Cherry-pick #17241 to 7.x: [Agent] Enable post install hooks

x-pack/agent/CHANGELOG.asciidoc

@@ -21,3 +21,4 @@
 - OS agnostic default configuration {pull}17016[17016]
 - Display the stability of the agent at enroll and start.  {pull}17336[17336]
 - Support for config constraints {pull}17112[17112]
+- Introduced post install hooks {pull}17241[17241]

x-pack/agent/pkg/agent/program/spec.go

@@ -27,12 +27,13 @@ var ErrMissingWhen = errors.New("program must define a 'When' expression")
 // NOTE: Current spec are build at compile time, we want to revisit that to allow other program
 // to register their spec in a secure way.
 type Spec struct {
-	Name         string               `yaml:"name"`
-	Cmd          string               `yaml:"cmd"`
-	Configurable string               `yaml:"configurable"`
-	Args         []string             `yaml:"args"`
-	Rules        *transpiler.RuleList `yaml:"rules"`
-	When         string               `yaml:"when"`
+	Name             string               `yaml:"name"`
+	Cmd              string               `yaml:"cmd"`
+	Configurable     string               `yaml:"configurable"`
+	Args             []string             `yaml:"args"`
+	Rules            *transpiler.RuleList `yaml:"rules"`
+	PostInstallSteps *transpiler.StepList `yaml:"post_install"`
+	When             string               `yaml:"when"`
 }
 
 // ReadSpecs reads all the specs that match the provided globbing path.

x-pack/agent/pkg/agent/program/spec_test.go

@@ -44,6 +44,10 @@ func TestSerialization(t *testing.T) {
 				"log",
 			),
 		),
+		PostInstallSteps: transpiler.NewStepList(
+			transpiler.DeleteFile("d-1", true),
+			transpiler.MoveFile("m-1", "m-2", false),
+		),
 		When: "1 == 1",
 	}
 	yml := `name: hello
@@ -85,6 +89,14 @@ rules:
     key: type
     values:
     - log
+post_install:
+- delete_file:
+    path: d-1
+    fail_on_missing: true
+- move_file:
+    path: m-1
+    target: m-2
+    fail_on_missing: false
 when: 1 == 1
 `
 	t.Run("serialization", func(t *testing.T) {

x-pack/agent/pkg/agent/transpiler/rules.go

@@ -85,7 +85,7 @@ func (r *RuleList) MarshalYAML() (interface{}, error) {
 	return doc, nil
 }
 
-// UnmarshalYAML unmashal a YAML document into a RuleList.
+// UnmarshalYAML unmarshal a YAML document into a RuleList.
 func (r *RuleList) UnmarshalYAML(unmarshal func(interface{}) error) error {
 	var unpackTo []map[string]interface{}
 

