Waterfall/BungeeCord-Patches/0057-Additional-DoS-mitigations.patch
Noah van der Aa f64b560a1e
Updated Upstream (BungeeCord) (#719)
Upstream has released updates that appear to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing

BungeeCord Changes:
b4ccdaa5 #2715: Improve BadPacketException message in MinecraftDecoder
3a116569 #3116: Do not fill in LogRecord caller data by default in slf4j wrapper
2479fab6 #3221: Use computeIfAbsent method in EventBus
51eb1ac6 Dependency upgrades
879f37f0 Upgrade to SnakeYAML 1.30 release
2021-12-23 20:56:40 +01:00

246 lines
12 KiB
Diff

From a97fd919809d2284cdc6a5d68168c99bfe795d9c Mon Sep 17 00:00:00 2001
From: "Five (Xer)" <admin@fivepb.me>
Date: Sat, 30 Jan 2021 18:04:14 +0100
Subject: [PATCH] Additional DoS mitigations
Some stricter length checks and cached exceptions to withstand more illegitimate connections
Courtesy of Tux and the Velocity Contributors. See:
https://github.com/VelocityPowered/Velocity/commit/5ceac16a821ea35572ff11412ace8929fd06e278
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java b/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
index 40281aa4..a310844d 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/DefinedPacket.java
@@ -44,6 +44,7 @@ public abstract class DefinedPacket
int len = readVarInt( buf );
if ( len > maxLen * 4 )
{
+ if(!MinecraftDecoder.DEBUG) throw STRING_TOO_MANY_BYTES_EXCEPTION; // Waterfall start: Additional DoS mitigations
throw new OverflowPacketException( "Cannot receive string longer than " + maxLen * 4 + " (got " + len + " bytes)" );
}
@@ -53,6 +54,7 @@ public abstract class DefinedPacket
String s = new String( b, Charsets.UTF_8 );
if ( s.length() > maxLen )
{
+ if(!MinecraftDecoder.DEBUG) throw STRING_TOO_LONG_EXCEPTION; // Waterfall start: Additional DoS mitigations
throw new OverflowPacketException( "Cannot receive string longer than " + maxLen + " (got " + s.length() + " characters)" );
}
@@ -284,4 +286,21 @@ public abstract class DefinedPacket
@Override
public abstract String toString();
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ private static final OverflowPacketException STRING_TOO_LONG_EXCEPTION
+ = new OverflowPacketException("A string was longer than allowed. For more "
+ + "information, launch Waterfall with -Dwaterfall.packet-decode-logging=true");
+ private static final OverflowPacketException STRING_TOO_MANY_BYTES_EXCEPTION
+ = new OverflowPacketException("A string had more data than allowed. For more "
+ + "information, launch Waterfall with -Dwaterfall.packet-decode-logging=true");
+
+ public int expectedMaxLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return -1;
+ }
+
+ public int expectedMinLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return 0;
+ }
+ // Waterfall end
}
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java b/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
index f5e414c1..ac83e325 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/MinecraftDecoder.java
@@ -3,7 +3,7 @@ package net.md_5.bungee.protocol;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.ChannelHandlerContext;
-import io.netty.handler.codec.DecoderException;
+import io.netty.handler.codec.CorruptedFrameException;
import io.netty.handler.codec.MessageToMessageDecoder;
import java.util.List;
import lombok.AllArgsConstructor;
@@ -56,10 +56,16 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf>
if ( packet != null )
{
packetTypeInfo = packet.getClass();
+ doLengthSanityChecks(in, packet, prot.getDirection(), packetId); // Waterfall: Additional DoS mitigations
packet.read( in, prot.getDirection(), protocolVersion );
if ( in.isReadable() )
{
+ // Waterfall start: Additional DoS mitigations
+ if(!DEBUG) {
+ throw PACKET_NOT_READ_TO_END;
+ }
+ // Waterfall end
throw new BadPacketException( "Packet " + protocol + ":" + prot.getDirection() + "/" + packetId + " (" + packet.getClass().getSimpleName() + ") larger than expected, extra bytes: " + in.readableBytes() );
}
} else
@@ -70,6 +76,11 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf>
out.add( new PacketWrapper( packet, slice ) );
slice = null;
} catch (BadPacketException | IndexOutOfBoundsException e) {
+ // Waterfall start: Additional DoS mitigations
+ if(!DEBUG) {
+ throw e;
+ }
+ // Waterfall end
final String packetTypeStr;
if (packetTypeInfo instanceof Integer) {
packetTypeStr = "id " + Integer.toHexString((Integer) packetTypeInfo);
@@ -87,4 +98,52 @@ public class MinecraftDecoder extends MessageToMessageDecoder<ByteBuf>
}
}
}
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ public static final boolean DEBUG = Boolean.getBoolean("waterfall.packet-decode-logging");
+
+ // Cached Exceptions:
+ private static final CorruptedFrameException PACKET_LENGTH_OVERSIZED =
+ new CorruptedFrameException("A packet could not be decoded because it was too large. For more "
+ + "information, launch Waterfall with -Dwaterfall.packet-decode-logging=true");
+ private static final CorruptedFrameException PACKET_LENGTH_UNDERSIZED =
+ new CorruptedFrameException("A packet could not be decoded because it was smaller than allowed. For more "
+ + "information, launch Waterfall with -Dwaterfall.packet-decode-logging=true");
+ private static final BadPacketException PACKET_NOT_READ_TO_END =
