From 8e0ad48c21bd7d5506ff44eb4c04f796b80045ce Mon Sep 17 00:00:00 2001
From: Samanta Navarro <ferivoz@riseup.net>
Date: Mon, 30 Jan 2023 11:54:49 +0000
Subject: [PATCH] Prevent out of boundary access

If lines start with '\0' then it is possible to trigger out of
boundary accesses.

Check if indices are valid before accessing them.

Signed-off-by: Samanta Navarro <ferivoz@riseup.net>
---
 src/login_nopam.c | 4 ++--
 src/suauth.c      | 3 ++-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/login_nopam.c b/src/login_nopam.c
index b09cffe4..18072a43 100644
--- a/src/login_nopam.c
+++ b/src/login_nopam.c
@@ -100,7 +100,7 @@ int login_access (const char *user, const char *from)
 			int end;
 			lineno++;
 			end = (int) strlen (line) - 1;
-			if (line[end] != '\n') {
+			if (line[0] == '\0' || line[end] != '\n') {
 				SYSLOG ((LOG_ERR,
 					 "%s: line %d: missing newline or line too long",
 					 TABLE, lineno));
@@ -320,7 +320,7 @@ static bool from_match (const char *tok, const char *string)
 		if (strchr (string, '.') == NULL) {
 			return true;
 		}
-	} else if (   (tok[(tok_len = strlen (tok)) - 1] == '.') /* network */
+	} else if (   (tok[0] != '\0' && tok[(tok_len = strlen (tok)) - 1] == '.') /* network */
 		   && (strncmp (tok, resolve_hostname (string), tok_len) == 0)) {
 		return true;
 	}
diff --git a/src/suauth.c b/src/suauth.c
index 2641d334..d68a3340 100644
--- a/src/suauth.c
+++ b/src/suauth.c
@@ -68,8 +68,9 @@ int check_su_auth (const char *actual_id,
 
 	while (fgets (temp, sizeof (temp), authfile_fd) != NULL) {
 		lines++;
+		endline = strlen(temp) - 1;
 
-		if (temp[endline = strlen (temp) - 1] != '\n') {
+		if (temp[0] == '\0' || temp[endline] != '\n') {
 			SYSLOG ((LOG_ERR,
 				 "%s, line %d: line too long or missing newline",
 				 SUAUTHFILE, lines));
-- 
2.27.0