feat: add support for webrtc and certhash (#261) (#262)

For use with the js implementation of the webrtc transport

The most relevant point of info, from [the draft spec](https://github.com/libp2p/specs/blob/4b8e890c49061eb62c9d16a9afd3aa0a738e6285/webrtc/README.md#addressing): 

> The TLS certificate fingerprint in /certhash is a [multibase](https://github.com/multiformats/multibase) encoded [multihash](https://github.com/multiformats/multihash).

src/convert.ts

@@ -4,6 +4,7 @@ import { getProtocol } from './protocols-table.js'
 import { CID } from 'multiformats/cid'
 import { base32 } from 'multiformats/bases/base32'
 import { base58btc } from 'multiformats/bases/base58'
+import { bases } from 'multiformats/basics'
 import * as Digest from 'multiformats/hashes/digest'
 import varint from 'varint'
 import { toString as uint8ArrayToString } from 'uint8arrays/to-string'
@@ -51,6 +52,8 @@ export function convertToString (proto: number | string, buf: Uint8Array) {
       return bytes2onion(buf)
     case 445: // onion3
       return bytes2onion(buf)
+    case 466: // certhash
+      return bytes2mb(buf)
     default:
       return uint8ArrayToString(buf, 'base16') // no clue. convert to hex
   }
@@ -84,11 +87,20 @@ export function convertToBytes (proto: string | number, str: string) {
       return onion2bytes(str)
     case 445: // onion3
       return onion32bytes(str)
+    case 466: // certhash
+      return mb2bytes(str)
     default:
       return uint8ArrayFromString(str, 'base16') // no clue. convert from hex
   }
 }
 
+const decoders = Object.values(bases).map((c) => c.decoder)
+const anybaseDecoder = (function () {
+  let acc = decoders[0].or(decoders[1])
+  decoders.slice(2).forEach((d) => (acc = acc.or(d)))
+  return acc
+})()
+
 function ip2bytes (ipString: string) {
   if (!ip.isIP(ipString)) {
     throw new Error('invalid ip address')
@@ -148,6 +160,22 @@ function mh2bytes (hash: string) {
   return uint8ArrayConcat([size, mh], size.length + mh.length)
 }
 
+function mb2bytes (mbstr: string) {
+  const mb = anybaseDecoder.decode(mbstr)
+  const size = Uint8Array.from(varint.encode(mb.length))
+  return uint8ArrayConcat([size, mb], size.length + mb.length)
+}
+function bytes2mb (buf: Uint8Array) {
+  const size = varint.decode(buf)
+  const hash = buf.slice(varint.decode.bytes)
+
+  if (hash.length !== size) {
+    throw new Error('inconsistent lengths')
+  }
+
+  return 'u' + uint8ArrayToString(hash, 'base64url')
+}
+
 /**
  * Converts bytes to bas58btc string
  */

src/protocols-table.ts

@@ -25,6 +25,7 @@ export const table: Array<[number, number, string, boolean?, boolean?]> = [
   [275, 0, 'p2p-webrtc-star'],
   [276, 0, 'p2p-webrtc-direct'],
   [277, 0, 'p2p-stardust'],
+  [280, 0, 'webrtc'],
   [290, 0, 'p2p-circuit'],
   [301, 0, 'udt'],
   [302, 0, 'utp'],
@@ -40,6 +41,7 @@ export const table: Array<[number, number, string, boolean?, boolean?]> = [
   [445, 296, 'onion3'],
   [446, V, 'garlic64'],
   [460, 0, 'quic'],
+  [466, V, 'certhash'],
   [477, 0, 'ws'],
   [478, 0, 'wss'],
   [479, 0, 'p2p-websocket-star'],

test/convert.spec.ts

@@ -87,4 +87,17 @@ describe('convert', () => {
       expect(convert.convertToString('sctp', buffer.subarray(5))).to.equal('1234')
     })
   })
+
+  it('can round-trip certhash, though encoding base may change', () => {
+    const myCertFingerprint = {
+      algorithm: 'sha-256',
+      value: 'f4:32:a0:45:34:62:85:e0:d8:d7:75:36:84:72:8e:b2:aa:9e:71:64:e4:eb:fe:06:51:64:42:64:fe:04:a8:d0'
+    }
+    const mb = 'f' + myCertFingerprint.value.replaceAll(':', '')
+    const bytes = convert.convertToBytes('certhash', mb)
+    const outcome = convert.convertToString(466, bytes)
+    expect(outcome).to.equal('u9DKgRTRiheDY13U2hHKOsqqecWTk6_4GUWRCZP4EqNA')
+    const bytesOut = convert.convertToBytes(466, outcome)
+    expect(bytesOut.toString()).to.equal(bytes.toString())
+  })
 })