cmd/snap: user session application autostart v3 (#4942)

Add support for `snap userd --autostart`. The command is expected to be run as part of user session startup and is responsible for starting snap applications that have placed a proper `*.desktop` file in `$SNAP_USER_DATA/.config/autostart`. The desktop file is matched against `autostart` declaration in snap's YAML.

For details see https://forum.snapcraft.io/t/development-sprint-march-5th-2018/4345/2

Signed-off-by: Maciej Borzecki <maciej.zenon.borzecki@canonical.com>

cmd/snap/cmd_run.go

@@ -237,28 +237,16 @@ func antialias(snapApp string, args []string) (string, []string) {
 	return actualApp, argsOut
 }
 
-func getSnapInfo(snapName string, revision snap.Revision) (*snap.Info, error) {
+func getSnapInfo(snapName string, revision snap.Revision) (info *snap.Info, err error) {
 	if revision.Unset() {
-		curFn := filepath.Join(dirs.SnapMountDir, snapName, "current")
-		realFn, err := os.Readlink(curFn)
-		if err != nil {
-			return nil, fmt.Errorf("cannot find current revision for snap %s: %s", snapName, err)
-		}
-		rev := filepath.Base(realFn)
-		revision, err = snap.ParseRevision(rev)
-		if err != nil {
-			return nil, fmt.Errorf("cannot read revision %s: %s", rev, err)
-		}
-	}
-
-	info, err := snap.ReadInfo(snapName, &snap.SideInfo{
-		Revision: revision,
-	})
-	if err != nil {
-		return nil, err
+		info, err = snap.ReadCurrentInfo(snapName)
+	} else {
+		info, err = snap.ReadInfo(snapName, &snap.SideInfo{
+			Revision: revision,
+		})
 	}
 
-	return info, nil
+	return info, err
 }
 
 func createOrUpdateUserDataSymlink(info *snap.Info, usr *user.User) error {

cmd/snap/cmd_userd.go

@@ -33,6 +33,8 @@ import (
 
 type cmdUserd struct {
 	userd userd.Userd
+
+	Autostart bool `long:"autostart"`
 }
 
 var shortUserdHelp = i18n.G("Start the userd service")
@@ -46,10 +48,9 @@ func init() {
 		longUserdHelp,
 		func() flags.Commander {
 			return &cmdUserd{}
-		},
-		nil,
-		[]argDesc{},
-	)
+		}, map[string]string{
+			"autostart": i18n.G("Autostart user applications"),
+		}, nil)
 	cmd.hidden = true
 }
 
@@ -58,6 +59,10 @@ func (x *cmdUserd) Execute(args []string) error {
 		return ErrExtraArgs
 	}
 
+	if x.Autostart {
+		return x.runAutostart()
+	}
+
 	if err := x.userd.Init(); err != nil {
 		return err
 	}
@@ -74,3 +79,10 @@ func (x *cmdUserd) Execute(args []string) error {
 
 	return x.userd.Stop()
 }
+
+func (x *cmdUserd) runAutostart() error {
+	if err := userd.AutostartSessionApps(); err != nil {
+		return fmt.Errorf("autostart failed for the following apps:\n%v", err)
+	}
+	return nil
+}

data/Makefile

@@ -2,3 +2,4 @@ all install clean:
 	$(MAKE) -C systemd $@
 	$(MAKE) -C dbus $@
 	$(MAKE) -C env $@
+	$(MAKE) -C desktop $@

data/desktop/Makefile

@@ -0,0 +1,38 @@
+#
+# Copyright (C) 2018 Canonical Ltd
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+BINDIR = /usr/bin
+SYSCONFXDGAUTOSTARTDIR = /etc/xdg/autostart
+
+SOURCES = snap-userd-autostart.desktop.in
+DESKTOP_FILES = $(SOURCES:.in=)
+
+.PHONY: all
+all: $(DESKTOP_FILES)
+
+.PHONY: install
+install: $(DESKTOP_FILES)
+	# NOTE: old (e.g. 14.04) GNU coreutils doesn't -D with -t
+	install -d -m 0755 $(DESTDIR)/$(SYSCONFXDGAUTOSTARTDIR)
+	install -m 0644 -t $(DESTDIR)/$(SYSCONFXDGAUTOSTARTDIR) $^
+
+.PHONY: clean
+clean:
+	rm -f $(DESKTOP_FILES)
+
+%: %.in
+	cat $< | \
+		sed s:@bindir@:$(BINDIR):g | \
+		cat > $@

data/desktop/snap-userd-autostart.desktop.in

@@ -0,0 +1,5 @@
+[Desktop Entry]
+Name=Snap user application autostart helper
+Comment=Helper program for launching snap applications that are configured to start automatically.
+Exec=@bindir@/snap userd --autostart
+Type=Application

