c/snap-exec: handle running component hooks in snap-exec

cmd/snap-exec/main.go

@@ -32,6 +32,7 @@ import (
 	"github.com/snapcore/snapd/logger"
 	"github.com/snapcore/snapd/osutil"
 	"github.com/snapcore/snapd/snap"
+	"github.com/snapcore/snapd/snap/snapdir"
 	"github.com/snapcore/snapd/snap/snapenv"
 )
 
@@ -81,22 +82,24 @@ func parseArgs(args []string) (app string, appArgs []string, err error) {
 }
 
 func run() error {
-	snapApp, extraArgs, err := parseArgs(os.Args[1:])
+	snapTarget, extraArgs, err := parseArgs(os.Args[1:])
 	if err != nil {
 		return err
 	}
 
+	snapName, componentName := snap.SplitSnapComponentInstanceName(snapTarget)
+
 	// the SNAP_REVISION is set by `snap run` - we can not (easily)
 	// find it in `snap-exec` because `snap-exec` is run inside the
 	// confinement and (generally) can not talk to snapd
 	revision := os.Getenv("SNAP_REVISION")
 
 	// Now actually handle the dispatching
 	if opts.Hook != "" {
-		return execHook(snapApp, revision, opts.Hook)
+		return execHook(snapName, componentName, revision, opts.Hook)
 	}
 
-	return execApp(snapApp, revision, opts.Command, extraArgs)
+	return execApp(snapName, revision, opts.Command, extraArgs)
 }
 
 const defaultShell = "/bin/bash"
@@ -128,12 +131,10 @@ func findCommand(app *snap.AppInfo, command string) (string, error) {
 	return cmd, nil
 }
 
-func absoluteCommandChain(snapInfo *snap.Info, commandChain []string) []string {
+func absoluteCommandChain(mountDir string, commandChain []string) []string {
 	chain := make([]string, 0, len(commandChain))
-	snapMountDir := snapInfo.MountDir()
-
 	for _, element := range commandChain {
-		chain = append(chain, filepath.Join(snapMountDir, element))
+		chain = append(chain, filepath.Join(mountDir, element))
 	}
 
 	return chain
@@ -245,7 +246,7 @@ func execApp(snapApp, revision, command string, args []string) error {
 	fullCmd = append(fullCmd, cmdArgs...)
 	fullCmd = append(fullCmd, args...)
 
-	fullCmd = append(absoluteCommandChain(app.Snap, app.CommandChain), fullCmd...)
+	fullCmd = append(absoluteCommandChain(app.Snap.MountDir(), app.CommandChain), fullCmd...)
 
 	logger.StartupStageTimestamp("snap-exec to app")
 	if err := syscallExec(fullCmd[0], fullCmd, env.ForExec()); err != nil {
@@ -255,7 +256,15 @@ func execApp(snapApp, revision, command string, args []string) error {
 	return nil
 }
 
-func execHook(snapName, revision, hookName string) error {
+func getComponentInfo(name string, snapInfo *snap.Info) (*snap.ComponentInfo, error) {
+	container := func(p string) (snap.Container, error) {
+		return snapdir.New(p), nil
+	}
+
+	return snap.ReadCurrentComponentInfo(name, snapInfo, container)
+}
+
+func execHook(snapName, componentName, revision, hookName string) error {
 	rev, err := snap.ParseRevision(revision)
 	if err != nil {
 		return err
@@ -268,7 +277,23 @@ func execHook(snapName, revision, hookName string) error {
 		return err
 	}
 
-	hook := info.Hooks[hookName]
+	var (
+		hook     *snap.HookInfo
+		mountDir string
+	)
+
+	if componentName == "" {
+		hook = info.Hooks[hookName]
+		mountDir = info.MountDir()
+	} else {
+		component, err := getComponentInfo(componentName, info)
+		if err != nil {
+			return err
+		}
+		hook = component.Hooks[hookName]
+		mountDir = snap.ComponentMountDir(component.Component.ComponentName, component.Revision, info.InstanceName())
+	}
+
 	if hook == nil {
 		return fmt.Errorf("cannot find hook %q in %q", hookName, snapName)
 	}
@@ -285,7 +310,9 @@ func execHook(snapName, revision, hookName string) error {
 		env.ExtendWithExpanded(eenv)
 	}
 
+	hookPath := filepath.Join(mountDir, "meta", "hooks", hookName)
+
 	// run the hook
-	cmd := append(absoluteCommandChain(hook.Snap, hook.CommandChain), filepath.Join(hook.Snap.HooksDir(), hook.Name))
+	cmd := append(absoluteCommandChain(mountDir, hook.CommandChain), hookPath)
 	return syscallExec(cmd[0], cmd, env.ForExec())
 }

cmd/snap-exec/main_test.go

@@ -76,10 +76,20 @@ apps:
   command-chain: [chain1, chain2]
  nostop:
   command: nostop
+components:
+ comp:
+  type: test
+  hooks:
+   install:
 `)
 
 var mockClassicYaml = append([]byte("confinement: classic\n"), mockYaml...)
 
