mac80211: 802.11w - Add BIP (AES-128-CMAC)

Implement Broadcast/Multicast Integrity Protocol for management frame
protection. This patch adds the needed definitions for the new
information element (MMIE) and implementation for the new "encryption"
type (though, BIP is actually not encrypting data, it provides only
integrity protection). These routines will be used by a follow-on patch
that enables BIP for multicast/broadcast robust management frames.

Signed-off-by: Jouni Malinen <j@w1.fi>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 135 insertions, 0 deletions

diff --git a/net/mac80211/aes_cmac.c b/net/mac80211/aes_cmac.c
new file mode 100644
index 00000000000..3d097b3d7b6
--- /dev/null
+++ b/net/mac80211/aes_cmac.c
@@ -0,0 +1,135 @@
+/*
+ * AES-128-CMAC with TLen 16 for IEEE 802.11w BIP
+ * Copyright 2008, 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.
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/crypto.h>
+#include <linux/err.h>
+
+#include <net/mac80211.h>
+#include "key.h"
+#include "aes_cmac.h"
+
+#define AES_BLOCK_SIZE 16
+#define AES_CMAC_KEY_LEN 16
+#define CMAC_TLEN 8 /* CMAC TLen = 64 bits (8 octets) */
+#define AAD_LEN 20
+
+
+static void gf_mulx(u8 *pad)
+{
+	int i, carry;
+
+	carry = pad[0] & 0x80;
+	for (i = 0; i < AES_BLOCK_SIZE - 1; i++)
+		pad[i] = (pad[i] << 1) | (pad[i + 1] >> 7);
+	pad[AES_BLOCK_SIZE - 1] <<= 1;
+	if (carry)
+		pad[AES_BLOCK_SIZE - 1] ^= 0x87;
+}
+
+
+static void aes_128_cmac_vector(struct crypto_cipher *tfm, u8 *scratch,
+				size_t num_elem,
+				const u8 *addr[], const size_t *len, u8 *mac)
+{
+	u8 *cbc, *pad;
+	const u8 *pos, *end;
+	size_t i, e, left, total_len;
+
+	cbc = scratch;
+	pad = scratch + AES_BLOCK_SIZE;
+
+	memset(cbc, 0, AES_BLOCK_SIZE);
+
+	total_len = 0;
+	for (e = 0; e < num_elem; e++)
+		total_len += len[e];
+	left = total_len;
+
+	e = 0;
+	pos = addr[0];
+	end = pos + len[0];
+
+	while (left >= AES_BLOCK_SIZE) {
+		for (i = 0; i < AES_BLOCK_SIZE; i++) {
+			cbc[i] ^= *pos++;
+			if (pos >= end) {
+				e++;
+				pos = addr[e];
+				end = pos + len[e];
+			}
+		}
+		if (left > AES_BLOCK_SIZE)
+			crypto_cipher_encrypt_one(tfm, cbc, cbc);
+		left -= AES_BLOCK_SIZE;
+	}
+
+	memset(pad, 0, AES_BLOCK_SIZE);
+	crypto_cipher_encrypt_one(tfm, pad, pad);
+	gf_mulx(pad);
+
+	if (left || total_len == 0) {
+		for (i = 0; i < left; i++) {
+			cbc[i] ^= *pos++;
+			if (pos >= end) {
+				e++;
+				pos = addr[e];
+				end = pos + len[e];
+			}
+		}
+		cbc[left] ^= 0x80;
+		gf_mulx(pad);
+	}
+
+	for (i = 0; i < AES_BLOCK_SIZE; i++)
+		pad[i] ^= cbc[i];
+	crypto_cipher_encrypt_one(tfm, pad, pad);
+	memcpy(mac, pad, CMAC_TLEN);
+}
+
+
+void ieee80211_aes_cmac(struct crypto_cipher *tfm, u8 *scratch, const u8 *aad,
+			const u8 *data, size_t data_len, u8 *mic)
+{
+	const u8 *addr[3];
+	size_t len[3];
+	u8 zero[CMAC_TLEN];
+
+	memset(zero, 0, CMAC_TLEN);
+	addr[0] = aad;
+	len[0] = AAD_LEN;
+	addr[1] = data;
+	len[1] = data_len - CMAC_TLEN;
+	addr[2] = zero;
+	len[2] = CMAC_TLEN;
+
+	aes_128_cmac_vector(tfm, scratch, 3, addr, len, mic);
+}
+
+
+struct crypto_cipher * ieee80211_aes_cmac_key_setup(const u8 key[])
+{
+	struct crypto_cipher *tfm;
+
+	tfm = crypto_alloc_cipher("aes", 0, CRYPTO_ALG_ASYNC);
+	if (IS_ERR(tfm))
+		return NULL;
+
+	crypto_cipher_setkey(tfm, key, AES_CMAC_KEY_LEN);
+
+	return tfm;
+}
+
+
+void ieee80211_aes_cmac_key_free(struct crypto_cipher *tfm)
+{
+	if (tfm)
+		crypto_free_cipher(tfm);
+}