wlantest: Add support for decrypting CCMP protected unicast Data frames

wlantest/Makefile

@@ -58,6 +58,7 @@ OBJS += rx_data.o
 OBJS += bss.o
 OBJS += sta.o
 OBJS += crc32.o
+OBJS += ccmp.o
 
 LIBS += -lpcap
 

wlantest/ccmp.c

@@ -0,0 +1,213 @@
+/*
+ * 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;
+}

wlantest/rx_data.c

@@ -691,13 +691,86 @@ static void rx_data_process(struct wlantest *wt, const u8 *dst, const u8 *src,
 }
 
 
+static void rx_data_bss_prot_group(struct wlantest *wt,
+				   const struct ieee80211_hdr *hdr,
+				   const u8 *qos, const u8 *dst, const u8 *src,
+				   const u8 *data, size_t len)
+{
+	struct wlantest_bss *bss;
+	int keyid;
+
+	bss = bss_get(wt, hdr->addr2);
+	if (bss == NULL)
+		return;
+	if (len < 4) {
+		wpa_printf(MSG_INFO, "Too short group addressed data frame");
+		return;
+	}
+
+	keyid = data[3] >> 6;
+	if (bss->gtk_len[keyid] == 0) {
+		wpa_printf(MSG_MSGDUMP, "No GTK known to decrypt the frame "
+			   "(A2=" MACSTR " KeyID=%d)",
+			   MAC2STR(hdr->addr2), keyid);
+		return;
+	}
+
+	/* TODO: try to decrypt */
+}
+
+
 static void rx_data_bss_prot(struct wlantest *wt,
 			     const struct ieee80211_hdr *hdr, const u8 *qos,
 			     const u8 *dst, const u8 *src, const u8 *data,
 			     size_t len)
 {
-	/* TODO: Try to decrypt and if success, call rx_data_process() with
-	 * prot = 1 */
+	struct wlantest_bss *bss;
+	struct wlantest_sta *sta;
+	int keyid;
+	u16 fc = le_to_host16(hdr->frame_control);
+	u8 *decrypted;
+	size_t dlen;
+
+	if (hdr->addr1[0] & 0x01) {
+		rx_data_bss_prot_group(wt, hdr, qos, dst, src, data, len);
+		return;
+	}
+
+	if (fc & WLAN_FC_TODS) {
+		bss = bss_get(wt, hdr->addr1);
+		if (bss == NULL)
+			return;
+		sta = sta_get(bss, hdr->addr2);
+	} else {
+		bss = bss_get(wt, hdr->addr2);
+		if (bss == NULL)
+			return;
+		sta = sta_get(bss, hdr->addr1);
+	}
+	if (sta == NULL || !sta->ptk_set) {
+		wpa_printf(MSG_MSGDUMP, "No PTK known to decrypt the frame");
+		return;
+	}
+
+	if (len < 4) {
+		wpa_printf(MSG_INFO, "Too short encrypted data frame");
+		return;
+	}
+
+	keyid = data[3] >> 6;
+	if (keyid != 0) {
+		wpa_printf(MSG_INFO, "Unexpected non-zero KeyID %d in "
+			   "individually addressed Data frame from " MACSTR,
+			   keyid, MAC2STR(hdr->addr2));
+	}
+
+	/* TODO: check PN for replay */
+	/* TODO: TKIP */
+
+	decrypted = ccmp_decrypt(sta->ptk.tk1, hdr, data, len, &dlen);
+	if (decrypted)
+		rx_data_process(wt, dst, src, decrypted, dlen, 1);
+	os_free(decrypted);
 }
 
 

wlantest/wlantest.h

@@ -20,6 +20,7 @@
 
 struct ieee802_11_elems;
 struct radius_msg;
+struct ieee80211_hdr;
 
 #define MAX_RADIUS_SECRET_LEN 128
 
@@ -121,4 +122,7 @@ void sta_deinit(struct wlantest_sta *sta);
 void sta_update_assoc(struct wlantest_sta *sta,
 		      struct ieee802_11_elems *elems);
 
+u8 * ccmp_decrypt(const u8 *tk, const struct ieee80211_hdr *hdr,
+		  const u8 *data, size_t data_len, size_t *decrypted_len);
+
 #endif /* WLANTEST_H */