From fb0af4f85e4285ae1641e9acb610c5512f0dfedd Mon Sep 17 00:00:00 2001 From: Evan Goode Date: Mon, 18 Nov 2024 21:44:54 -0500 Subject: [PATCH] initial commit --- .github/workflows/nix-build.yml | 18 +++ .gitignore | 5 + LICENSE | 121 ++++++++++++++++++ README.md | 23 ++++ flake.lock | 60 +++++++++ flake.nix | 41 ++++++ pom.xml | 66 ++++++++++ shell.nix | 4 + .../java/org/unmojang/ProxyFix/Premain.java | 67 ++++++++++ 9 files changed, 405 insertions(+) create mode 100644 .github/workflows/nix-build.yml create mode 100644 .gitignore create mode 100644 LICENSE create mode 100644 README.md create mode 100644 flake.lock create mode 100644 flake.nix create mode 100644 pom.xml create mode 100644 shell.nix create mode 100644 src/main/java/org/unmojang/ProxyFix/Premain.java diff --git a/.github/workflows/nix-build.yml b/.github/workflows/nix-build.yml new file mode 100644 index 0000000..657cd53 --- /dev/null +++ b/.github/workflows/nix-build.yml @@ -0,0 +1,18 @@ +name: nix build +on: + pull_request: + push: + workflow_dispatch: +jobs: + nix-build: + runs-on: ubuntu-latest + steps: + - uses: actions/checkout@v3 + - uses: cachix/install-nix-action@v20 + with: + github_access_token: ${{ secrets.GITHUB_TOKEN }} + extra_nix_config: | + extra-platforms = aarch64-linux + - uses: DeterminateSystems/magic-nix-cache-action@main + - run: nix build + - run: nix flake check diff --git a/.gitignore b/.gitignore new file mode 100644 index 0000000..b331fa4 --- /dev/null +++ b/.gitignore @@ -0,0 +1,5 @@ +.direnv +.envrc +.idea +target +result diff --git a/LICENSE b/LICENSE new file mode 100644 index 0000000..0e259d4 --- /dev/null +++ b/LICENSE @@ -0,0 +1,121 @@ +Creative Commons Legal Code + +CC0 1.0 Universal + + CREATIVE COMMONS CORPORATION IS NOT A LAW FIRM AND DOES NOT PROVIDE + LEGAL SERVICES. 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Affirmer understands and acknowledges that Creative Commons is not a + party to this document and has no duty or obligation with respect to + this CC0 or use of the Work. diff --git a/README.md b/README.md new file mode 100644 index 0000000..99af14c --- /dev/null +++ b/README.md @@ -0,0 +1,23 @@ +# Java Proxy Fix + +This is a Java agent that remaps all calls to `java.net.URL.openConnection(java.net.Proxy proxy)` to `java.net.URL.openConnection()`, meaning that `URL.openConnection` will always ignore the proxy supplied to it and use the system proxy instead (e.g. the proxy specified by the `http.proxyHost` and `https.proxyHost` system properties. + +This is useful for MITMing communication between Minecraft servers and Minecraft authentication servers (such as Drasl). Minecraft often calls `URL.openConnection(Proxy.NO_PROXY)` when communicating with authentication servers (see usages of `YggdrasilAuthenticationService` in the Minecraft source). So we can use this Java agent to get the Minecraft server to respect `-Dhttps.proxyHost` and inspect the traffic using mitmproxy or similar. + +I could have sworn I'd seen something like this before, but I couldn't find it, so I wrote another one with some help from the LLM. + +## Example usage + +``` +java -Xmx512M -Xms512M \ + -Dminecraft.api.env=custom \ + -Dminecraft.api.auth.host=https://drasl.unmojang.org/auth \ + -Dminecraft.api.account.host=https://drasl.unmojang.org/account \ + -Dminecraft.api.session.host=https://drasl.unmojang.org/session \ + -Dminecraft.api.services.host=https://drasl.unmojang.org/services \ + -Djavax.net.ssl.trustStore=/home/user/cacerts -Djavax.net.ssl.trustStorePassword=changeit -Dhttp.proxyHost=localhost -Dhttp.proxyPort=8080 -Dhttps.proxyHost=localhost -Dhttps.proxyPort=8080 \ + -javaagent:ProxyFix-1.0-SNAPSHOT-jar-with-dependencies.jar \ + -jar server.jar nogui +``` + +See also https://github.com/unmojang/drasl/blob/master/doc/troubleshooting.md. diff --git a/flake.lock b/flake.lock new file mode 100644 index 0000000..256969d --- /dev/null +++ b/flake.lock @@ -0,0 +1,60 @@ +{ + "nodes": { + "flake-utils": { + "inputs": { + "systems": "systems" + }, + "locked": { + "lastModified": 1731533236, + "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=", + "owner": "numtide", + "repo": "flake-utils", + "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b", + "type": "github" + }, + "original": { + "owner": "numtide", + "repo": "flake-utils", + "type": "github" + } + }, + "nixpkgs": { + "locked": { + "lastModified": 1731676054, + "narHash": "sha256-OZiZ3m8SCMfh3B6bfGC/Bm4x3qc1m2SVEAlkV6iY7Yg=", + "owner": "NixOS", + "repo": "nixpkgs", + "rev": "5e4fbfb6b3de1aa2872b76d49fafc942626e2add", + "type": "github" + }, + "original": { + "id": "nixpkgs", + "ref": "nixos-unstable", + "type": "indirect" + } + }, + "root": { + "inputs": { + "flake-utils": "flake-utils", + "nixpkgs": "nixpkgs" + } + }, + "systems": { + "locked": { + "lastModified": 