[Agent] Handle abs paths on windows correctly

x-pack/elastic-agent/CHANGELOG.asciidoc

@@ -16,6 +16,7 @@
 - Fixed tests on windows {pull}16922[16922]
 - Fixed installers for SNAPSHOTs and windows {pull}17077[17077]
 - Fixed merge of config {pull}17399[17399]
+- Handle abs paths on windows correctly {pull}17461[17461]
 
 ==== New features
 

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

@@ -128,12 +128,16 @@ type DeleteFileStep struct {
 
 // Execute executes delete file step.
 func (r *DeleteFileStep) Execute(rootDir string) error {
-	path, isSubpath := joinPaths(rootDir, r.Path)
+	path, isSubpath, err := joinPaths(rootDir, r.Path)
+	if err != nil {
+		return err
+	}
+
 	if !isSubpath {
 		return fmt.Errorf("invalid path value for operation 'Delete': %s", path)
 	}
 
-	err := os.Remove(path)
+	err = os.Remove(path)
 
 	if os.IsNotExist(err) && r.FailOnMissing {
 		// is not found and should be reported
@@ -166,17 +170,25 @@ type MoveFileStep struct {
 
 // Execute executes move file step.
 func (r *MoveFileStep) Execute(rootDir string) error {
-	path, isSubpath := joinPaths(rootDir, r.Path)
+	path, isSubpath, err := joinPaths(rootDir, r.Path)
+	if err != nil {
+		return err
+	}
+
 	if !isSubpath {
 		return fmt.Errorf("invalid path value for operation 'Move': %s", path)
 	}
 
-	target, isSubpath := joinPaths(rootDir, r.Target)
+	target, isSubpath, err := joinPaths(rootDir, r.Target)
+	if err != nil {
+		return err
+	}
+
 	if !isSubpath {
 		return fmt.Errorf("invalid target value for operation 'Move': %s", target)
 	}
 
-	err := os.Rename(path, target)
+	err = os.Rename(path, target)
 
 	if os.IsNotExist(err) && r.FailOnMissing {
 		// is not found and should be reported
@@ -201,21 +213,36 @@ func MoveFile(path, target string, failOnMissing bool) *MoveFileStep {
 }
 
 // joinPaths joins paths and returns true if path is subpath of rootDir
-func joinPaths(rootDir, path string) (string, bool) {
+func joinPaths(rootDir, path string) (string, bool, error) {
+	rootDir = filepath.FromSlash(rootDir)
+	path = filepath.FromSlash(path)
+
+	if runtime.GOOS == "windows" {
+		// if is unix absolute fix to win absolute
+		if strings.HasPrefix(path, "\\") {
+			abs, err := filepath.Abs(rootDir) // get current volume
+			if err != nil {
+				return "", false, err
+			}
+			vol := filepath.VolumeName(abs)
+			path = filepath.Join(vol, path)
+		}
+	}
+
 	if !filepath.IsAbs(path) {
 		path = filepath.Join(rootDir, path)
 	}
 
-	absRoot := filepath.Clean(filepath.FromSlash(rootDir))
-	absPath := filepath.Clean(filepath.FromSlash(path))
+	absRoot := filepath.Clean(rootDir)
+	absPath := filepath.Clean(path)
 
 	// path on windows are case insensitive
 	if !isFsCaseSensitive(rootDir) {
 		absRoot = strings.ToLower(absRoot)
 		absPath = strings.ToLower(absPath)
 	}
 
-	return absPath, strings.HasPrefix(absPath, absRoot)
+	return absPath, strings.HasPrefix(absPath, absRoot), nil
 }
 
 func isFsCaseSensitive(rootDir string) bool {

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

@@ -41,18 +41,18 @@ func TestIsSubpath(t *testing.T) {
 			{"/a", "/a/b/c", "/a/b/c", true},
 			{"/a", "/A/b/c", "/a/b/c", true},
 		},
-		// (Windows issue) See issue:
-		//"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},
-		//},
+		"windows": {
+			{"c:/", "/a", "c:\\a", true},
+			{"c:/a", "b", "c:\\a\\b", true},
+			{"c:/a", "b/c", "c:\\a\\b\\c", true},
+			{"c:/a/b", "/a/c", "c:\\a\\c", false},
+			{"c:/a/b", "/a/b/../c", "c:\\a\\c", false},
+			{"c:/a/b", "../c", "c:\\a\\c", false},
+			{"c:/a", "/a/b/c", "c:\\a\\b\\c", true},
+			{"c:/a", "/A/b/c", "c:\\a\\b\\c", true},
+			{"c:/a", "c:/A/b/c", "c:\\a\\b\\c", true},
+			{"c:/a", "c:/b/c", "c:\\b\\c", false},
+		},
 	}
 
 	osSpecificTests, found := testCases[runtime.GOOS]
@@ -62,7 +62,8 @@ func TestIsSubpath(t *testing.T) {
 
 	for _, test := range osSpecificTests {
 		t.Run(fmt.Sprintf("[%s] root:'%s path: %s'", runtime.GOOS, test.root, test.path), func(t *testing.T) {
-			newPath, result := joinPaths(test.root, test.path)
+			newPath, result, err := joinPaths(test.root, test.path)
+			assert.NoError(t, err)
 			assert.Equal(t, test.resultPath, newPath)
 			assert.Equal(t, test.isSubpath, result)
 		})