feature: add Landlock support

Based on 5315 by ChrysoliteAzalea.

It is based on the same underlying structure, but with a lot of
refactoring/simplification and with bugfixes and improvements.

Co-authored-by: Kelvin M. Klann <[email protected]>
Co-authored-by: Азалия Смарагдова <[email protected]>

README

@@ -197,7 +197,8 @@ avoidr (https://github.com/avoidr)
 	- fixed mpv profile
 	- various other fixes
 Азалия Смарагдова/ChrysoliteAzalea (https://github.com/ChrysoliteAzalea)
-	-  add support for custom AppArmor profiles (--apparmor=)
+	- add support for custom AppArmor profiles (--apparmor=)
+	- add Landlock support
 backspac (https://github.com/backspac)
 	- firecfg fixes
 	- add steam-runtime alias

config.mk.in

@@ -38,6 +38,7 @@ HAVE_FIRETUNNEL=@HAVE_FIRETUNNEL@
 HAVE_FORCE_NONEWPRIVS=@HAVE_FORCE_NONEWPRIVS@
 HAVE_GLOBALCFG=@HAVE_GLOBALCFG@
 HAVE_IDS=@HAVE_IDS@
+HAVE_LANDLOCK=@HAVE_LANDLOCK@
 HAVE_LTS=@HAVE_LTS@
 HAVE_NETWORK=@HAVE_NETWORK@
 HAVE_ONLY_SYSCFG_PROFILES=@HAVE_ONLY_SYSCFG_PROFILES@
@@ -60,6 +61,7 @@ MANFLAGS = \
 	$(HAVE_FORCE_NONEWPRIVS) \
 	$(HAVE_GLOBALCFG) \
 	$(HAVE_IDS) \
+	$(HAVE_LANDLOCK) \
 	$(HAVE_LTS) \
 	$(HAVE_NETWORK) \
 	$(HAVE_ONLY_SYSCFG_PROFILES) \

configure

@@ -675,6 +675,7 @@ HAVE_OVERLAYFS
 HAVE_DBUSPROXY
 EXTRA_LDFLAGS
 EXTRA_CFLAGS
+HAVE_LANDLOCK
 HAVE_SELINUX
 AA_LIBS
 AA_CFLAGS
@@ -737,6 +738,7 @@ enable_sanitizer
 enable_ids
 enable_apparmor
 enable_selinux
+enable_landlock
 enable_dbusproxy
 enable_output
 enable_usertmpfs
@@ -1396,6 +1398,7 @@ Optional Features:
   --enable-ids            enable ids
   --enable-apparmor       enable apparmor
   --enable-selinux        SELinux labeling support
+  --enable-landlock       Landlock self-restriction support
   --disable-dbusproxy     disable dbus proxy
   --disable-output        disable --output logging
   --disable-usertmpfs     disable tmpfs as regular user
@@ -3739,6 +3742,58 @@ then :
 
 fi
 
+HAVE_LANDLOCK=""
+
+# Check whether --enable-landlock was given.
+if test ${enable_landlock+y}
+then :
+  enableval=$enable_landlock;
+fi
+
+ac_header= ac_cache=
+for ac_item in $ac_header_c_list
+do
+  if test $ac_cache; then
+    ac_fn_c_check_header_compile "$LINENO" $ac_header ac_cv_header_$ac_cache "$ac_includes_default"
+    if eval test \"x\$ac_cv_header_$ac_cache\" = xyes; then
+      printf "%s\n" "#define $ac_item 1" >> confdefs.h
+    fi
+    ac_header= ac_cache=
+  elif test $ac_header; then
+    ac_cache=$ac_item
+  else
+    ac_header=$ac_item
+  fi
+done
+
+
+
+
+
+
+
+
+if test $ac_cv_header_stdlib_h = yes && test $ac_cv_header_string_h = yes
+then :
+
+printf "%s\n" "#define STDC_HEADERS 1" >>confdefs.h
+
+fi
+if test "x$enable_landlock" != "xno"
+then :
+
+	ac_fn_c_check_header_compile "$LINENO" "linux/landlock.h" "ac_cv_header_linux_landlock_h" "$ac_includes_default"
+if test "x$ac_cv_header_linux_landlock_h" = xyes
+then :
+  HAVE_LANDLOCK="-DHAVE_LANDLOCK"
+else $as_nop
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: header not found: linux/landlock.h, building without Landlock support" >&5
+printf "%s\n" "$as_me: WARNING: header not found: linux/landlock.h, building without Landlock support" >&2;}
+fi
+
+
+fi
+
 
 
 
@@ -4112,6 +4167,7 @@ if test "x$enable_lts" = "xyes"
 then :
 
 	HAVE_LTS="-DHAVE_LTS"
+	HAVE_LANDLOCK=""
 	HAVE_IDS=""
 	HAVE_DBUSPROXY=""
 	HAVE_OVERLAYFS=""
@@ -4132,35 +4188,6 @@ then :
 
