Extract OTP constants into defines

This patch extracts the HOTP and TOTP slot count as well as the maximum
length for the OTP slot name and secret into defines in device_proto.h,
similar to the PWS constants.

Author: robinkrahl

NitrokeyManager.cc

@@ -470,8 +470,8 @@ using nitrokey::misc::strcpyT;
     }
 
     bool NitrokeyManager::is_internal_hotp_slot_number(uint8_t slot_number) const { return slot_number < 0x20; }
-    bool NitrokeyManager::is_valid_hotp_slot_number(uint8_t slot_number) const { return slot_number < 3; }
-    bool NitrokeyManager::is_valid_totp_slot_number(uint8_t slot_number) const { return slot_number < 0x10-1; } //15
+    bool NitrokeyManager::is_valid_hotp_slot_number(uint8_t slot_number) const { return slot_number < HOTP_SLOT_COUNT; }
+    bool NitrokeyManager::is_valid_totp_slot_number(uint8_t slot_number) const { return slot_number < TOTP_SLOT_COUNT; }
     uint8_t NitrokeyManager::get_internal_slot_number_for_totp(uint8_t slot_number) const { return (uint8_t) (0x20 + slot_number); }
     uint8_t NitrokeyManager::get_internal_slot_number_for_hotp(uint8_t slot_number) const { return (uint8_t) (0x10 + slot_number); }
 
@@ -636,9 +636,8 @@ using nitrokey::misc::strcpyT;
       payload2.id = 0;
       auto secret_bin = misc::hex_string_to_byte(secret);
       auto remaining_secret_length = secret_bin.size();
-      const auto maximum_OTP_secret_size = 40;
-      if(remaining_secret_length > maximum_OTP_secret_size){
-        throw TargetBufferSmallerThanSource(remaining_secret_length, maximum_OTP_secret_size);
+      if(remaining_secret_length > OTP_SECRET_LENGTH){
+        throw TargetBufferSmallerThanSource(remaining_secret_length, OTP_SECRET_LENGTH);
       }
 
       while (remaining_secret_length>0){

libnitrokey/device_proto.h

@@ -52,6 +52,11 @@
 #define PWS_SEND_TAB 2
 #define PWS_SEND_CR 3
 
+#define HOTP_SLOT_COUNT 3
+#define TOTP_SLOT_COUNT 15
+#define OTP_SLOTNAME_LENGTH 15
+#define OTP_SECRET_LENGTH 40
+
 #include <mutex>
 #include "DeviceCommunicationExceptions.h"
 #define bzero(b,len) (memset((b), '\0', (len)), (void) 0)