+ new BadPacketException("Couldn't read all bytes from a packet. For more "
+ + "information, launch Waterfall with -Dwaterfall.packet-decode-logging=true");
+
+
+ private void doLengthSanityChecks(ByteBuf buf, DefinedPacket packet,
+ ProtocolConstants.Direction direction, int packetId) throws Exception {
+ int expectedMinLen = packet.expectedMinLength(buf, direction, protocolVersion);
+ int expectedMaxLen = packet.expectedMaxLength(buf, direction, protocolVersion);
+ if (expectedMaxLen != -1 && buf.readableBytes() > expectedMaxLen) {
+ throw handleOverflow(packet, expectedMaxLen, buf.readableBytes(), packetId);
+ }
+ if (buf.readableBytes() < expectedMinLen) {
+ throw handleUnderflow(packet, expectedMaxLen, buf.readableBytes(), packetId);
+ }
+ }
+
+ private Exception handleOverflow(DefinedPacket packet, int expected, int actual, int packetId) {
+ if (DEBUG) {
+ throw new CorruptedFrameException( "Packet " + packet.getClass() + " " + packetId
+ + " Protocol " + protocolVersion + " was too big (expected "
+ + expected + " bytes, got " + actual + " bytes)");
+ } else {
+ return PACKET_LENGTH_OVERSIZED;
+ }
+ }
+
+ private Exception handleUnderflow(DefinedPacket packet, int expected, int actual, int packetId) {
+ if (DEBUG) {
+ throw new CorruptedFrameException( "Packet " + packet.getClass() + " " + packetId
+ + " Protocol " + protocolVersion + " was too small (expected "
+ + expected + " bytes, got " + actual + " bytes)");
+ } else {
+ return PACKET_LENGTH_UNDERSIZED;
+ }
+ }
+ // Waterfall end
}
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/packet/EncryptionResponse.java b/protocol/src/main/java/net/md_5/bungee/protocol/packet/EncryptionResponse.java
index 388f6cdb..53575ce0 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/packet/EncryptionResponse.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/packet/EncryptionResponse.java
@@ -38,4 +38,16 @@ public class EncryptionResponse extends DefinedPacket
{
handler.handle( this );
}
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ public int expectedMaxLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ // It turns out these come out to the same length, whether we're talking >=1.8 or not.
+ // The length prefix always winds up being 2 bytes.
+ return 260;
+ }
+
+ public int expectedMinLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return expectedMaxLength(buf, direction, protocolVersion);
+ }
+ // Waterfall end
}
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/packet/LoginRequest.java b/protocol/src/main/java/net/md_5/bungee/protocol/packet/LoginRequest.java
index 08ee376e..cfd8e64e 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/packet/LoginRequest.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/packet/LoginRequest.java
@@ -7,6 +7,7 @@ import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import net.md_5.bungee.protocol.AbstractPacketHandler;
import net.md_5.bungee.protocol.DefinedPacket;
+import net.md_5.bungee.protocol.ProtocolConstants;
@Data
@NoArgsConstructor
@@ -34,4 +35,12 @@ public class LoginRequest extends DefinedPacket
{
handler.handle( this );
}
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ public int expectedMaxLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ // Accommodate the rare (but likely malicious) use of UTF-8 usernames, since it is technically
+ // legal on the protocol level.
+ return 1 + (16 * 4);
+ }
+ // Waterfall end
}
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/packet/PingPacket.java b/protocol/src/main/java/net/md_5/bungee/protocol/packet/PingPacket.java
index 5f24d425..3163a771 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/packet/PingPacket.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/packet/PingPacket.java
@@ -7,6 +7,7 @@ import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import net.md_5.bungee.protocol.AbstractPacketHandler;
import net.md_5.bungee.protocol.DefinedPacket;
+import net.md_5.bungee.protocol.ProtocolConstants;
@Data
@NoArgsConstructor
@@ -34,4 +35,14 @@ public class PingPacket extends DefinedPacket
{
handler.handle( this );
}
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ public int expectedMaxLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return 8;
+ }
+
+ public int expectedMinLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return 8;
+ }
+ // Waterfall end
}
diff --git a/protocol/src/main/java/net/md_5/bungee/protocol/packet/StatusRequest.java b/protocol/src/main/java/net/md_5/bungee/protocol/packet/StatusRequest.java
index 738f0c92..ec33d337 100644
--- a/protocol/src/main/java/net/md_5/bungee/protocol/packet/StatusRequest.java
+++ b/protocol/src/main/java/net/md_5/bungee/protocol/packet/StatusRequest.java
@@ -6,6 +6,7 @@ import lombok.EqualsAndHashCode;
import lombok.NoArgsConstructor;
import net.md_5.bungee.protocol.AbstractPacketHandler;
import net.md_5.bungee.protocol.DefinedPacket;
+import net.md_5.bungee.protocol.ProtocolConstants;
@Data
@NoArgsConstructor
@@ -28,4 +29,10 @@ public class StatusRequest extends DefinedPacket
{
handler.handle( this );
}
+
+ // Waterfall start: Additional DoS mitigations, courtesy of Velocity
+ public int expectedMaxLength(ByteBuf buf, ProtocolConstants.Direction direction, int protocolVersion) {
+ return 0;
+ }
+ // Waterfall end
}
--
2.34.1