track Mac installations on Posthog

Nos/Extensions/Bundle+Current.swift

@@ -1,4 +1,5 @@
 import Foundation
+import Security
 
 private class CurrentBundle {}
 
@@ -33,16 +34,63 @@ extension Bundle {
     /// Checks the app's receipt URL to determine if it contains the TestFlight-specific
     /// "sandboxReceipt" identifier.
     /// - Returns: `true` if the app was installed through TestFlight, `false` otherwise.
-    private var isTestFlight: Bool {
+    private var isIosTestFlight: Bool {
         Bundle.main.appStoreReceiptURL?.lastPathComponent == "sandboxReceipt"
     }
 
+    /// Returns whether the bundle was signed for TestFlight beta distribution by checking
+    /// the existence of a specific extension (marker OID) on the code signing certificate.
+    ///
+    /// This routine is inspired by the source code from ProcInfo, the underlying library
+    /// of the WhatsYourSign code signature checking tool developed by Objective-See. Initially,
+    /// it checked the common name but was changed to an extension check to make it more
+    /// future-proof.
+    ///
+    /// For more information, see the following references:
+    /// - https://github.com/objective-see/ProcInfo/blob/master/procInfo/Signing.m#L184-L247
+    /// - https://gist.github.com/lukaskubanek/cbfcab29c0c93e0e9e0a16ab09586996#gistcomment-3993808
+    private var isMacTestFlight: Bool {
+    #if os(macOS)
+        var status = noErr
+
+        var code: SecStaticCode?
+        status = SecStaticCodeCreateWithPath(bundleURL as CFURL, [], &code)
+
+        guard status == noErr, let code = code else { return false }
+
+        var requirement: SecRequirement?
+        status = SecRequirementCreateWithString(
+            "anchor apple generic and certificate leaf[field.1.2.840.113635.100.6.1.25.1]" as CFString,
+            [], // default
+            &requirement
+        )
+
+        guard status == noErr, let requirement = requirement else { return false }
+
+        status = SecStaticCodeCheckValidity(
+            code,
+            [], // default
+            requirement
+        )
+
+        return status == errSecSuccess
+    #else
+        return false
+    #endif
+    }
+
     /// Returns the app's installation source: debug, TestFlight, or App Store.
     var installationSource: InstallationSource {
     #if DEBUG
         return .debug
     #else
-        return isTestFlight ? .testFlight : .appStore
+        #if os(iOS)
+            return isIosTestFlight ? .testFlight : .appStore
+        #elseif os(macOS)
+            return isMacTestFlight ? .testFlight : .appStore
+        #else
+            return .debug
+        #endif
     #endif
     }
 }