x-pack/agent/pkg/agent/transpiler/steps.go

@@ -0,0 +1,248 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package transpiler
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	"gopkg.in/yaml.v2"
+)
+
+// StepList is a container that allow the same tree to be executed on multiple defined Step.
+type StepList struct {
+	Steps []Step
+}
+
+// NewStepList returns a new list of rules to be executed.
+func NewStepList(steps ...Step) *StepList {
+	return &StepList{Steps: steps}
+}
+
+// Step is an execution step which needs to be run.
+type Step interface {
+	Execute(rootDir string) error
+}
+
+// Execute executes a list of steps.
+func (r *StepList) Execute(rootDir string) error {
+	var err error
+	for _, step := range r.Steps {
+		err = step.Execute(rootDir)
+		if err != nil {
+			return err
+		}
+	}
+
+	return nil
+}
+
+// MarshalYAML marsharl a steps list to YAML.
+func (r *StepList) MarshalYAML() (interface{}, error) {
+	doc := make([]map[string]Step, 0, len(r.Steps))
+
+	for _, step := range r.Steps {
+		var name string
+		switch step.(type) {
+		case *DeleteFileStep:
+			name = "delete_file"
+		case *MoveFileStep:
+			name = "move_file"
+
+		default:
+			return nil, fmt.Errorf("unknown rule of type %T", step)
+		}
+
+		subdoc := map[string]Step{
+			name: step,
+		}
+
+		doc = append(doc, subdoc)
+	}
+	return doc, nil
+}
+
+// UnmarshalYAML unmarshal a YAML document into a RuleList.
+func (r *StepList) UnmarshalYAML(unmarshal func(interface{}) error) error {
+	var unpackTo []map[string]interface{}
+
+	err := unmarshal(&unpackTo)
+	if err != nil {
+		return err
+	}
+
+	// NOTE: this is a bit of a hack because I want to make sure
+	// the unpack strategy stay in the struct implementation and yaml
+	// doesn't have a RawMessage similar to the JSON package, so partial unpack
+	// is not possible.
+	unpack := func(in interface{}, out interface{}) error {
+		b, err := yaml.Marshal(in)
+		if err != nil {
+			return err
+		}
+		return yaml.Unmarshal(b, out)
+	}
+
+	var steps []Step
+
+	for _, m := range unpackTo {
+		ks := keys(m)
+		if len(ks) > 1 {
+			return fmt.Errorf("unknown rule identifier, expecting one identifier and received %d", len(ks))
+		}
+
+		name := ks[0]
+		fields := m[name]
+
+		var s Step
+		switch name {
+		case "delete_file":
+			s = &DeleteFileStep{}
+		case "move_file":
+			s = &MoveFileStep{}
+		default:
+			return fmt.Errorf("unknown rule of type %s", name)
+		}
+
+		if err := unpack(fields, s); err != nil {
+			return err
+		}
+
+		steps = append(steps, s)
+	}
+	r.Steps = steps
+	return nil
+}
+
+// DeleteFileStep removes a file from disk.
+type DeleteFileStep struct {
+	Path string
+	// FailOnMissing fails if file is already missing
+	FailOnMissing bool `yaml:"fail_on_missing" config:"fail_on_missing"`
+}
+
+// Execute executes delete file step.
+func (r *DeleteFileStep) Execute(rootDir string) error {
+	path, isSubpath := joinPaths(rootDir, r.Path)
+	if !isSubpath {
+		return fmt.Errorf("invalid path value for operation 'Delete': %s", path)
+	}
+
+	err := os.Remove(path)
+
+	if os.IsNotExist(err) && r.FailOnMissing {
+		// is not found and should be reported
+		return err
+	}
+
+	if err != nil && !os.IsNotExist(err) {
+		// report others
+		return err
+	}
+
+	return nil
+}
+
+// DeleteFile creates a DeleteFileStep
+func DeleteFile(path string, failOnMissing bool) *DeleteFileStep {
+	return &DeleteFileStep{
+		Path:          path,
+		FailOnMissing: failOnMissing,
+	}
+}
+
+// MoveFileStep moves a file to a new location.
+type MoveFileStep struct {
+	Path   string
+	Target string
+	// FailOnMissing fails if file is already missing
+	FailOnMissing bool `yaml:"fail_on_missing" config:"fail_on_missing"`
+}
+
+// Execute executes move file step.
+func (r *MoveFileStep) Execute(rootDir string) error {
+	path, isSubpath := joinPaths(rootDir, r.Path)
+	if !isSubpath {
+		return fmt.Errorf("invalid path value for operation 'Move': %s", path)
+	}
+
+	target, isSubpath := joinPaths(rootDir, r.Target)
+	if !isSubpath {
+		return fmt.Errorf("invalid target value for operation 'Move': %s", target)
+	}
+
+	err := os.Rename(path, target)
+
+	if os.IsNotExist(err) && r.FailOnMissing {
+		// is not found and should be reported
+		return err
+	}
+
+	if err != nil && !os.IsNotExist(err) {
+		// report others
+		return err
+	}
+
+	return nil
+}
+
+// MoveFile creates a MoveFileStep
+func MoveFile(path, target string, failOnMissing bool) *MoveFileStep {
+	return &MoveFileStep{
+		Path:          path,
+		Target:        target,
+		FailOnMissing: failOnMissing,
+	}
+}
+
+// joinPaths joins paths and returns true if path is subpath of rootDir
+func joinPaths(rootDir, path string) (string, bool) {
+	if !filepath.IsAbs(path) {
+		path = filepath.Join(rootDir, path)
+	}
+
+	absRoot := filepath.Clean(filepath.FromSlash(rootDir))
+	absPath := filepath.Clean(filepath.FromSlash(path))
+
+	// path on windows are case insensitive
+	if !isFsCaseSensitive(rootDir) {
+		absRoot = strings.ToLower(absRoot)
+		absPath = strings.ToLower(absPath)
+	}
+
+	return absPath, strings.HasPrefix(absPath, absRoot)
+}
+
+func isFsCaseSensitive(rootDir string) bool {
+	defaultCaseSens := runtime.GOOS != "windows" && runtime.GOOS != "darwin"
+
+	dir := filepath.Dir(rootDir)
+	base := filepath.Base(rootDir)
+	// if rootdir not exist create it
+	if _, err := os.Stat(rootDir); os.IsNotExist(err) {
+		os.MkdirAll(rootDir, 0775)
+		defer os.RemoveAll(rootDir)
+	}
+
+	lowDir := filepath.Join(base, strings.ToLower(dir))
+	upDir := filepath.Join(base, strings.ToUpper(dir))
+
+	if _, err := os.Stat(rootDir); err != nil {
+		return defaultCaseSens
+	}
+
+	// check lower/upper dir
+	if _, lowErr := os.Stat(lowDir); os.IsNotExist(lowErr) {
+		return true
+	}
+	if _, upErr := os.Stat(upDir); os.IsNotExist(upErr) {
+		return true
+	}
+
+	return defaultCaseSens
+}

