((L[0] & 0x80) == 0)
{
/* then k1 := L << 1; */
for (i = 0; i < 15; i++)
k1[i] = ((L[i] << 1) & 0xfe) | ((L[i + 1] & 0x80) ? 1 : 0);
k1[15] = ((L[15] << 1) & 0xfe);
}
else
{
/* else k1 := (L << 1) XOR const_Rb; */
for (i = 0; i < 15; i++)
k1[i] = (((L[i] << 1) & 0xfe) | ((L[i + 1] & 0x80) ? 1 : 0))
^ rb[i];
k1[15] = ((L[15] << 1) & 0xfe) ^ rb[15];
}
/* Step 3. if MSB(k1) is equal to 0 */
if ((k1[0] & 0x80) == 0)
{
/* then k2 := k2 << 1; */
for (i = 0; i < 15; i++)
k2[i] = ((k1[i] << 1) & 0xfe) | ((k1[i + 1] & 0x80) ? 1 : 0);
k2[15] = ((k1[15] << 1) & 0xfe);
}
else
{
/* else k2 := (k2 << 1) XOR const_Rb; */
for (i = 0; i < 15; i++)
k2[i] = (((k1[i] << 1) & 0xfe) | ((k1[i + 1] & 0x80) ? 1 : 0))
^ rb[i];
k2[15] = ((k1[15] << 1) & 0xfe) ^ rb[15];
}
return OGS_OK;
}
/* From RFC 4493
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Algorithm AES-CMAC +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ +
+ Input : K ( 128-bit key ) +
+ : M ( message to be authenticated ) +
+ : len ( length of the message in octets ) +
+ Output : T ( message authentication code ) +
+ +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Constants: const_Zero is 0x00000000000000000000000000000000 +
+ const_Bsize is 16 +
+ +
+ Variables: K1, K2 for 128-bit subkeys +
+ M_i is the i-th block (i=1..ceil(len/const_Bsize)) +
+ M_last is the last block xor-ed with K1 or K2 +
+ n for number of blocks to be processed +
+ r for number of octets of last block +
+ flag for denoting if last block is complete or not +
+ +
+ Step 1. (K1,K2) := Generate_Subkey(K); +
+ Step 2. n := ceil(len/const_Bsize); +
+ Step 3. if n = 0 +
+ then +
+ n := 1; +
+ flag := false; +
+ else +
+ if len mod const_Bsize is 0 +
+ then flag := true; +
+ else flag := false; +
+ +
+ Step 4. if flag is true +
+ then M_last := M_n XOR K1; +
+ else M_last := padding(M_n) XOR K2; +
+ Step 5. X := const_Zero; +
+ Step 6. for i := 1 to n-1 do +
+ begin +
+ Y := X XOR M_i; +
+ X := AES-128(K,Y); +
+ end +
+ Y := M_last XOR X; +
+ T := AES-128(K,Y); +
+ Step 7. return T; +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
int ogs_aes_cmac_calculate(uint8_t *cmac, const uint8_t *key,
const uint8_t *msg, const uint32_t len)
{
uint8_t x[16] = {
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
};
uint8_t y[16], m_last[16];
uint8_t k1[16], k2[16];
int i, j, n, bs, flag;
uint32_t rk[OGS_AES_RKLENGTH(OGS_AES_MAX_KEY_BITS)];
int nrounds;
ogs_assert(cmac);
ogs_assert(key);
ogs_assert(msg);
/* Step 1. (K1,K2) := Generate_Subkey(K); */
_generate_subkey(k1, k2, key);
/* Step 2. n := ceil(len/const_Bsize); */
n = (len + 15) / OGS_AES_BLOCK_SIZE;
/* Step 3. if n = 0
then
n := 1;
flag := false;
else
if len mod const_Bsize is 0
then flag := true;
else flag := false;
*/
if (n == 0)
{
n = 1;
flag = 0;
}
else
{
if (len % OGS_AES_BLOCK_SIZE == 0)
flag = 1;
else
flag = 0;
}
/* Step 4. if flag is true
then M_last := M_n XOR K1;
else M_last := padding(M_n) XOR K2;
*/
bs = (n - 1) * OGS_AES_BLOCK_SIZE;
if (flag)
{
for (i = 0; i < 16; i++)
m_last[i] = msg[bs + i] ^ k1[i];
}
else
{
for (i = 0; i < len % OGS_AES_BLOCK_SIZE; i++)
m_last[i] = msg[bs + i] ^ k2[i];
m_last[i] = 0x80 ^ k2[i];
for (i = i + 1; i < OGS_AES_BLOCK_SIZE; i++)
m_last[i] = 0x00 ^ k2[i];
}
/* Step 5. X := const_Zero; */
/* Step 6. for i := 1 to n-1 do
begin
Y := X XOR M_i;
X := AES-128(K,Y);
end
Y := M_last XOR X;
T := AES-128(K,Y);
*/
nrounds = ogs_aes_setup_enc(rk, key, 128);
for (i = 0; i <= n - 2; i++)
{
bs = i * OGS_AES_BLOCK_SIZE;
for (j = 0; j < 16; j++)
y[j] = x[j] ^ msg[bs + j];
ogs_aes_encrypt(rk, nrounds, y, x);
}
bs = (n - 1) * OGS_AES_BLOCK_SIZE;
for (j = 0; j < 16; j++)
y[j] = m_last[j] ^ x[j];
ogs_aes_encrypt(rk, nrounds, y, cmac);
return OGS_OK;
}
/* From RFC 4493
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ Algorithm Verify_MAC +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+ +
+ Input : K ( 128-bit Key ) +
+ : M ( message to be verified ) +
+ : len ( length of the message in octets ) +
+ : T' ( the received MAC to be verified ) +
+ Output : INVALID or VALID +
+ +
+-------------------------------------------------------------------+
+ +
+ Step 1. T* := AES-CMAC(K,M,len); +
+ Step 2. if T* is equal to T' +
+ then +
+ return VALID; +
+ else +
+ return INVALID; +
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ */
int ogs_aes_cmac_verify(uint8_t *cmac, const uint8_t *key,
const uint8_t *msg, const uint32_t len)
{
int rv;
uint8_t cmac_calc[16];
rv = ogs_aes_cmac_calculate(cmac_calc, key, msg, len);
if (rv != OGS_OK)
return rv;
if (memcmp(cmac_calc, cmac, 16) != 0)
return OGS_ERR_INVALID_CMAC;
return OGS_OK;
}
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