I'm out of tolerance for Java for today, it still doesn't work.

src/main/java/net/flashii/mcexts/RPC.java

@@ -22,6 +22,7 @@ import java.util.Map;
 import java.util.UUID;
 import com.google.gson.Gson;
 import com.google.gson.GsonBuilder;
+import net.flashii.mcexts.Tools;
 
 public class RPC {
     private static final String DEFAULT_SECRET = "meow";
@@ -74,6 +75,9 @@ public class RPC {
         throws GeneralSecurityException, IOException, InterruptedException {
         boolean hasBody = bodyStr != null;
         String time = getRequestTimestamp();
+
+        Tools.Log.info("[FII RPC] {} {} @ {}", hasBody ? "POST" : "GET", path, time);
+
         String hash = createRequestSignature(time, URLs.getRpcPath(path), sigStr);
 
         URI url;

src/main/java/net/flashii/mcexts/Tools.java

@@ -0,0 +1,8 @@
+package net.flashii.mcexts;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Tools {
+    public static final Logger Log = LoggerFactory.getLogger("fiiexts");
+}

src/main/java/net/flashii/mcexts/mixin/PlayerListHudMixin.java

@@ -1,5 +1,6 @@
 package net.flashii.mcexts.mixin;
 
+import net.flashii.mcexts.Tools;
 import net.minecraft.client.MinecraftClient;
 import net.minecraft.client.gui.hud.PlayerListHud;
 import org.spongepowered.asm.mixin.Mixin;
@@ -15,7 +16,9 @@ public abstract class PlayerListHudMixin {
             target = "Lnet/minecraft/client/MinecraftClient;isInSingleplayer()Z"
         )
     )
-    public boolean redirectIsInSinglePlayer(MinecraftClient client) {
+    public boolean isInSinglePlayer(MinecraftClient client) {
+        Tools.Log.info("[FII MIXIN] Redirected isInSingleplayer call in PlayerListHud.render!!!");
+
         // always enable BL
         return true;
     }

src/main/java/net/flashii/mcexts/mixin/PlayerManagerMixin.java

@@ -6,6 +6,7 @@ import java.security.GeneralSecurityException;
 import com.mojang.authlib.GameProfile;
 import net.flashii.mcexts.RPC;
 import net.flashii.mcexts.RPCPayload;
+import net.flashii.mcexts.Tools;
 import net.minecraft.server.PlayerManager;
 import net.minecraft.text.Text;
 import net.minecraft.util.Formatting;
@@ -29,13 +30,15 @@ public abstract class PlayerManagerMixin {
 
             if(!payload.is("auth:ok")) {
                 if(payload.is("error")) {
-                    authText = Text.literal(
+                    String errorCode = payload.getAttrStr("code");
-                        payload.getAttrStr(payload.hasAttr("text") ? "text" : "code")
+                    String errorText = payload.hasAttr("text") ? payload.getAttrStr("text") : errorCode;
-                    ).formatted(Formatting.RED);
+                    Tools.Log.info("[FII AUTH] <{}:{}:{}> Error: {} {}", profile.getId(), profile.getName(), sockAddr, errorCode, errorText);
+                    authText = Text.literal(errorText).formatted(Formatting.RED);
                 } else if(payload.is("auth:authorise")) {
                     String userName = payload.getAttrStr("user_name");
                     int userColour = payload.hasAttr("user_colour") ? payload.getAttrInt("user_colour") : 0xFFFFFF;
                     String url = payload.getAttrStr("url");
+                    Tools.Log.info("[FII AUTH] <{}:{}:{}> Authorising: {} {} {}", profile.getId(), profile.getName(), sockAddr, userName, userColour, url);
 
                     authText = Text.literal("Welcome back, ")
                         .append(Text.literal(userName).styled(style -> style.withColor(userColour).withBold(true)))
@@ -47,6 +50,7 @@ public abstract class PlayerManagerMixin {
                 } else if(payload.is("auth:link")) {
                     String code = payload.getAttrStr("code");
                     String url = payload.getAttrStr("url");
+                    Tools.Log.info("[FII AUTH] <{}:{}:{}> Linking: {} {}", profile.getId(), profile.getName(), sockAddr, code, url);
 