x-pack/agent/pkg/agent/transpiler/steps_test.go

@@ -0,0 +1,66 @@
+// Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+// or more contributor license agreements. Licensed under the Elastic License;
+// you may not use this file except in compliance with the Elastic License.
+
+package transpiler
+
+import (
+	"fmt"
+	"runtime"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestIsSubpath(t *testing.T) {
+	testCases := map[string][]struct {
+		root       string
+		path       string
+		resultPath string
+		isSubpath  bool
+	}{
+		"linux": {
+			{"/", "a", "/a", true},
+			{"/a", "b", "/a/b", true},
+			{"/a", "b/c", "/a/b/c", true},
+			{"/a/b", "/a/c", "/a/c", false},
+			{"/a/b", "/a/b/../c", "/a/c", false},
+			{"/a/b", "../c", "/a/c", false},
+			{"/a", "/a/b/c", "/a/b/c", true},
+			{"/a", "/A/b/c", "/A/b/c", false},
+		},
+		"darwin": {
+			{"/", "a", "/a", true},
+			{"/a", "b", "/a/b", true},
+			{"/a", "b/c", "/a/b/c", true},
+			{"/a/b", "/a/c", "/a/c", false},
+			{"/a/b", "/a/b/../c", "/a/c", false},
+			{"/a/b", "../c", "/a/c", false},
+			{"/a", "/a/b/c", "/a/b/c", true},
+			{"/a", "/A/b/c", "/a/b/c", true},
+		},
+		"windows": {
+			{"/", "a", "\\a", true},
+			{"/a", "b", "\\a\\b", true},
+			{"/a", "b/c", "\\a\\b\\c", true},
+			{"/a/b", "/a/c", "\\a\\c", false},
+			{"/a/b", "/a/b/../c", "\\a\\c", false},
+			{"/a/b", "../c", "\\a\\c", false},
+			{"/a", "/a/b/c", "\\a\\b\\c", true},
+			{"/a", "/A/b/c", "\\a\\b\\c", true},
+		},
+	}
+
+	osSpecificTests, found := testCases[runtime.GOOS]
+	if !found {
+		return
+	}
+
+	for _, test := range osSpecificTests {
+		t.Run(fmt.Sprintf("[%s]'%s-%s'", runtime.GOOS, test.root, test.path), func(t *testing.T) {
+			newPath, result := joinPaths(test.root, test.path)
+			assert.Equal(t, test.resultPath, newPath)
+			assert.Equal(t, test.isSubpath, result)
+		})
+	}
+}