#54 want API for accessing x509 extensions

Reviewed by: Cody Peter Mello <[email protected]>
Approved by: Cody Peter Mello <[email protected]>

Author: Alex Wilson

README.md

@@ -507,6 +507,24 @@ is valid for. The possible strings at the moment are:
              Authority)
  * `'crl'` -- key can be used to sign Certificate Revocation Lists (CRLs)
 
+### `Certificate#getExtension(nameOrOid)`
+
+Retrieves information about a certificate extension, if present, or returns
+`undefined` if not. The string argument `nameOrOid` should be either the OID
+(for X509 extensions) or the name (for OpenSSH extensions) of the extension
+to retrieve.
+
+The object returned will have the following properties:
+
+ * `format` -- String, set to either `'x509'` or `'openssh'`
+ * `name` or `oid` -- String, only one set based on value of `format`
+ * `data` -- Buffer, the raw data inside the extension
+
+### `Certificate#getExtensions()`
+
+Returns an Array of all present certificate extensions, in the same manner and
+format as `getExtension()`.
+
 ### `Certificate#isExpired([when])`
 
 Tests whether the Certificate is currently expired (i.e. the `validFrom` and

lib/certificate.js

@@ -120,6 +120,37 @@ Certificate.prototype.isSignedBy = function (issuerCert) {
 	return (this.isSignedByKey(issuerCert.subjectKey));
 };
 
+Certificate.prototype.getExtension = function (keyOrOid) {
+	assert.string(keyOrOid, 'keyOrOid');
+	var ext = this.getExtensions().filter(function (maybeExt) {
+		if (maybeExt.format === 'x509')
+			return (maybeExt.oid === keyOrOid);
+		if (maybeExt.format === 'openssh')
+			return (maybeExt.name === keyOrOid);
+		return (false);
+	})[0];
+	return (ext);
+};
+
+Certificate.prototype.getExtensions = function () {
+	var exts = [];
+	var x509 = this.signatures.x509;
+	if (x509 && x509.extras && x509.extras.exts) {
+		x509.extras.exts.forEach(function (ext) {
+			ext.format = 'x509';
+			exts.push(ext);
+		});
+	}
+	var openssh = this.signatures.openssh;
+	if (openssh && openssh.exts) {
+		openssh.exts.forEach(function (ext) {
+			ext.format = 'openssh';
+			exts.push(ext);
+		});
+	}
+	return (exts);
+};
+
 Certificate.prototype.isSignedByKey = function (issuerKey) {
 	utils.assertCompatible(issuerKey, Key, [1, 2], 'issuerKey');
 
@@ -370,8 +401,9 @@ Certificate.isCertificate = function (obj, ver) {
 /*
  * API versions for Certificate:
  * [1,0] -- initial ver
+ * [1,1] -- openssh format now unpacks extensions
  */
-Certificate.prototype._sshpkApiVersion = [1, 0];
+Certificate.prototype._sshpkApiVersion = [1, 1];
 
 Certificate._oldVersionDetect = function (obj) {
 	return ([1, 0]);

lib/formats/openssh-cert.js

@@ -122,8 +122,23 @@ function fromBuffer(data, algo, partial) {
 	cert.validFrom = int64ToDate(sshbuf.readInt64());
 	cert.validUntil = int64ToDate(sshbuf.readInt64());
 
-	cert.signatures.openssh.critical = sshbuf.readBuffer();
-	cert.signatures.openssh.exts = sshbuf.readBuffer();
+	var exts = [];
+	var extbuf = new SSHBuffer({ buffer: sshbuf.readBuffer() });
+	var ext;
+	while (!extbuf.atEnd()) {
+		ext = { critical: true };
+		ext.name = extbuf.readString();
+		ext.data = extbuf.readBuffer();
+		exts.push(ext);
+	}
+	extbuf = new SSHBuffer({ buffer: sshbuf.readBuffer() });
+	while (!extbuf.atEnd()) {
+		ext = { critical: false };
+		ext.name = extbuf.readString();
+		ext.data = extbuf.readBuffer();
+		exts.push(ext);
+	}
+	cert.signatures.openssh.exts = exts;
 
 	/* reserved */
 	sshbuf.readBuffer();
@@ -278,13 +293,27 @@ function toBuffer(cert, noSig) {
 	buf.writeInt64(dateToInt64(cert.validFrom));
 	buf.writeInt64(dateToInt64(cert.validUntil));
 
-	if (sig.critical === undefined)
-		sig.critical = Buffer.alloc(0);
-	buf.writeBuffer(sig.critical);
+	var exts = sig.exts;
+	if (exts === undefined)
+		exts = [];
 
