From 8263076d9af8465b1c94fc2e0bee01b6cd15be27 Mon Sep 17 00:00:00 2001
From: Alva Swanson <alvasw@protonmail.com>
Date: Fri, 2 Dec 2022 21:52:40 +0100
Subject: [PATCH] Add ability to check whether a given onion service is online

When another peer connects to us over Tor the connecting peer can lie
about its onion address. We can challenge the peer to sign a payload to
proof that the connecting peer has the private key of the provided onion
address. This change adds the ability to check whether the onion service
is known to the Tor directory servers.
---
 .../network/p2p/node/transport/ClearNetTransport.java    | 9 +++++++++
 .../bisq/network/p2p/node/transport/I2PTransport.java    | 5 +++++
 .../bisq/network/p2p/node/transport/TorTransport.java    | 5 +++++
 .../java/bisq/network/p2p/node/transport/Transport.java  | 2 ++
 tor/src/main/java/bisq/tor/Tor.java                      | 4 ++++
 tor/src/main/java/bisq/tor/TorController.java            | 8 ++++++++
 6 files changed, 33 insertions(+)

diff --git a/network/src/main/java/bisq/network/p2p/node/transport/ClearNetTransport.java b/network/src/main/java/bisq/network/p2p/node/transport/ClearNetTransport.java
index 286325fff0..3b0d4193fe 100644
--- a/network/src/main/java/bisq/network/p2p/node/transport/ClearNetTransport.java
+++ b/network/src/main/java/bisq/network/p2p/node/transport/ClearNetTransport.java
@@ -83,4 +83,13 @@ public CompletableFuture<Void> shutdown() {
     public Optional<Address> getServerAddress(String serverId) {
         return Optional.empty();
     }
+
+    @Override
+    public boolean isAddressAvailable(Address address) {
+        try (Socket ignored = getSocket(address)) {
+            return true;
+        } catch (IOException e) {
+            return false;
+        }
+    }
 }
diff --git a/network/src/main/java/bisq/network/p2p/node/transport/I2PTransport.java b/network/src/main/java/bisq/network/p2p/node/transport/I2PTransport.java
index 54bbb43595..f248ba2c4d 100644
--- a/network/src/main/java/bisq/network/p2p/node/transport/I2PTransport.java
+++ b/network/src/main/java/bisq/network/p2p/node/transport/I2PTransport.java
@@ -175,6 +175,11 @@ public Socket getSocket(Address address) throws IOException {
         }
     }
 
+    @Override
+    public boolean isAddressAvailable(Address address) {
+        throw new UnsupportedOperationException("isAddressAvailable needs to be implemented for I2P.");
+    }
+
     @Override
     public CompletableFuture<Void> shutdown() {
         initializeCalled = false;
diff --git a/network/src/main/java/bisq/network/p2p/node/transport/TorTransport.java b/network/src/main/java/bisq/network/p2p/node/transport/TorTransport.java
index 6e2533e461..153c9e1611 100644
--- a/network/src/main/java/bisq/network/p2p/node/transport/TorTransport.java
+++ b/network/src/main/java/bisq/network/p2p/node/transport/TorTransport.java
@@ -90,6 +90,11 @@ public Socket getSocket(Address address) throws IOException {
         return socket;
     }
 
+    @Override
+    public boolean isAddressAvailable(Address address) {
+        return tor.isHiddenServiceAvailable(address.getHost());
+    }
+
     public Optional<Socks5Proxy> getSocksProxy() throws IOException {
         return Optional.of(tor.getSocks5Proxy(null));
     }
diff --git a/network/src/main/java/bisq/network/p2p/node/transport/Transport.java b/network/src/main/java/bisq/network/p2p/node/transport/Transport.java
index 3f40bfb823..2aee3d028b 100644
--- a/network/src/main/java/bisq/network/p2p/node/transport/Transport.java
+++ b/network/src/main/java/bisq/network/p2p/node/transport/Transport.java
@@ -83,5 +83,7 @@ default Optional<Socks5Proxy> getSocksProxy() throws IOException {
 
     Optional<Address> getServerAddress(String serverId);
 
+    boolean isAddressAvailable(Address address);
+
     CompletableFuture<Void> shutdown();
 }
diff --git a/tor/src/main/java/bisq/tor/Tor.java b/tor/src/main/java/bisq/tor/Tor.java
index abcdfa3ff5..482a5dba5b 100644
--- a/tor/src/main/java/bisq/tor/Tor.java
+++ b/tor/src/main/java/bisq/tor/Tor.java
@@ -282,6 +282,10 @@ public Optional<String> getHostName(String serverId) {
         return Optional.empty();
     }
 
+    public boolean isHiddenServiceAvailable(String onionUrl) {
+        return torController.isHiddenServiceAvailable(onionUrl);
+    }
+
     private void setState(State newState) {
         log.info("Set new state {}", newState);
         checkArgument(newState.ordinal() > state.get().ordinal(),
diff --git a/tor/src/main/java/bisq/tor/TorController.java b/tor/src/main/java/bisq/tor/TorController.java
index 40b434b14a..f65024f52c 100644
--- a/tor/src/main/java/bisq/tor/TorController.java
+++ b/tor/src/main/java/bisq/tor/TorController.java
@@ -119,6 +119,14 @@ int getProxyPort() throws IOException {
         return Integer.parseInt(port);
     }
 
+    boolean isHiddenServiceAvailable(String onionUrl) {
+        try {
+            return torControlConnection().isHSAvailable(onionUrl);
+        } catch (IOException e) {
+            return false;
+        }
+    }
+
     TorControlConnection.CreateHiddenServiceResult createHiddenService(int hiddenServicePort,
                                                                        int localPort) throws IOException {
         assertState();