/** BEGIN COPYRIGHT BLOCK
 * Copyright (C) 2005 Red Hat, Inc.
 * All rights reserved.
 *
 * License: GPL (version 3 or any later version).
 * See LICENSE for details. 
 * END COPYRIGHT BLOCK **/

#ifdef HAVE_CONFIG_H
#  include <config.h>
#endif

/*
 * Based on MD5 Password Encryption/Comparison routines by David Irving,
 * Fred Brittain, and Aaron Gagnon --  University of Maine Farmington
 * Donated to the RedHat Directory Server Project 2005-06-10 
 */

#include <string.h>
#include <sys/types.h>
#include <stdio.h>
#include <pk11func.h>
#include <nss.h>
#include <nssb64.h>
#include <sechash.h>
#include "pwdstorage.h"

#define MD5_DEFAULT_SALT_LENGTH 4
#define MD5_MAX_SALT_LENGTH 16
#define SALTED_MD5_SUBSYSTEM_NAME "Salted MD5 password hash"

int
smd5_pw_cmp( const char *userpwd, const char *dbpwd )
{
   int rc=-1;
   PK11Context *ctx=NULL;
   unsigned int outLen;
   unsigned char userhash[MD5_LENGTH];
   int hash_len;
   char quick_dbhash[MD5_LENGTH + MD5_DEFAULT_SALT_LENGTH + 1];
   char *dbhash = quick_dbhash;
   struct berval salt;
   char *hashresult = NULL;

   ctx = PK11_CreateDigestContext(SEC_OID_MD5);
   if (ctx == NULL) {
	   slapi_log_error(SLAPI_LOG_PLUGIN, SALTED_MD5_SUBSYSTEM_NAME,
					   "Could not create context for digest operation for password compare");
	   goto loser;
   }

   /*
    * Decode hash stored in database.
    */
   hash_len = pwdstorage_base64_decode_len(dbpwd, 0);
   if ( hash_len >= sizeof(quick_dbhash) ) { /* get more space: */
      dbhash = (char*) slapi_ch_calloc( hash_len + 1, sizeof(char) );
      if ( dbhash == NULL ) goto loser;
   } else {
      memset( quick_dbhash, 0, sizeof(quick_dbhash) );
   }

   hashresult = PL_Base64Decode( dbpwd, 0, dbhash );
   if (NULL == hashresult) {
      slapi_log_error( SLAPI_LOG_PLUGIN, SALTED_MD5_SUBSYSTEM_NAME,
            "smd5_pw_cmp: userPassword \"%s\" is the wrong length "
            "or is not properly encoded BASE64\n", dbpwd );
      goto loser;
   }

   salt.bv_val = (void*)(dbhash + MD5_LENGTH); /* salt starts after hash value */
   salt.bv_len = hash_len - MD5_LENGTH; /* remaining bytes must be salt */

   /* create the hash */
   memset( userhash, 0, sizeof(userhash) );
   PK11_DigestBegin(ctx);
   PK11_DigestOp(ctx, (const unsigned char *)userpwd, strlen(userpwd));
   PK11_DigestOp(ctx, (unsigned char*)(salt.bv_val), salt.bv_len);
   PK11_DigestFinal(ctx, userhash, &outLen, sizeof userhash);
   PK11_DestroyContext(ctx, 1);

   /* Compare everything up to the salt. */
   rc = memcmp( userhash, dbhash, MD5_LENGTH );

loser:
   if ( dbhash && dbhash != quick_dbhash ) slapi_ch_free_string( (char **)&dbhash );
   return rc;
}

char *
smd5_pw_enc( const char *pwd )
{
   char * bver, *enc=NULL;
   PK11Context *ctx=NULL;
   unsigned int outLen;
   unsigned char hash_out[MD5_LENGTH + MD5_DEFAULT_SALT_LENGTH];
   unsigned char b2a_out[(MD5_LENGTH*2) + (MD5_MAX_SALT_LENGTH*2)]; /* conservative */
   unsigned char *salt = hash_out + MD5_LENGTH;
   struct berval saltval;
   SECItem binary_item;

   ctx = PK11_CreateDigestContext(SEC_OID_MD5);
   if (ctx == NULL) {
	   slapi_log_error(SLAPI_LOG_PLUGIN, SALTED_MD5_SUBSYSTEM_NAME,
					   "Could not create context for digest operation for password encoding");
	   return NULL;
   }

   /* prepare the hash output area */
   memset( hash_out, 0, sizeof(hash_out) );

   /* generate a new random salt */
   slapi_rand_array( (void *)salt, MD5_DEFAULT_SALT_LENGTH );
   saltval.bv_val = (void*)salt;
   saltval.bv_len = MD5_DEFAULT_SALT_LENGTH;

   /* create the hash */
   PK11_DigestBegin(ctx);
   PK11_DigestOp(ctx, (const unsigned char *)pwd, strlen(pwd));
   PK11_DigestOp(ctx, (unsigned char*)(saltval.bv_val), saltval.bv_len);
   PK11_DigestFinal(ctx, hash_out, &outLen, sizeof hash_out);
   PK11_DestroyContext(ctx, 1);

   /* convert the binary hash to base64 */
   binary_item.data = hash_out;
   binary_item.len = outLen + MD5_DEFAULT_SALT_LENGTH;
   bver = NSSBase64_EncodeItem(NULL, (char *)b2a_out, sizeof b2a_out, &binary_item);
   if (bver) {
	   enc = slapi_ch_smprintf("%c%s%c%s", PWD_HASH_PREFIX_START, SALTED_MD5_SCHEME_NAME,
							   PWD_HASH_PREFIX_END, bver );
   } else {
	   slapi_log_error(SLAPI_LOG_PLUGIN, SALTED_MD5_SUBSYSTEM_NAME,
					   "Could not base64 encode hashed value for password encoding");
   }
	   
   return( enc );
}