Derive correct UUID for offline players in lobby logic

Cargo.lock

@@ -175,6 +175,15 @@ version = "1.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"
 
+[[package]]
+name = "block-buffer"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4152116fd6e9dadb291ae18fc1ec3575ed6d84c29642d97890f4b4a3417297e4"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "blocking"
 version = "1.1.0"
@@ -391,6 +400,15 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "digest"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3dd60d1080a57a05ab032377049e0591415d2b31afd7028356dbf3cc6dcb066"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "doc-comment"
 version = "0.3.3"
@@ -609,6 +627,16 @@ dependencies = [
  "slab",
 ]
 
+[[package]]
+name = "generic-array"
+version = "0.14.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "501466ecc8a30d1d3b7fc9229b122b2ce8ed6e9d9223f1138d4babb253e51817"
+dependencies = [
+ "typenum",
+ "version_check",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.2.3"
@@ -774,6 +802,7 @@ dependencies = [
  "futures",
  "libc",
  "log",
+ "md-5",
  "minecraft-protocol",
  "named-binary-tag",
  "notify",
@@ -815,6 +844,17 @@ dependencies = [
  "value-bag",
 ]
 
+[[package]]
+name = "md-5"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b5a279bb9607f9f53c22d496eade00d138d1bdcccd07d74650387cf94942a15"
+dependencies = [
+ "block-buffer",
+ "digest",
+ "opaque-debug",
+]
+
 [[package]]
 name = "md5"
 version = "0.6.1"
@@ -1009,6 +1049,12 @@ version = "1.8.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "692fcb63b64b1758029e0a96ee63e049ce8c5948587f2f7208df04625e5f6b56"
 
+[[package]]
+name = "opaque-debug"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "624a8340c38c1b80fd549087862da4ba43e08858af025b236e509b6649fc13d5"
+
 [[package]]
 name = "os_str_bytes"
 version = "4.2.0"
@@ -1559,6 +1605,12 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "typenum"
+version = "1.14.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b63708a265f51345575b27fe43f9500ad611579e764c79edbc2037b1121959ec"
+
 [[package]]
 name = "unicase"
 version = "2.6.0"

Cargo.toml

@@ -42,6 +42,7 @@ dotenv = "0.15"
 flate2 = { version = "1.0", default-features = false, features = ["default"] }
 futures = { version = "0.3", default-features = false, features = ["executor"] }
 log = "0.4"
+md-5 = "0.9"
 minecraft-protocol = { git = "https://github.com/timvisee/rust-minecraft-protocol", rev = "356ea54" }
 notify = "4.0"
 pretty_env_logger = "0.4"

src/lobby.rs

@@ -20,10 +20,9 @@ use tokio::net::tcp::{ReadHalf, WriteHalf};
 use tokio::net::TcpStream;
 use tokio::select;
 use tokio::time;
-use uuid::Uuid;
 
 use crate::config::*;
-use crate::mc;
+use crate::mc::{self, uuid};
 use crate::net;
 use crate::proto;
 use crate::proto::client::{Client, ClientInfo, ClientState};
@@ -198,10 +197,7 @@ async fn respond_login_success(
 ) -> Result<(), ()> {
     packet::write_packet(
         LoginSuccess {
-            uuid: Uuid::new_v3(
-                &Uuid::new_v3(&Uuid::nil(), b"OfflinePlayer"),
-                login_start.name.as_bytes(),
-            ),
+            uuid: uuid::offline_player_uuid(&login_start.name),
             username: login_start.name.clone(),
         },
         client,

src/mc/mod.rs

@@ -2,6 +2,7 @@ pub mod ban;
 #[cfg(feature = "rcon")]
 pub mod rcon;
 pub mod server_properties;
+pub mod uuid;
 
 /// Minecraft ticks per second.
 #[allow(unused)]

src/mc/uuid.rs

@@ -0,0 +1,26 @@
+use md5::{Digest, Md5};
+use uuid::Uuid;
+
+/// Offline player namespace.
+const OFFLINE_PLAYER_NAMESPACE: &str = "OfflinePlayer:";
+
+/// Get UUID for given player username.
+pub fn player_uuid(username: &str) -> Uuid {
+    Uuid::from_bytes(jdk_name_uuid_from_bytes(username.as_bytes()))
+}
+
+/// Get UUID for given offline player username.
+pub fn offline_player_uuid(username: &str) -> Uuid {
+    player_uuid(&format!("{}{}", OFFLINE_PLAYER_NAMESPACE, username))
+}
+
+/// Java's `UUID.nameUUIDFromBytes`.
+///
+/// Static factory to retrieve a type 3 (name based) `Uuid` based on the specified byte array.
+///
+/// Ported from: https://github.com/AdoptOpenJDK/openjdk-jdk8u/blob/9a91972c76ddda5c1ce28b50ca38cbd8a30b7a72/jdk/src/share/classes/java/util/UUID.java#L153-L175
+fn jdk_name_uuid_from_bytes(data: &[u8]) -> [u8; 16] {
+    let mut hasher = Md5::new();
+    hasher.update(data);
+    hasher.finalize().into()
+}