hostap/wlantest/ccmp.c

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/*
* CTR with CBC-MAC Protocol (CCMP)
* Copyright (c) 2010, Jouni Malinen <j@w1.fi>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* Alternatively, this software may be distributed under the terms of BSD
* license.
*
* See README and COPYING for more details.
*/
#include "utils/includes.h"
#include "utils/common.h"
#include "common/ieee802_11_defs.h"
#include "crypto/aes.h"
#include "wlantest.h"
static void ccmp_aad_nonce(const struct ieee80211_hdr *hdr, const u8 *data,
u8 *aad, size_t *aad_len, u8 *nonce)
{
u16 fc, stype, seq;
int qos = 0, addr4 = 0;
u8 *pos;
nonce[0] = 0;
fc = le_to_host16(hdr->frame_control);
stype = WLAN_FC_GET_STYPE(fc);
if ((fc & (WLAN_FC_TODS | WLAN_FC_FROMDS)) ==
(WLAN_FC_TODS | WLAN_FC_FROMDS))
addr4 = 1;
if (WLAN_FC_GET_TYPE(fc) == WLAN_FC_TYPE_DATA) {
fc &= ~0x0070; /* Mask subtype bits */
if (stype & 0x08) {
const u8 *qc;
qos = 1;
fc &= ~WLAN_FC_ORDER;
qc = (const u8 *) (hdr + 1);
if (addr4)
qc += ETH_ALEN;
nonce[0] = qc[0] & 0x0f;
}
} else if (WLAN_FC_GET_TYPE(fc) == WLAN_FC_TYPE_MGMT)
nonce[0] |= 0x10; /* Management */
fc &= ~(WLAN_FC_RETRY | WLAN_FC_PWRMGT | WLAN_FC_MOREDATA);
fc |= WLAN_FC_ISWEP;
WPA_PUT_LE16(aad, fc);
pos = aad + 2;
os_memcpy(pos, hdr->addr1, 3 * ETH_ALEN);
pos += 3 * ETH_ALEN;
seq = le_to_host16(hdr->seq_ctrl);
seq &= ~0xfff0; /* Mask Seq#; do not modify Frag# */
WPA_PUT_LE16(pos, seq);
pos += 2;
os_memcpy(pos, hdr + 1, addr4 * ETH_ALEN + qos * 2);
pos += addr4 * ETH_ALEN;
if (qos) {
pos[0] &= 0x70;
if (1 /* FIX: either device has SPP A-MSDU Capab = 0 */)
pos[0] &= 0x80;
pos++;
*pos++ = 0x00;
}
*aad_len = pos - aad;
os_memcpy(nonce + 1, hdr->addr2, ETH_ALEN);
nonce[7] = data[7]; /* PN5 */
nonce[8] = data[6]; /* PN4 */
nonce[9] = data[5]; /* PN3 */
nonce[10] = data[4]; /* PN2 */
nonce[11] = data[1]; /* PN1 */
nonce[12] = data[0]; /* PN0 */
}
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++;
}
u8 * ccmp_decrypt(const u8 *tk, const struct ieee80211_hdr *hdr,
const u8 *data, size_t data_len, size_t *decrypted_len)
{
u8 aad[2 + 30], nonce[13];
size_t aad_len;
u8 b[AES_BLOCK_SIZE], x[AES_BLOCK_SIZE], a[AES_BLOCK_SIZE];
void *aes;
const u8 *m, *mpos, *mic;
size_t mlen, last;
int i;
u8 *plain, *ppos;
u8 t[8];
if (data_len < 8 + 8)
return NULL;
plain = os_malloc(data_len);
if (plain == NULL)
return NULL;
aes = aes_encrypt_init(tk, 16);
if (aes == NULL) {
os_free(plain);
return NULL;
}
m = data + 8;