-	if (sig.exts === undefined)
-		sig.exts = Buffer.alloc(0);
-	buf.writeBuffer(sig.exts);
+	var extbuf = new SSHBuffer({});
+	exts.forEach(function (ext) {
+		if (ext.critical !== true)
+			return;
+		extbuf.writeString(ext.name);
+		extbuf.writeBuffer(ext.data);
+	});
+	buf.writeBuffer(extbuf.toBuffer());
+
+	extbuf = new SSHBuffer({});
+	exts.forEach(function (ext) {
+		if (ext.critical === true)
+			return;
+		extbuf.writeString(ext.name);
+		extbuf.writeBuffer(ext.data);
+	});
+	buf.writeBuffer(extbuf.toBuffer());
 
 	/* reserved */
 	buf.writeBuffer(Buffer.alloc(0));

lib/formats/x509.js

@@ -242,7 +242,8 @@ function readExtension(cert, buf, der) {
 	var extId = der.readOID();
 	var id;
 	var sig = cert.signatures.x509;
-	sig.extras.exts = [];
+	if (!sig.extras.exts)
+		sig.extras.exts = [];
 
 	var critical;
 	if (der.peek() === asn1.Ber.Boolean)

test/assets/openssh-exts.pub

@@ -0,0 +1 @@
+[email protected] 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 id_ecdsa2

test/assets/yubikey.pem

@@ -0,0 +1,16 @@
+-----BEGIN CERTIFICATE-----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+-----END CERTIFICATE-----
+

test/certs.js

@@ -7,6 +7,8 @@ var fs = require('fs');
 var path = require('path');
 var crypto = require('crypto');
 var sinon = require('sinon');
+var asn1 = require('asn1');
+var SSHBuffer = require('../lib/ssh-buffer');
 
 var testDir = path.join(__dirname, 'assets');
 
@@ -250,6 +252,17 @@ test('example cert: digicert ca (x509)', function (t) {
 	t.strictEqual(cert.subjects.length, 1);
 	t.deepEqual(cert.purposes.sort(),
 	    ['ca', 'clientAuth', 'crl', 'serverAuth', 'signature']);
+	var exts = cert.getExtensions();
+	t.strictEqual(exts.length, 8);
+	exts.forEach(function (ext) {
+		t.strictEqual(ext.format, 'x509');
+		t.strictEqual(typeof (ext.oid), 'string');
+	});
+	var basicExt = cert.getExtension('2.5.29.19');
+	t.strictEqual(basicExt.oid, '2.5.29.19');
+	t.strictEqual(basicExt.critical, true);
+	t.strictEqual(basicExt.format, 'x509');
+	t.strictEqual(basicExt.pathLen, 0);
 	t.end();
 });
 
@@ -386,3 +399,47 @@ test('cert with doubled-up DN attribute', function (t) {
 
 	t.end();
 });
+
+test('example cert: yubikey attestation cert', function (t) {
+	var cert = sshpk.parseCertificate(
+	    fs.readFileSync(path.join(testDir, 'yubikey.pem')),
+	    'pem');
+	t.strictEqual(cert.subjectKey.type, 'ecdsa');
+	t.strictEqual(cert.subjects[0].cn, 'YubiKey PIV Attestation 9e');
+
+	var serialExt = cert.getExtension('1.3.6.1.4.1.41482.3.7');
+	t.ok(serialExt);
+	var der = new asn1.Ber.Reader(serialExt.data);
+	t.strictEqual(der.readInt(), 5213681);
+
+	var policyExt = cert.getExtension('1.3.6.1.4.1.41482.3.8');
+	t.ok(policyExt);
+	t.strictEqual(policyExt.data[0], 0x01); /* never require PIN */
+	t.strictEqual(policyExt.data[1], 0x01); /* never require touch */
+
+	t.end();
+});
+
+test('example cert: openssh extensions', function (t) {
+	var cert = sshpk.parseCertificate(
+	    fs.readFileSync(path.join(testDir, 'openssh-exts.pub')),
+	    'openssh');
+	t.strictEqual(cert.subjectKey.type, 'ecdsa');
+	t.strictEqual(cert.subjects[0].uid, 'foo');
+
+	var forceCmdExt = cert.getExtension('force-command');
+	t.ok(forceCmdExt);
+	t.strictEqual(forceCmdExt.name, 'force-command');
+	t.strictEqual(forceCmdExt.critical, true);
+
+	var cmdbuf = new SSHBuffer({ buffer: forceCmdExt.data });
+	var cmd = cmdbuf.readString();
+	t.strictEqual(cmd, 'foobarcmd');
+	t.ok(cmdbuf.atEnd());
+
+	t.ok(cert.getExtension('permit-port-forwarding'));
+	t.notOk(cert.getExtension('source-address'));
+	t.notOk(cert.getExtension('permit-pty'));
+
+	t.end();
+});