Explicit dns servers (#1281)

* add ability to setup explicit dns servers * cleanup * fix * reorder * pr feedback
bluesky-social · Jul 4, 2023 · 0ceed96 · 0ceed96
1 parent dd4d91c
commit 0ceed96
Show file tree

Hide file tree

Showing 4 changed files with 66 additions and 8 deletions.
diff --git a/packages/identity/src/handle/index.ts b/packages/identity/src/handle/index.ts
@@ -6,9 +6,12 @@ const PREFIX = 'did='
 
 export class HandleResolver {
   public timeout: number
+  private backupNameservers: string[] | undefined
+  private backupNameserverIps: string[] | undefined
 
   constructor(opts: HandleResolverOpts = {}) {
     this.timeout = opts.timeout ?? 3000
+    this.backupNameservers = opts.backupNameservers
   }
 
   async resolve(handle: string): Promise<string | undefined> {
@@ -23,7 +26,11 @@ export class HandleResolver {
       httpAbort.abort()
       return dnsRes
     }
-    return httpPromise
+    const res = await httpPromise
+    if (res) {
+      return res
+    }
+    return this.resolveDnsBackup(handle)
   }
 
   async resolveDns(handle: string): Promise<string | undefined> {
@@ -33,12 +40,7 @@ export class HandleResolver {
     } catch (err) {
       return undefined
     }
-    const results = chunkedResults.map((chunks) => chunks.join(''))
-    const found = results.filter((i) => i.startsWith(PREFIX))
-    if (found.length !== 1) {
-      return undefined
-    }
-    return found[0].slice(PREFIX.length)
+    return this.parseDnsResult(chunkedResults)
   }
 
   async resolveHttp(
@@ -57,4 +59,44 @@ export class HandleResolver {
       return undefined
     }
   }
+
+  async resolveDnsBackup(handle: string): Promise<string | undefined> {
+    let chunkedResults: string[][]
+    try {
+      const backupIps = await this.getBackupNameserverIps()
+      if (!backupIps || backupIps.length < 1) return undefined
+      const resolver = new dns.Resolver()
+      resolver.setServers(backupIps)
+      chunkedResults = await resolver.resolveTxt(`${SUBDOMAIN}.${handle}`)
+    } catch (err) {
+      return undefined
+    }
+    return this.parseDnsResult(chunkedResults)
+  }
+
+  parseDnsResult(chunkedResults: string[][]): string | undefined {
+    const results = chunkedResults.map((chunks) => chunks.join(''))
+    const found = results.filter((i) => i.startsWith(PREFIX))
+    if (found.length !== 1) {
+      return undefined
+    }
+    return found[0].slice(PREFIX.length)
+  }
+
+  private async getBackupNameserverIps(): Promise<string[] | undefined> {
+    if (!this.backupNameservers) {
+      return undefined
+    } else if (!this.backupNameserverIps) {
+      const responses = await Promise.allSettled(
+        this.backupNameservers.map((h) => dns.lookup(h)),
+      )
+      for (const res of responses) {
+        if (res.status === 'fulfilled') {
+          this.backupNameserverIps ??= []
+          this.backupNameserverIps.push(res.value.address)
+        }
+      }
+    }
+    return this.backupNameserverIps
+  }
 }
diff --git a/packages/identity/src/types.ts b/packages/identity/src/types.ts
@@ -4,10 +4,12 @@ export type IdentityResolverOpts = {
   timeout?: number
   plcUrl?: string
   didCache?: DidCache
+  backupNameservers?: string[]
 }
 
 export type HandleResolverOpts = {
   timeout?: number
+  backupNameservers?: string[]
 }
 
 export type DidResolverOpts = {

diff --git a/packages/pds/src/config.ts b/packages/pds/src/config.ts
@@ -35,6 +35,7 @@ export interface ServerConfigValues {
   databaseLocation?: string
 
   availableUserDomains: string[]
+  handleResolveNameservers?: string[]
 
   imgUriSalt: string
   imgUriKey: string
@@ -136,6 +137,10 @@ export class ServerConfig {
       ? process.env.AVAILABLE_USER_DOMAINS.split(',')
       : []
 
+    const handleResolveNameservers = process.env.HANDLE_RESOLVE_NAMESERVERS
+      ? process.env.HANDLE_RESOLVE_NAMESERVERS.split(',')
+      : []
+
     const imgUriSalt =
       process.env.IMG_URI_SALT || '9dd04221f5755bce5f55f47464c27e1e'
     const imgUriKey =
@@ -215,6 +220,7 @@ export class ServerConfig {
       termsOfServiceUrl,
       databaseLocation,
       availableUserDomains,
+      handleResolveNameservers,
       imgUriSalt,
       imgUriKey,
       imgUriEndpoint,
@@ -368,6 +374,10 @@ export class ServerConfig {
     return this.cfg.availableUserDomains
   }
 
+  get handleResolveNameservers() {
+    return this.cfg.handleResolveNameservers
+  }
+
   get imgUriSalt() {
     return this.cfg.imgUriSalt
   }

diff --git a/packages/pds/src/index.ts b/packages/pds/src/index.ts
@@ -96,7 +96,11 @@ export class PDS {
       config.didCacheStaleTTL,
       config.didCacheMaxTTL,
     )
-    const idResolver = new IdResolver({ plcUrl: config.didPlcUrl, didCache })
+    const idResolver = new IdResolver({
+      plcUrl: config.didPlcUrl,
+      didCache,
+      backupNameservers: config.handleResolveNameservers,
+    })
 
     const messageDispatcher = new MessageDispatcher()
     const sequencer = new Sequencer(db)