Fall back to system gpg utilities when unable to decode signature

src/js/crypto.js

@@ -249,6 +249,55 @@ function importPrivateKey() {
     }, ".asc");
 }
 
+/**
+ * Call the native system GPG to "decrypt" a PGP signature. This should work when the hacky "base64 decode and search for strings" method fails.
+ * @param {String} sigdata
+ * @param {Function} callback (string) message, (string) fingerprint, (bool) success
+ * @returns {undefined}
+ */
+function readSignatureExternally(sigdata, callback) {
+    const exec = require('child_process').exec;
+    const os = require('os');
+    const process = require('process');
+
+    const sigfilepath = getNewTempFilePath() + ".asc";
+    writeToFile(sigfilepath, sigdata);
+
+    var gpgexecutable = "gpg";
+    switch (os.platform()) {
+        case "win32":
+            // Most systems will have it here
+            gpgexecutable = '"C:\\Program Files (x86)\\gnupg\\bin\\gpg.exe"';
+            if (!fs.existsSync(gpgexecutable)) {
+                // Let's hope it's in %PATH%
+                gpgexecutable = "gpg.exe";
+            }
+            break;
+        case "linux":
+            break;
+        default:
+            break;
+    }
+
+    var command = gpgexecutable + " -vv --decrypt " + sigfilepath;
+    exec(command, function (error, stdout, stderr) {
+        console.log(stdout);
+        var msg = null;
+        if (stdout.length > 50) {
+            msg = stdout;
+        } else {
+            callback(null, null, false);
+        }
+
+        var keyid = null;
+        var keyidregex = /(keyid|RSA key) ([A-F0-9]+)/;
+        if (keyidregex.test(stderr)) {
+            keyid = stderr.match(keyidregex)[2];
+        }
+        callback(msg, keyid, true);
+    });
+}
+
 function calculateSHA256HashOfBuffer(buffer) {
     const hasha = require('hasha');
     var hashstr = hasha(Buffer.from(buffer), {algorithm: 'sha256'});

src/js/filesystem.js

@@ -94,6 +94,24 @@ function deleteFile(path) {
 }
 
 function getBasename(fullpath) {
-    var path = require("path");
+    const path = require("path");
     return path.basename(fullpath);
+}
+
+/**
+ * Get the path to a nonexistent, randomly-named temporary file.
+ * @returns {String}
+ */
+function getNewTempFilePath() {
+    const fs = require('fs');
+    const path = require("path");
+    const crypto = require('crypto');
+    const os = require('os');
+
+    const randomname = crypto.randomBytes(6).readUIntLE(0,6).toString(36);
+    var temppath = path.join(os.tmpdir(), "nwjs-app-");
+
+    var folder = fs.mkdtempSync(temppath);
+
+    return path.join(folder, randomname);
 }

src/js/pdf.js

@@ -83,8 +83,14 @@ function analyzeSignedPDF() {
                             var msg = window.atob(base64).split("START", 2)[1].split("END", 2)[0];
                             parseAndDisplaySignature(msg, pdfhash, false, null);
                         } catch (ex) {
+                            readSignatureExternally(sigdata, function (msg, keyprint, ok) {
+                                if (!ok) {
+                                    showAlert("Error: could not parse signature data.");
+                                    return;
+                                }
+                                parseAndDisplaySignature(msg, pdfhash, false, keyprint);
+                            });
                             console.error(ex);
-                            showAlert("Error: could not parse signature data.");
                         }
                     });
                 });
@@ -233,9 +239,14 @@ then run the analyze tool again to prove if it was changed since notarization.")
     }
 
     if (typeof fingerprint == "string") {
-        var fingerprintstart = fingerprint.substr(0, fingerprint.length - 16);
-        var fingerprintend = fingerprint.substr(-16);
-        $("#verifyModalDetailedInfoList").append('<li class="list-group-item"><i class="fas fa-fingerprint fa-fw"></i> Signature fingerprint: ' + fingerprintstart + '<b>' + fingerprintend + '</b></li>');
+        if (fingerprint.length > 16) {
+            var fingerprintstart = fingerprint.substr(0, fingerprint.length - 16);
+            var fingerprintend = fingerprint.substr(-16);
+        } else {
+            var fingerprintstart = "";
+            var fingerprintend = fingerprint;
+        }
+        $("#verifyModalDetailedInfoList").append('<li class="list-group-item"><i class="fas fa-fingerprint fa-fw"></i> Signature key ID: ' + fingerprintstart + '<b>' + fingerprintend + '</b></li>');
     }
     new bootstrap.Modal(document.getElementById('verifyModal')).show();
 }