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/*
* Counter with CBC-MAC (CCM) with AES
*
* Copyright (c) 2010-2012, Jouni Malinen <j@w1.fi>
*
* This software may be distributed under the terms of the BSD license.
* See README for more details.
*/
#include "includes.h"
#include "common.h"
#include "aes.h"
#include "aes_wrap.h"
static void xor_aes_block(u8 *dst, const u8 *src)
{
u32 *d = (u32 *) dst;
u32 *s = (u32 *) src;
*d++ ^= *s++;
*d++ ^= *s++;
*d++ ^= *s++;
*d++ ^= *s++;
}
static void aes_ccm_auth_start(void *aes, size_t M, size_t L, const u8 *nonce,
const u8 *aad, size_t aad_len, size_t plain_len,
u8 *x)
{
u8 aad_buf[2 * AES_BLOCK_SIZE];
u8 b[AES_BLOCK_SIZE];
/* Authentication */
/* B_0: Flags | Nonce N | l(m) */
b[0] = aad_len ? 0x40 : 0 /* Adata */;
b[0] |= (((M - 2) / 2) /* M' */ << 3);
b[0] |= (L - 1) /* L' */;
os_memcpy(&b[1], nonce, 15 - L);
WPA_PUT_BE16(&b[AES_BLOCK_SIZE - L], plain_len);
wpa_hexdump_key(MSG_EXCESSIVE, "CCM B_0", b, AES_BLOCK_SIZE);
aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */
if (!aad_len)
return;
WPA_PUT_BE16(aad_buf, aad_len);
os_memcpy(aad_buf + 2, aad, aad_len);
os_memset(aad_buf + 2 + aad_len, 0, sizeof(aad_buf) - 2 - aad_len);
xor_aes_block(aad_buf, x);
aes_encrypt(aes, aad_buf, x); /* X_2 = E(K, X_1 XOR B_1) */
if (aad_len > AES_BLOCK_SIZE - 2) {
xor_aes_block(&aad_buf[AES_BLOCK_SIZE], x);
/* X_3 = E(K, X_2 XOR B_2) */
aes_encrypt(aes, &aad_buf[AES_BLOCK_SIZE], x);
}
}
static void aes_ccm_auth(void *aes, const u8 *data, size_t len, u8 *x)
{
size_t last = len % AES_BLOCK_SIZE;
size_t i;
for (i = 0; i < len / AES_BLOCK_SIZE; i++) {
/* X_i+1 = E(K, X_i XOR B_i) */
xor_aes_block(x, data);
data += AES_BLOCK_SIZE;
aes_encrypt(aes, x, x);
}
if (last) {
/* XOR zero-padded last block */
for (i = 0; i < last; i++)
x[i] ^= *data++;
aes_encrypt(aes, x, x);
}
}
static void aes_ccm_encr_start(size_t L, const u8 *nonce, u8 *a)
{
/* A_i = Flags | Nonce N | Counter i */
a[0] = L - 1; /* Flags = L' */
os_memcpy(&a[1], nonce, 15 - L);
}
static void aes_ccm_encr(void *aes, size_t L, const u8 *in, size_t len, u8 *out,
u8 *a)
{
size_t last = len % AES_BLOCK_SIZE;
size_t i;
/* crypt = msg XOR (S_1 | S_2 | ... | S_n) */
for (i = 1; i <= len / AES_BLOCK_SIZE; i++) {
WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
/* S_i = E(K, A_i) */
aes_encrypt(aes, a, out);
xor_aes_block(out, in);
out += AES_BLOCK_SIZE;
in += AES_BLOCK_SIZE;
}
if (last) {
WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], i);
aes_encrypt(aes, a, out);
/* XOR zero-padded last block */
for (i = 0; i < last; i++)
*out++ ^= *in++;
}
}
static void aes_ccm_encr_auth(void *aes, size_t M, u8 *x, u8 *a, u8 *auth)
{
size_t i;
u8 tmp[AES_BLOCK_SIZE];
wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", x, M);
/* U = T XOR S_0; S_0 = E(K, A_0) */
WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
aes_encrypt(aes, a, tmp);
for (i = 0; i < M; i++)
auth[i] = x[i] ^ tmp[i];
wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M);
}
static void aes_ccm_decr_auth(void *aes, size_t M, u8 *a, const u8 *auth, u8 *t)
{
size_t i;
u8 tmp[AES_BLOCK_SIZE];
wpa_hexdump_key(MSG_EXCESSIVE, "CCM U", auth, M);
/* U = T XOR S_0; S_0 = E(K, A_0) */
WPA_PUT_BE16(&a[AES_BLOCK_SIZE - 2], 0);
aes_encrypt(aes, a, tmp);
for (i = 0; i < M; i++)
t[i] = auth[i] ^ tmp[i];
wpa_hexdump_key(MSG_EXCESSIVE, "CCM T", t, M);
}
/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */
int aes_ccm_ae(const u8 *key, size_t key_len, const u8 *nonce,
size_t M, const u8 *plain, size_t plain_len,
const u8 *aad, size_t aad_len, u8 *crypt, u8 *auth)
{
const size_t L = 2;
void *aes;
u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
if (aad_len > 30 || M > AES_BLOCK_SIZE)
return -1;
aes = aes_encrypt_init(key, key_len);
if (aes == NULL)
return -1;
aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, plain_len, x);
aes_ccm_auth(aes, plain, plain_len, x);
/* Encryption */
aes_ccm_encr_start(L, nonce, a);
aes_ccm_encr(aes, L, plain, plain_len, crypt, a);
aes_ccm_encr_auth(aes, M, x, a, auth);
aes_encrypt_deinit(aes);
return 0;
}
/* AES-CCM with fixed L=2 and aad_len <= 30 assumption */
int aes_ccm_ad(const u8 *key, size_t key_len, const u8 *nonce,
size_t M, const u8 *crypt, size_t crypt_len,
const u8 *aad, size_t aad_len, const u8 *auth, u8 *plain)
{
const size_t L = 2;
void *aes;
u8 x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
u8 t[AES_BLOCK_SIZE];
if (aad_len > 30 || M > AES_BLOCK_SIZE)
return -1;
aes = aes_encrypt_init(key, key_len);
if (aes == NULL)
return -1;
/* Decryption */
aes_ccm_encr_start(L, nonce, a);
aes_ccm_decr_auth(aes, M, a, auth, t);
/* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */
aes_ccm_encr(aes, L, crypt, crypt_len, plain, a);
aes_ccm_auth_start(aes, M, L, nonce, aad, aad_len, crypt_len, x);
aes_ccm_auth(aes, plain, crypt_len, x);
aes_encrypt_deinit(aes);
if (os_memcmp_const(x, t, M) != 0) {
wpa_printf(MSG_EXCESSIVE, "CCM: Auth mismatch");
return -1;
}
return 0;
}
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