                     authText = Text.literal("This seems to be the first time you're connecting!\n")
                         .append(Text.literal("Visit "))
@@ -55,16 +59,22 @@ public abstract class PlayerManagerMixin {
                         .append(Text.literal(code).formatted(Formatting.LIGHT_PURPLE))
                         .append(Text.literal("\n\nAfter you've approved the attempt, connect to the server again and you should be good to go."));
                 } else {
+                    Tools.Log.info("[FII AUTH] <{}:{}:{}> Unknown response: {}", profile.getId(), profile.getName(), sockAddr, payload.getName());
                     authText = Text.literal("Flashii authentication server returned an unknown response, yell at flashwave about this.").formatted(Formatting.RED);
                 }
+            } else {
+                Tools.Log.info("[FII AUTH] <{}:{}:{}> Authentication successful!", profile.getId(), profile.getName(), sockAddr);
             }
         } catch(IOException ex) {
+            Tools.Log.error("[FII AUTH] <{}:{}:{}> IOException!!", profile.getId(), profile.getName(), sockAddr);
             authText = Text.literal("Flashii authentication server failed to respond, yell at flashwave about this.").formatted(Formatting.RED);
             ex.printStackTrace();
         } catch(GeneralSecurityException ex) {
+            Tools.Log.error("[FII AUTH] <{}:{}:{}> GeneralSecurityException!!", profile.getId(), profile.getName(), sockAddr);
             authText = Text.literal("Problem with request verification, yell at flashwave about this.").formatted(Formatting.RED);
             ex.printStackTrace();
         } catch(InterruptedException ex) {
+            Tools.Log.error("[FII AUTH] <{}:{}:{}> InterruptedException!!", profile.getId(), profile.getName(), sockAddr);
             authText = Text.literal("Problem with connecting to the Flashii authentication server, yell at flashwave about this.").formatted(Formatting.RED);
             ex.printStackTrace();
         }

src/main/java/net/flashii/mcexts/mixin/PlayerSkinProviderMixin.java

@@ -4,6 +4,7 @@ import com.mojang.authlib.GameProfile;
 import java.util.concurrent.CompletableFuture;
 import net.minecraft.client.texture.PlayerSkinProvider;
 import net.minecraft.client.util.SkinTextures;
+import net.flashii.mcexts.Tools;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
@@ -16,16 +17,27 @@ public abstract class PlayerSkinProviderMixin {
         at = @At("RETURN"),
         cancellable = true
     )
-    private void modifyFetchSkinTexturesReturn(GameProfile profile, CallbackInfoReturnable<CompletableFuture<SkinTextures>> cir) {
+    private void fetchSkinTextures(GameProfile profile, CallbackInfoReturnable<CompletableFuture<SkinTextures>> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted PlayerSkinProvider.fetchSkinTextures!!!");
+
         CompletableFuture<SkinTextures> future = cir.getReturnValue();
         cir.setReturnValue(future.thenApply(st -> {
+            Tools.Log.info(
+                "[FII MIXIN] future texture:{} textureUrl:{} capeTexture:{} elytraTexture:{} model:{} secure:{}",
+                st.texture(),
+                st.textureUrl(),
+                st.capeTexture(),
+                st.elytraTexture(),
+                st.model(),
+                st.secure()
+            );
             return new SkinTextures(
                 st.texture(),
                 st.textureUrl(),
                 st.capeTexture(),
                 st.elytraTexture(),
                 st.model(),
-                true
+                st.secure()
             );
         }));
         cir.cancel();

src/main/java/net/flashii/mcexts/mixin/TextureUrlCheckerMixin.java

@@ -2,6 +2,7 @@ package net.flashii.mcexts.mixin;
 
 import com.mojang.authlib.yggdrasil.TextureUrlChecker;
 import net.flashii.mcexts.URLs;
+import net.flashii.mcexts.Tools;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
@@ -16,6 +17,8 @@ public abstract class TextureUrlCheckerMixin {
         remap = false
     )
     private static void isAllowedTextureDomain(String url, CallbackInfoReturnable<Boolean> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted TextureUrlChecker.isAllowedTextureDomain!!!");
+
         if(url == null || url.startsWith(URLs.getTexturesHostPrefix())) {
             cir.setReturnValue(true);
             cir.cancel();

src/main/java/net/flashii/mcexts/mixin/YggdrasilEnvironmentMixin.java

@@ -17,7 +17,7 @@ public abstract class YggdrasilEnvironmentMixin {
             ordinal = 0
         )
     )
-    private Environment redirectEnvironmentCreation(String sessionHost, String servicesHost, String name) {
+    private Environment init(String sessionHost, String servicesHost, String name) {
         return new Environment(URLs.getSessionHost(), servicesHost, name);
     }
 }

src/main/java/net/flashii/mcexts/mixin/YggdrasilMinecraftSessionServiceMixin.java

