--- a/common-algo.c	Thu May 17 00:12:42 2012 +0800
+++ b/common-algo.c	Thu May 17 00:26:12 2012 +0800
@@ -297,7 +297,7 @@
 	return ret_list;
 }
 
-static int
+static algo_type*
 check_algo(const char* algo_name, algo_type *algos)
 {
 	algo_type *a;
@@ -305,32 +305,25 @@
 	{
 		if (strcmp(a->name, algo_name) == 0)
 		{
-			a->usable = 2;
-			return DROPBEAR_SUCCESS;
+			return a;
 		}
 	}
 
-	return DROPBEAR_FAILURE;
+	return NULL;
 }
 
-/* helper for check_user_algos */
 static void
 try_add_algo(const char *algo_name, algo_type *algos, 
-		const char *algo_desc, char ** out_list, int *num_ret)
+		const char *algo_desc, algo_type * new_algos, int *num_ret)
 {
-	if (check_algo(algo_name, algos) == DROPBEAR_FAILURE)
+	algo_type *match_algo = check_algo(algo_name, algos);
+	if (!match_algo)
 	{
 		dropbear_log(LOG_WARNING, "This Dropbear program does not support '%s' %s algorithm", algo_name, algo_desc);
 		return;
 	}
 
-	if (*num_ret != 0)
-	{
-		**out_list = ',';
-		(*out_list)++;
-	}
-
-	*out_list += sprintf(*out_list, "%s", algo_name);
+	new_algos[*num_ret] = *match_algo;
 	(*num_ret)++;
 }
 
@@ -338,41 +331,32 @@
  * options. Any that are not acceptable are removed in-place. Returns the
  * number of valid algorithms. */
 int
-check_user_algos(char* user_algo_list, algo_type * algos, 
+check_user_algos(const char* user_algo_list, algo_type * algos, 
 		const char *algo_desc)
 {
+	algo_type new_algos[MAX_PROPOSED_ALGO];
 	/* this has two passes. first we sweep through the given list of
 	 * algorithms and mark them as usable=2 in the algo_type[] array... */
 	int num_ret = 0;
 	char *work_list = m_strdup(user_algo_list);
 	char *last_name = work_list;
-	char *out_list = user_algo_list;
 	char *c;
 	for (c = work_list; *c; c++)
 	{
 		if (*c == ',')
 		{
 			*c = '\0';
-			try_add_algo(last_name, algos, algo_desc, &out_list, &num_ret);
+			try_add_algo(last_name, algos, algo_desc, new_algos, &num_ret);
 			last_name = c++;
 		}
 	}
-	try_add_algo(last_name, algos, algo_desc, &out_list, &num_ret);
+	try_add_algo(last_name, algos, algo_desc, new_algos, &num_ret);
 	m_free(work_list);
 
-	/* ...then we mark anything with usable==1 as usable=0, and 
-	 * usable==2 as usable=1. */
-	algo_type *a;
-	for (a = algos; a->name != NULL; a++)
-	{
-		if (a->usable == 1)
-		{
-			a->usable = 0;
-		} else if (a->usable == 2)
-		{
-			a->usable = 1;
-		}
-	}
+	new_algos[num_ret].name = NULL;
+
+	/* Copy one more as a blank delimiter */
+	memcpy(algos, new_algos, sizeof(*new_algos) * (num_ret+1));
 	return num_ret;
 }
 #endif // ENABLE_USER_ALGO_LIST