From e9fcb9b332c5510fd174e50604cd321c3cae6b3a Mon Sep 17 00:00:00 2001
From: Holger Vogt <holger.vogt@uni-due.de>
Date: Thu, 1 Sep 2022 16:57:54 +0200
Subject: [PATCH] Prevent crash in gettok() and similar functions by checking
 for NULL input. Return NULL instead.

---
 src/misc/string.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/src/misc/string.c b/src/misc/string.c
index 580cc0167..5a06b9599 100644
--- a/src/misc/string.c
+++ b/src/misc/string.c
@@ -393,6 +393,9 @@ gettok(char **s)
     int paren;
     const char *token, *token_e;
 
+    if (!*s)
+        return NULL;
+
     paren = 0;
 
     *s = skip_ws(*s);
@@ -599,6 +602,10 @@ void findtok_noparen(char **p_str, char **p_token, char **p_token_end)
 char *gettok_noparens(char **s)
 {
     char *token, *token_e;
+
+    if (!*s)
+        return NULL;
+
     findtok_noparen(s, &token, &token_e);
     if (token == (char *) NULL) {
         return (char *) NULL; /* return NULL if we come to end of line */
@@ -654,6 +661,10 @@ void findtok_np(char** p_str, char** p_token, char** p_token_end)
 char* gettok_np(char** s)
 {
     char* token, * token_e;
+
+    if (!*s)
+        return NULL;
+
     findtok_np(s, &token, &token_e);
     if (token == (char*)NULL) {
         return (char*)NULL; /* return NULL if we come to end of line */
@@ -673,6 +684,9 @@ gettok_model(char **s)
     char c;
     const char *token, *token_e;
 
+    if (!*s)
+        return NULL;
+
     *s = skip_ws(*s);
 
     if (!**s)
@@ -706,6 +720,9 @@ gettok_instance(char **s)
     char c;
     const char *token, *token_e;
 
+    if (!*s)
+        return NULL;
+
     *s = skip_ws(*s);
 
     if (!**s)
@@ -740,6 +757,9 @@ gettok_char(char **s, char p, bool inc_p, bool nested)
     char c;
     const char *token, *token_e;
 
+    if (!*s)
+        return NULL;
+
     *s = skip_ws(*s);
 
     if (!**s)