@@ -0,0 +1,101 @@
+package net.flashii.mcexts.mixin;
+
+import com.mojang.authlib.GameProfile;
+import com.mojang.authlib.SignatureState;
+import com.mojang.authlib.minecraft.MinecraftProfileTextures;
+import com.mojang.authlib.properties.Property;
+import com.mojang.authlib.yggdrasil.ProfileResult;
+import com.mojang.authlib.yggdrasil.YggdrasilMinecraftSessionService;
+import java.util.UUID;
+import java.util.concurrent.CompletableFuture;
+import net.minecraft.client.util.SkinTextures;
+import net.flashii.mcexts.Tools;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.ModifyArg;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
+
+@Mixin(YggdrasilMinecraftSessionService.class)
+public abstract class YggdrasilMinecraftSessionServiceMixin {
+    @Inject(
+        method = "getPackedTextures(Lcom/mojang/authlib/GameProfile;)Lcom/mojang/authlib/properties/Property;",
+        at = @At("RETURN"),
+        cancellable = true,
+        remap = false
+    )
+    private void getPackedTextures(GameProfile profile, CallbackInfoReturnable<Property> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted YggdrasilMinecraftSessionService.getPackedTextures!!!");
+        Tools.Log.info("[FII MIXIN] {}", profile);
+
+        Property prop = cir.getReturnValue();
+        if(prop == null)
+            Tools.Log.info("[FII MIXIN] prop is null");
+        else
+            Tools.Log.info("[FII MIXIN] name:{} value:{} signature:{}", prop.name(), prop.value(), prop.signature());
+    }
+
+    @Inject(
+        method = "unpackTextures(Lcom/mojang/authlib/properties/Property;)Lcom/mojang/authlib/minecraft/MinecraftProfileTextures;",
+        at = @At("RETURN"),
+        cancellable = true,
+        remap = false
+    )
+    private void unpackTextures(Property packedTextures, CallbackInfoReturnable<MinecraftProfileTextures> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted YggdrasilMinecraftSessionService.unpackTextures!!!");
+
+        MinecraftProfileTextures textures = cir.getReturnValue();
+        Tools.Log.info("[FII MIXIN] skin:{} cape:{} elytra:{} signature:{}", textures.skin(), textures.cape(), textures.elytra(), textures.signatureState());
+    }
+
+    @Inject(
+        method = "getSecurePropertyValue(Lcom/mojang/authlib/properties/Property;)Ljava/lang/String;",
+        at = @At("HEAD"),
+        cancellable = true,
+        remap = false
+    )
+    private void getSecurePropertyValue(Property property, CallbackInfoReturnable<String> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted YggdrasilMinecraftSessionService.getSecurePropertyValue!!!");
+
+        cir.setReturnValue(property.value());
+        cir.cancel();
+    }
+
+    @Inject(
+        method = "getPropertySignatureState(Lcom/mojang/authlib/properties/Property;)Lcom/mojang/authlib/SignatureState;",
+        at = @At("HEAD"),
+        cancellable = true,
+        remap = false
+    )
+    private void getPropertySignatureState(Property property, CallbackInfoReturnable<SignatureState> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted YggdrasilMinecraftSessionService.getPropertySignatureState!!!");
+
+        cir.setReturnValue(SignatureState.SIGNED);
+        cir.cancel();
+    }
+
+    @Inject(
+        method = "fetchProfileUncached(Ljava/util/UUID;Z)Lcom/mojang/authlib/yggdrasil/ProfileResult;",
+        at = @At("RETURN"),
+        cancellable = true,
+        remap = false
+    )
+    private void fetchProfileUncached(UUID profileId, boolean requireSecure, CallbackInfoReturnable<ProfileResult> cir) {
+        Tools.Log.info("[FII MIXIN] Intercepted YggdrasilMinecraftSessionService.fetchProfileUncached!!!");
+        Tools.Log.info("[FII MIXIN] {}", cir.getReturnValue().profile());
+    }
+
+    @ModifyArg(
+        method = "fetchProfile",
+        at = @At(
+            value = "INVOKE",
+            target = "Lcom/mojang/authlib/yggdrasil/YggdrasilMinecraftSessionService;fetchProfileUncached(Ljava/util/UUID;Z)Lcom/mojang/authlib/yggdrasil/ProfileResult;"
+        ),
+        index = 1,
+        remap = false
+    )
+    private boolean modifyFetchProfileUncachedArg(boolean requireSecure) {
+        Tools.Log.info("[FII MIXIN] Intercepted requireSecure argument for YggdrasilMinecraftSessionService.fetchProfileUncached in fetchProfile!!!");
+        return false;
+    }
+}

src/main/resources/flashii-extensions.mixins.json

@@ -6,7 +6,8 @@
         "PlayerSkinProviderMixin",
         "PlayerListHudMixin",
         "TextureUrlCheckerMixin",
-        "YggdrasilEnvironmentMixin"
+        "YggdrasilEnvironmentMixin",
+        "YggdrasilMinecraftSessionServiceMixin"
     ],
     "server": [
         "PlayerManagerMixin",