chadtmiller.com/pds.js

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import { describe, expect, it } from 'vitest';
import { decodeJwt, expiryOf } from '#/lib/jwt.js';

/**
 * @param {object} header @param {object} payload
 * @returns {string}
 */
function jwt(header, payload) {
  const part = (value) =>
    btoa(JSON.stringify(value))
      .replace(/\+/g, '-')
      .replace(/\//g, '_')
      .replace(/=+$/, '');
  return `${part(header)}.${part(payload)}.c2ln`;
}

describe('decodeJwt', () => {
  it('reads both segments of a space credential', () => {
    const token = jwt(
      { alg: 'ES256', typ: 'atproto-space-credential+jwt', kid: '#atproto' },
      {
        iss: 'did:plc:authority',
        sub: 'at://did:plc:authority/space/com.example.forum/general',
        cnf: { jkt: 'a-thumbprint' },
        exp: 1_800_000_000,
      },
    );
    const decoded = decodeJwt(token);
    expect(decoded?.header.typ).toBe('atproto-space-credential+jwt');
    expect(decoded?.payload.cnf.jkt).toBe('a-thumbprint');
  });

  // A segment whose length is not a multiple of four is the normal case: these
  // tokens are base64url with the padding stripped.
  it('decodes a segment whose padding was stripped', () => {
    const token = jwt({ alg: 'ES256' }, { iss: 'did:plc:a' });
    expect(token.split('.')[1].length % 4).not.toBe(0);
    expect(decodeJwt(token)?.payload.iss).toBe('did:plc:a');
  });

  it('answers null for anything that is not a JWT', () => {
    expect(decodeJwt('not-a-token')).toBeNull();
    expect(decodeJwt('')).toBeNull();
    expect(decodeJwt('a.b.c')).toBeNull();
  });
});

describe('expiryOf', () => {
  it('reads exp as milliseconds', () => {
    expect(expiryOf(jwt({}, { exp: 1_800_000_000 }))).toBe(1_800_000_000_000);
  });

  // A token stating no expiry gets a held-for-ten-minutes fallback at the call
  // site, which only fires because this answers zero rather than NaN.
  it('answers zero for a token that states none', () => {
    expect(expiryOf(jwt({}, { iss: 'did:plc:a' }))).toBe(0);
    expect(expiryOf('rubbish')).toBe(0);
  });
});