Add runtime Tor-egress self-check (fail-closed) for Nostr relays

Runtime-verified whether Apple's URLSession honors connectionProxyDictionary SOCKS settings for Nostr relay traffic (plain HTTPS + URLSessionWebSocketTask), since the app routes all Nostr traffic through Arti's local SOCKS5 proxy solely via those keys and Apple does not officially support SOCKS for URLSession on iOS. Verification harness (scripts/tor-egress-verification/): a minimal SOCKS5 CONNECT proxy that logs arriving connections, plus a Swift probe that runs an HTTPS GET and a WebSocket ping through a URLSession configured with the proxy dict. Result: on macOS (kCFNetworkProxiesSOCKS* constants) and the iOS simulator (raw "SOCKSProxy"/"SOCKSPort" string keys, the exact app path) BOTH HTTP and WebSocket are proxied, do remote DNS through the proxy, and the proxied session is fail-closed (every request errors when the SOCKS proxy is down). The feared direct-egress leak did not reproduce on the tested platforms. Defense-in-depth for the platform Apple does not guarantee (physical iOS): add TorEgressVerifier, which performs a canary request through the proxied session and asserts the exit is a Tor node (check.torproject.org IsTor==true), positively detecting a direct egress even if the OS silently ignored the proxy. Policy: verifiedTor allows (cached for a TTL); notTor refuses (leak detected, never open relays); unreachable allows-with-warning (session stays fail-closed by construction). Wired into TorManager.awaitEgressReady() and required by both NostrRelayManager and GeoRelayDirectory before opening connections. Cache is invalidated on Tor restart/dormant/shutdown. Never falls back to a direct connection. Probe is injected so the policy/caching is unit-tested offline; the live-network harness lives under scripts/ and is not run by CI. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-25 15:45:20 +00:00 · 2026-07-01 23:34:10 +02:00
parent f688e529f6
commit c7ee2a4cb4
9 changed files with 675 additions and 2 deletions
@@ -0,0 +1,90 @@
+// Standalone harness: does Apple's URLSession honor connectionProxyDictionary
+// SOCKS settings for a plain HTTPS GET and for URLSessionWebSocketTask?
+//
+// Build:  swiftc -O proxy_probe.swift -o proxy_probe
+// Usage:  proxy_probe <http|ws> <cf|raw> <proxyPort> [targetURL]
+//
+// Prints a single RESULT line: RESULT <mode> <keyStyle> <outcome> <detail>
+// The caller correlates this with the SOCKS proxy's connection log to decide
+// whether the request was proxied.
+#if canImport(CFNetwork)
+import CFNetwork
+#endif
+import Foundation
+
+let args = CommandLine.arguments
+guard args.count >= 4 else {
+    FileHandle.standardError.write(Data("usage: proxy_probe <http|ws> <cf|raw> <proxyPort> [targetURL]\n".utf8))
+    exit(2)
+}
+let mode = args[1]
+let keyStyle = args[2]
+let proxyPort = Int(args[3]) ?? 19999
+let host = "127.0.0.1"
+
+func makeProxyDict() -> [AnyHashable: Any] {
+    switch keyStyle {
+#if os(macOS)
+    case "cf":
+        // The exact constants the app uses on macOS.
+        return [
+            kCFNetworkProxiesSOCKSEnable as String: 1,
+            kCFNetworkProxiesSOCKSProxy as String: host,
+            kCFNetworkProxiesSOCKSPort as String: proxyPort
+        ]
+#endif
+    default:
+        // The exact raw string keys the app uses on iOS.
+        return [
+            "SOCKSEnable": 1,
+            "SOCKSProxy": host,
+            "SOCKSPort": proxyPort
+        ]
+    }
+}
+
+let cfg = URLSessionConfiguration.ephemeral
+cfg.waitsForConnectivity = false
+cfg.timeoutIntervalForRequest = 20
+cfg.connectionProxyDictionary = makeProxyDict()
+let session = URLSession(configuration: cfg)
+
+func emit(_ outcome: String, _ detail: String) {
+    print("RESULT \(mode) \(keyStyle) \(outcome) \(detail)")
+    exit(outcome == "ERROR" ? 1 : 0)
+}
+
+let sem = DispatchSemaphore(value: 0)
+
+if mode == "http" {
+    let target = URL(string: args.count >= 5 ? args[4] : "https://raw.githubusercontent.com/permissionlesstech/georelays/refs/heads/main/nostr_relays.csv")!
+    let task = session.dataTask(with: target) { data, resp, err in
+        if let err = err {
+            emit("ERROR", "\(err.localizedDescription)")
+        } else if let http = resp as? HTTPURLResponse {
+            emit("OK", "status=\(http.statusCode) bytes=\(data?.count ?? 0)")
+        } else {
+            emit("OK", "bytes=\(data?.count ?? 0)")
+        }
+    }
+    task.resume()
+} else {
+    // WebSocket
+    let target = URL(string: args.count >= 5 ? args[4] : "wss://relay.damus.io")!
+    let ws = session.webSocketTask(with: target)
+    ws.resume()
+    // A successful ping proves the TLS+WS handshake completed end-to-end.
+    ws.sendPing { err in
+        if let err = err {
+            emit("ERROR", "\(err.localizedDescription)")
+        } else {
+            emit("OK", "ws-ping-ok")
+        }
+    }
+}
+
+// Global watchdog so we never hang.
+DispatchQueue.global().asyncAfter(deadline: .now() + 25) {
+    emit("ERROR", "timeout")
+}
+sem.wait()