1681028828, + "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=", + "owner": "nix-systems", + "repo": "default", + "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e", + "type": "github" + }, + "original": { + "owner": "nix-systems", + "repo": "default", + "type": "github" + } + } + }, + "root": "root", + "version": 7 +} diff --git a/flake.nix b/flake.nix new file mode 100644 index 0000000..b3de57f --- /dev/null +++ b/flake.nix @@ -0,0 +1,41 @@ +{ + description = "Java Agent with Maven and ASM"; + + inputs.nixpkgs.url = "nixpkgs/nixos-unstable"; + inputs.flake-utils.url = "github:numtide/flake-utils"; + + outputs = + { + self, + nixpkgs, + flake-utils, + }: + flake-utils.lib.eachDefaultSystem ( + system: + let + pkgs = import nixpkgs { inherit system; }; + in + { + # Build the Java agent with Maven + packages.default = pkgs.maven.buildMavenPackage { + pname = "proxy-fix"; + version = "1.0"; + src = ./.; + mvnHash = "sha256-6RIG79Inz7FrhX5/+t5KMrdcPqDPRffibeEK+2xecRc="; + + installPhase = '' + mkdir -p $out/ + cp target/ProxyFix-1.0-SNAPSHOT-jar-with-dependencies.jar $out/ + ''; + }; + + # Development shell with JDK 21 and Maven + devShells.default = pkgs.mkShell { + buildInputs = with pkgs; [ + jdk21 + maven + ]; + }; + } + ); +} diff --git a/pom.xml b/pom.xml new file mode 100644 index 0000000..9d956da --- /dev/null +++ b/pom.xml @@ -0,0 +1,66 @@ + + 4.0.0 + org.unmojang + ProxyFix + 1.0-SNAPSHOT + + + + org.ow2.asm + asm + 9.7 + + + + + + + org.apache.maven.plugins + maven-compiler-plugin + 3.13.0 + + 1.8 + 1.8 + + + + org.apache.maven.plugins + maven-jar-plugin + 3.4.2 + + + default-jar + none + + + + + org.apache.maven.plugins + maven-assembly-plugin + 3.7.1 + + + + org.unmojang.ProxyFix.Premain + true + true + + + + jar-with-dependencies + + + + + assemble-all + package + + single + + + + + + + diff --git a/shell.nix b/shell.nix new file mode 100644 index 0000000..7761460 --- /dev/null +++ b/shell.nix @@ -0,0 +1,4 @@ +{ pkgs ? import {}}: +pkgs.mkShell { + nativeBuildInputs = with pkgs; [ jdk21 ]; +} diff --git a/src/main/java/org/unmojang/ProxyFix/Premain.java b/src/main/java/org/unmojang/ProxyFix/Premain.java new file mode 100644 index 0000000..b0eadaa --- /dev/null +++ b/src/main/java/org/unmojang/ProxyFix/Premain.java @@ -0,0 +1,67 @@ +package org.unmojang.ProxyFix; + +import java.lang.instrument.ClassFileTransformer; +import java.lang.instrument.Instrumentation; +import java.lang.Class; +import java.security.ProtectionDomain; +import java.io.*; +import org.objectweb.asm.*; + +public class Premain { + public static void premain(String agentArgs, Instrumentation inst) { + System.out.println("[ProxyFix] Running..."); + inst.addTransformer(new URLTransformer(), true); + try { + Class urlClass = Class.forName("java.net.URL"); + inst.retransformClasses(urlClass); + } catch (Exception e) { + e.printStackTrace(); + } + } + + static class URLTransformer implements ClassFileTransformer { + @Override + public byte[] transform(ClassLoader loader, String className, Class classBeingRedefined, + ProtectionDomain protectionDomain, byte[] classFileBuffer) { + if ("java/net/URL".equals(className)) { + return transformURLClass(classFileBuffer); + } + return classFileBuffer; + } + + private byte[] transformURLClass(byte[] classFileBuffer) { + ClassReader classReader = new ClassReader(classFileBuffer); + ClassWriter classWriter = new ClassWriter(ClassWriter.COMPUTE_FRAMES | ClassWriter.COMPUTE_MAXS); + + classReader.accept(new ClassVisitor(Opcodes.ASM9, classWriter) { + @Override + public MethodVisitor visitMethod(int access, String name, String descriptor, + String signature, String[] exceptions) { + MethodVisitor mv = super.visitMethod(access, name, descriptor, signature, exceptions); + + if ("openConnection".equals(name) && + "(Ljava/net/Proxy;)Ljava/net/URLConnection;".equals(descriptor)) { + System.out.println("[ProxyFix] Rewriting URL.openConnection"); + return new MethodVisitor(Opcodes.ASM9, mv) { + @Override + public void visitCode() { + super.visitCode(); + mv.visitVarInsn(Opcodes.ALOAD, 0); + mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, + "java/net/URL", + "openConnection", + "()Ljava/net/URLConnection;", + false); + mv.visitInsn(Opcodes.ARETURN); + } + }; + } + return mv; + } + }, 0); + System.out.println("[ProxyFix] Transformed URL class."); + + return classWriter.toByteArray(); + } + } +}