interfaces/desktop-launch: support confined snaps launching other snaps

interfaces/builtin/desktop_launch.go

@@ -0,0 +1,65 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2019 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/>.
+ *
+ */
+
+package builtin
+
+const desktopLaunchSummary = `allows snaps to identify and launch desktop applications in (or from) other snaps`
+
+const desktopLaunchBaseDeclarationPlugs = `
+  desktop-launch:
+    allow-installation: false
+    deny-auto-connection: true
+`
+
+const desktopLaunchBaseDeclarationSlots = `
+  desktop-launch:
+    allow-installation:
+      slot-snap-type:
+        - core
+    deny-auto-connection: true
+`
+
+const desktopLaunchConnectedPlugAppArmor = `
+# Description: Can identify and launch other snaps.
+
+# Access to the desktop and icon files installed by snaps
+/var/lib/snapd/desktop/applications/{,*} r,
+/var/lib/snapd/desktop/icons/{,*} r,
+
+#include <abstractions/dbus-session-strict>
+
+dbus (send)
+    bus=session
+    path=/io/snapcraft/PrivilegedDesktopLauncher
+    interface=io.snapcraft.PrivilegedDesktopLauncher
+    peer=(label=unconfined),member=OpenDesktopEntry
+    peer=(label=unconfined),
+`
+
+// Only implicitOnClassic since userd isn't yet usable on core
+func init() {
+	registerIface(&commonInterface{
+		name:                  "desktop-launch",
+		summary:               desktopLaunchSummary,
+		implicitOnClassic:     true,
+		baseDeclarationPlugs:  desktopLaunchBaseDeclarationPlugs,
+		baseDeclarationSlots:  desktopLaunchBaseDeclarationSlots,
+		connectedPlugAppArmor: desktopLaunchConnectedPlugAppArmor,
+	})
+}

interfaces/builtin/desktop_launch_test.go

@@ -0,0 +1,101 @@
+// -*- Mode: Go; indent-tabs-mode: t -*-
+
+/*
+ * Copyright (C) 2019 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/>.
+ *
+ */
+
+package builtin_test
+
+import (
+	. "gopkg.in/check.v1"
+
+	"github.com/snapcore/snapd/interfaces"
+	"github.com/snapcore/snapd/interfaces/apparmor"
+	"github.com/snapcore/snapd/interfaces/builtin"
+	"github.com/snapcore/snapd/snap"
+	"github.com/snapcore/snapd/testutil"
+)
+
+type desktopLaunchSuite struct {
+	iface    interfaces.Interface
+	slotInfo *snap.SlotInfo
+	slot     *interfaces.ConnectedSlot
+	plugInfo *snap.PlugInfo
+	plug     *interfaces.ConnectedPlug
+}
+
+var _ = Suite(&desktopLaunchSuite{
+	iface: builtin.MustInterface("desktop-launch"),
+})
+
+const desktopLaunchConsumerYaml = `
+name: other
+version: 0
+apps:
+ app:
+    command: foo
+    plugs: [desktop-launch]
+`
+
+const desktopLaunchCoreYaml = `name: core
+version: 0
+type: os
+slots:
+  desktop-launch:
+`
+
+func (s *desktopLaunchSuite) SetUpTest(c *C) {
+	s.plug, s.plugInfo = MockConnectedPlug(c, desktopLaunchConsumerYaml, nil, "desktop-launch")
+	s.slot, s.slotInfo = MockConnectedSlot(c, desktopLaunchCoreYaml, nil, "desktop-launch")
+}
+
+func (s *desktopLaunchSuite) TestName(c *C) {
+	c.Assert(s.iface.Name(), Equals, "desktop-launch")
+}
+
+func (s *desktopLaunchSuite) TestSanitizeSlot(c *C) {
+	c.Assert(interfaces.BeforePrepareSlot(s.iface, s.slotInfo), IsNil)
+}
+
+func (s *desktopLaunchSuite) TestSanitizePlug(c *C) {
+	c.Assert(interfaces.BeforePreparePlug(s.iface, s.plugInfo), IsNil)
+}
+
+func (s *desktopLaunchSuite) TestConnectedPlugSnippet(c *C) {
+	apparmorSpec := &apparmor.Specification{}
+	err := apparmorSpec.AddConnectedPlug(s.iface, s.plug, s.slot)
+	c.Assert(err, IsNil)
+	c.Assert(apparmorSpec.SecurityTags(), DeepEquals, []string{"snap.other.app"})
+	c.Assert(apparmorSpec.SnippetForTag("snap.other.app"), testutil.Contains, `Can identify and launch other snaps.`)
+	c.Assert(apparmorSpec.SnippetForTag("snap.other.app"), testutil.Contains, `member=OpenDesktopEntry`)
+	c.Assert(apparmorSpec.SnippetForTag("snap.other.app"), testutil.Contains, `peer=(label=unconfined),`)
+}
+
+func (s *desktopLaunchSuite) TestInterfaces(c *C) {
+	c.Check(builtin.Interfaces(), testutil.DeepContains, s.iface)
+}
+
+func (s *desktopLaunchSuite) TestStaticInfo(c *C) {
+	si := interfaces.StaticInfoOf(s.iface)
+	c.Assert(si.ImplicitOnCore, Equals, false)
+	c.Assert(si.ImplicitOnClassic, Equals, true)
+	c.Assert(si.Summary, Equals, `allows snaps to identify and launch desktop applications in (or from) other snaps`)
+	c.Assert(si.BaseDeclarationSlots, testutil.Contains, "desktop-launch")
+	c.Assert(si.BaseDeclarationSlots, testutil.Contains, "deny-auto-connection: true")
+	c.Assert(si.BaseDeclarationPlugs, testutil.Contains, "desktop-launch")
+	c.Assert(si.BaseDeclarationPlugs, testutil.Contains, "deny-auto-connection: true")
+	c.Assert(si.BaseDeclarationPlugs, testutil.Contains, "allow-installation: false")
+}

