Handle->DID resolution via /.well-known/atproto-did endpoint

Sources/ATResolve/ATResolver.swift

@@ -40,20 +40,67 @@ public struct ATResolver<Provider: ResponseProviding> {
 	}
 
 	public func didForDomain(_ name: String) async throws -> String? {
-		// I don't understand exactly why, but this triggers a timeout. When I do it with `dig` it returns right away...
-		if name.hasSuffix(".bsky.social") {
+		return await withTaskGroup(of: Optional<String>.self) { group in
+			let provider = provider
+			group.addTask {
+				await Self.checkWellKnown(handle: name, provider: provider)
+			}
+
+			group.addTask {
+				await Self.checkDNS(handle: name)
+			}
+
+			let first = await group.next()
+			if let first {
+				return first
+			}
+
+			return await group.next() ?? nil
+		}
+	}
+
+	static func checkWellKnown(handle: String, provider: Provider) async -> String? {
+		do {
+			let dataResult = try await provider.data(
+				for: .init(
+					host: handle,
+					path: "/.well-known/atproto-did",
+					method: .get,
+					headers: ["Accept": "text/plain;charset=UTF-8"],
+					queryItems: []
+				)
+			)
+			let result = String(data: dataResult, encoding: .utf8)
+
+			if let result {
+				//workaround if we get erroneous 200 code but body return is e.g.
+				//"404 error"
+				guard result.hasPrefix("did:") else {
+					return nil
+				}
+			}
+			return result
+		} catch {
 			return nil
 		}
-
-		let resolver = try AsyncDNSResolver()
-
-		let txtRecords = try await resolver.queryTXT(name: "_atproto." + name)
-
-		let didRecord = txtRecords.first { record in
-			record.txt.hasPrefix("did=")
+	}
+
+	static func checkDNS(handle: String) async -> String? {
+		do {
+			// Only check Cloudflare and Google DNS servers
+			var dnsOptions = CAresDNSResolver.Options.default
+			dnsOptions.servers = ["1.1.1.1", "1.0.0.1", "8.8.8.8", "8.8.4.4"]
+			let resolver = try AsyncDNSResolver(options: dnsOptions)
+			let txtRecords = try await resolver.queryTXT(
+				name: "_atproto." + handle
+			)
+			let didRecord = txtRecords.first { record in
+				record.txt.hasPrefix("did=")
+			}
+			return didRecord?.txt.components(separatedBy: "=").last
+		} catch {
+			return nil
 		}
-
-		return didRecord?.txt.components(separatedBy: "=").last
 	}
 
 	public func didForHandle(_ handle: String) async throws -> String? {
@@ -95,8 +142,6 @@ public struct ATResolver<Provider: ResponseProviding> {
 	}
 }
 
-extension ATResolver: Sendable where Provider: Sendable {}
-
 #if canImport(Foundation)
 import Foundation
 

Sources/ATResolve/Networking.swift

@@ -18,6 +18,7 @@ extension URLSession: ResponseProviding {
 			throw URLError(.badURL)
 		}
 		var urlRequest = URLRequest(url: url)
+		urlRequest.timeoutInterval = 3
 		urlRequest.httpMethod = request.method.rawValue
 		for (key, value) in request.headers {
 			urlRequest.addValue(value, forHTTPHeaderField: key)

Sources/ATResolve/ResponseProviding.swift

@@ -28,7 +28,7 @@ public struct Request: Sendable {
 	public let queryItems: [(String, String?)]
 }
 
-public protocol ResponseProviding {
+public protocol ResponseProviding: Sendable {
 	func data(for: Request) async throws -> Data
 }
 

Tests/ATResolveTests/ATResolveTests.swift

@@ -42,6 +42,27 @@ struct ATResolveTests {
 
 		#expect(profile != nil)
 	}
+
+	@Test
+	func timedTestWellKnownTimeout() async throws {
+		// The /.well-known endpoint times out for @thisismissem.social
+		// It should time out after 3 seconds, so this test should be ~3 seconds
+		try await timedTest {
+			let resolver = ATResolver(provider: URLSession.shared)
+			let profile = try await resolver.resolveHandle("thisismissem.social")
+			#expect(profile?.did == "did:plc:5w4eqcxzw5jv5qfnmzxcakfy")
+		}
+	}
+
+	@Test
+	func timedTestDNSTimeout() async throws {
+		// DNS should time out for any .bsky.social handle
+		try await timedTest {
+			let resolver = ATResolver(provider: URLSession.shared)
+			let profile = try await resolver.resolveHandle("cjrdev.bsky.social")
+			#expect(profile?.did == "did:plc:wlef3srsa3hlyzj2hy6yncrh")
+		}
+	}
 
 	@Test func decodeWithCustomProvider() async throws {
 		struct CustomProvider: ResponseProviding {
@@ -60,4 +81,11 @@ struct ATResolveTests {
 
 		#expect(response.pds?.serviceEndpoint == "https://milkcap.us-west.host.bsky.network")
 	}
+
+	private func timedTest(_ test: () async throws  -> ()) async throws {
+		let start = CFAbsoluteTimeGetCurrent()
+		try await test()
+		let diff = CFAbsoluteTimeGetCurrent() - start
+		print("This test took \(diff) seconds")
+	}
 }