From a7c1d0adfda3c326fde19746d3ff62f1b5b447dc Mon Sep 17 00:00:00 2001
From: Karol Babioch <karol@babioch.de>
Date: Fri, 4 May 2018 16:16:39 +0200
Subject: [PATCH] Check whether fullpath can be constructed correctly

This checks the return code of snprintf() and makes sure that fullpath
actually fits into a buffer of size PATH_MAX. Otherwise, it will output
an error and exit.
---
 ykpamcfg.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/ykpamcfg.c b/ykpamcfg.c
index fece317..0a56d73 100644
--- a/ykpamcfg.c
+++ b/ykpamcfg.c
@@ -166,8 +166,13 @@ do_add_hmac_chalresp(YK_KEY *yk, uint8_t slot, bool verbose, char *output_dir, u
   
   if (!output_dir){
       char fullpath[PATH_MAX];
-      snprintf(fullpath, PATH_MAX, "%s/.yubico", p->pw_dir);
-      
+      int i = snprintf(fullpath, PATH_MAX, "%s/.yubico", p->pw_dir);
+
+      if (i < 0 || i >= PATH_MAX) {
+        fprintf(stderr, "Failed to construct fullpath: %s\n", p->pw_dir);
+	goto out;
+      }
+
       //check if directory exists     
       if (stat(fullpath,&st)!=0 ){     
 	if(mkdir(fullpath, S_IRWXU)==-1){