netdev - [RFC PATCH 1/2] mac80211: fils_aead: clone shared CMAC functions into private version

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Message-Id: <1486149955-11825-2-git-send-email-ard.biesheuvel@linaro.org>
Date:   Fri,  3 Feb 2017 19:25:54 +0000
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     johannes@...solutions.net, linux-wireless@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        jouni@....qualcomm.com, Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: [RFC PATCH 1/2] mac80211: fils_aead: clone shared CMAC functions into private version

Before reworking the AES CMAC mac80211 code, clone the routines that it
shares with the FILS AEAD driver into its own source file, and remove the
external declaration from aes_cmac.h. This will allow us to carry over one
user at a time from the open coded CMAC code to the crypto API.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@...aro.org>
---
 net/mac80211/aes_cmac.h  |  4 --
 net/mac80211/fils_aead.c | 68 ++++++++++++++++++++
 2 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/net/mac80211/aes_cmac.h b/net/mac80211/aes_cmac.h
index c827e1d5de8b..3702041f44fd 100644
--- a/net/mac80211/aes_cmac.h
+++ b/net/mac80211/aes_cmac.h
@@ -11,10 +11,6 @@
 
 #include <linux/crypto.h>
 
-void gf_mulx(u8 *pad);
-void aes_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
-		     const u8 *addr[], const size_t *len, u8 *mac,
-		     size_t mac_len);
 struct crypto_cipher *ieee80211_aes_cmac_key_setup(const u8 key[],
 						   size_t key_len);
 void ieee80211_aes_cmac(struct crypto_cipher *tfm, const u8 *aad,
diff --git a/net/mac80211/fils_aead.c b/net/mac80211/fils_aead.c
index ecfdd97758a3..ec493e68957c 100644
--- a/net/mac80211/fils_aead.c
+++ b/net/mac80211/fils_aead.c
@@ -15,6 +15,74 @@
 #include "aes_cmac.h"
 #include "fils_aead.h"
 
+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_cmac_vector(struct crypto_cipher *tfm, size_t num_elem,
+			    const u8 *addr[], const size_t *len, u8 *mac,
+			    size_t mac_len)
+{
+	u8 cbc[AES_BLOCK_SIZE], pad[AES_BLOCK_SIZE];
+	const u8 *pos, *end;
+	size_t i, e, left, total_len;
+
+	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, mac_len);
+}
+
 static int aes_s2v(struct crypto_cipher *tfm,
 		   size_t num_elem, const u8 *addr[], size_t len[], u8 *v)
 {
-- 
2.7.4