--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/md5/hmac_md5.c	Fri Sep 26 17:05:23 2008 +0200
@@ -0,0 +1,80 @@
+/*
+** Function: hmac_md5
+*/
+
+#include <string.h>
+#include "global.h"
+#include "md5.h"
+#include "hmac_md5.h"
+
+void hmac_md5(unsigned char *text, int text_len,
+	      unsigned char* key, int key_len, unsigned char *digest)
+     /* text;     pointer to data stream */
+     /* text_len; length of data stream */
+     /* key;      pointer to authentication key */
+     /* key_len;  length of authentication key */
+     /* digest;   caller digest to be filled in */
+
+{
+  MD5_CTX context;
+  unsigned char k_ipad[65];    /* inner padding -
+				* key XORd with ipad
+				*/
+  unsigned char k_opad[65];    /* outer padding -
+				* key XORd with opad
+				*/
+  unsigned char tk[16];
+  int i;
+  /* if key is longer than 64 bytes reset it to key=MD5(key) */
+  if (key_len > 64) {
+
+    MD5_CTX      tctx;
+
+    MD5Init(&tctx);
+    MD5Update(&tctx, key, key_len);
+    MD5Final(tk, &tctx);
+
+    key = tk;
+    key_len = 16;
+  }
+
+  /*
+   * the HMAC_MD5 transform looks like:
+   *
+   * MD5(K XOR opad, MD5(K XOR ipad, text))
+   *
+   * where K is an n byte key
+   * ipad is the byte 0x36 repeated 64 times
+   * opad is the byte 0x5c repeated 64 times
+   * and text is the data being protected
+   */
+
+  /* start out by storing key in pads */
+  bzero( k_ipad, sizeof k_ipad);
+  bzero( k_opad, sizeof k_opad);
+  bcopy( key, k_ipad, key_len);
+  bcopy( key, k_opad, key_len);
+
+  /* XOR key with ipad and opad values */
+  for (i=0; i<64; i++) {
+    k_ipad[i] ^= 0x36;
+    k_opad[i] ^= 0x5c;
+  }
+  /*
+   * perform inner MD5
+   */
+  MD5Init(&context);                   /* init context for 1st
+					* pass */
+  MD5Update(&context, k_ipad, 64);      /* start with inner pad */
+  MD5Update(&context, text, text_len); /* then text of datagram */
+  MD5Final(digest, &context);          /* finish up 1st pass */
+  /*
+   * perform outer MD5
+   */
+  MD5Init(&context);                   /* init context for 2nd
+					* pass */
+  MD5Update(&context, k_opad, 64);     /* start with outer pad */
+  MD5Update(&context, digest, 16);     /* then results of 1st
+					* hash */
+  MD5Final(digest, &context);          /* finish up 2nd pass */
+}