Add verification helper.

- Reduce duplicate code.
- Small cleanups.
- Add note about deprecated OID alias.

Author: davidlehn

CHANGELOG.md

@@ -12,8 +12,9 @@ Forge ChangeLog
   links](https://github.com/digitalbazaar/forge/issues/825).
 
 ### Changed
-- [x509]: Reduce duplicate code with a helper function to create a signature
-  digest given an signature algorithm OID.
+- [x509]: Reduce duplicate code. Add helper function to create a signature
+  digest given an signature algorithm OID. Add helper function to verify
+  signatures.
 
 ## 1.1.0 - 2022-01-06
 

lib/x509.js

@@ -700,24 +700,19 @@ var _readSignatureParameters = function(oid, obj, fillDefaults) {
 var _createSignatureDigest = function(options) {
   switch(oids[options.signatureOid]) {
     case 'sha1WithRSAEncryption':
+    // depreacted alias
     case 'sha1WithRSASignature':
       return forge.md.sha1.create();
-      break;
     case 'md5WithRSAEncryption':
       return forge.md.md5.create();
-      break;
     case 'sha256WithRSAEncryption':
       return forge.md.sha256.create();
-      break;
     case 'sha384WithRSAEncryption':
       return forge.md.sha384.create();
-      break;
     case 'sha512WithRSAEncryption':
       return forge.md.sha512.create();
-      break;
     case 'RSASSA-PSS':
       return forge.md.sha256.create();
-      break;
     default:
       var error = new Error(
         'Could not compute ' + options.type + ' digest. ' +
@@ -727,6 +722,68 @@ var _createSignatureDigest = function(options) {
   }
 };
 
+/**
+ * Verify signature on certificate or CSR.
+ *
+ * @param options:
+ *   certificate the certificate or CSR to verify.
+ *   md the signature digest.
+ *   signature the signature
+ * @return a created md instance. throws if unknown oid.
+ */
+var _verifySignature = function(options) {
+  var cert = options.certificate;
+  var scheme;
+
+  switch(cert.signatureOid) {
+    case oids.sha1WithRSAEncryption:
+    // depreacted alias
+    case oids.sha1WithRSASignature:
+      /* use PKCS#1 v1.5 padding scheme */
+      break;
+    case oids['RSASSA-PSS']:
+      var hash, mgf;
+
+      /* initialize mgf */
+      hash = oids[cert.signatureParameters.mgf.hash.algorithmOid];
+      if(hash === undefined || forge.md[hash] === undefined) {
+        var error = new Error('Unsupported MGF hash function.');
+        error.oid = cert.signatureParameters.mgf.hash.algorithmOid;
+        error.name = hash;
+        throw error;
+      }
+
+      mgf = oids[cert.signatureParameters.mgf.algorithmOid];
+      if(mgf === undefined || forge.mgf[mgf] === undefined) {
+        var error = new Error('Unsupported MGF function.');
+        error.oid = cert.signatureParameters.mgf.algorithmOid;
+        error.name = mgf;
+        throw error;
+      }
+
+      mgf = forge.mgf[mgf].create(forge.md[hash].create());
+
+      /* initialize hash function */
+      hash = oids[cert.signatureParameters.hash.algorithmOid];
+      if(hash === undefined || forge.md[hash] === undefined) {
+        var error = new Error('Unsupported RSASSA-PSS hash function.');
+        error.oid = cert.signatureParameters.hash.algorithmOid;
+        error.name = hash;
+        throw error;
+      }
+
+      scheme = forge.pss.create(
+        forge.md[hash].create(), mgf, cert.signatureParameters.saltLength
+      );
+      break;
+  }
+
+  // verify signature on cert using public key
+  return cert.publicKey.verify(
+    options.md.digest().getBytes(), options.signature, scheme
+  );
+};
+
 /**
  * Converts an X.509 certificate from PEM format.
  *
@@ -1127,53 +1184,9 @@ pki.createCertificate = function() {
     }
 
