Support detached signature verification for tars and zips

src/SignCheck/Microsoft.SignCheck/Utils.cs

@@ -189,7 +189,7 @@ public static (int exitCode, string output, string error) RunBashCommand(string
         }
 
         /// <summary>
-        /// Download the Microsoft and Azure Linux public keys and import them into the keyring.
+        /// Download the Microsoft, Azure Linux, and .NET release public keys and import them into the keyring.
         /// </summary>
         public static void DownloadAndConfigurePublicKeys(string tempDir)
         {
@@ -198,7 +198,8 @@ public static void DownloadAndConfigurePublicKeys(string tempDir)
                 "https://packages.microsoft.com/keys/microsoft.asc", // Microsoft public key
                 "https://packages.microsoft.com/keys/microsoft-2025.asc", // Microsoft public key for distributions that do not allow SHA1
                 "https://packages.microsoft.com/keys/microsoft-rolling.asc", // Non-SHA1 Microsoft public keys for non-Azure Linux distributions
-                "https://raw.githubusercontent.com/microsoft/azurelinux/3.0/SPECS/azurelinux-repos/MICROSOFT-RPM-GPG-KEY" // Azure linux public key
+                "https://raw.githubusercontent.com/microsoft/azurelinux/3.0/SPECS/azurelinux-repos/MICROSOFT-RPM-GPG-KEY", // Azure linux public key
+                "https://dot.net/release-key-2023", // .NET release public key
             };
             foreach (string keyUrl in keyUrls)
             {

src/SignCheck/Microsoft.SignCheck/Verification/DebVerifier.cs

@@ -9,7 +9,7 @@
 
 namespace Microsoft.SignCheck.Verification
 {
-    public class DebVerifier : LinuxPackageVerifier
+    public class DebVerifier : PgpVerifier
     {
         public DebVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options) : base(log, exclusions, options, ".deb") { }
 

src/SignCheck/Microsoft.SignCheck/Verification/LinuxPackageVerifier.cs → src/SignCheck/Microsoft.SignCheck/Verification/PgpVerifier.cs

@@ -10,9 +10,12 @@
 
 namespace Microsoft.SignCheck.Verification
 {
-    public abstract class LinuxPackageVerifier : ArchiveVerifier
+    public abstract class PgpVerifier : ArchiveVerifier
     {
-        protected LinuxPackageVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options, string fileExtension) : base(log, exclusions, options, fileExtension) { }
+        protected PgpVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options, string fileExtension)
+            : base(log, exclusions, options, fileExtension)
+        {
+        }
 
         public override SignatureVerificationResult VerifySignature(string path, string parent, string virtualPath)
             => VerifySupportedFileType(path, parent, virtualPath);
@@ -21,16 +24,39 @@ public override SignatureVerificationResult VerifySignature(string path, string
         /// Returns the paths to the signature document and the signable content.
         /// Used to verify the signature of the package using gpg.
         /// </summary>
-        /// <param name="path"></param>
-        /// <param name="tempDir"></param>
-        /// <returns></returns>
         protected abstract (string signatureDocument, string signableContent) GetSignatureDocumentAndSignableContent(string path, string tempDir);
 
+        /// <summary>
+        /// Verifies the signature of a file using a detached .sig file.
+        /// If the .sig file exists, verifies as a supported file type; otherwise, as unsupported.
+        /// </summary>
+        protected SignatureVerificationResult VerifyDetachedSignature(string path, string parent, string virtualPath)
+        {
+            if (File.Exists(path + ".sig"))
+            {
+                return VerifySupportedFileType(path, parent, virtualPath);
+            }
+            return VerifyUnsupportedFileType(path, parent, virtualPath);
+        }
+
+        /// <summary>
+        /// Returns the paths to the detached signature document and the signable content.
+        /// For use by verifiers whose signatures are stored in a separate .sig file.
+        /// </summary>
+        protected static (string signatureDocument, string signableContent) GetDetachedSignatureDocumentAndSignableContent(string path, string tempDir)
+        {
+            string signature = $"{path}.sig";
+            string signatureDocument = Path.Combine(tempDir, Path.GetFileName(signature));
+            File.Copy(signature, signatureDocument, overwrite: true);
+
+            return (signatureDocument, path);
+        }
+
         protected override bool IsSigned(string path, SignatureVerificationResult svr)
         {
             if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
             {
-                throw new PlatformNotSupportedException("Linux package verification is not supported on Windows.");
+                throw new PlatformNotSupportedException("Pgp verification is not supported on Windows.");
             }
 
             string tempDir = Path.Combine(Path.GetTempPath(), Path.GetRandomFileName());

src/SignCheck/Microsoft.SignCheck/Verification/RpmVerifier.cs

@@ -11,7 +11,7 @@
 
 namespace Microsoft.SignCheck.Verification
 {
-    public class RpmVerifier : LinuxPackageVerifier
+    public class RpmVerifier : PgpVerifier
     {
         public RpmVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options) : base(log, exclusions, options, ".rpm") { }
 

src/SignCheck/Microsoft.SignCheck/Verification/TarVerifier.cs

@@ -10,18 +10,21 @@
 
 namespace Microsoft.SignCheck.Verification
 {
-    public class TarVerifier : ArchiveVerifier
+    public class TarVerifier : PgpVerifier
     {
         public TarVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options, string fileExtension) : base(log, exclusions, options, fileExtension)
         {
             if (fileExtension != ".tar" && fileExtension != ".gz" && fileExtension != ".tgz")
             {
-                throw new ArgumentException("fileExtension must be .tar or .gz");
+                throw new ArgumentException("fileExtension must be .tar, .gz, or .tgz");
             }
         }
 
         public override SignatureVerificationResult VerifySignature(string path, string parent, string virtualPath)
-            => VerifyUnsupportedFileType(path, parent, virtualPath);
+            => VerifyDetachedSignature(path, parent, virtualPath);
+
+        protected override (string signatureDocument, string signableContent) GetSignatureDocumentAndSignableContent(string path, string tempDir)
+            => GetDetachedSignatureDocumentAndSignableContent(path, tempDir);
 
         protected override IEnumerable<ArchiveEntry> ReadArchiveEntries(string archivePath)
         {

src/SignCheck/Microsoft.SignCheck/Verification/ZipVerifier.cs

@@ -8,15 +8,15 @@
 
 namespace Microsoft.SignCheck.Verification
 {
-    public class ZipVerifier : ArchiveVerifier
+    public class ZipVerifier : PgpVerifier
     {
-        public ZipVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options, string fileExtension = ".zip") : base(log, exclusions, options, fileExtension)
-        {
-
-        }
+        public ZipVerifier(Log log, Exclusions exclusions, SignatureVerificationOptions options, string fileExtension = ".zip") : base(log, exclusions, options, fileExtension) { }
 
         public override SignatureVerificationResult VerifySignature(string path, string parent, string virtualPath)
-            => VerifyUnsupportedFileType(path, parent, virtualPath);
+            => VerifyDetachedSignature(path, parent, virtualPath);
+
+        protected override (string signatureDocument, string signableContent) GetSignatureDocumentAndSignableContent(string path, string tempDir)
+            => GetDetachedSignatureDocumentAndSignableContent(path, tempDir);
 
         protected override IEnumerable<ArchiveEntry> ReadArchiveEntries(string archivePath)
         {