Implement BUF_strnlen() and use it instead of strlen().

crypto/buffer/buf_str.c

@@ -62,6 +62,16 @@
 #include "cryptlib.h"
 #include <openssl/buffer.h>
 
+size_t BUF_strnlen(const char *str, size_t maxlen)
+	{
+	const char *p;
+
+	for (p = str; *p != '\0' && maxlen-- != 0; ++p)
+		;
+
+	return p - str;
+	}
+
 char *BUF_strdup(const char *str)
 	{
 	if (str == NULL) return(NULL);
@@ -75,7 +85,7 @@ char *BUF_strndup(const char *str, size_t siz)
 
 	if (str == NULL) return(NULL);
 
-	len = strlen(str);
+	len = BUF_strnlen(str, siz);
 	if (siz > len)
 	    siz = len;