adduser/addgroup: check username for invalid chars

(by Tito <farmatito AT tiscali.it>). +129 bytes when enabled.

include/libbb.h

@@ -637,7 +637,11 @@ const char* get_cached_groupname(gid_t gid);
 void clear_username_cache(void);
 /* internally usernames are saved in fixed-sized char[] buffers */
 enum { USERNAME_MAX_SIZE = 16 - sizeof(int) };
-
+#if ENABLE_FEATURE_CHECK_NAMES
+void die_if_bad_username(const char* name);
+#else
+#define die_if_bad_username(name) ((void)(name))
+#endif
 
 int execable_file(const char *name);
 char *find_execable(const char *filename);

libbb/Kbuild

@@ -122,6 +122,7 @@ lib-$(CONFIG_MKFS_MINIX) += find_mount_point.o
 lib-$(CONFIG_SELINUX) += selinux_common.o
 lib-$(CONFIG_HWCLOCK) += rtc.o
 lib-$(CONFIG_RTCWAKE) += rtc.o
+lib-$(CONFIG_FEATURE_CHECK_NAMES) += die_if_bad_username.o
 
 # We shouldn't build xregcomp.c if we don't need it - this ensures we don't
 # require regex.h to be in the include dir even if we don't need it thereby

loginutils/Config.in

@@ -82,6 +82,18 @@ config FEATURE_DEL_USER_FROM_GROUP
 	  If called with two non-option arguments, deluser
 	  or delgroup will remove an user from a specified group.
 
+config FEATURE_CHECK_NAMES
+	bool "Enable sanity check on user/group names in adduser and addgroup"
+	default n
+	depends on ADDUSER || ADDGROUP
+	help
+	  Enable sanity check on user and group names in adduser and addgroup.
+	  To avoid problems, the user or group name should consist only of
+	  letters, digits, underscores, periods, at signs and dashes,
+	  and not start with a dash (as defined by IEEE Std 1003.1-2001).
+	  For compatibility with Samba machine accounts "$" is also supported
+	  at the end of the user or group name.
+
 config ADDUSER
 	bool "adduser"
 	default n

loginutils/addgroup.c

@@ -173,8 +173,11 @@ int addgroup_main(int argc ATTRIBUTE_UNUSED, char **argv)
 #endif
 	} else
 #endif /* ENABLE_FEATURE_ADDUSER_TO_GROUP */
+	{
+		die_if_bad_username(argv[0]);
 		new_group(argv[0], gid);
 
+	}
 	/* Reached only on success */
 	return EXIT_SUCCESS;
 }

loginutils/adduser.c

@@ -111,6 +111,7 @@ int adduser_main(int argc ATTRIBUTE_UNUSED, char **argv)
 
 	/* fill in the passwd struct */
 	pw.pw_name = argv[0];
+	die_if_bad_username(pw.pw_name);
 	if (!pw.pw_dir) {
 		/* create string for $HOME if not specified already */
 		pw.pw_dir = xasprintf("/home/%s", argv[0]);