Use strnlen to determine string length

strnlen stops scanning after reaching big_string_size and returns last position
in the searched string.
If a string terminator is not found then the big_string_size is returned hence
the modification of the later size-checking condition.

Signed-off-by: Szczepan Zalega <szczepan@nitrokey.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/misc.cc b/misc.cc
index eaaad50..59185f3 100644
--- a/misc.cc
+++ b/misc.cc
@@ -34,10 +34,10 @@ namespace misc {
 
 
 ::std::vector<uint8_t> hex_string_to_byte(const char* hexString){
-    const size_t big_string_size = 256; //arbitrary 'big' number
-    const size_t s_size = strlen(hexString);
+    const size_t big_string_size = 257; //arbitrary 'big' number
+    const size_t s_size = strnlen(hexString, big_string_size);
     const size_t d_size = s_size/2;
-    if (s_size%2!=0 || s_size>big_string_size){
+    if (s_size%2!=0 || s_size>=big_string_size){
         throw InvalidHexString(0);
     }
     auto data = ::std::vector<uint8_t>();