Add support for ed25519 private keys in pkcs8 (#92)

Reviewed by: Brian Bennett
TritonDataCenter · Oct 19, 2023 · 8df0385 · 8df0385
1 parent 3e83664
commit 8df0385
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Showing 4 changed files with 42 additions and 21 deletions.
diff --git a/bin/sshpk-conv b/bin/sshpk-conv
@@ -91,12 +91,12 @@ if (require.main === module) {
 		console.error('sshpk-conv: converts between SSH key formats\n');
 		console.error(help);
 		console.error('\navailable key formats:');
-		console.error('	 - pem, pkcs1	  eg id_rsa');
-		console.error('	 - ssh		  eg id_rsa.pub');
-		console.error('	 - pkcs8	  format you want for openssl');
-		console.error('	 - openssh	  like output of ssh-keygen -o');
-		console.error('	 - rfc4253	  raw OpenSSH wire format');
-		console.error('	 - dnssec	  dnssec-keygen format');
+		console.error('  - pem, pkcs1     eg id_rsa');
+		console.error('  - ssh            eg id_rsa.pub');
+		console.error('  - pkcs8          format you want for openssl');
+		console.error('  - openssh        like output of ssh-keygen -o');
+		console.error('  - rfc4253        raw OpenSSH wire format');
+		console.error('  - dnssec         dnssec-keygen format');
 		console.error('  - putty          PuTTY ppk format');
 		console.error('\navailable fingerprint formats:');
 		console.error('  - hex            colon-separated hex for SSH');

diff --git a/lib/formats/pkcs8.js b/lib/formats/pkcs8.js
@@ -385,13 +385,17 @@ function readPkcs8EdDSAPrivate(der) {
 	var k = der.readString(asn1.Ber.OctetString, true);
 	k = utils.zeroPadToLength(k, 32);
 
-	var A;
-	if (der.peek() === asn1.Ber.BitString) {
-		A = utils.readBitString(der);
-		A = utils.zeroPadToLength(A, 32);
-	} else {
-		A = utils.calculateED25519Public(k);
+	var A, tag;
+	while ((tag = der.peek()) !== null) {
+		if (tag === (asn1.Ber.Context | 1)) {
+			A = utils.readBitString(der, tag);
+		} else {
+			der.readSequence(tag);
+			der._offset += der.length;
+		}
 	}
+	if (A === undefined)
+		A = utils.calculateED25519Public(k);
 
 	var key = {
 		type: 'ed25519',
@@ -435,8 +439,11 @@ function writePkcs8(der, key) {
 	der.startSequence();
 
 	if (PrivateKey.isPrivateKey(key)) {
-		var sillyInt = Buffer.from([0]);
-		der.writeBuffer(sillyInt, asn1.Ber.Integer);
+		var version = 0;
+		if (key.type === 'ed25519')
+			version = 1;
+		var vbuf = Buffer.from([version]);
+		der.writeBuffer(vbuf, asn1.Ber.Integer);
 	}
 
 	der.startSequence();
@@ -465,9 +472,9 @@ function writePkcs8(der, key) {
 	case 'ed25519':
 		der.writeOID('1.3.101.112');
 		if (PrivateKey.isPrivateKey(key))
-			throw (new Error('Ed25519 private keys in pkcs8 ' +
-			    'format are not supported'));
-		writePkcs8EdDSAPublic(key, der);
+			writePkcs8EdDSAPrivate(key, der);
+		else
+			writePkcs8EdDSAPublic(key, der);
 		break;
 	default:
 		throw (new Error('Unsupported key type: ' + key.type));
@@ -624,8 +631,13 @@ function writePkcs8EdDSAPublic(key, der) {
 function writePkcs8EdDSAPrivate(key, der) {
 	der.endSequence();
 
-	var k = utils.mpNormalize(key.part.k.data, true);
 	der.startSequence(asn1.Ber.OctetString);
+	var k = utils.mpNormalize(key.part.k.data);
+	/* RFCs call for storing exactly 32 bytes, so strip any leading zeros */
+	while (k.length > 32 && k[0] === 0x00)
+		k = k.slice(1);
 	der.writeBuffer(k, asn1.Ber.OctetString);
 	der.endSequence();
+
+	utils.writeBitString(der, key.part.A.data, asn1.Ber.Context | 1);
 }
diff --git a/package.json b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "sshpk",
-  "version": "1.17.0",
+  "version": "1.18.0",
   "description": "A library for finding and using SSH public keys",
   "main": "lib/index.js",
   "scripts": {
@@ -49,8 +49,7 @@
     "ecc-jsbn": "~0.1.1",
     "bcrypt-pbkdf": "^1.0.0"
   },
-  "optionalDependencies": {
-  },
+  "optionalDependencies": {},
   "devDependencies": {
     "tape": "^3.5.0",
     "benchmark": "^1.0.0",

diff --git a/test/private-key.js b/test/private-key.js
@@ -127,6 +127,16 @@ test('PrivateKey load ed25519 key (w/ public curdle-pkix-05)', function (t) {
 	t.end();
 });
 
+test('PrivateKey convert ed25519 key from pkcs1 to pkcs8', function (t) {
+	var keyPem = fs.readFileSync(path.join(testDir, 'id_ed25519.pem'));
+	var key = sshpk.parsePrivateKey(keyPem, 'pem');
+	var newPem = key.toString('pkcs8');
+	var key2 = sshpk.parsePrivateKey(newPem, 'pem');
+	t.strictEqual(key.type, 'ed25519');
+	t.strictEqual(key.size, 256);
+	t.end();
+});
+
 test('PrivateKey invalid ed25519 key (not DER)', function (t) {
 	var keyPem = fs.readFileSync(path.join(testDir,
 	    'ed25519-invalid-ber.pem'));