Add helpers for parseCertificate and parseCertificateBundle

Co-Authored-By: Alper Dedeoglu <39748566+alperdedeoglu@users.noreply.github.com>

package.json

@@ -33,6 +33,8 @@
   },
   "dependencies": {
     "@grpc/grpc-js": "^1.9.11",
+    "@peculiar/webcrypto": "^1.4.3",
+    "@peculiar/x509": "^1.9.5",
     "@protobuf-ts/grpc-transport": "^2.9.1",
     "@protobuf-ts/runtime": "^2.9.1",
     "@protobuf-ts/runtime-rpc": "^2.9.1",

src/index.ts

@@ -1,4 +1,6 @@
 import {ChannelCredentials} from '@grpc/grpc-js'
+import {Crypto} from '@peculiar/webcrypto'
+import * as x509 from '@peculiar/x509'
 import {GrpcTransport} from '@protobuf-ts/grpc-transport'
 import {SpiffeWorkloadAPIClient} from './proto/spiffe/workload/workload.client'
 
@@ -16,6 +18,82 @@ export function createClient(baseURL?: string) {
   return new SpiffeWorkloadAPIClient(transport)
 }
 
+/**
+ * Utility function to parse a raw certificate. Can be used to convert the
+ * raw certificate into a PEM certificate:
+ *
+ * ```typescript
+ * const cert = parseCertificate(data)
+ * const pem = cert.toString('pem')
+ * ```
+ *
+ * **Note:** if you have a certificate bundle, use `parseCertificateBundle` instead, as
+ * this function will incorrectly parse bundles as a single certificate.
+ *
+ * @param data The raw data of the certificate
+ * @returns [X509Certificate](https://peculiarventures.github.io/x509/classes/X509Certificate.html)
+ * @see https://github.com/PeculiarVentures/x509
+ */
+export function parseCertificate(data: Uint8Array): x509.X509Certificate {
+  initCryptoProvider()
+
+  return new x509.X509Certificate(data)
+}
+
+/**
+ * Utility function to parse a certificate bundle. Can be used to convert the
+ * bundle into a PEM chain:
+ *
+ * ```typescript
+ * const certs = parseCertificateBundle(data)
+ * const pemChain = certs.toString('pem-chain')
+ * ```
+ *
+ * @param data The raw data of the certificate bundle
+ * @returns [X509Certificates](https://peculiarventures.github.io/x509/classes/X509Certificates.html)
+ * @see https://github.com/PeculiarVentures/x509
+ */
+export function parseCertificateBundle(data: Uint8Array): x509.X509Certificates {
+  initCryptoProvider()
+
+  let currentIndex = 0
+  const certs: x509.X509Certificate[] = []
+
+  while (currentIndex < data.length) {
+    const beginOfSequence = currentIndex
+
+    // Skip the first tag byte
+    currentIndex += 1
+
+    // Get the second byte for length value representing bytes
+    let length = data[currentIndex++]
+    if (length === 0x80) throw new TypeError('Indefinite length encoding not supported')
+    if (length & 0x80) {
+      const lengthBytes = length & 0x7f
+      length = 0
+      for (let i = 0; i < lengthBytes; i++) {
+        length = (length << 8) | data[currentIndex++]
+      }
+    }
+
+    certs.push(new x509.X509Certificate(data.slice(beginOfSequence, currentIndex + length)))
+
+    // Move the current index to the next tag
+    currentIndex += length
+  }
+
+  return new x509.X509Certificates(certs)
+}
+
+function initCryptoProvider() {
+  try {
+    x509.cryptoProvider.get()
+  } catch {
+    const crypto = new Crypto()
+    x509.cryptoProvider.set(crypto)
+  }
+}
+
 export * from './proto/google/protobuf/struct'
 export * from './proto/spiffe/workload/workload'
 export * from './proto/spiffe/workload/workload.client'