interfaces/policy/basedeclaration_test.go

@@ -599,6 +599,7 @@ var (
 		"cups-control":            {"app", "core"},
 		"dbus":                    {"app"},
 		"docker-support":          {"core"},
+		"desktop-launch":          {"core"},
 		"dummy":                   {"app"},
 		"fwupd":                   {"app", "core"},
 		"gpio":                    {"core", "gadget"},
@@ -702,6 +703,7 @@ func (s *baseDeclSuite) TestPlugInstallation(c *C) {
 	restricted := map[string]bool{
 		"block-devices":         true,
 		"classic-support":       true,
+		"desktop-launch":        true,
 		"docker-support":        true,
 		"greengrass-support":    true,
 		"gpio-control":          true,
@@ -934,6 +936,7 @@ func (s *baseDeclSuite) TestSanity(c *C) {
 		"audio-playback":        true,
 		"classic-support":       true,
 		"core-support":          true,
+		"desktop-launch":        true,
 		"docker-support":        true,
 		"greengrass-support":    true,
 		"gpio-control":          true,
@@ -1200,3 +1203,21 @@ plugs:
 	c.Check(err, IsNil)
 	c.Check(arity.SlotsPerPlugAny(), Equals, false)
 }
+
+func (s *baseDeclSuite) TestAutoConnectionDesktopLaunchOverride(c *C) {
+	cand := s.connectCand(c, "desktop-launch", "", "")
+	_, err := cand.CheckAutoConnect()
+	c.Check(err, NotNil)
+	c.Assert(err, ErrorMatches, "auto-connection denied by plug rule of interface \"desktop-launch\"")
+
+	plugsSlots := `
+plugs:
+  desktop-launch:
+    allow-auto-connection: true
+`
+
+	snapDecl := s.mockSnapDecl(c, "some-snap", "some-snap-with-desktop-launch-id", "canonical", plugsSlots)
+	cand.PlugSnapDeclaration = snapDecl
+	_, err = cand.CheckAutoConnect()
+	c.Check(err, IsNil)
+}

tests/lib/snaps/test-snapd-policy-app-consumer/meta/snap.yaml

@@ -95,6 +95,9 @@ apps:
   desktop:
     command: bin/run
     plugs: [ desktop ]
+  desktop-launch:
+    command: bin/run
+    plugs: [ desktop-launch ]
   desktop-legacy:
     command: bin/run
     plugs: [ desktop-legacy ]

