Fix, derToRaw does not handle r/s with leading 0s. (#117)

* Updating the derToRaw function to handle signature parts that have leading (excluded) zeros.

* Adding test to validate that signatures with non-standard r/s can be parsed properly.

* Fixing linting issues

* Delete deno.lock

* Making the asn1 tests use static values. Moving from Buffer to Javascript native types for padding the array in derToRaw.

* Modifying derToRaw to only slice the buffer when it is not exactly 32 bytes.

* Making rEnd const

* Fixing typo in tests. Cleaning up redundent code in derToRaw.

* Bumping version.

Co-authored-by: James Cullum (Pseudonym) <JamesCullum@users.noreply.github.com>

lib/toolbox.js

@@ -56,17 +56,25 @@ pkijs.setEngine(
 	}),
 );
 
+function extractBigNum(fullArray, start, end, expectedLength) {
+	let num = fullArray.slice(start, end);
+	if (num.length !== expectedLength){
+		num = Array(expectedLength).fill(0).concat(...num).slice(num.length);
+	}
+	return num;
+}
+
 /*
     Convert signature from DER to raw
     Expects Uint8Array
 */
 function derToRaw(signature) {
-	const rStart = signature[4] === 0 ? 5 : 4;
-	const rEnd = rStart + 32;
-	const sStart = signature[rEnd + 2] === 0 ? rEnd + 3 : rEnd + 2;
+	const rStart = 4;
+	const rEnd = rStart + signature[3];
+	const sStart = rEnd + 2;
 	return new Uint8Array([
-		...signature.slice(rStart, rEnd),
-		...signature.slice(sStart),
+		...extractBigNum(signature, rStart, rEnd, 32),
+		...extractBigNum(signature, sStart, signature.length, 32),
 	]);
 }
 

package.json

@@ -1,6 +1,6 @@
 {
 	"name": "fido2-lib",
-	"version": "3.3.4",
+	"version": "3.3.5",
 	"description": "A library for performing FIDO 2.0 / WebAuthn functionality",
 	"type": "module",
 	"main": "dist/main.cjs",

rollup.config.js

@@ -16,6 +16,7 @@ const externals = [
 	"@peculiar/webcrypto",
 ];
 const tests = [
+	"test/asn1.test.js",
 	"test/certUtils.test.js",
 	"test/extAppId.test.js",
 	"test/ext.test.js",

