Diff: crypto/crypto_hmac_sha256.c

Revision:

4:cbaf466d717d

Parent:

2:527a66d0a1a9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/crypto/crypto_hmac_sha256.c	Tue Jun 10 14:23:09 2014 +0000
@@ -0,0 +1,92 @@
+/*
+MiniTLS - A super trimmed down TLS/SSL Library for embedded devices
+Author: Donatien Garnier
+Copyright (C) 2013-2014 AppNearMe Ltd
+
+This program 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 2
+of the License, or (at your option) any later version.
+
+This program 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 this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*//**
+ * \file crypto_hmac_sha256.c
+ * \copyright Copyright (c) AppNearMe Ltd 2013
+ * \author Donatien Garnier
+ */
+
+#define __DEBUG__ 0
+#ifndef __MODULE__
+#define __MODULE__ "crypto_hmac_sha256.c"
+#endif
+
+#include "core/fwk.h"
+#include "inc/minitls_errors.h"
+
+#include "crypto_hmac_sha256.h"
+
+void crypto_hmac_sha256_init(crypto_hmac_sha256_t* mac, const uint8_t* key, size_t size) //FIXME add crypto_err_t
+{
+  if(size > SHA256_BLOCK_SIZE)
+  {
+    //If key is longer than block size, hash the key first
+    crypto_sha256_init(&mac->hash);
+    crypto_sha256_update(&mac->hash, key, size);
+    crypto_sha256_end(&mac->hash, mac->key_pad);
+    size = SHA256_SIZE;
+  }
+  else
+  {
+    //Copy key
+    memcpy(mac->key_pad, key, size);
+  }
+
+  //Pad key with 0s
+  memset(mac->key_pad + size, 0, SHA256_BLOCK_SIZE - size);
+
+  //XOR with 0x36363636...
+  for( int i = 0; i < SHA256_BLOCK_SIZE / sizeof(uint32_t); i++)
+  {
+    //XOR by blocks
+    *(((uint32_t*)mac->key_pad) + i) ^= 0x36363636UL;
+  }
+
+  //Init hash
+  crypto_sha256_init(&mac->hash);
+  crypto_sha256_update(&mac->hash, mac->key_pad, SHA256_BLOCK_SIZE);
+}
+
+void crypto_hmac_sha256_update(crypto_hmac_sha256_t* mac, const uint8_t* data, size_t size)
+{
+  crypto_sha256_update(&mac->hash, data, size);
+}
+
+void crypto_hmac_sha256_end(crypto_hmac_sha256_t* mac, uint8_t* out)
+{
+  //Complete hash
+  uint8_t* hash1 = out; //Save memory
+  crypto_sha256_end(&mac->hash, hash1);
+
+  //Compute second key
+  //XOR initial padded key with 0x5c5c5c5c...
+  for( int i = 0; i < SHA256_BLOCK_SIZE / sizeof(uint32_t); i++)
+  {
+    //XOR by blocks
+    *(((uint32_t*)mac->key_pad) + i) ^= (0x5c5c5c5cUL ^ 0x36363636UL);
+  }
+
+  //Compute final hash
+  crypto_sha256_init(&mac->hash);
+  crypto_sha256_update(&mac->hash, mac->key_pad, SHA256_BLOCK_SIZE);
+  crypto_sha256_update(&mac->hash, hash1, SHA256_SIZE);
+  crypto_sha256_end(&mac->hash, out);
+}
+
+