dirs/dirs.go

@@ -113,6 +113,9 @@ const (
 	// are in the snap confinement environment.
 	CoreLibExecDir   = "/usr/lib/snapd"
 	CoreSnapMountDir = "/snap"
+
+	// Directory with snap data inside user's home
+	UserHomeSnapDir = "snap"
 )
 
 var (
@@ -179,7 +182,7 @@ func SetRootDir(rootdir string) {
 	}
 
 	SnapDataDir = filepath.Join(rootdir, "/var/snap")
-	SnapDataHomeGlob = filepath.Join(rootdir, "/home/*/snap/")
+	SnapDataHomeGlob = filepath.Join(rootdir, "/home/*/", UserHomeSnapDir)
 	SnapAppArmorDir = filepath.Join(rootdir, snappyDir, "apparmor", "profiles")
 	SnapConfineAppArmorDir = filepath.Join(rootdir, snappyDir, "apparmor", "snap-confine")
 	AppArmorCacheDir = filepath.Join(rootdir, "/var/cache/apparmor")

packaging/fedora/snapd.spec

@@ -620,6 +620,7 @@ popd
 %{_datadir}/dbus-1/services/io.snapcraft.Launcher.service
 %{_datadir}/dbus-1/services/io.snapcraft.Settings.service
 %{_datadir}/polkit-1/actions/io.snapcraft.snapd.policy
+%{_sysconfdir}/xdg/autostart/snap-userd-autostart.desktop
 %config(noreplace) %{_sysconfdir}/sysconfig/snapd
 %dir %{_sharedstatedir}/snapd
 %dir %{_sharedstatedir}/snapd/assertions

packaging/opensuse-42.2/snapd.spec

@@ -313,6 +313,7 @@ fi
 %{_mandir}/man1/snap.1.gz
 /usr/share/dbus-1/services/io.snapcraft.Launcher.service
 /usr/share/dbus-1/services/io.snapcraft.Settings.service
+%{_sysconfdir}/xdg/autostart/snap-userd-autostart.desktop
 
 %changelog
 

snap/info.go

@@ -304,12 +304,12 @@ func (s *Info) DataDir() string {
 
 // UserDataDir returns the user-specific data directory of the snap.
 func (s *Info) UserDataDir(home string) string {
-	return filepath.Join(home, "snap", s.Name(), s.Revision.String())
+	return filepath.Join(home, dirs.UserHomeSnapDir, s.Name(), s.Revision.String())
 }
 
 // UserCommonDataDir returns the user-specific data directory common across revision of the snap.
 func (s *Info) UserCommonDataDir(home string) string {
-	return filepath.Join(home, "snap", s.Name(), "common")
+	return filepath.Join(home, dirs.UserHomeSnapDir, s.Name(), "common")
 }
 
 // CommonDataDir returns the data directory common across revisions of the snap.
@@ -780,6 +780,22 @@ func ReadInfo(name string, si *SideInfo) (*Info, error) {
 	return info, nil
 }
 
+// ReadCurrentInfo reads the snap information from the installed snap in 'current' revision
+func ReadCurrentInfo(snapName string) (*Info, error) {
+	curFn := filepath.Join(dirs.SnapMountDir, snapName, "current")
+	realFn, err := os.Readlink(curFn)
+	if err != nil {
+		return nil, fmt.Errorf("cannot find current revision for snap %s: %s", snapName, err)
+	}
+	rev := filepath.Base(realFn)
+	revision, err := ParseRevision(rev)
+	if err != nil {
+		return nil, fmt.Errorf("cannot read revision %s: %s", rev, err)
+	}
+
+	return ReadInfo(snapName, &SideInfo{Revision: revision})
+}
+
 // ReadInfoFromSnapFile reads the snap information from the given File
 // and completes it with the given side-info if this is not nil.
 func ReadInfoFromSnapFile(snapf Container, si *SideInfo) (*Info, error) {

snap/info_test.go

@@ -195,6 +195,23 @@ func (s *infoSuite) TestReadInfo(c *C) {
 	c.Check(snapInfo2, DeepEquals, snapInfo1)
 }
 
+func (s *infoSuite) TestReadCurrentInfo(c *C) {
+	si := &snap.SideInfo{Revision: snap.R(42)}
+
+	snapInfo1 := snaptest.MockSnapCurrent(c, sampleYaml, si)
+
+	snapInfo2, err := snap.ReadCurrentInfo("sample")
+	c.Assert(err, IsNil)
+
+	c.Check(snapInfo2.Name(), Equals, "sample")
+	c.Check(snapInfo2.Revision, Equals, snap.R(42))
+	c.Check(snapInfo2, DeepEquals, snapInfo1)
+
+	snapInfo3, err := snap.ReadCurrentInfo("not-sample")
+	c.Check(snapInfo3, IsNil)
+	c.Assert(err, ErrorMatches, `cannot find current revision for snap not-sample:.*`)
+}
+
 func (s *infoSuite) TestInstallDate(c *C) {
 	si := &snap.SideInfo{Revision: snap.R(1)}
 	info := snaptest.MockSnap(c, sampleYaml, si)

snap/snaptest/snaptest.go

@@ -68,6 +68,18 @@ func MockSnap(c *check.C, yamlText string, sideInfo *snap.SideInfo) *snap.Info {
 	return snapInfo
 }
 
