Add option to disable EC2 metadata (IMDS) calls without token (#4866)

* Add option to disable IMDS v1 fallback when token is not returned (#4840)
* Add support for disable IMDS v1 fallback for regions

Author: cenedhryn

.changes/next-release/feature-AWSSDKforJavav2-2c52c12.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Adds setting to disable making EC2 Instance Metadata Service (IMDS) calls without a token header when prefetching a token does not work. This feature can be configured through environment variables (AWS_EC2_METADATA_V1_DISABLED), system property (aws.disableEc2MetadataV1) or AWS config file (ec2_metadata_v1_disabled). When you configure this setting to true, no calls without token headers will be made to IMDS."
+}

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/InstanceProfileCredentialsProvider.java

@@ -31,6 +31,7 @@
 import software.amazon.awssdk.annotations.SdkPublicApi;
 import software.amazon.awssdk.annotations.SdkTestInternalApi;
 import software.amazon.awssdk.auth.credentials.internal.Ec2MetadataConfigProvider;
+import software.amazon.awssdk.auth.credentials.internal.Ec2MetadataDisableV1Resolver;
 import software.amazon.awssdk.auth.credentials.internal.HttpCredentialsLoader;
 import software.amazon.awssdk.auth.credentials.internal.HttpCredentialsLoader.LoadedCredentials;
 import software.amazon.awssdk.auth.credentials.internal.StaticResourcesEndpointProvider;
@@ -40,6 +41,7 @@
 import software.amazon.awssdk.profiles.ProfileFile;
 import software.amazon.awssdk.profiles.ProfileFileSupplier;
 import software.amazon.awssdk.profiles.ProfileFileSystemSetting;
+import software.amazon.awssdk.profiles.ProfileProperty;
 import software.amazon.awssdk.regions.util.HttpResourcesUtils;
 import software.amazon.awssdk.regions.util.ResourcesEndpointProvider;
 import software.amazon.awssdk.utils.Logger;
@@ -53,10 +55,13 @@
 
 /**
  * Credentials provider implementation that loads credentials from the Amazon EC2 Instance Metadata Service.
- *
- * <P>
+ * <p>
  * If {@link SdkSystemSetting#AWS_EC2_METADATA_DISABLED} is set to true, it will not try to load
  * credentials from EC2 metadata service and will return null.
+ * <p>
+ * If {@link SdkSystemSetting#AWS_EC2_METADATA_V1_DISABLED} or {@link ProfileProperty#EC2_METADATA_V1_DISABLED}
+ * is set to true, credentials will only be loaded from EC2 metadata service if a token is successfully retrieved -
+ * fallback to load credentials without a token will be disabled.
  */
 @SdkPublicApi
 public final class InstanceProfileCredentialsProvider
@@ -73,6 +78,7 @@ public final class InstanceProfileCredentialsProvider
     private final Clock clock;
     private final String endpoint;
     private final Ec2MetadataConfigProvider configProvider;
+    private final Ec2MetadataDisableV1Resolver ec2MetadataDisableV1Resolver;
     private final HttpCredentialsLoader httpCredentialsLoader;
     private final CachedSupplier<AwsCredentials> credentialsCache;
 
@@ -92,15 +98,18 @@ private InstanceProfileCredentialsProvider(BuilderImpl builder) {
         this.endpoint = builder.endpoint;
         this.asyncCredentialUpdateEnabled = builder.asyncCredentialUpdateEnabled;
         this.asyncThreadName = builder.asyncThreadName;
-        this.profileFile = builder.profileFile;
-        this.profileName = builder.profileName;
+        this.profileFile = Optional.ofNullable(builder.profileFile)
+                                   .orElseGet(() -> ProfileFileSupplier.fixedProfileFile(ProfileFile.defaultProfileFile()));
+        this.profileName = Optional.ofNullable(builder.profileName)
+                                   .orElseGet(ProfileFileSystemSetting.AWS_PROFILE::getStringValueOrThrow);
 
         this.httpCredentialsLoader = HttpCredentialsLoader.create();
         this.configProvider =
             Ec2MetadataConfigProvider.builder()
-                                     .profileFile(builder.profileFile)
-                                     .profileName(builder.profileName)
+                                     .profileFile(profileFile)
+                                     .profileName(profileName)
                                      .build();
+        this.ec2MetadataDisableV1Resolver = Ec2MetadataDisableV1Resolver.create(profileFile, profileName);
 
         if (Boolean.TRUE.equals(builder.asyncCredentialUpdateEnabled)) {
             Validate.paramNotBlank(builder.asyncThreadName, "asyncThreadName");
@@ -135,7 +144,6 @@ public static InstanceProfileCredentialsProvider create() {
         return builder().build();
     }
 