 fi
 
-ac_header= ac_cache=
-for ac_item in $ac_header_c_list
-do
-  if test $ac_cache; then
-    ac_fn_c_check_header_compile "$LINENO" $ac_header ac_cv_header_$ac_cache "$ac_includes_default"
-    if eval test \"x\$ac_cv_header_$ac_cache\" = xyes; then
-      printf "%s\n" "#define $ac_item 1" >> confdefs.h
-    fi
-    ac_header= ac_cache=
-  elif test $ac_header; then
-    ac_cache=$ac_item
-  else
-    ac_header=$ac_item
-  fi
-done
-
-
-
-
-
-
-
-
-if test $ac_cv_header_stdlib_h = yes && test $ac_cv_header_string_h = yes
-then :
-
-printf "%s\n" "#define STDC_HEADERS 1" >>confdefs.h
-
-fi
 ac_fn_c_check_header_compile "$LINENO" "linux/seccomp.h" "ac_cv_header_linux_seccomp_h" "$ac_includes_default"
 if test "x$ac_cv_header_linux_seccomp_h" = xyes
 then :
@@ -5360,6 +5387,7 @@ Features:
    firetunnel support: $HAVE_FIRETUNNEL
    global config: $HAVE_GLOBALCFG
    IDS support: $HAVE_IDS
+   Landlock support: $HAVE_LANDLOCK
    LTS: $HAVE_LTS
    manpage support: $HAVE_MAN
    network: $HAVE_NETWORK

configure.ac

@@ -81,6 +81,16 @@ AS_IF([test "x$enable_selinux" = "xyes"], [
 	LIBS="$LIBS -lselinux"
 ])
 
+HAVE_LANDLOCK=""
+AC_SUBST([HAVE_LANDLOCK])
+AC_ARG_ENABLE([landlock],
+    [AS_HELP_STRING([--enable-landlock], [Landlock self-restriction support])])
+AS_IF([test "x$enable_landlock" != "xno"], [
+	AC_CHECK_HEADER([linux/landlock.h],
+	    [HAVE_LANDLOCK="-DHAVE_LANDLOCK"],
+	    [AC_MSG_WARN([header not found: linux/landlock.h, building without Landlock support])])
+])
+
 AC_SUBST([EXTRA_CFLAGS])
 AC_SUBST([EXTRA_LDFLAGS])
 
@@ -264,6 +274,7 @@ AC_ARG_ENABLE([lts],
     [AS_HELP_STRING([--enable-lts], [enable long-term support software version (LTS)])])
 AS_IF([test "x$enable_lts" = "xyes"], [
 	HAVE_LTS="-DHAVE_LTS"
+	HAVE_LANDLOCK=""
 	HAVE_IDS=""
 	HAVE_DBUSPROXY=""
 	HAVE_OVERLAYFS=""
@@ -324,6 +335,7 @@ Features:
    firetunnel support: $HAVE_FIRETUNNEL
    global config: $HAVE_GLOBALCFG
    IDS support: $HAVE_IDS
+   Landlock support: $HAVE_LANDLOCK
    LTS: $HAVE_LTS
    manpage support: $HAVE_MAN
    network: $HAVE_NETWORK

contrib/syntax/lists/profile_commands_arg0.list

@@ -12,6 +12,7 @@ keep-config-pulse
 keep-dev-shm
 keep-shell-rc
 keep-var-tmp
+landlock
 machine-id
 memory-deny-write-execute
 netfilter

contrib/syntax/lists/profile_commands_arg1.list

@@ -29,6 +29,11 @@ ip6
 iprange
 join-or-start
 keep-fd
+landlock.execute
+landlock.proc
+landlock.read
+landlock.special
+landlock.write
 mac
 mkdir
 mkfile

src/bash_completion/firejail.bash_completion.in

@@ -42,6 +42,25 @@ _firejail()
             _filedir -d
             return 0
             ;;
+        --landlock)
+            return 0
+            ;;
+        --landlock.read)
+            _filedir
+            return 0
+            ;;
+        --landlock.write)
+            _filedir
+            return 0
+            ;;
+        --landlock.special)
+            _filedir
+            return 0
+            ;;
+        --landlock.execute)
+            _filedir
+            return 0
+            ;;
         --tmpfs)
             _filedir
             return 0

src/firejail/checkcfg.c

@@ -363,6 +363,13 @@ static const char *const compiletime_support =
 		"disabled"
 #endif
 
+	"\n\t- Landlock support is "
+#ifdef HAVE_LANDLOCK
+		"enabled"
+#else
+		"disabled"
+#endif
+
 	"\n\t- networking support is "
 #ifdef HAVE_NETWORK
 		"enabled"

src/firejail/firejail.h

@@ -281,6 +281,9 @@ extern int arg_overlay;		// overlay option
 extern int arg_overlay_keep;	// place overlay diff in a known directory
 extern int arg_overlay_reuse;	// allow the reuse of overlays
 
+extern int arg_landlock;		// add basic Landlock rules
+extern int arg_landlock_proc;		// 0 - no access; 1 -read-only; 2 - read-write
+
 extern int arg_seccomp;	// enable default seccomp filter
 extern int arg_seccomp32;	// enable default seccomp filter for 32 bit arch
 extern int arg_seccomp_postexec;	// need postexec ld.preload library?
@@ -950,4 +953,23 @@ void run_ids(int argc, char **argv);
 // oom.c
 void oom_set(const char *oom_string);
 
+// landlock.c
+#ifdef HAVE_LANDLOCK
+int ll_get_fd(void);
+int ll_read(const char *allowed_path);
+int ll_write(const char *allowed_path);
+int ll_special(const char *allowed_path);
+int ll_exec(const char *allowed_path);
+int ll_basic_system(void);
+int ll_restrict(__u32 flags);
+#else
+static inline int ll_get_fd(void) { return -1; }
+static inline int ll_read(...) { return 0; }
+static inline int ll_write(...) { return 0; }
+static inline int ll_special(...) { return 0; }
+static inline int ll_exec(...) { return 0; }
+static inline int ll_basic_system(void) { return 0; }
+static inline int ll_restrict(...) { return 0; }
+#endif /* HAVE_LANDLOCK */
+
 #endif