Convert script to Swift Package Manager library (#5)

* Convert to Swift Package Manager module

* Update Makefile to use SPM build

This also avoids the incredibly cursed SDK parsing

* Switch from a Swift version check to a module import check

The check for the Swift 6.0 compiler was trying to do the same thing
(ensure that the 15.0 SDK or newer was in use before compiling code that
would error on earlier SDKs), but there were niche situations where it
would not work.

Thanks to <https://marcoeidinger.github.io/appleframeworks/>, I have
found a framework (CoreHID) that only exists in the 15.0 SDK or newer,
so I have switched to checking if that module can be imported.

* Use Swift's ability to create a universal binary

* Restore legacy build in Makefile

* fix makefile

---------

Co-authored-by: Logicer <[email protected]>

.gitignore

@@ -4,3 +4,4 @@
 *.swp
 *.swo
 ._*
+/.build

Makefile

@@ -2,25 +2,24 @@ VERSION = $(shell cat VERSION)
 LIBRARY_PREFIX = pam_watchid
 LIBRARY_NAME = $(LIBRARY_PREFIX).so
 DESTINATION = /usr/local/lib/pam
-TARGET = apple-darwin$(shell uname -r)
+TARGET = apple-macosx10.15
 PAM_FILE_BASE = /etc/pam.d/sudo
 PAM_TEXT = auth sufficient $(LIBRARY_NAME)
 PAM_TID_TEXT = auth       sufficient     pam_tid.so
 
-# Determine if the macOS Sequoia SDK or later is available.
-DEFINES =
-# Due to the different ways in which the CLT and Xcode structure their SDK paths, one of the following will always be an empty string depending on what is configured by xcode-select. 
-CLT_SDK_MAJOR_VER = $(shell xcrun --sdk macosx --show-sdk-path | xargs readlink -f | xargs basename | sed 's/MacOSX//' | cut -d. -f1)
-XCODE_SDK_MAJOR_VER = $(shell xcrun --sdk macosx --show-sdk-path | xargs basename | sed 's/MacOSX//' | cut -d. -f1)
-SDK_REQUIRED_MAJOR_VER = 15
-ifeq "$(SDK_REQUIRED_MAJOR_VER)" "$(word 1, $(sort $(SDK_REQUIRED_MAJOR_VER) $(XCODE_SDK_MAJOR_VER) $(CLT_SDK_MAJOR_VER)))"
-	DEFINES += -DSEQUOIASDK
-endif
-
 all:
-	swiftc watchid-pam-extension.swift $(DEFINES) -o $(LIBRARY_PREFIX)_x86_64.so -target x86_64-$(TARGET) -emit-library
-	swiftc watchid-pam-extension.swift $(DEFINES) -o $(LIBRARY_PREFIX)_arm64.so -target arm64-$(TARGET) -emit-library
+ifeq ($(shell [[ '$(shell xcode-select -p)' == '/Library/Developer/CommandLineTools' ]] && echo true),true)
+# Legacy build
+# For CLT due to poor support for building swift packages.
+# Swift packages do work in macOS Sonoma and later with the CLT, but are an order of magnitude slower than Xcode. 
+	swiftc Sources/pam-watchid/pam_watchid.swift -o $(LIBRARY_PREFIX)_x86_64.so -target x86_64-$(TARGET) -emit-library
+	swiftc Sources/pam-watchid/pam_watchid.swift -o $(LIBRARY_PREFIX)_arm64.so -target arm64-$(TARGET) -emit-library
 	lipo -create $(LIBRARY_PREFIX)_arm64.so $(LIBRARY_PREFIX)_x86_64.so -output $(LIBRARY_NAME)
+else
+# Swift Package Manager build
+	swift build -c release --arch x86_64 --arch arm64
+	mv .build/apple/Products/Release/libpam-watchid.dylib $(LIBRARY_NAME)
+endif
 
 install: all
 	sudo mkdir -p $(DESTINATION)

Package.swift

@@ -0,0 +1,22 @@
+// swift-tools-version:5.1
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "pam-watchid",
+    platforms: [.macOS(.v10_15)],
+    products: [
+        // Products define the executables and libraries a package produces, making them visible to other packages.
+        .library(
+            name: "pam-watchid",
+            type: .dynamic,
+            targets: ["pam-watchid"]),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package, defining a module or a test suite.
+        // Targets can depend on other targets in this package and products from dependencies.
+        .target(
+            name: "pam-watchid"),
+    ]
+)

watchid-pam-extension.swift → Sources/pam-watchid/pam_watchid.swift

@@ -80,7 +80,7 @@ private func parseArguments(argc: Int, argv: vchar) -> [String: String] {
 
 private extension LAPolicy {
     static var deviceOwnerAuthenticationIgnoringUserID: LAPolicy {
-#if SEQUOIASDK
+#if canImport(CoreHID) // Check for the 15.0 SDK
         if #available(macOS 15, *) {
             return .deviceOwnerAuthenticationWithBiometricsOrCompanion
         } else {