Add command to show details about a signed object

docs/index.html

@@ -131,6 +131,7 @@ <h3 id="cli">Command Line Tool</h3>
   <li><a href="#timestamp-options">timestamp</a></li>
   <li><a href="#extract-options">extract</a></li>
   <li>remove</li>
+  <li><a href="#show">show</a></li>
   <li><a href="#tag-options">tag</a></li>
 </ul>
 
@@ -368,6 +369,27 @@ <h4 id="extract-options">extract</h4>
 
 <br>
 
+<h4 id="show">Show signature</h4>
+
+<p>To check whether a file has been signed and with which certificate, use the show command to list details about any signature present on the file.</p>
+
+<pre>
+  jsign show foo.exe
+  Signature 0
+  Digest Algorithm:   SHA256
+  Digest Value:       c481bb3892d066ffacba0650adaa4c252580b776b1dd6026cf4a8bea6c813939
+  Is Timestamped?     false
+  Certificate
+    Subject:          CN=net.jsign.signing-cert
+    Issuer:           CN=net.jsign.issuing-cert
+    Not Before:       Fri Dec 03 14:34:46 CST 2021
+    Not After:        Wed May 24 14:34:46 CST 2119
+    Expired:          false
+    Serial:           148957645726085760686199624248870688956
+</pre>
+
+<br>
+
 <h4 id="tag-options">tag</h4>
 
 <dl>
@@ -1040,7 +1062,6 @@ <h3 id="github-actions">GitHub Actions</h3>
                                   ${{ github.workspace }}/dist/application.exe
 </pre>
 
-
 <h3 id="api">API</h3>
 
 <p>Jsign also provides a simple API for signing files and can be embedded in another application.</p>

jsign-cli/src/main/java/net/jsign/JsignCLI.java

@@ -147,6 +147,10 @@ private Map<String, Options> getOptions() {
 
         map.put("remove", options);
 
+        options = new Options();
+
+        map.put("show", options);
+
         options = new Options();
         options.addOption(Option.builder().hasArg().longOpt(PARAM_VALUE).argName("VALUE").desc("The value of the unsigned attribute").build());
 

jsign-core/src/main/java/net/jsign/SignerHelper.java

@@ -333,6 +333,9 @@ public void execute(File file) throws SignerException {
             case "remove":
                 remove(file);
                 break;
+            case "show":
+                show(file);
+                break;
             case "tag":
                 tag(file);
                 break;
@@ -496,6 +499,32 @@ private void attach(Signable signable, File detachedSignature) throws IOExceptio
         // todo warn if the hashes don't match
     }
 
+    private void printSignatures(Signable signable) throws IOException {
+        List<CMSSignedData> signatures = signable.getSignatures();
+        for (int i = 0; i < signatures.size(); i++) {
+            CMSSignedData signature = signatures.get(i);
+            SignerInformation signerInformation = signature.getSignerInfos().iterator().next();
+
+            String digestAlgorithmName = new DefaultAlgorithmNameFinder().getAlgorithmName(signerInformation.getDigestAlgorithmID());
+            SignerId signerId = signerInformation.getSID();
+            X509CertificateHolder cert = (X509CertificateHolder) signature.getCertificates().getMatches(signerId).iterator().next();
+
+            byte[] digest = signable.computeDigest(DigestAlgorithm.of(signerInformation.getDigestAlgorithmID().getAlgorithm()));
+
+            System.out.println("Signature " + i);
+            System.out.println("  Digest Algorithm:   " + digestAlgorithmName);
+            System.out.println("  Digest Value:       " + Hex.toHexString(digest));
+            System.out.println("  Is Timestamped?     " + SignatureUtils.isTimestamped(signature));
+            System.out.println("  Certificate");
+            System.out.println("    Subject:          " + cert.getSubject());
+            System.out.println("    Issuer:           " + cert.getIssuer());
+            System.out.println("    Not Before:       " + cert.getNotBefore());
+            System.out.println("    Not After:        " + cert.getNotAfter());
+            System.out.println("    Expired:          " + cert.getNotAfter().before(new Date()));
+            System.out.println("    Serial:           " + cert.getSerialNumber());
+        }
+    }
+
     private void detach(Signable signable, File detachedSignature) throws IOException {
         List<CMSSignedData> signatures = signable.getSignatures();
 
@@ -576,6 +605,20 @@ private void remove(File file) throws SignerException {
         }
     }
 
+    private void show(File file) throws SignerException {
+        if (!file.exists()) {
+            throw new SignerException("Couldn't find " + file);
+        }
+
+        try (Signable signable = Signable.of(file)) {
+            printSignatures(signable);
+        } catch (UnsupportedOperationException | IllegalArgumentException e) {
+            throw new SignerException(e.getMessage(), e);
+        } catch (Exception e) {
+            throw new SignerException("Couldn't show the signatures of" + file, e);
+        }
+    }
+
     private void tag(File file) throws SignerException {
         if (!file.exists()) {
             throw new SignerException("Couldn't find " + file);