test/asn1.test.js

@@ -0,0 +1,132 @@
+import base64 from "@hexagon/base64";
+
+// Testing lib
+import * as chai from "chai";
+import * as chaiAsPromised from "chai-as-promised";
+
+import { Fido2Lib } from "../lib/main.js";
+import { ecdsaPublicKey } from "./fixtures/ecdsaPublicKey.js";
+
+chai.use(chaiAsPromised.default);
+const assert = chai.assert;
+
+const base64urlToArrayBuffer = (str) => {
+	return base64.toArrayBuffer(str);
+};
+
+const verifyAssertion = async (signature) => {
+	const input = {
+		credId: "UmFuZG9tQ3JlZElk",
+		clientData: "eyJ0eXBlIjoid2ViYXV0aG4uZ2V0IiwiY2hhbGxlbmdlIjoiTjJKaE1XVTRNV0ppWm1FeE4yRXlNVGM1T0RBeE5HUmpObU0yWm1JMVl6WTROVEJqTkRWak5EUXdOV1kzWkRKaU5tSTNNalpqT1dZMFpHTTJaRGt4WVEiLCJvcmlnaW4iOiJodHRwOi8vbG9jYWxob3N0OjMwMDAiLCJjcm9zc09yaWdpbiI6ZmFsc2V9",
+		authenticatorData: "SZYN5YgOjGh0NBcPZHZgW4/krrmihjLHmVzzuoMdl2MFAAAADw==",
+		signature: signature,
+		userHandle: "UmFuZG9tVXNlcklk",
+	};
+	const fido2 = new Fido2Lib({
+		timeout: 42,
+		rpId: "localhost",
+		rpName: "localhost",
+		challengeSize: 128,
+		attestation: "direct",
+		cryptoParams: [-7, -257],
+		authenticatorRequireResidentKey: true,
+		authenticatorUserVerification: "required",
+	});
+
+	const challenge = "N2JhMWU4MWJiZmExN2EyMTc5ODAxNGRjNmM2ZmI1YzY4NTBjNDVjNDQwNWY3ZDJiNmI3MjZjOWY0ZGM2ZDkxYQ";
+	return await fido2.assertionResult(
+		{
+			rawId: base64urlToArrayBuffer(input.credId),
+			response: {
+				clientDataJSON: input.clientData,
+				authenticatorData: base64urlToArrayBuffer(input.authenticatorData),
+				signature: input.signature,
+				userHandle: input.userHandle,
+			},
+		},
+		{
+			rpId: "localhost",
+			challenge: challenge,
+			origin: "http://localhost:3000",
+			factor: "first",
+			publicKey: ecdsaPublicKey.examplePem,
+			prevCounter: 1,
+			userHandle: input.userHandle,
+		}
+	);
+};
+
+describe("ECDSA ASN.1/Der to Raw conversion", function() {
+	it("can verify an ECDSA signature with r < 32 bytes and s = 32 bytes", async function() {
+		// r < 32 bytes | s = 32 bytes
+		const signature = "MEQCHyj3uP1iWNTCw0FpsiTe-e7dulZqWqepuXFmCwRmLBYCIQDQnxAkeQFwX-dmfg8XFz3TIx7wfh0MKw0hTCjc2WgMVw";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r = 32 bytes and s < 32 bytes", async function() {
+		// r = 32 bytes | s < 32 bytes
+		const signature = "MEMCIGWd6pkFRvBAfse-jGeYfVhlWDKIRyQZyBA32IpdvbMEAh81mQqkXyT2dej9BdABFXdpqR8nzHO1Tq6gfLGjaiX1";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r < 32 bytes and s < 32 bytes", async function() {
+		// r < 32 bytes | s < 32 bytes
+		const signature = "MEICHxWF148JkFV86_NzU-APP-yhVuUHEiVatHdeD6K6A0ACHwWsMWQo33oSBgJ3aSVeY1di7B_TU4GDAT0l3QtvPYg";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r = 33 bytes and s < 32 bytes", async function() {
+		// r = 33 bytes | s < 32 bytes
+		const signature = "MEQCIQCw1qPkCZQl1ZGJProqe9MC8rGLAsAHZbAHDe9YNAFRSwIfAvp9Ar5cQm-5ANS3zG0P105PmPRRur6F3i03AiLwBw";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r < 32 bytes and s = 33 bytes", async function() {
+		// r < 32 bytes | s = 33 bytes
+		const signature = "MEQCHxipYKPnzWezEzFiZWqvJ8Z4-nAJXnFHV4IarB1g818CIQDdVn-OE3uEjRd--Uqj3IA-Zr5RBJor_K9ZCxXuPpalbg";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r = 32 bytes (0 padded) and s >= 32 bytes", async function() {
+		// r = 32 (0 padded) | s >= 32 bytes
+		const signature = "MEUCIADqTxqhzztnVk7XXwEeYhlBADK74-he2RsIbvB918TbAiEA4IYFEPc0-3rYRUhZzlWT2oLscUwszPL-9oZOnaFcNZw";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r >= 32 bytes and s = 32 bytes (0 padded)", async function() {
+		// r >= 32 bytes | s = 32 (0 padded)
+		const signature = "MEUCIQCAvO4-mEuaX2tYR-AJ8t8vv1AxCqkJgfxIR1XL4yCy8AIgANf3_Cp4LzlzkG4U8VS0WCVrR6_pTBM5mwhUcERNakc";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r = 30 bytes and s >= 32 bytes", async function() {
+		// r = 30 bytes | s >= 32 bytes
+		const signature = "MEMCHhCs-kZTCokgrPfb1CaKEznJjqVisSBzMAqv6S24AQIhAOBeIIWXFgOJwA-39dKfzcuG6woJ03tiR0N2ME9Lp206";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+	it("can verify an ECDSA signature with r >= 32 bytes and s < 30 bytes", async function() {
+		// r >= 32 bytes | s < 30 bytes
+		const signature = "MEECID8aNcMNP3Q-mPSIdPc-ocNyH1vLo_Lh8JgxFXAV7s6DAh0pc_2hHfN6OBPpj_2asyt6I4FBz-ZeVbaGtI9UXQ";
+
+		const result = await verifyAssertion(signature);
+		assert.strictEqual(result.audit.validRequest, true);
+		assert.strictEqual(result.audit.validExpectations, true);
+	});
+});

test/fixtures/ecdsaPublicKey.js

@@ -0,0 +1,7 @@
+// privateKey = "-----BEGIN PRIVATE KEY-----\nMIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgu9nv4cQyNEFUkAfb\n3KwStEnfml2iyzgFGVSnIBHrDjuhRANCAAQkFAXLiJbHHbIw7r7xnGN36pWb54FV\na+lkH5NN27NE2ZKytnq6jF04++6rdDgxJ4qkPX7QrrfQuuCFhujSZ+KH\n-----END PRIVATE KEY-----\n"
+const ecdsaPublicKey = {
+	examplePem:
+		"-----BEGIN PUBLIC KEY-----\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEJBQFy4iWxx2yMO6+8Zxjd+qVm+eB\nVWvpZB+TTduzRNmSsrZ6uoxdOPvuq3Q4MSeKpD1+0K630LrghYbo0mfihw==\n-----END PUBLIC KEY-----\n",
+};
+
+export { ecdsaPublicKey };