Authenticate through Mojang's session server; check client version

Stop sending the Minecraft access token to the Saturn server. The connect loop now: 1. fetches GET /versions and compares this client's mod version: supported -> connect; deprecated -> warn, connect; neither -> warn, don't connect (warnings are shown once per status change) 2. requests auth_challenge with the username to get a server id 3. calls Mojang's session `join` with the access token and server id (the token only goes to Mojang); a refused token gives up 4. requests auth_verify, which the server confirms with `hasJoined` Add SaturnProvider.getModVersion() and showWarning() for the version check and its toast. Refs saturnclientmc/saturnclient#7 Co-Authored-By: Claude Opus 5.5 <[email protected]>
2026-09-25 15:22:37 +02:00
parent 510760d590
commit 2de394ebbf
4 changed files with 206 additions and 9 deletions
@@ -0,0 +1,60 @@
+package org.saturnclient.client;
+
+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.time.Duration;
+import java.util.UUID;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.node.ObjectNode;
+
+/**
+ * Mojang's session server "join" call, the same one vanilla makes when joining
+ * an online-mode server. The access token is only ever sent to Mojang; the
+ * Saturn server then confirms the join with {@code hasJoined}.
+ */
+public final class MojangSession {
+    private static final URI JOIN_URI = URI.create("https://sessionserver.mojang.com/session/minecraft/join");
+    private static final ObjectMapper MAPPER = new ObjectMapper();
+
+    public enum JoinResult {
+        JOINED,
+        /** Mojang refused the access token; retrying won't help. */
+        REJECTED,
+        /** Network or server error; worth retrying. */
+        FAILED
+    }
+
+    private MojangSession() {
+    }
+
+    public static JoinResult join(HttpClient http, String accessToken, UUID profile, String serverId) {
+        ObjectNode body = MAPPER.createObjectNode()
+                .put("accessToken", accessToken)
+                .put("selectedProfile", profile.toString().replace("-", ""))
+                .put("serverId", serverId);
+
+        HttpRequest request = HttpRequest.newBuilder(JOIN_URI)
+                .timeout(Duration.ofSeconds(10))
+                .header("Content-Type", "application/json")
+                .POST(HttpRequest.BodyPublishers.ofString(body.toString()))
+                .build();
+
+        try {
+            int status = http.send(request, HttpResponse.BodyHandlers.discarding()).statusCode();
+
+            if (status == 204 || status == 200) {
+                return JoinResult.JOINED;
+            }
+
+            return status == 401 || status == 403 ? JoinResult.REJECTED : JoinResult.FAILED;
+        } catch (InterruptedException e) {
+            Thread.currentThread().interrupt();
+            return JoinResult.FAILED;
+        } catch (Exception e) {
+            return JoinResult.FAILED;
+        }
+    }
+}