smartacme/ts/acme/acme.classes.crypto.ts

import * as crypto from 'node:crypto';
import type { IAcmeCsrOptions } from './acme.interfaces.js';

/**
 * All cryptographic operations for the ACME protocol.
 * Uses node:crypto for key gen, JWK, JWS signing.
 * Uses @peculiar/x509 for CSR generation (no native Node.js CSR API).
 */
export class AcmeCrypto {
  /**
   * Generate an RSA private key in PEM format
   */
  static createRsaPrivateKey(modulusLength = 2048): string {
    const { privateKey } = crypto.generateKeyPairSync('rsa', {
      modulusLength,
      publicKeyEncoding: { type: 'spki', format: 'pem' },
      privateKeyEncoding: { type: 'pkcs8', format: 'pem' },
    });
    return privateKey;
  }

  /**
   * Export public JWK from PEM private key, keys sorted alphabetically per RFC 7638
   */
  static getJwk(keyPem: string): Record<string, string> {
    const keyObj = crypto.createPublicKey(keyPem);
    const jwk = keyObj.export({ format: 'jwk' }) as Record<string, any>;
    if (jwk.kty === 'RSA') {
      return { e: jwk.e, kty: jwk.kty, n: jwk.n };
    } else if (jwk.kty === 'EC') {
      return { crv: jwk.crv, kty: jwk.kty, x: jwk.x, y: jwk.y };
    }
    throw new Error(`Unsupported key type: ${jwk.kty}`);
  }

  /**
   * Compute JWK Thumbprint (SHA-256, base64url) per RFC 7638
   */
  static getJwkThumbprint(jwk: Record<string, string>): string {
    let canonical: string;
    if (jwk.kty === 'RSA') {
      canonical = JSON.stringify({ e: jwk.e, kty: jwk.kty, n: jwk.n });
    } else if (jwk.kty === 'EC') {
      canonical = JSON.stringify({ crv: jwk.crv, kty: jwk.kty, x: jwk.x, y: jwk.y });
    } else {
      throw new Error(`Unsupported key type: ${jwk.kty}`);
    }
    const hash = crypto.createHash('sha256').update(canonical).digest();
    return hash.toString('base64url');
  }

  /**
   * Create a flattened JWS for ACME requests (RFC 7515)
   * payload=null means POST-as-GET (empty string payload)
   */
  static createJws(
    keyPem: string,
    url: string,
    payload: any | null,
    options: { nonce: string; kid?: string; jwk?: Record<string, string> },
  ): { protected: string; payload: string; signature: string } {
    const header: Record<string, any> = {
      alg: AcmeCrypto.getAlg(keyPem),
      nonce: options.nonce,
      url,
    };
    if (options.kid) {
      header.kid = options.kid;
    } else if (options.jwk) {
      header.jwk = options.jwk;
    } else {
      header.jwk = AcmeCrypto.getJwk(keyPem);
    }

    const protectedB64 = Buffer.from(JSON.stringify(header)).toString('base64url');
    const payloadB64 =
      payload !== null ? Buffer.from(JSON.stringify(payload)).toString('base64url') : '';

    const signingInput = `${protectedB64}.${payloadB64}`;
    const keyObj = crypto.createPrivateKey(keyPem);
    const alg = AcmeCrypto.getAlg(keyPem);

    let signature: Buffer;
    if (alg.startsWith('RS')) {
      signature = crypto.sign('sha256', Buffer.from(signingInput), keyObj);
    } else if (alg.startsWith('ES')) {
      signature = crypto.sign('sha256', Buffer.from(signingInput), {
        key: keyObj,
        dsaEncoding: 'ieee-p1363',
      });
    } else {
      throw new Error(`Unsupported algorithm: ${alg}`);
    }

    return {
      protected: protectedB64,
      payload: payloadB64,
      signature: signature.toString('base64url'),
    };
  }

