anastasis

commit a02cdf22bc54e981c522aa3896299087ed518703
parent ab96bdfada8ecb22c60b752fa9699fc454899b2d
Author: Christian Grothoff <christian@grothoff.org>
Date:   Wed, 29 Jul 2026 13:08:26 +0200

CH_AHV: reject empty input instead of reading before the buffer

Diffstat:
M
src/reducer/validation_CH_AHV.c
 | 
8
+++++++-

1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/src/reducer/validation_CH_AHV.c b/src/reducer/validation_CH_AHV.c
@@ -38,10 +38,16 @@ CH_AHV_check (const char *ahv_number)
 {
   unsigned int checknum;
   unsigned int next_ten;
-  const char *pos = &ahv_number[strlen (ahv_number) - 1];
+  size_t len = strlen (ahv_number);
+  const char *pos;
   bool phase = true;
   unsigned int calculation = 0;
 
+  /* Guard against empty input: strlen()-1 would wrap and read one byte
+     before the buffer.  A valid AHV number is 13 digits (optionally dotted). */
+  if (0 == len)
+    return false;
+  pos = &ahv_number[len - 1];
   checknum = *pos - 48;
   while (pos > ahv_number)
   {