Support multiple signaturePublickeys

Allow authentication servers to specify an array of profile property
public keys instead of just one.

Adds a new field, `signaturePublickeys`, to the authlib-injector
metadata route at the root of the API. `signaturePublickeys` is an
array of strings containing public keys in the same format as the
`signaturePublickey`. Any of the keys specified either in
`signaturePublickeys` or as the `signaturePublickey` can be used to
verify the signature of a textures payload.

With this change, authentication server A can forward a texture payload
from authentication server B, and the client could accept a texture
signed by either authentication server.

src/main/java/moe/yushi/authlibinjector/APIMetadata.java

@@ -19,11 +19,14 @@
 import static java.text.MessageFormat.format;
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
+import static java.util.Collections.emptySet;
 import static java.util.Collections.unmodifiableList;
 import static java.util.Collections.unmodifiableMap;
+import static java.util.Collections.unmodifiableSet;
 import static java.util.Objects.requireNonNull;
 import static java.util.Optional.ofNullable;
 import static java.util.stream.Collectors.toList;
+import static java.util.stream.Collectors.toSet;
 import static moe.yushi.authlibinjector.util.JsonUtils.asJsonArray;
 import static moe.yushi.authlibinjector.util.JsonUtils.asJsonObject;
 import static moe.yushi.authlibinjector.util.JsonUtils.parseJson;
@@ -32,6 +35,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.TreeMap;
 import moe.yushi.authlibinjector.internal.org.json.simple.JSONObject;
 import moe.yushi.authlibinjector.util.JsonUtils;
@@ -54,24 +58,33 @@ public static APIMetadata parse(String apiRoot, String metadataResponse) throws
 						.map(JsonUtils::asJsonString)
 						.map(KeyUtils::parseSignaturePublicKey);
 
+		Set<PublicKey> decodedPublickeys =
+				ofNullable(response.get("signaturePublickeys"))
+						.map(it -> asJsonArray(it).stream()
+								.map(JsonUtils::asJsonString)
+								.map(KeyUtils::parseSignaturePublicKey)
+								.collect(toSet()))
+						.orElse(emptySet());
+		decodedPublickey.ifPresent(decodedPublickeys::add);
+
 		Map<String, Object> meta =
 				ofNullable(response.get("meta"))
 						.map(it -> (Map<String, Object>) new TreeMap<>(asJsonObject(it)))
 						.orElse(emptyMap());
 
-		return new APIMetadata(apiRoot, unmodifiableList(skinDomains), unmodifiableMap(meta), decodedPublickey);
+		return new APIMetadata(apiRoot, unmodifiableList(skinDomains), unmodifiableMap(meta), unmodifiableSet(decodedPublickeys));
 	}
 
 	private String apiRoot;
 	private List<String> skinDomains;
-	private Optional<PublicKey> decodedPublickey;
+	private Set<PublicKey> decodedPublickeys;
 	private Map<String, Object> meta;
 
-	public APIMetadata(String apiRoot, List<String> skinDomains, Map<String, Object> meta, Optional<PublicKey> decodedPublickey) {
+	public APIMetadata(String apiRoot, List<String> skinDomains, Map<String, Object> meta, Set<PublicKey> decodedPublickeys) {
 		this.apiRoot = requireNonNull(apiRoot);
 		this.skinDomains = requireNonNull(skinDomains);
 		this.meta = requireNonNull(meta);
-		this.decodedPublickey = requireNonNull(decodedPublickey);
+		this.decodedPublickeys = requireNonNull(decodedPublickeys);
 	}
 
 	public String getApiRoot() {
@@ -86,12 +99,12 @@ public Map<String, Object> getMeta() {
 		return meta;
 	}
 
-	public Optional<PublicKey> getDecodedPublickey() {
-		return decodedPublickey;
+	public Set<PublicKey> getDecodedPublickeys() {
+		return decodedPublickeys;
 	}
 
 	@Override
 	public String toString() {
-		return format("APIMetadata [apiRoot={0}, skinDomains={1}, decodedPublickey={2}, meta={3}]", apiRoot, skinDomains, decodedPublickey, meta);
+		return format("APIMetadata [apiRoot={0}, skinDomains={1}, decodedPublickeys={2}, meta={3}]", apiRoot, skinDomains, decodedPublickeys, meta);
 	}
 }

src/main/java/moe/yushi/authlibinjector/AuthlibInjector.java

@@ -296,7 +296,7 @@ private static ClassTransformer createTransformer(APIMetadata config) {
 		SkinWhitelistTransformUnit.getWhitelistedDomains().addAll(config.getSkinDomains());
 
 		transformer.units.add(new YggdrasilKeyTransformUnit());
-		config.getDecodedPublickey().ifPresent(YggdrasilKeyTransformUnit.PUBLIC_KEYS::add);
+		YggdrasilKeyTransformUnit.PUBLIC_KEYS.addAll(config.getDecodedPublickeys());
 		transformer.units.add(new VelocityProfileKeyTransformUnit());
 		transformer.units.add(new BungeeCordProfileKeyTransformUnit());
 		MainArgumentsTransformer.getArgumentsListeners().add(new AccountTypeTransformer()::transform);

src/test/java/moe/yushi/authlibinjector/test/DefaultURLRedirectorTest.java

@@ -18,6 +18,7 @@
 
 import static java.util.Collections.emptyList;
 import static java.util.Collections.emptyMap;
+import static java.util.Collections.emptySet;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import java.util.Optional;
 import org.junit.jupiter.api.Test;
@@ -27,7 +28,7 @@
 public class DefaultURLRedirectorTest {
 
 	private String apiRoot = "https://yggdrasil.example.com/";
-	private DefaultURLRedirector redirector = new DefaultURLRedirector(new APIMetadata(apiRoot, emptyList(), emptyMap(), Optional.empty()));
+	private DefaultURLRedirector redirector = new DefaultURLRedirector(new APIMetadata(apiRoot, emptyList(), emptyMap(), emptySet()));
 
 	private void testTransform(String domain, String path, String output) {
 		assertEquals(redirector.redirect(domain, path).get(), output);