mlen = data_len - 8 - 8;
last = mlen % AES_BLOCK_SIZE;
os_memset(aad, 0, sizeof(aad));
ccmp_aad_nonce(hdr, data, &aad[2], &aad_len, nonce);
WPA_PUT_BE16(aad, aad_len);
wpa_hexdump(MSG_EXCESSIVE, "CCMP AAD", &aad[2], aad_len);
wpa_hexdump(MSG_EXCESSIVE, "CCMP nonce", nonce, 13);
/* CCM: M=8 L=2, Adata=1, M' = (M-2)/2 = 3, L' = L-1 = 1 */
/* A_i = Flags | Nonce N | Counter i */
a[0] = 0x01; /* Flags = L' */
os_memcpy(&a[1], nonce, 13);
/* Decryption */
mic = data + data_len - 8;
wpa_hexdump(MSG_EXCESSIVE, "CCMP U", mic, 8);
/* U = T XOR S_0; S_0 = E(K, A_0) */
WPA_PUT_BE16(&a[14], 0);
aes_encrypt(aes, a, x);
for (i = 0; i < 8; i++)
t[i] = mic[i] ^ x[i];
wpa_hexdump(MSG_EXCESSIVE, "CCMP T", t, 8);
/* plaintext = msg XOR (S_1 | S_2 | ... | S_n) */
ppos = plain;
mpos = m;
for (i = 1; i <= mlen / AES_BLOCK_SIZE; i++) {
WPA_PUT_BE16(&a[14], i);
/* S_i = E(K, A_i) */
aes_encrypt(aes, a, ppos);
xor_aes_block(ppos, mpos);
ppos += AES_BLOCK_SIZE;
mpos += AES_BLOCK_SIZE;
}
if (last) {
WPA_PUT_BE16(&a[14], i);
aes_encrypt(aes, a, ppos);
/* XOR zero-padded last block */
for (i = 0; i < last; i++)
*ppos++ ^= *mpos++;
}
wpa_hexdump(MSG_EXCESSIVE, "CCMP decrypted", plain, mlen);
/* Authentication */
/* B_0: Flags | Nonce N | l(m) */
b[0] = 0x40 /* Adata */ | (3 /* M' */ << 3) | 1 /* L' */;
os_memcpy(&b[1], nonce, 13);
WPA_PUT_BE16(&b[14], mlen);
wpa_hexdump(MSG_EXCESSIVE, "CCMP B_0", b, AES_BLOCK_SIZE);
aes_encrypt(aes, b, x); /* X_1 = E(K, B_0) */
wpa_hexdump(MSG_EXCESSIVE, "CCMP B_1", aad, AES_BLOCK_SIZE);
xor_aes_block(aad, x);
aes_encrypt(aes, aad, x); /* X_2 = E(K, X_1 XOR B_1) */
wpa_hexdump(MSG_EXCESSIVE, "CCMP B_2", &aad[AES_BLOCK_SIZE],
AES_BLOCK_SIZE);
xor_aes_block(&aad[AES_BLOCK_SIZE], x);
aes_encrypt(aes, &aad[AES_BLOCK_SIZE], x); /* X_3 = E(K, X_2 XOR B_2)
*/
ppos = plain;
for (i = 0; i < mlen / AES_BLOCK_SIZE; i++) {
/* X_i+1 = E(K, X_i XOR B_i) */
xor_aes_block(x, ppos);
ppos += AES_BLOCK_SIZE;
aes_encrypt(aes, x, x);
}
if (last) {
/* XOR zero-padded last block */
for (i = 0; i < last; i++)
x[i] ^= *ppos++;
aes_encrypt(aes, x, x);
}
aes_encrypt_deinit(aes);
if (os_memcmp(x, t, 8) != 0) {
wpa_printf(MSG_INFO, "Invalid CCMP MIC in frame from " MACSTR,
MAC2STR(hdr->addr2));
os_free(plain);
return NULL;
}
*decrypted_len = mlen;
return plain;
}
void ccmp_get_pn(u8 *pn, const u8 *data)
{
pn[0] = data[7]; /* PN5 */
pn[1] = data[6]; /* PN4 */
pn[2] = data[5]; /* PN3 */
pn[3] = data[4]; /* PN2 */
pn[4] = data[1]; /* PN1 */
pn[5] = data[0]; /* PN0 */
}