fix: handle macOS /tmp symlink in sandbox allowWrite paths (#23)

Author: jy-tan

internal/sandbox/macos.go

@@ -84,6 +84,38 @@ func getAncestorDirectories(pathStr string) []string {
 	return ancestors
 }
 
+// expandMacOSTmpPaths mirrors /tmp paths to /private/tmp equivalents and vice versa.
+// On macOS, /tmp is a symlink to /private/tmp, and symlink resolution can fail if paths
+// don't exist yet. Adding both variants ensures sandbox rules match kernel-resolved paths.
+func expandMacOSTmpPaths(paths []string) []string {
+	seen := make(map[string]bool)
+	for _, p := range paths {
+		seen[p] = true
+	}
+
+	var additions []string
+	for _, p := range paths {
+		var mirror string
+		switch {
+		case p == "/tmp":
+			mirror = "/private/tmp"
+		case p == "/private/tmp":
+			mirror = "/tmp"
+		case strings.HasPrefix(p, "/tmp/"):
+			mirror = "/private" + p
+		case strings.HasPrefix(p, "/private/tmp/"):
+			mirror = strings.TrimPrefix(p, "/private")
+		}
+
+		if mirror != "" && !seen[mirror] {
+			seen[mirror] = true
+			additions = append(additions, mirror)
+		}
+	}
+
+	return append(paths, additions...)
+}
+
 // getTmpdirParent gets the TMPDIR parent if it matches macOS pattern.
 func getTmpdirParent() []string {
 	tmpdir := os.Getenv("TMPDIR")
@@ -505,6 +537,9 @@ func WrapCommandMacOS(cfg *config.Config, command string, httpPort, socksPort in
 	// Build allow paths: default + configured
 	allowPaths := append(GetDefaultWritePaths(), cfg.Filesystem.AllowWrite...)
 
+	// Expand /tmp <-> /private/tmp for macOS symlink compatibility
+	allowPaths = expandMacOSTmpPaths(allowPaths)
+
 	// Enable local binding if ports are exposed or if explicitly configured
 	allowLocalBinding := cfg.Network.AllowLocalBinding || len(exposedPorts) > 0
 

internal/sandbox/macos_test.go

@@ -176,3 +176,70 @@ func TestMacOS_ProfileNetworkSection(t *testing.T) {
 		})
 	}
 }
+
+// TestExpandMacOSTmpPaths verifies that /tmp and /private/tmp paths are properly mirrored.
+func TestExpandMacOSTmpPaths(t *testing.T) {
+	tests := []struct {
+		name  string
+		input []string
+		want  []string
+	}{
+		{
+			name:  "mirrors /tmp to /private/tmp",
+			input: []string{".", "/tmp"},
+			want:  []string{".", "/tmp", "/private/tmp"},
+		},
+		{
+			name:  "mirrors /private/tmp to /tmp",
+			input: []string{".", "/private/tmp"},
+			want:  []string{".", "/private/tmp", "/tmp"},
+		},
+		{
+			name:  "no change when both present",
+			input: []string{".", "/tmp", "/private/tmp"},
+			want:  []string{".", "/tmp", "/private/tmp"},
+		},
+		{
+			name:  "no change when neither present",
+			input: []string{".", "~/.cache"},
+			want:  []string{".", "~/.cache"},
+		},
+		{
+			name:  "mirrors /tmp/fence to /private/tmp/fence",
+			input: []string{".", "/tmp/fence"},
+			want:  []string{".", "/tmp/fence", "/private/tmp/fence"},
+		},
+		{
+			name:  "mirrors /private/tmp/fence to /tmp/fence",
+			input: []string{".", "/private/tmp/fence"},
+			want:  []string{".", "/private/tmp/fence", "/tmp/fence"},
+		},
+		{
+			name:  "mirrors nested subdirectory",
+			input: []string{".", "/tmp/foo/bar"},
+			want:  []string{".", "/tmp/foo/bar", "/private/tmp/foo/bar"},
+		},
+		{
+			name:  "no duplicate when mirror already present",
+			input: []string{".", "/tmp/fence", "/private/tmp/fence"},
+			want:  []string{".", "/tmp/fence", "/private/tmp/fence"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := expandMacOSTmpPaths(tt.input)
+
+			if len(got) != len(tt.want) {
+				t.Errorf("expandMacOSTmpPaths() = %v, want %v", got, tt.want)
+				return
+			}
+
+			for i, v := range got {
+				if v != tt.want[i] {
+					t.Errorf("expandMacOSTmpPaths()[%d] = %v, want %v", i, v, tt.want[i])
+				}
+			}
+		})
+	}
+}