+var mockComponentYaml = []byte(`component: snapname+comp
+type: test
+version: 1.0
+`)
+
 var mockHookYaml = []byte(`name: snapname
 version: 1.0
 hooks:
@@ -91,6 +101,12 @@ version: 1.0
 hooks:
  configure:
   command-chain: [chain1, chain2]
+components:
+ comp:
+  type: test
+  hooks:
+   install:
+    command-chain: [chain3, chain4]
 `)
 
 var binaryTemplate = `#!/bin/sh
@@ -287,7 +303,7 @@ func (s *snapExecSuite) TestSnapExecHookIntegration(c *C) {
 	defer restore()
 
 	// launch and verify it ran correctly
-	err := snapExec.ExecHook("snapname", "42", "configure")
+	err := snapExec.ExecHook("snapname", "", "42", "configure")
 	c.Assert(err, IsNil)
 	c.Check(execArgv0, Equals, fmt.Sprintf("%s/snapname/42/meta/hooks/configure", dirs.SnapMountDir))
 	c.Check(execArgs, DeepEquals, []string{execArgv0})
@@ -312,7 +328,7 @@ func (s *snapExecSuite) TestSnapExecHookCommandChainIntegration(c *C) {
 	chain2_path := fmt.Sprintf("%s/snapname/42/chain2", dirs.SnapMountDir)
 	hook_path := fmt.Sprintf("%s/snapname/42/meta/hooks/configure", dirs.SnapMountDir)
 
-	err := snapExec.ExecHook("snapname", "42", "configure")
+	err := snapExec.ExecHook("snapname", "", "42", "configure")
 	c.Assert(err, IsNil)
 	c.Check(execArgv0, Equals, chain1_path)
 	c.Check(execArgs, DeepEquals, []string{chain1_path, chain2_path, hook_path})
@@ -324,7 +340,7 @@ func (s *snapExecSuite) TestSnapExecHookMissingHookIntegration(c *C) {
 		Revision: snap.R("42"),
 	})
 
-	err := snapExec.ExecHook("snapname", "42", "missing-hook")
+	err := snapExec.ExecHook("snapname", "", "42", "missing-hook")
 	c.Assert(err, NotNil)
 	c.Assert(err, ErrorMatches, "cannot find hook \"missing-hook\" in \"snapname\"")
 }
@@ -663,3 +679,57 @@ func (s *snapExecSuite) TestSnapExecCompleteClassicNoReexec(c *C) {
 	c.Check(execEnv, testutil.Contains, "SNAP_DATA=/var/snap/snapname/42")
 	c.Check(execEnv, testutil.Contains, "TMPDIR=/var/tmp99")
 }
+
+func (s *snapExecSuite) TestSnapExecComponentHookIntegration(c *C) {
+	dirs.SetRootDir(c.MkDir())
+	snapInfo := snaptest.MockSnap(c, string(mockYaml), &snap.SideInfo{
+		Revision: snap.R(42),
+	})
+	snaptest.MockComponentCurrent(c, string(mockComponentYaml), snapInfo, snap.ComponentSideInfo{
+		Revision: snap.R(21),
+	})
+
+	execArgv0 := ""
+	execArgs := []string{}
+	restore := snapExec.MockSyscallExec(func(argv0 string, argv []string, env []string) error {
+		execArgv0 = argv0
+		execArgs = argv
+		return nil
+	})
+	defer restore()
+
+	hookPath := filepath.Join(dirs.SnapMountDir, "/snapname/components/mnt/comp/21/meta/hooks/install")
+
+	err := snapExec.ExecHook("snapname", "comp", "42", "install")
+	c.Assert(err, IsNil)
+	c.Check(execArgv0, Equals, hookPath)
+	c.Check(execArgs, DeepEquals, []string{execArgv0})
+}
+
+func (s *snapExecSuite) TestSnapExecComponentHookCommandChainIntegration(c *C) {
+	dirs.SetRootDir(c.MkDir())
+	snapInfo := snaptest.MockSnap(c, string(mockHookCommandChainYaml), &snap.SideInfo{
+		Revision: snap.R(42),
+	})
+	snaptest.MockComponentCurrent(c, string(mockComponentYaml), snapInfo, snap.ComponentSideInfo{
+		Revision: snap.R(21),
+	})
+
+	execArgv0 := ""
+	execArgs := []string{}
+	restore := snapExec.MockSyscallExec(func(argv0 string, argv []string, env []string) error {
+		execArgv0 = argv0
+		execArgs = argv
+		return nil
+	})
+	defer restore()
+
+	chain3Path := filepath.Join(dirs.SnapMountDir, "/snapname/components/mnt/comp/21/chain3")
+	chain4Path := filepath.Join(dirs.SnapMountDir, "/snapname/components/mnt/comp/21/chain4")
+	hookPath := filepath.Join(dirs.SnapMountDir, "/snapname/components/mnt/comp/21/meta/hooks/install")
+
+	err := snapExec.ExecHook("snapname", "comp", "42", "install")
+	c.Assert(err, IsNil)
+	c.Check(execArgv0, Equals, chain3Path)
+	c.Check(execArgs, DeepEquals, []string{chain3Path, chain4Path, hookPath})
+}