From faa5a3a83ad0cb5e2c303edbfd8cd823c9d94c17 Mon Sep 17 00:00:00 2001
From: Karel Zak <kzak@redhat.com>
Date: Thu, 10 Feb 2022 12:03:17 +0100
Subject: [PATCH] chsh, chfn: remove readline support [CVE-2022-0563]

The readline library uses INPUTRC= environment variable to get a path
to the library config file. When the library cannot parse the
specified file, it prints an error message containing data from the
file.

Unfortunately, the library does not use secure_getenv() (or a similar
concept) to avoid vulnerabilities that could occur if set-user-ID or
set-group-ID programs.

Reported-by: Rory Mackie <rory.mackie@trailofbits.com>
Signed-off-by: Karel Zak <kzak@redhat.com>

---
 login-utils/Makemodule.am |  2 +-
 login-utils/chfn.c        | 16 ++++----------
 login-utils/chsh.c        | 45 ++++-----------------------------------
 3 files changed, 9 insertions(+), 54 deletions(-)

diff --git a/login-utils/Makemodule.am b/login-utils/Makemodule.am
index 75c0a67..2d0547a 100644
--- a/login-utils/Makemodule.am
+++ b/login-utils/Makemodule.am
@@ -109,7 +109,7 @@ chfn_chsh_sources = \
 	login-utils/ch-common.c
 chfn_chsh_cflags = $(SUID_CFLAGS) $(AM_CFLAGS)
 chfn_chsh_ldflags = $(SUID_LDFLAGS) $(AM_LDFLAGS)
-chfn_chsh_ldadd = libcommon.la $(READLINE_LIBS)
+chfn_chsh_ldadd = libcommon.la
 
 if CHFN_CHSH_PASSWORD
 chfn_chsh_ldadd += -lpam
diff --git a/login-utils/chfn.c b/login-utils/chfn.c
index ece5cdc..8f00d15 100644
--- a/login-utils/chfn.c
+++ b/login-utils/chfn.c
@@ -56,11 +56,6 @@
 # include "auth.h"
 #endif
 
-#ifdef HAVE_LIBREADLINE
-# define _FUNCTION_DEF
-# include <readline/readline.h>
-#endif
-
 struct finfo {
 	char *full_name;
 	char *office;
@@ -228,24 +223,21 @@ static char *ask_new_field(struct chfn_control *ctl, const char *question,
 {
 	int len;
 	char *buf = NULL; /* leave initialized to NULL or getline segfaults */
-#ifndef HAVE_LIBREADLINE
 	size_t dummy = 0;
-#endif
 
 	if (!def_val)
 		def_val = "";
+
 	while (true) {
 		printf("%s [%s]:", question, def_val);
 		__fpurge(stdin);
-#ifdef HAVE_LIBREADLINE
-		rl_bind_key('\t', rl_insert);
-		if ((buf = readline(" ")) == NULL)
-#else
+
 		putchar(' ');
 		fflush(stdout);
+
 		if (getline(&buf, &dummy, stdin) < 0)
-#endif
 			errx(EXIT_FAILURE, _("Aborted."));
+
 		/* remove white spaces from string end */
 		ltrim_whitespace((unsigned char *) buf);
 		len = rtrim_whitespace((unsigned char *) buf);
diff --git a/login-utils/chsh.c b/login-utils/chsh.c
index 3b446be..b7e7017 100644
--- a/login-utils/chsh.c
+++ b/login-utils/chsh.c
@@ -50,7 +50,6 @@
 # include "selinux-utils.h"
 #endif
 
-
 #ifdef HAVE_LIBUSER
 # include <libuser/user.h>
 # include "libuser.h"
@@ -58,11 +57,6 @@
 # include "auth.h"
 #endif
 
-#ifdef HAVE_LIBREADLINE
-# define _FUNCTION_DEF
-# include <readline/readline.h>
-#endif
-
 struct sinfo {
 	char *username;
 	char *shell;
@@ -121,33 +115,6 @@ static void print_shells(void)
 	endusershell();
 }
 
-#ifdef HAVE_LIBREADLINE
-static char *shell_name_generator(const char *text, int state)
-{
-	static size_t len;
-	char *s;
-
-	if (!state) {
-		setusershell();
-		len = strlen(text);
-	}
-
-	while ((s = getusershell())) {
-		if (strncmp(s, text, len) == 0)
-			return xstrdup(s);
-	}
-	return NULL;
-}
-
-static char **shell_name_completion(const char *text,
-				    int start __attribute__((__unused__)),
-				    int end __attribute__((__unused__)))
-{
-	rl_attempted_completion_over = 1;
-	return rl_completion_matches(text, shell_name_generator);
-}
-#endif
-
 /*
  *  parse_argv () --
  *	parse the command line arguments, and fill in "pinfo" with any
@@ -198,22 +165,18 @@ static char *ask_new_shell(char *question, char *oldshell)
 {
 	int len;
 	char *ans = NULL;
-#ifdef HAVE_LIBREADLINE
-	rl_attempted_completion_function = shell_name_completion;
-#else
 	size_t dummy = 0;
-#endif
+
 	if (!oldshell)
 		oldshell = "";
 	printf("%s [%s]:", question, oldshell);
-#ifdef HAVE_LIBREADLINE
-	if ((ans = readline(" ")) == NULL)
-#else
+
 	putchar(' ');
 	fflush(stdout);
+
 	if (getline(&ans, &dummy, stdin) < 0)
-#endif
 		return NULL;
+
 	/* remove the newline at the end of ans. */
 	ltrim_whitespace((unsigned char *) ans);
 	len = rtrim_whitespace((unsigned char *) ans);
-- 
2.27.0

