From e27747ab9c32b6f72b04bb24cbc51e95384c1747 Mon Sep 17 00:00:00 2001
From: Joel Gustafson <joelgustafson@protonmail.com>
Date: Wed, 7 Dec 2022 05:08:08 -0500
Subject: [PATCH] fix: treat /dns, /dns4, and /dns6 addrs as public (#406)

Updates filtering rules to treat dns addresses as public.

Closes #377

Co-authored-by: Alex Potsides <alex@achingbrain.net>
---
 src/utils.ts           | 23 ++++++++++++++++++++++-
 test/kad-utils.spec.ts | 35 +++++++++++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)

diff --git a/src/utils.ts b/src/utils.ts
index 7031c7ae..058d919f 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -19,6 +19,16 @@ export function removePrivateAddresses (peer: PeerInfo): PeerInfo {
     multiaddrs: peer.multiaddrs.filter(multiaddr => {
       const [[type, addr]] = multiaddr.stringTuples()
 
+      // treat /dns, /dns4, and /dns6 addrs as public
+      if (type === 53 || type === 54 || type === 55) {
+        // localhost can be a dns address but it's private
+        if (addr === 'localhost') {
+          return false
+        }
+
+        return true
+      }
+
       if (type !== 4 && type !== 6) {
         return false
       }
@@ -45,6 +55,10 @@ export function removePublicAddresses (peer: PeerInfo): PeerInfo {
     multiaddrs: peer.multiaddrs.filter(multiaddr => {
       const [[type, addr]] = multiaddr.stringTuples()
 
+      if (addr === 'localhost') {
+        return true
+      }
+
       if (type !== 4 && type !== 6) {
         return false
       }
@@ -53,7 +67,14 @@ export function removePublicAddresses (peer: PeerInfo): PeerInfo {
         return false
       }
 
-      return isPrivateIp(addr)
+      const isPrivate = isPrivateIp(addr)
+
+      if (isPrivate == null) {
+        // not an ip address
+        return false
+      }
+
+      return isPrivate
     })
   }
 }
diff --git a/test/kad-utils.spec.ts b/test/kad-utils.spec.ts
index c8068605..9a5f91cc 100644
--- a/test/kad-utils.spec.ts
+++ b/test/kad-utils.spec.ts
@@ -4,6 +4,7 @@ import { expect } from 'aegir/chai'
 import { concat as uint8ArrayConcat } from 'uint8arrays/concat'
 import { fromString as uint8ArrayFromString } from 'uint8arrays/from-string'
 import { toString as uint8ArrayToString } from 'uint8arrays/to-string'
+import { multiaddr } from '@multiformats/multiaddr'
 import * as utils from '../src/utils.js'
 import { createPeerId, createPeerIds } from './utils/create-peer-id.js'
 
@@ -60,4 +61,38 @@ describe('kad utils', () => {
       })
     })
   })
+
+  describe('removePrivateAddresses', () => {
+    it('filters private multiaddrs', async () => {
+      const id = await createPeerId()
+
+      const multiaddrs = [
+        multiaddr('/dns4/example.com/tcp/4001'),
+        multiaddr('/ip4/192.168.0.1/tcp/4001'),
+        multiaddr('/ip4/1.1.1.1/tcp/4001'),
+        multiaddr('/dns4/localhost/tcp/4001')
+      ]
+
+      const peerInfo = utils.removePrivateAddresses({ id, multiaddrs, protocols: [] })
+      expect(peerInfo.multiaddrs.map((ma) => ma.toString()))
+        .to.eql(['/dns4/example.com/tcp/4001', '/ip4/1.1.1.1/tcp/4001'])
+    })
+  })
+
+  describe('removePublicAddresses', () => {
+    it('filters public multiaddrs', async () => {
+      const id = await createPeerId()
+
+      const multiaddrs = [
+        multiaddr('/dns4/example.com/tcp/4001'),
+        multiaddr('/ip4/192.168.0.1/tcp/4001'),
+        multiaddr('/ip4/1.1.1.1/tcp/4001'),
+        multiaddr('/dns4/localhost/tcp/4001')
+      ]
+
+      const peerInfo = utils.removePublicAddresses({ id, multiaddrs, protocols: [] })
+      expect(peerInfo.multiaddrs.map((ma) => ma.toString()))
+        .to.eql(['/ip4/192.168.0.1/tcp/4001', '/dns4/localhost/tcp/4001'])
+    })
+  })
 })