+// MockSnapCurrent does the same as MockSnap but additionally creates the
+// 'current' symlink.
+//
+// The caller is responsible for mocking root directory with dirs.SetRootDir()
+// and for altering the overlord state if required.
+func MockSnapCurrent(c *check.C, yamlText string, sideInfo *snap.SideInfo) *snap.Info {
+	si := MockSnap(c, yamlText, sideInfo)
+	err := os.Symlink(si.MountDir(), filepath.Join(si.MountDir(), "../current"))
+	c.Assert(err, check.IsNil)
+	return si
+}
+
 // MockInfo parses the given snap.yaml text and returns a validated snap.Info object including the optional SideInfo.
 //
 // The result is just kept in memory, there is nothing kept on disk. If that is

snap/snaptest/snaptest_test.go

@@ -72,6 +72,20 @@ func (s *snapTestSuite) TestMockSnap(c *C) {
 	c.Check(snapInfo.Plugs["network"].Interface, Equals, "network")
 }
 
+func (s *snapTestSuite) TestMockSnapCurrent(c *C) {
+	snapInfo := snaptest.MockSnapCurrent(c, sampleYaml, &snap.SideInfo{Revision: snap.R(42)})
+	// Data from YAML is used
+	c.Check(snapInfo.Name(), Equals, "sample")
+	// Data from SideInfo is used
+	c.Check(snapInfo.Revision, Equals, snap.R(42))
+	// The YAML is placed on disk
+	c.Check(filepath.Join(dirs.SnapMountDir, "sample", "42", "meta", "snap.yaml"),
+		testutil.FileEquals, sampleYaml)
+	link, err := os.Readlink(filepath.Join(dirs.SnapMountDir, "sample", "current"))
+	c.Check(err, IsNil)
+	c.Check(link, Equals, filepath.Join(dirs.SnapMountDir, "sample", "42"))
+}
+
 func (s *snapTestSuite) TestMockInfo(c *C) {
 	snapInfo := snaptest.MockInfo(c, sampleYaml, &snap.SideInfo{Revision: snap.R(42)})
 	// Data from YAML is used

tests/lib/snaps/test-snapd-xdg-autostart/bin/foobar

@@ -0,0 +1,26 @@
+#!/bin/sh
+
+dump_autostart() {
+    dfpath="$SNAP_USER_DATA/.config/autostart/foo.desktop"
+
+    test -e "$dfpath" && return
+
+    echo "generating autostart file $dfpath"
+
+    mkdir -p $SNAP_USER_DATA/.config/autostart
+    cat <<EOF > $dfpath
+[Desktop Entry]
+Name=foo autostart
+Exec=/foo/bar/baz/bin/foobar --autostart a b c
+EOF
+}
+
+case "$1" in
+    --autostart)
+        echo "autostarting with args '$@'" | tee $SNAP_USER_DATA/foo-autostarted
+        ;;
+    *)
+        echo "regular run with args '$@'"
+        dump_autostart
+        ;;
+esac

tests/lib/snaps/test-snapd-xdg-autostart/meta/snap.yaml

@@ -0,0 +1,6 @@
+name: test-snapd-xdg-autostart
+version: 1.0
+apps:
+  foo:
+    command: bin/foobar
+    autostart: foo.desktop

tests/main/snap-userd-desktop-app-autostart/task.yaml

@@ -0,0 +1,29 @@
+summary: Check that snap userd can autostart user session applications
+
+execute: |
+    echo "When the snap is installed"
+    . $TESTSLIB/snaps.sh
+    install_local test-snapd-xdg-autostart
+
+    # run the app directly, it will dump a *.desktop file
+    snap run test-snapd-xdg-autostart.foo
+
+    echo "And snap application autostart file exists"
+    test -e ~/snap/test-snapd-xdg-autostart/current/.config/autostart/foo.desktop
+
+    echo "Applications can be automatically started by snap userd --autostart"
+
+    test ! -e ~/snap/test-xdg-snap-autostart/current/foo-autostarted
+    snap userd --autostart > autostart.log 2>&1
+
+    # when app is autostarted it dumps a file at $SNAP_USER_DATA/foo-autostarted,
+    # applications are forked by userd, but userd does not wait for them
+    for i in `seq 20`; do
+        test -e ~/snap/test-snapd-xdg-autostart/current/foo-autostarted && break
+        sleep 1
+    done
+    test -e ~/snap/test-snapd-xdg-autostart/current/foo-autostarted
+
+restore: |
+    rm -f ~/snap/test-snapd-xdg-autostart/current/foo-autostarted
+    rm -f ~/snap/test-snapd-xdg-autostart/current/.config/autostart/foo.desktop