vendor: import KillerPDF 1.7.5 source (GPL-3.0) as the base for MMD PDF

2026-08-27 06:58:22 +02:00
commit 532485a830
577 changed files with 149058 additions and 0 deletions
@@ -0,0 +1,62 @@
+using System;
+using System.Security.Cryptography.X509Certificates;
+using PdfSharp.Drawing;
+using PdfSharp.Pdf;
+using PdfSharp.Pdf.IO;
+using PdfSharp.Pdf.Signatures;
+
+namespace KillerPDF.Services.Signing
+{
+    /// <summary>
+    /// Cryptographic (PAdES / PKCS#7) PDF signing, isolated from the rest of the app. Everything else
+    /// in KillerPDF uses PdfSharpCore; this module uses PDFsharp 6.2 (the <c>PdfSharp.*</c> namespace),
+    /// and the two coexist without clashing. There are deliberately no WPF or Windows-only types here,
+    /// so the whole module ports to Avalonia / Linux / Mac unchanged.
+    ///
+    /// v1 milestone: an invisible-but-valid signature (Adobe still lists it in the Signatures panel),
+    /// SHA-256, no timestamp. The .NET Framework build of PDFsharp cannot timestamp; once the plumbing
+    /// is validated we swap the default signer for a Bouncy Castle IDigitalSigner to get portable
+    /// crypto plus timestamps/LTV. A visible signature appearance comes after that.
+    /// </summary>
+    internal sealed class PdfSigner
+    {
+        public sealed record SignInfo(string Reason, string Location, string Contact);
+
+        /// <summary>
+        /// Signs <paramref name="inputPath"/> with <paramref name="cert"/> and writes the signed copy
+        /// to <paramref name="outputPath"/>. Throws on failure.
+        /// </summary>
+        public void Sign(string inputPath, string outputPath, X509Certificate2 cert, SignInfo info)
+        {
+            if (cert is null) throw new ArgumentNullException(nameof(cert));
+            if (!cert.HasPrivateKey)
+                throw new InvalidOperationException(
+                    "The selected certificate has no private key, so it cannot sign.");
+
+            // Open the finalized PDF. (NOTE: confirm the exact open-mode enum on first build - PDFsharp
+            // 6.2 may want PdfReadAccuracy / a different overload here.)
+            using PdfDocument document = PdfReader.Open(inputPath, PdfDocumentOpenMode.Modify);
+
+            var options = new DigitalSignatureOptions
+            {
+                ContactInfo = info.Contact,
+                Location    = info.Location,
+                Reason      = info.Reason,
+                // Invisible for v1: a zero rectangle and no AppearanceHandler. If PDFsharp requires a
+                // non-null AppearanceHandler, that is the first thing to add (a minimal drawn field).
+                Rectangle   = new XRect(0, 0, 0, 0),
+            };
+
+            // Our own SignedCms-based signer: drives the cert's modern (CNG) key provider, so it
+            // works with cloud / token keys (Certum SimplySign) as well as software .pfx keys, where
+            // PdfSharpDefaultSigner throws "An internal error occurred". Same IDigitalSigner slot, so a
+            // Bouncy Castle variant can later swap in here for portability + timestamps.
+            var signer = new KillerCmsSigner(cert);
+
+            // Associates the signer + options with the document; the signature is produced on Save.
+            _ = DigitalSignatureHandler.ForDocument(document, signer, options);
+
+            document.Save(outputPath);
+        }
+    }
+}