-
     @Override
     public AwsCredentials resolveCredentials() {
         return credentialsCache.get();
@@ -225,17 +233,15 @@ private String getToken(String imdsHostname) {
             return HttpResourcesUtils.instance().readResource(tokenEndpoint, "PUT");
         } catch (SdkServiceException e) {
             if (e.statusCode() == 400) {
+
                 throw SdkClientException.builder()
                                         .message("Unable to fetch metadata token.")
                                         .cause(e)
                                         .build();
             }
-
-            log.debug(() -> "Ignoring non-fatal exception while attempting to load metadata token from instance profile.", e);
-            return null;
+            return handleTokenErrorResponse(e);
         } catch (Exception e) {
-            log.debug(() -> "Ignoring non-fatal exception while attempting to load metadata token from instance profile.", e);
-            return null;
+            return handleTokenErrorResponse(e);
         }
     }
 
@@ -247,6 +253,27 @@ private URI getTokenEndpoint(String imdsHostname) {
         return URI.create(finalHost + TOKEN_RESOURCE);
     }
 
+    private String handleTokenErrorResponse(Exception e) {
+        if (isInsecureFallbackDisabled()) {
+            String message = String.format("Failed to retrieve IMDS token, and fallback to IMDS v1 is disabled via the "
+                                           + "%s system property, %s environment variable, or %s configuration file profile"
+                                           + " setting.",
+                                           SdkSystemSetting.AWS_EC2_METADATA_V1_DISABLED.environmentVariable(),
+                                           SdkSystemSetting.AWS_EC2_METADATA_V1_DISABLED.property(),
+                                           ProfileProperty.EC2_METADATA_V1_DISABLED);
+            throw SdkClientException.builder()
+                                    .message(message)
+                                    .cause(e)
+                                    .build();
+        }
+        log.debug(() -> "Ignoring non-fatal exception while attempting to load metadata token from instance profile.", e);
+        return null;
+    }
+
+    private boolean isInsecureFallbackDisabled() {
+        return ec2MetadataDisableV1Resolver.resolve();
+    }
+
     private String[] getSecurityCredentials(String imdsHostname, String metadataToken) {
         ResourcesEndpointProvider securityCredentialsEndpoint =
             new StaticResourcesEndpointProvider(URI.create(imdsHostname + SECURITY_CREDENTIALS_RESOURCE),

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/internal/Ec2MetadataDisableV1Resolver.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+package software.amazon.awssdk.auth.credentials.internal;
+
+import java.util.Optional;
+import java.util.function.Supplier;
+import software.amazon.awssdk.annotations.SdkInternalApi;
+import software.amazon.awssdk.core.SdkSystemSetting;
+import software.amazon.awssdk.profiles.ProfileFile;
+import software.amazon.awssdk.profiles.ProfileProperty;
+import software.amazon.awssdk.utils.Lazy;
+import software.amazon.awssdk.utils.OptionalUtils;
+
+@SdkInternalApi
+public final class Ec2MetadataDisableV1Resolver {
+    private final Supplier<ProfileFile> profileFile;
+    private final String profileName;
+    private final Lazy<Boolean> resolvedValue;
+
+    private Ec2MetadataDisableV1Resolver(Supplier<ProfileFile> profileFile, String profileName) {
+        this.profileFile = profileFile;
+        this.profileName = profileName;
+        this.resolvedValue = new Lazy<>(this::doResolve);
+    }
+
+    public static Ec2MetadataDisableV1Resolver create(Supplier<ProfileFile> profileFile, String profileName) {
+        return new Ec2MetadataDisableV1Resolver(profileFile, profileName);
+    }
+
+    public boolean resolve() {
+        return resolvedValue.getValue();
+    }
+
+    public boolean doResolve() {
+        return OptionalUtils.firstPresent(fromSystemSettings(),
+                                          () -> fromProfileFile(profileFile, profileName))
+                            .orElse(false);
+    }
+
+    private static Optional<Boolean> fromSystemSettings() {
+        return SdkSystemSetting.AWS_EC2_METADATA_V1_DISABLED.getBooleanValue();
+    }
+
+    private static Optional<Boolean> fromProfileFile(Supplier<ProfileFile> profileFile, String profileName) {
+        return profileFile.get()
+                          .profile(profileName)
+                          .flatMap(p -> p.booleanProperty(ProfileProperty.EC2_METADATA_V1_DISABLED));
+    }
+
+}

core/auth/src/main/java/software/amazon/awssdk/auth/credentials/internal/ProfileCredentialsUtils.java

@@ -262,15 +262,10 @@ private AwsCredentialsProvider credentialSourceCredentialProvider(CredentialSour
             case ECS_CONTAINER:
                 return ContainerCredentialsProvider.builder().build();
             case EC2_INSTANCE_METADATA:
-                // The IMDS credentials provider should source the endpoint config properties from the currently active profile
-                Ec2MetadataConfigProvider configProvider = Ec2MetadataConfigProvider.builder()
-                        .profileFile(() -> profileFile)
-                        .profileName(name)
-                        .build();
-
                 return InstanceProfileCredentialsProvider.builder()
-                        .endpoint(configProvider.getEndpoint())
-                        .build();
+                                                         .profileFile(profileFile)
+                                                         .profileName(name)
+                                                         .build();
             case ENVIRONMENT:
                 return AwsCredentialsProviderChain.builder()
                     .addCredentialsProvider(SystemPropertyCredentialsProvider.create())