tests/main/interfaces-desktop-launch/task.yaml

@@ -0,0 +1,56 @@
+summary: Ensure that the desktop-launch interface works.
+
+details: |
+    The desktop-launch interface allows a snap to launch other snaps via
+    the desktop files they provide to the host system.
+
+systems: [-ubuntu-core-*]
+
+prepare: |
+    if ! tests.session has-session-systemd-and-dbus; then
+        exit 0
+    fi
+    tests.session -u test prepare
+    tests.session -u test exec systemctl --user \
+      set-environment XDG_DATA_DIRS=/usr/share:/var/lib/snapd/desktop
+
+restore: |
+    if ! tests.session has-session-systemd-and-dbus; then
+        exit 0
+    fi
+    tests.session -u test restore
+    rm -f ~test/snap/test-app/current/launch-data.txt
+
+execute: |
+    if ! tests.session has-session-systemd-and-dbus; then
+        exit 0
+    fi
+
+    #shellcheck source=tests/lib/snaps.sh
+    . "$TESTSLIB"/snaps.sh
+
+    echo "Install the application snap"
+    install_local test-app
+    echo "The snap installs a desktop file"
+    [ -f /var/lib/snapd/desktop/applications/test-app_test-app.desktop ]
+
+    echo "Install the launcher snap"
+    install_local test-launcher
+
+    echo "The desktop-launch plug is initially disconnected"
+    snap connections test-launcher | MATCH "desktop-launch +test-launcher:desktop-launch +- +-"
+
+    echo "The plug can be connected"
+    snap connect test-launcher:desktop-launch
+    snap connections test-launcher | MATCH "desktop-launch +test-launcher:desktop-launch +:desktop-launch +manual"
+
+    echo "The launcher snap can launch other snaps via userd"
+    tests.session -u test exec test-launcher \
+        test-app_test-app.desktop
+
+    echo "The app snap records that it has been launched"
+    launch_data=~test/snap/test-app/current/launch-data.txt
+    retry -n 5 --wait 1 test -s "$launch_data"
+
+    echo "The app was invoked with the arguments in the desktop file"
+    MATCH "^args=arg-before arg-after$" < "$launch_data"

tests/main/interfaces-desktop-launch/test-app/bin/app.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+echo "App launched"
+
+cat << EOF > "$SNAP_USER_DATA"/launch-data.txt
+args=$*
+DISPLAY=${DISPLAY}
+WAYLAND_DISPLAY=${WAYLAND_DISPLAY}
+XDG_CURRENT_DESKTOP=${XDG_CURRENT_DESKTOP}
+XDG_SESSION_DESKTOP=${XDG_SESSION_DESKTOP}
+XDG_SESSION_TYPE=${XDG_SESSION_TYPE}
+EOF

tests/main/interfaces-desktop-launch/test-app/meta/gui/test-app.desktop

@@ -0,0 +1,5 @@
+[Desktop Entry]
+Type=Application
+Name=test-app
+Comment=A desktop file for test-app
+Exec=test-app arg-before %U arg-after

tests/main/interfaces-desktop-launch/test-app/meta/snap.yaml

@@ -0,0 +1,9 @@
+name: test-app
+version: 1.0
+summary: Basic desktop app test snap
+description: A basic snap to act as a target for the launcher
+
+apps:
+  test-app:
+    command: bin/app.sh
+    plugs: [desktop]

tests/main/interfaces-desktop-launch/test-launcher/bin/launcher.sh

@@ -0,0 +1,6 @@
+#!/bin/sh
+
+exec dbus-send --session --print-reply \
+    --dest=io.snapcraft.Launcher /io/snapcraft/PrivilegedDesktopLauncher \
+    io.snapcraft.PrivilegedDesktopLauncher.OpenDesktopEntry \
+    string:"$1"

tests/main/interfaces-desktop-launch/test-launcher/meta/snap.yaml

@@ -0,0 +1,9 @@
+name: test-launcher
+version: 1.0
+summary: Basic desktop launcher snap
+description: A basic snap that attempts to launch other snaps
+
+apps:
+  test-launcher:
+    command: bin/launcher.sh
+    plugs: [desktop-launch]

usersession/userd/export_test.go

@@ -30,3 +30,19 @@ func MockSnapFromSender(f func(*dbus.Conn, dbus.Sender) (string, error)) func()
 		snapFromSender = origSnapFromSender
 	}
 }
+
+var (
+	DesktopFileSearchPath          = desktopFileSearchPath
+	DesktopFileIDToFilename        = desktopFileIDToFilename
+	VerifyDesktopFileLocation      = verifyDesktopFileLocation
+	ParseExecCommand               = parseExecCommand
+	ReadExecCommandFromDesktopFile = readExecCommandFromDesktopFile
+)
+
+func MockRegularFileExists(f func(string) (bool, bool, error)) func() {
+	old := regularFileExists
+	regularFileExists = f
+	return func() {
+		regularFileExists = old
+	}
+}