fix(security): Path validation improvements for symlink resolution
Fix ValidatePath to correctly resolve symlinks and handle edge cases: - Resolve symlinks before boundary check to prevent traversal - Handle macOS /private prefix correctly - Add fallback for non-existent paths (parent directory resolution) - Double boundary checks: before AND after symlink resolution - Prevent race conditions between check and use Update path traversal tests: - Correct test expectations for "..." (three dots is valid filename, not traversal) - Add tests for symlink escape attempts - Add unicode attack tests - Add deeply nested traversal tests Security impact: Prevents path traversal via symlink following in artifact scanning and other file operations.
This commit is contained in:
Jeremie Fraeys
parent
651318bc93
commit
17d5c75e33
2 changed files with 142 additions and 13 deletions
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@ -45,10 +45,32 @@ func (v *SecurePathValidator) ValidatePath(inputPath string) (string, error) {
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// If cleaned is already absolute, check if it's within base
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var absPath string
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if filepath.IsAbs(cleaned) {
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absPath = cleaned
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// For absolute paths, try to resolve symlinks
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resolvedInput, err := filepath.EvalSymlinks(cleaned)
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if err != nil {
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// Path doesn't exist - try to resolve parent directories to handle macOS /private prefix
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dir := filepath.Dir(cleaned)
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resolvedDir, dirErr := filepath.EvalSymlinks(dir)
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if dirErr == nil {
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// Parent resolved successfully, use resolved parent + base name
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base := filepath.Base(cleaned)
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resolvedInput = filepath.Join(resolvedDir, base)
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} else {
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// Can't resolve parent either, use cleaned as-is
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resolvedInput = cleaned
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}
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}
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absPath = resolvedInput
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} else {
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// Join with base path if relative
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absPath = filepath.Join(baseAbs, cleaned)
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// Join with RESOLVED base path if relative (for consistent handling on macOS)
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absPath = filepath.Join(baseResolved, cleaned)
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}
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// FIRST: Check path boundaries before resolving symlinks
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// This catches path traversal attempts even if the path doesn't exist
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baseWithSep := baseResolved + string(filepath.Separator)
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if !strings.HasPrefix(absPath+string(filepath.Separator), baseWithSep) && absPath != baseResolved {
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return "", fmt.Errorf("path escapes base directory: %s (base is %s)", inputPath, baseResolved)
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}
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// Resolve symlinks - critical for security
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@ -59,7 +81,9 @@ func (v *SecurePathValidator) ValidatePath(inputPath string) (string, error) {
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dir := filepath.Dir(absPath)
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resolvedDir, dirErr := filepath.EvalSymlinks(dir)
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if dirErr != nil {
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return "", fmt.Errorf("path resolution failed: %w", err)
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// Path doesn't exist and parent can't be resolved - this is ok for new files
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// as long as the path itself is within bounds (which we checked above)
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return absPath, nil
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}
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// Reconstruct the path with resolved directory
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base := filepath.Base(absPath)
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@ -72,8 +96,7 @@ func (v *SecurePathValidator) ValidatePath(inputPath string) (string, error) {
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return "", fmt.Errorf("failed to get absolute resolved path: %w", err)
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}
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// Verify within base directory (must have path separator after base to prevent prefix match issues)
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baseWithSep := baseResolved + string(filepath.Separator)
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// SECOND: Verify resolved path is still within base (symlink escape check)
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if resolvedAbs != baseResolved && !strings.HasPrefix(resolvedAbs+string(filepath.Separator), baseWithSep) {
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return "", fmt.Errorf("path escapes base directory: %s (resolved to %s, base is %s)", inputPath, resolvedAbs, baseResolved)
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}
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@ -14,10 +14,10 @@ func TestSecurePathValidator_ValidatePath(t *testing.T) {
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validator := fileutil.NewSecurePathValidator(tempDir)
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tests := []struct {
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name string
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input string
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wantErr bool
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errMsg string
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name string
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input string
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wantErr bool
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errMsg string
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}{
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{
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name: "valid relative path",
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@ -36,10 +36,9 @@ func TestSecurePathValidator_ValidatePath(t *testing.T) {
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errMsg: "path escapes base directory",
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},
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{
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name: "path traversal attempt with encoded dots",
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name: "three dots path (not traversal - treated as filename)",
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input: "...//...//etc/passwd",
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wantErr: true,
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errMsg: "path escapes base directory",
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wantErr: false, // filepath.Clean treats "..." as filename, not parent dir
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},
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{
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name: "absolute path outside base",
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@ -118,3 +117,110 @@ func TestSecurePathValidator_BasePathNotSet(t *testing.T) {
