From 57f53f038c4e1383c5b8a76b74bd6212177f71ed Mon Sep 17 00:00:00 2001
From: Andreas Schildbach <andreas.schildbach@bloq.com>
Date: Wed, 4 Mar 2020 17:15:07 +0100
Subject: [PATCH] Peer: Prevent connecting to remote peers if required services
 are not supported.

---
 .../src/main/java/org/bitcoinj/core/Peer.java | 28 ++++++++++++-------
 .../java/org/bitcoinj/core/PeerGroup.java     |  2 +-
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/core/src/main/java/org/bitcoinj/core/Peer.java b/core/src/main/java/org/bitcoinj/core/Peer.java
index 06d25f1b2..2ed96f2df 100644
--- a/core/src/main/java/org/bitcoinj/core/Peer.java
+++ b/core/src/main/java/org/bitcoinj/core/Peer.java
@@ -68,6 +68,7 @@ public class Peer extends PeerSocketHandler {
 
     private final NetworkParameters params;
     private final AbstractBlockChain blockChain;
+    private final long requiredServices;
     private final Context context;
 
     private final CopyOnWriteArrayList<ListenerRegistration<BlocksDownloadedEventListener>> blocksDownloadedEventListeners
@@ -206,7 +207,7 @@ public class Peer extends PeerSocketHandler {
      */
     public Peer(NetworkParameters params, VersionMessage ver, PeerAddress remoteAddress,
                 @Nullable AbstractBlockChain chain) {
-        this(params, ver, remoteAddress, chain, Integer.MAX_VALUE);
+        this(params, ver, remoteAddress, chain, 0, Integer.MAX_VALUE);
     }
 
     /**
@@ -224,12 +225,13 @@ public class Peer extends PeerSocketHandler {
      * used to keep track of which peers relayed transactions and offer more descriptive logging.</p>
      */
     public Peer(NetworkParameters params, VersionMessage ver, PeerAddress remoteAddress,
-                @Nullable AbstractBlockChain chain, int downloadTxDependencyDepth) {
+                @Nullable AbstractBlockChain chain, long requiredServices, int downloadTxDependencyDepth) {
         super(params, remoteAddress);
         this.params = Preconditions.checkNotNull(params);
         this.versionMessage = Preconditions.checkNotNull(ver);
         this.vDownloadTxDependencyDepth = chain != null ? downloadTxDependencyDepth : 0;
         this.blockChain = chain;  // Allowed to be null.
+        this.requiredServices = requiredServices;
         this.vDownloadData = chain != null;
         this.getDataFutures = new CopyOnWriteArrayList<>();
         this.getAddrFutures = new LinkedList<>();
@@ -520,33 +522,39 @@ public class Peer extends PeerSocketHandler {
         future.set(m);
     }
 
-    private void processVersionMessage(VersionMessage m) throws ProtocolException {
+    private void processVersionMessage(VersionMessage peerVersionMessage) throws ProtocolException {
         if (vPeerVersionMessage != null)
             throw new ProtocolException("Got two version messages from peer");
-        vPeerVersionMessage = m;
+        vPeerVersionMessage = peerVersionMessage;
         // Switch to the new protocol version.
         log.info(toString());
         // bitcoinj is a client mode implementation. That means there's not much point in us talking to other client
         // mode nodes because we can't download the data from them we need to find/verify transactions. Some bogus
         // implementations claim to have a block chain in their services field but then report a height of zero, filter
         // them out here.
-        if (!vPeerVersionMessage.hasLimitedBlockChain() ||
-                (!params.allowEmptyPeerChain() && vPeerVersionMessage.bestHeight == 0)) {
+        if (!peerVersionMessage.hasLimitedBlockChain() ||
+                (!params.allowEmptyPeerChain() && peerVersionMessage.bestHeight == 0)) {
             // Shut down the channel gracefully.
             log.info("{}: Peer does not have at least a recent part of the block chain.", this);
             close();
             return;
         }
-        if ((vPeerVersionMessage.localServices
-                & VersionMessage.NODE_BITCOIN_CASH) == VersionMessage.NODE_BITCOIN_CASH) {
+        if ((peerVersionMessage.localServices & requiredServices) != requiredServices) {
+            log.info("{}: Peer doesn't support these required services: {}", this,
+                    VersionMessage.toStringServices(requiredServices & ~peerVersionMessage.localServices));
+            // Shut down the channel gracefully.
+            close();
+            return;
+        }
+        if ((peerVersionMessage.localServices & VersionMessage.NODE_BITCOIN_CASH) == VersionMessage.NODE_BITCOIN_CASH) {
             log.info("{}: Peer follows an incompatible block chain.", this);
             // Shut down the channel gracefully.
             close();
             return;
         }
-        if (vPeerVersionMessage.bestHeight < 0)
+        if (peerVersionMessage.bestHeight < 0)
             // In this case, it's a protocol violation.
-            throw new ProtocolException("Peer reports invalid best height: " + vPeerVersionMessage.bestHeight);
+            throw new ProtocolException("Peer reports invalid best height: " + peerVersionMessage.bestHeight);
         // Now it's our turn ...
         // Send an ACK message stating we accept the peers protocol version.
         sendMessage(new VersionAck());
diff --git a/core/src/main/java/org/bitcoinj/core/PeerGroup.java b/core/src/main/java/org/bitcoinj/core/PeerGroup.java
index 23d0ac816..25625dbbb 100644
--- a/core/src/main/java/org/bitcoinj/core/PeerGroup.java
+++ b/core/src/main/java/org/bitcoinj/core/PeerGroup.java
@@ -1382,7 +1382,7 @@ public class PeerGroup implements TransactionBroadcaster {
     /** You can override this to customise the creation of {@link Peer} objects. */
     @GuardedBy("lock")
     protected Peer createPeer(PeerAddress address, VersionMessage ver) {
-        return new Peer(params, ver, address, chain, downloadTxDependencyDepth);
+        return new Peer(params, ver, address, chain, requiredServices, downloadTxDependencyDepth);
     }
 
     /**