  /**
   * Create a CSR (PKCS#10) via @peculiar/x509
   * Returns [privateKeyPem, csrPem]
   */
  static async createCsr(
    options: IAcmeCsrOptions,
    existingKeyPem?: string,
  ): Promise<[string, string]> {
    const x509 = await import('@peculiar/x509');
    const { webcrypto } = crypto;
    x509.cryptoProvider.set(webcrypto as any);

    let keys: CryptoKeyPair;
    let keyPem: string;

    if (existingKeyPem) {
      keys = await AcmeCrypto.importKeyPairToWebCrypto(existingKeyPem, webcrypto);
      keyPem = existingKeyPem;
    } else {
      keys = (await webcrypto.subtle.generateKey(
        {
          name: 'RSASSA-PKCS1-v1_5',
          modulusLength: 2048,
          publicExponent: new Uint8Array([1, 0, 1]),
          hash: 'SHA-256',
        },
        true,
        ['sign', 'verify'],
      )) as CryptoKeyPair;

      const pkcs8 = await webcrypto.subtle.exportKey('pkcs8', keys.privateKey);
      const b64 = Buffer.from(pkcs8).toString('base64');
      const lines = b64.match(/.{1,64}/g)!;
      keyPem = `-----BEGIN PRIVATE KEY-----\n${lines.join('\n')}\n-----END PRIVATE KEY-----\n`;
    }

    // Collect all DNS names for SAN (CN is always included)
    const sanNames: string[] = [options.commonName];
    if (options.altNames) {
      for (const name of options.altNames) {
        if (!sanNames.includes(name)) {
          sanNames.push(name);
        }
      }
    }

    const csr = await x509.Pkcs10CertificateRequestGenerator.create({
      name: `CN=${options.commonName}`,
      keys,
      signingAlgorithm: { name: 'RSASSA-PKCS1-v1_5' },
      extensions: [
        new x509.SubjectAlternativeNameExtension(
          sanNames.map((name) => ({ type: 'dns' as const, value: name })),
        ),
      ],
    });

    // Convert to PEM
    const csrPem = csr.toString('pem');

    return [keyPem, csrPem];
  }

  /**
   * Convert PEM to raw DER Buffer (strip headers, decode base64)
   */
  static pemToBuffer(pem: string): Buffer {
    const lines = pem
      .split('\n')
      .filter((line) => !line.startsWith('-----') && line.trim().length > 0);
    return Buffer.from(lines.join(''), 'base64');
  }

  /**
   * Determine JWS algorithm from key type
   */
  private static getAlg(keyPem: string): string {
    const keyObj = crypto.createPrivateKey(keyPem);
    const keyType = keyObj.asymmetricKeyType;
    if (keyType === 'rsa') return 'RS256';
    if (keyType === 'ec') {
      const details = keyObj.asymmetricKeyDetails;
      if (details?.namedCurve === 'prime256v1' || details?.namedCurve === 'P-256') return 'ES256';
      if (details?.namedCurve === 'secp384r1' || details?.namedCurve === 'P-384') return 'ES384';
      return 'ES256';
    }
    throw new Error(`Unsupported key type: ${keyType}`);
  }

  /**
   * Import a PEM private key into WebCrypto as a CryptoKeyPair
   */
  private static async importKeyPairToWebCrypto(
    keyPem: string,
    wc: typeof crypto.webcrypto,
  ): Promise<CryptoKeyPair> {
    const keyObj = crypto.createPrivateKey(keyPem);
    const pkcs8Der = keyObj.export({ type: 'pkcs8', format: 'der' });
    const privateKey = await wc.subtle.importKey(
      'pkcs8',
      pkcs8Der,
      { name: 'RSASSA-PKCS1-v1_5', hash: 'SHA-256' },
      true,
      ['sign'],
    );

    const pubKeyObj = crypto.createPublicKey(keyPem);
    const spkiDer = pubKeyObj.export({ type: 'spki', format: 'der' });
    const publicKey = await wc.subtle.importKey(
      'spki',
      spkiDer,
      { name: 'RSASSA-PKCS1-v1_5', hash: 'SHA-256' },
      true,
      ['verify'],
    );

    return { privateKey: privateKey as unknown as CryptoKey, publicKey: publicKey as unknown as CryptoKey };
  }
}