     if(md !== null) {
-      var scheme;
-
-      switch(child.signatureOid) {
-        case oids.sha1WithRSAEncryption:
-        case oids.sha1WithRSASignature:
-          scheme = undefined; /* use PKCS#1 v1.5 padding scheme */
-          break;
-        case oids['RSASSA-PSS']:
-          var hash, mgf;
-
-          /* initialize mgf */
-          hash = oids[child.signatureParameters.mgf.hash.algorithmOid];
-          if(hash === undefined || forge.md[hash] === undefined) {
-            var error = new Error('Unsupported MGF hash function.');
-            error.oid = child.signatureParameters.mgf.hash.algorithmOid;
-            error.name = hash;
-            throw error;
-          }
-
-          mgf = oids[child.signatureParameters.mgf.algorithmOid];
-          if(mgf === undefined || forge.mgf[mgf] === undefined) {
-            var error = new Error('Unsupported MGF function.');
-            error.oid = child.signatureParameters.mgf.algorithmOid;
-            error.name = mgf;
-            throw error;
-          }
-
-          mgf = forge.mgf[mgf].create(forge.md[hash].create());
-
-          /* initialize hash function */
-          hash = oids[child.signatureParameters.hash.algorithmOid];
-          if(hash === undefined || forge.md[hash] === undefined) {
-            throw {
-              message: 'Unsupported RSASSA-PSS hash function.',
-              oid: child.signatureParameters.hash.algorithmOid,
-              name: hash
-            };
-          }
-
-          scheme = forge.pss.create(forge.md[hash].create(), mgf,
-            child.signatureParameters.saltLength);
-          break;
-      }
-
-      // verify signature on cert using public key
-      rval = cert.publicKey.verify(
-        md.digest().getBytes(), child.signature, scheme);
+      rval = _verifySignature({
+        certificate: cert, md: md, signature: child.signature
+      });
     }
 
     return rval;
@@ -1826,52 +1839,9 @@ pki.createCertificationRequest = function() {
     }
 
     if(md !== null) {
-      var scheme;
-
-      switch(csr.signatureOid) {
-        case oids.sha1WithRSAEncryption:
-        case oids.sha1WithRSASignature:
-          /* use PKCS#1 v1.5 padding scheme */
-          break;
-        case oids['RSASSA-PSS']:
-          var hash, mgf;
-
-          /* initialize mgf */
-          hash = oids[csr.signatureParameters.mgf.hash.algorithmOid];
-          if(hash === undefined || forge.md[hash] === undefined) {
-            var error = new Error('Unsupported MGF hash function.');
-            error.oid = csr.signatureParameters.mgf.hash.algorithmOid;
-            error.name = hash;
-            throw error;
-          }
-
-          mgf = oids[csr.signatureParameters.mgf.algorithmOid];
-          if(mgf === undefined || forge.mgf[mgf] === undefined) {
-            var error = new Error('Unsupported MGF function.');
-            error.oid = csr.signatureParameters.mgf.algorithmOid;
-            error.name = mgf;
-            throw error;
-          }
-
-          mgf = forge.mgf[mgf].create(forge.md[hash].create());
-
-          /* initialize hash function */
-          hash = oids[csr.signatureParameters.hash.algorithmOid];
-          if(hash === undefined || forge.md[hash] === undefined) {
-            var error = new Error('Unsupported RSASSA-PSS hash function.');
-            error.oid = csr.signatureParameters.hash.algorithmOid;
-            error.name = hash;
-            throw error;
-          }
-
-          scheme = forge.pss.create(forge.md[hash].create(), mgf,
-            csr.signatureParameters.saltLength);
-          break;
-      }
-
-      // verify signature on csr using its public key
-      rval = csr.publicKey.verify(
-        md.digest().getBytes(), csr.signature, scheme);
+      rval = _verifySignature({
+        certificate: csr, md: md, signature: csr.signature
+      });
     }
 
     return rval;