From 77b2c81275e8081dbba30ee9b9aa1a0bf65c4cd4 Mon Sep 17 00:00:00 2001
From: Jouni Malinen <j@w1.fi>
Date: Sun, 9 Sep 2012 13:37:50 +0300
Subject: [PATCH] Add aes_gmac() as a wrapper for AES GMAC operations using GCM

This is otherwise identical to aes_gcm_ae() but does not use the
plain/crypt pointers since no data is encrypted.

Signed-hostap: Jouni Malinen <j@w1.fi>
---
 src/crypto/aes-gcm.c  |  8 ++++++++
 src/crypto/aes_wrap.h |  3 +++
 tests/test-aes.c      | 14 ++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/src/crypto/aes-gcm.c b/src/crypto/aes-gcm.c
index d3105edaf..f6f4074b0 100644
--- a/src/crypto/aes-gcm.c
+++ b/src/crypto/aes-gcm.c
@@ -311,3 +311,11 @@ int aes_gcm_ad(const u8 *key, size_t key_len, const u8 *iv, size_t iv_len,
 
 	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);
+}
diff --git a/src/crypto/aes_wrap.h b/src/crypto/aes_wrap.h
index 5b0928e20..63925dfdc 100644
--- a/src/crypto/aes_wrap.h
+++ b/src/crypto/aes_wrap.h
@@ -49,5 +49,8 @@ int __must_check aes_gcm_ad(const u8 *key, size_t key_len,
 			    const u8 *crypt, size_t crypt_len,
 			    const u8 *aad, size_t aad_len, const u8 *tag,
 			    u8 *plain);
+int __must_check 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);
 
 #endif /* AES_WRAP_H */
diff --git a/tests/test-aes.c b/tests/test-aes.c
index d917b73bf..84c959cbd 100644
--- a/tests/test-aes.c
+++ b/tests/test-aes.c
@@ -407,6 +407,20 @@ static int test_gcm(void)
 			ret++;
 		}
 
+		if (p_len == 0) {
+			if (aes_gmac(k, k_len, iv, iv_len, aad, aad_len, tag) <
+			    0) {
+				printf("GMAC failed (test case %d)\n", i);
+				ret++;
+				continue;
+			}
+
+			if (os_memcmp(tag, t, sizeof(tag)) != 0) {
+				printf("GMAC tag mismatch (test case %d)\n", i);
+				ret++;
+			}
+		}
+
 		if (aes_gcm_ad(k, k_len, iv, iv_len, c, p_len, aad, aad_len,
 			       t, tmp) < 0) {
 			printf("GCM-AD failed (test case %d)\n", i);