suaveplan/packages/identity/auth/webauthn/src/__fixtures__/deterministic-keys.ts

/**
 * Deterministic test keys for the webauthn fixture suite.
 *
 * ES256 (P-256), ES384, ES512 use hardcoded scalars; ECDSA via
 * `@noble/curves` uses RFC 6979 deterministic-k so signatures round-trip
 * byte-stably given the same message. Ed25519 is deterministic by spec.
 * Public keys are memoised across the suite.
 *
 * `@noble/curves` is added as a devDependency on `@suaveplan/webauthn`
 * specifically for these fixtures (it is the same transitive dep that
 * `@suaveplan/crypto-curve` already depends on; fixture-only).
 */
import { p256 as nobleP256 } from "@noble/curves/p256";
import { p384 as nobleP384 } from "@noble/curves/p384";
import { p521 as nobleP521 } from "@noble/curves/p521";
import type { Ec2Key, OkpKey } from "@suaveplan/cbor/cose";
import { ed25519 } from "@suaveplan/crypto-curve";

const P256_PRIV = Uint8Array.from([
    0x70, 0x83, 0x95, 0xab, 0x2c, 0x46, 0x3d, 0x68, 0xa1, 0x10, 0x4f, 0x37,
    0x29, 0xb5, 0xd5, 0x42, 0x0c, 0x18, 0x21, 0x9f, 0xa0, 0x60, 0xff, 0xff,
    0x5c, 0x4d, 0x16, 0x97, 0x21, 0x83, 0x9b, 0x55,
]);

const P384_PRIV = Uint8Array.from(
    Array.from({ length: 48 }, (_v, i) => (i * 7 + 3) & 0xff)
);

const P521_PRIV = Uint8Array.from([
    0x00, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45,
    0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd,
    0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45,
    0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd,
    0xef, 0x01, 0x23, 0x45, 0x67, 0x89, 0xab, 0xcd, 0xef, 0x01, 0x23, 0x45,
    0x67, 0x89, 0xab, 0xcd, 0xef, 0x77,
]);

const ED25519_PRIV = new Uint8Array(32).fill(0xa5);

export interface EcTestKey {
    readonly priv: Uint8Array;
    readonly pubUncompressed: Uint8Array;
    readonly x: Uint8Array;
    readonly y: Uint8Array;
    readonly coseKey: Ec2Key;
}

export interface EddsaTestKey {
    readonly priv: Uint8Array;
    readonly pub: Uint8Array;
    readonly coseKey: OkpKey;
}

let p256Cache: EcTestKey | undefined;
let p384Cache: EcTestKey | undefined;
let p521Cache: EcTestKey | undefined;
let edCache: EddsaTestKey | undefined;

function ecBuild(
    priv: Uint8Array,
    pubUncompressed: Uint8Array,
    coordLen: number,
    crv: "P-256" | "P-384" | "P-521",
    alg: "ES256" | "ES384" | "ES512"
): EcTestKey {
    const x = pubUncompressed.slice(1, 1 + coordLen);
    const y = pubUncompressed.slice(1 + coordLen, 1 + 2 * coordLen);
    return {
        priv,
        pubUncompressed,
        x,
        y,
        coseKey: {
            kty: "EC2",
            crv,
            alg,
            x,
            y,
        },
    };
}

/** Deterministic P-256 keypair for ES256 webauthn tests. */
export function getEcdsaP256TestKey(): EcTestKey {
    if (p256Cache !== undefined) {
        return p256Cache;
    }
    const pub = nobleP256.getPublicKey(P256_PRIV, false);
    p256Cache = ecBuild(P256_PRIV, pub, 32, "P-256", "ES256");
    return p256Cache;
}

/** Deterministic P-384 keypair for ES384 webauthn tests. */
export function getEcdsaP384TestKey(): EcTestKey {
    if (p384Cache !== undefined) {
        return p384Cache;
    }
    const pub = nobleP384.getPublicKey(P384_PRIV, false);
    p384Cache = ecBuild(P384_PRIV, pub, 48, "P-384", "ES384");
    return p384Cache;
}

/** Deterministic P-521 keypair for ES512 webauthn tests. */
export function getEcdsaP521TestKey(): EcTestKey {
    if (p521Cache !== undefined) {
        return p521Cache;
    }
    const pub = nobleP521.getPublicKey(P521_PRIV, false);
    p521Cache = ecBuild(P521_PRIV, pub, 66, "P-521", "ES512");
    return p521Cache;
}

/** Deterministic Ed25519 keypair for EdDSA webauthn tests. */
export function getEd25519TestKey(): EddsaTestKey {
    if (edCache !== undefined) {
        return edCache;
    }
    const pub = ed25519.getPublicKey(ED25519_PRIV);
    edCache = {
        priv: ED25519_PRIV,
        pub,
        coseKey: {
            kty: "OKP",
            crv: "Ed25519",
            alg: "EdDSA",
            x: pub,
        },
    };
    return edCache;
}

/** ECDSA-sign a digest with P-256. Returns DER signature. */
export function signEcdsaP256Der(
    digest: Uint8Array,
    priv: Uint8Array
): Uint8Array {
    return nobleP256.sign(digest, priv).toBytes("der");
}

export function signEcdsaP384Der(
    digest: Uint8Array,
    priv: Uint8Array
): Uint8Array {
    return nobleP384.sign(digest, priv).toBytes("der");
}

export function signEcdsaP521Der(
    digest: Uint8Array,
    priv: Uint8Array
): Uint8Array {
    return nobleP521.sign(digest, priv).toBytes("der");
}