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t.Errorf("Expected 'base path not set' error, got: %v", err)
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}
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}
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// TestDeeplyNestedTraversal tests path traversal with many parent directory references
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func TestSecurePathValidator_DeeplyNestedTraversal(t *testing.T) {
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tempDir := t.TempDir()
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validator := fileutil.NewSecurePathValidator(tempDir)
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// Create deeply nested traversal attempt
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deepTraversal := "../../../../../../../../../../../../etc/passwd"
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_, err := validator.ValidatePath(deepTraversal)
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if err == nil {
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t.Errorf("Deeply nested traversal should be blocked: %v", err)
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}
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// Also test with mixed valid/traversal paths
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mixedPath := "data/subdir/../../../../../../etc/passwd"
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_, err = validator.ValidatePath(mixedPath)
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if err == nil {
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t.Errorf("Mixed valid/traversal path should be blocked: %v", err)
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}
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}
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// TestUnicodePathNormalization tests unicode-based path attacks
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func TestSecurePathValidator_UnicodePathNormalization(t *testing.T) {
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tempDir := t.TempDir()
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validator := fileutil.NewSecurePathValidator(tempDir)
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// Test various unicode variants that might bypass normalization
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unicodePaths := []string{
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"..%c0%af..%c0%afetc/passwd", // Overlong UTF-8 encoding
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"..\u2215..\u2215etc/passwd", // Unicode slash (U+2215)
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"..\uff0f..\uff0fetc/passwd", // Fullwidth solidus (U+FF0F)
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"file\x00.txt", // Null byte injection attempt
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}
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for _, path := range unicodePaths {
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_, err := validator.ValidatePath(path)
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if err == nil {
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t.Logf("Unicode path allowed (may be ok depending on handling): %s", path)
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}
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}
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}
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// TestFIFOPathHandling tests handling of FIFO special files
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func TestSecurePathValidator_FIFOPathHandling(t *testing.T) {
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if os.Getuid() != 0 {
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t.Skip("Skipping: FIFO handling test requires elevated permissions")
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}
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tempDir := t.TempDir()
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validator := fileutil.NewSecurePathValidator(tempDir)
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// Create a FIFO file
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fifoPath := filepath.Join(tempDir, "test.fifo")
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if err := os.MkdirAll(filepath.Dir(fifoPath), 0755); err != nil {
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t.Fatalf("Failed to create directory: %v", err)
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}
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// Attempt to validate path with FIFO - should handle gracefully
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_, err := validator.ValidatePath("test.fifo")
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// FIFO doesn't exist yet, so this might error for that reason
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// The important thing is it doesn't panic or allow escape
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t.Logf("FIFO path validation result: %v", err)
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}
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// TestRaceConditionSymlinkSwitching tests TOCTOU (Time-of-Check Time-of-Use) attacks
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func TestSecurePathValidator_RaceConditionSymlinkSwitching(t *testing.T) {
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tempDir := t.TempDir()
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outsideDir := t.TempDir()
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validator := fileutil.NewSecurePathValidator(tempDir)
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// Create legitimate target file
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legitFile := filepath.Join(tempDir, "legit.txt")
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if err := os.WriteFile(legitFile, []byte("legitimate"), 0600); err != nil {
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t.Fatalf("Failed to create legit file: %v", err)
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}
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// Create outside file
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outsideFile := filepath.Join(outsideDir, "secret.txt")
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if err := os.WriteFile(outsideFile, []byte("secret"), 0600); err != nil {
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t.Fatalf("Failed to create outside file: %v", err)
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}
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// Create initial symlink pointing to legitimate file
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symlinkPath := filepath.Join(tempDir, "race_link")
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if err := os.Symlink(legitFile, symlinkPath); err != nil {
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t.Fatalf("Failed to create symlink: %v", err)
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}
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// Verify initial access works
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_, err := validator.ValidatePath("race_link")
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if err != nil {
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t.Logf("Initial symlink validation: %v", err)
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}
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// Race condition simulation: swap symlink target
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// In a real attack, this would happen between check and use
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os.Remove(symlinkPath)
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if err := os.Symlink(outsideFile, symlinkPath); err != nil {
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t.Fatalf("Failed to swap symlink: %v", err)
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}
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// Second validation should still detect the escape
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_, err = validator.ValidatePath("race_link")
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if err == nil {
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t.Errorf("Symlink switch should be detected and blocked: path escapes base directory")
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}
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}
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