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/*
* Galois/Counter Mode (GCM) and GMAC with AES
*
* Copyright (c) 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 inc32(u8 *block)
{
u32 val;
val = WPA_GET_BE32(block + AES_BLOCK_SIZE - 4);
val++;
WPA_PUT_BE32(block + AES_BLOCK_SIZE - 4, val);
}
static void xor_block(u8 *dst, const u8 *src)
{
u32 *d = (u32 *) dst;
u32 *s = (u32 *) src;
*d++ ^= *s++;
*d++ ^= *s++;
*d++ ^= *s++;
*d++ ^= *s++;
}
static void shift_right_block(u8 *v)
{
u32 val;
val = WPA_GET_BE32(v + 12);
val >>= 1;
if (v[11] & 0x01)
val |= 0x80000000;
WPA_PUT_BE32(v + 12, val);
val = WPA_GET_BE32(v + 8);
val >>= 1;
if (v[7] & 0x01)
val |= 0x80000000;
WPA_PUT_BE32(v + 8, val);
val = WPA_GET_BE32(v + 4);
val >>= 1;
if (v[3] & 0x01)
val |= 0x80000000;
WPA_PUT_BE32(v + 4, val);
val = WPA_GET_BE32(v);
val >>= 1;
WPA_PUT_BE32(v, val);
}
/* Multiplication in GF(2^128) */
static void gf_mult(const u8 *x, const u8 *y, u8 *z)
{
u8 v[16];
int i, j;
os_memset(z, 0, 16); /* Z_0 = 0^128 */
os_memcpy(v, y, 16); /* V_0 = Y */
for (i = 0; i < 16; i++) {
for (j = 0; j < 8; j++) {
if (x[i] & BIT(7 - j)) {
/* Z_(i + 1) = Z_i XOR V_i */
xor_block(z, v);
} else {
/* Z_(i + 1) = Z_i */
}
if (v[15] & 0x01) {
/* V_(i + 1) = (V_i >> 1) XOR R */
shift_right_block(v);
/* R = 11100001 || 0^120 */
v[0] ^= 0xe1;
} else {
/* V_(i + 1) = V_i >> 1 */
shift_right_block(v);
}
}
}
}
static void ghash_start(u8 *y)
{
/* Y_0 = 0^128 */
os_memset(y, 0, 16);
}
static void ghash(const u8 *h, const u8 *x, size_t xlen, u8 *y)
{
size_t m, i;
const u8 *xpos = x;
u8 tmp[16];
m = xlen / 16;
for (i = 0; i < m; i++) {
/* Y_i = (Y^(i-1) XOR X_i) dot H */
xor_block(y, xpos);
xpos += 16;
/* dot operation:
* multiplication operation for binary Galois (finite) field of
* 2^128 elements */
gf_mult(y, h, tmp);
os_memcpy(y, tmp, 16);
}
if (x + xlen > xpos) {
/* Add zero padded last block */
size_t last = x + xlen - xpos;
os_memcpy(tmp, xpos, last);
os_memset(tmp + last, 0, sizeof(tmp) - last);
/* Y_i = (Y^(i-1) XOR X_i) dot H */
xor_block(y, tmp);
/* dot operation:
* multiplication operation for binary Galois (finite) field of
* 2^128 elements */
gf_mult(y, h, tmp);
os_memcpy(y, tmp, 16);
}
/* Return Y_m */
}
static void aes_gctr(void *aes, const u8 *icb, const u8 *x, size_t xlen, u8 *y)
{
size_t i, n, last;
u8 cb[AES_BLOCK_SIZE], tmp[AES_BLOCK_SIZE];
const u8 *xpos = x;
u8 *ypos = y;
if (xlen == 0)
return;
n = xlen / 16;
os_memcpy(cb, icb, AES_BLOCK_SIZE);
/* Full blocks */
for (i = 0; i < n; i++) {
aes_encrypt(aes, cb, ypos);
xor_block(ypos, xpos);
xpos += AES_BLOCK_SIZE;
ypos += AES_BLOCK_SIZE;
inc32(cb);
}
last = x + xlen - xpos;
if (last) {
/* Last, partial block */
aes_encrypt(aes, cb, tmp);
for (i = 0; i < last; i++)
*ypos++ = *xpos++ ^ tmp[i];
}
}
static void * aes_gcm_init_hash_subkey(const u8 *key, size_t key_len, u8 *H)
{
void *aes;
aes = aes_encrypt_init(key, key_len);
if (aes == NULL)
return NULL;
/* Generate hash subkey H = AES_K(0^128) */
os_memset(H, 0, AES_BLOCK_SIZE);
aes_encrypt(aes, H, H);
