1 files changed, 77 insertions, 0 deletions
diff --git a/lib/hmac_sha256.c b/lib/hmac_sha256.c
new file mode 100644
index 0000000..be7f50a
--- /dev/null
+++ b/lib/hmac_sha256.c
@@ -0,0 +1,77 @@
+/* This file is part of Eclat
+   Copyright (C) 2012, 2013 Sergey Poznyakoff
+ 
+   Eclat is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+ 
+   Eclat is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+ 
+   You should have received a copy of the GNU General Public License
+   along with Eclat.  If not, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+#include "libeclat.h"
+#include "sha256.h"
+#include <string.h>
+
+#define IPAD 0x36
+#define OPAD 0x5c
+
+void
+hmac_sha256(const void *text, size_t textlen,
+	    const void *key, size_t keylen,
+	    void *digest)
+{
+	size_t i;
+	struct sha256_ctx ctx;
+	char innerhash[SHA256_DIGEST_SIZE];
+	char keybuf[SHA256_DIGEST_SIZE];
+	unsigned char ipad[64];    /* inner padding - key ^ ipad[64] */
+        unsigned char opad[64];    /* outer padding - key ^ opad[64] */
+	unsigned char *kp = (unsigned char *)key;
+	
+	/* if key is longer than 64 bytes reset it to key=SHA256(key) */
+	if (keylen > 64) {
+		struct sha256_ctx keyhash;
+
+		sha256_init_ctx(&keyhash);
+		sha256_process_bytes(key, keylen, &keyhash);
+		sha256_finish_ctx(&keyhash, keybuf);
+		key = keybuf;
+		keylen = sizeof(keybuf);
+	}
+
+	/* Compute SHA256(K XOR opad, SHA256(K XOR ipad, text)),
+	   where
+	     K is an key, padded to 64 bytes with zeros,
+	     ipad and opad are the respective defines above repeated 64 times
+	     text is the text argument (textlen bytes long)
+         */
+	memset(ipad, IPAD,  sizeof(ipad));
+	memset(opad, OPAD, sizeof(opad));
+
+	for (i = 0; i < keylen; i++, kp++) {
+		ipad[i] ^= *kp;
+		opad[i] ^= *kp;
+	}
+
+	/* Compute inner hash */
+	sha256_init_ctx(&ctx);
+	sha256_process_block(ipad, sizeof(ipad), &ctx);
+	sha256_process_bytes(text, textlen, &ctx);
+	sha256_finish_ctx(&ctx, innerhash);
+
+	/* Compute outer hash */
+	sha256_init_ctx(&ctx);
+	sha256_process_block(opad, sizeof(opad), &ctx);
+	sha256_process_bytes(innerhash, sizeof(innerhash), &ctx);
+	sha256_finish_ctx(&ctx, digest);
+}
+	
+	
+