svn commit: r343939 - stable/12/libexec/getty

[Stefan Esser]

Author: se
Date: Sat Feb  9 14:21:29 2019
New Revision: 343939
URL: https://svnweb.freebsd.org/changeset/base/343939

Log:
  MFC r343479: Fix potential buffer overflow and undefined behavior.
  
  The buffer allocated in read_chat() could be 1 element too short, if the
  chatstr parameter passed in is 1 or 3 charachters long (e.g. "a" or "a b").
  The allocation of the pointer array does not account for the terminating
  NULL pointer in that case.
  
  Overlapping source and destination strings are undefined in strcpy().
  Instead of moving a string to the left by one character just increment the
  char pointer before it is assigned to the results array.

Modified:
  stable/12/libexec/getty/chat.c

Modified: stable/12/libexec/getty/chat.c
==============================================================================
--- stable/12/libexec/getty/chat.c	Sat Feb  9 14:19:09 2019	(r343938)
+++ stable/12/libexec/getty/chat.c	Sat Feb  9 14:21:29 2019	(r343939)
@@ -141,7 +141,7 @@ read_chat(char **chatstr)
 		int l;
 
 		if ((l=strlen(str)) > 0 && (tmp=malloc(l + 1)) != NULL &&
-		    (res=malloc((l / 2 + 1) * sizeof(char *))) != NULL) {
+		    (res=malloc(((l + 1) / 2 + 1) * sizeof(char *))) != NULL) {
 			static char ws[] = " \t";
 			char * p;
 
@@ -216,7 +216,7 @@ read_chat(char **chatstr)
 					q = strrchr(p+1, *p);
 					if (q != NULL && *q == *p && q[1] == '\0') {
 						*q = '\0';
-						strcpy(p, p+1);
+						p++;
 					}
 				}