wpa_hexdump_key(MSG_EXCESSIVE, "Hash subkey H for GHASH",
H, AES_BLOCK_SIZE);
return aes;
}
static void aes_gcm_prepare_j0(const u8 *iv, size_t iv_len, const u8 *H, u8 *J0)
{
u8 len_buf[16];
if (iv_len == 12) {
/* Prepare block J_0 = IV || 0^31 || 1 [len(IV) = 96] */
os_memcpy(J0, iv, iv_len);
os_memset(J0 + iv_len, 0, AES_BLOCK_SIZE - iv_len);
J0[AES_BLOCK_SIZE - 1] = 0x01;
} else {
/*
* s = 128 * ceil(len(IV)/128) - len(IV)
* J_0 = GHASH_H(IV || 0^(s+64) || [len(IV)]_64)
*/
ghash_start(J0);
ghash(H, iv, iv_len, J0);
WPA_PUT_BE64(len_buf, 0);
WPA_PUT_BE64(len_buf + 8, iv_len * 8);
ghash(H, len_buf, sizeof(len_buf), J0);
}
}
static void aes_gcm_gctr(void *aes, const u8 *J0, const u8 *in, size_t len,
u8 *out)
{
u8 J0inc[AES_BLOCK_SIZE];
if (len == 0)
return;
os_memcpy(J0inc, J0, AES_BLOCK_SIZE);
inc32(J0inc);
aes_gctr(aes, J0inc, in, len, out);
}
static void aes_gcm_ghash(const u8 *H, const u8 *aad, size_t aad_len,
const u8 *crypt, size_t crypt_len, u8 *S)
{
u8 len_buf[16];
/*
* u = 128 * ceil[len(C)/128] - len(C)
* v = 128 * ceil[len(A)/128] - len(A)
* S = GHASH_H(A || 0^v || C || 0^u || [len(A)]64 || [len(C)]64)
* (i.e., zero padded to block size A || C and lengths of each in bits)
*/
ghash_start(S);
ghash(H, aad, aad_len, S);
ghash(H, crypt, crypt_len, S);
WPA_PUT_BE64(len_buf, aad_len * 8);
WPA_PUT_BE64(len_buf + 8, crypt_len * 8);
ghash(H, len_buf, sizeof(len_buf), S);
wpa_hexdump_key(MSG_EXCESSIVE, "S = GHASH_H(...)", S, 16);
}
/**
* aes_gcm_ae - GCM-AE_K(IV, P, A)
*/
int aes_gcm_ae(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
const u8 *plain, size_t plain_len,
const u8 *aad, size_t aad_len, u8 *crypt, u8 *tag)
{
u8 H[AES_BLOCK_SIZE];
u8 J0[AES_BLOCK_SIZE];
u8 S[16];
void *aes;
aes = aes_gcm_init_hash_subkey(key, key_len, H);
if (aes == NULL)
return -1;
aes_gcm_prepare_j0(iv, iv_len, H, J0);
/* C = GCTR_K(inc_32(J_0), P) */
aes_gcm_gctr(aes, J0, plain, plain_len, crypt);
aes_gcm_ghash(H, aad, aad_len, crypt, plain_len, S);
/* T = MSB_t(GCTR_K(J_0, S)) */
aes_gctr(aes, J0, S, sizeof(S), tag);
/* Return (C, T) */
aes_encrypt_deinit(aes);
return 0;
}
/**
* aes_gcm_ad - GCM-AD_K(IV, C, A, T)
*/
int aes_gcm_ad(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
const u8 *crypt, size_t crypt_len,
const u8 *aad, size_t aad_len, const u8 *tag, u8 *plain)
{
u8 H[AES_BLOCK_SIZE];
u8 J0[AES_BLOCK_SIZE];
u8 S[16], T[16];
void *aes;
aes = aes_gcm_init_hash_subkey(key, key_len, H);
if (aes == NULL)
return -1;
aes_gcm_prepare_j0(iv, iv_len, H, J0);
/* P = GCTR_K(inc_32(J_0), C) */
aes_gcm_gctr(aes, J0, crypt, crypt_len, plain);
aes_gcm_ghash(H, aad, aad_len, crypt, crypt_len, S);
/* T' = MSB_t(GCTR_K(J_0, S)) */
aes_gctr(aes, J0, S, sizeof(S), T);
aes_encrypt_deinit(aes);
if (os_memcmp_const(tag, T, 16) != 0) {
wpa_printf(MSG_EXCESSIVE, "GCM: Tag mismatch");
return -1;
}
return 0;
}
int aes_gmac(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
const u8 *aad, size_t aad_len, u8 *tag)
{
return aes_gcm_ae(key, key_len, iv, iv_len, NULL, 0, aad, aad_len, NULL,
tag);
}
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