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The AWS SDK for Java - Core module holds the classes that are used by the individual service clients to interact with Amazon Web Services. Users need to depend on aws-java-sdk artifact for accessing individual client classes.
/*
* Copyright 2011-2024 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.
* You may obtain a copy of the License at:
*
* http://aws.amazon.com/apache2.0
*
* 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 com.amazonaws.auth;
import com.amazonaws.SdkClientException;
import com.amazonaws.annotation.SdkInternalApi;
import com.amazonaws.util.DateUtils;
import com.amazonaws.util.json.Jackson;
import com.fasterxml.jackson.databind.JsonNode;
import java.util.Random;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import java.util.Date;
/**
* Helper class that contains the common behavior of the
* CredentialsProviders that loads the credentials from a
* local endpoint.
*/
@SdkInternalApi
abstract class BaseCredentialsFetcher {
private static final Log LOG = LogFactory.getLog(BaseCredentialsFetcher.class);
private static final Random JITTER = new Random();
/**
* The threshold after the last attempt to load credentials (in
* milliseconds) at which credentials are attempted to be refreshed.
*/
private static final int REFRESH_THRESHOLD = 1000 * 60 * 60;
private static final int FIFTEEN_MINUTES_IN_MILLIS = 1000 * 60 * 15;
/**
* The threshold before credentials expire (in milliseconds) at which
* this class will attempt to load new credentials.
*/
private static final int EXPIRATION_THRESHOLD = FIFTEEN_MINUTES_IN_MILLIS;
/** The name of the Json Object that contains the access key.*/
private static final String ACCESS_KEY_ID = "AccessKeyId";
/** The name of the Json Object that contains the secret access key.*/
private static final String SECRET_ACCESS_KEY = "SecretAccessKey";
/** The name of the Json Object that contains the token.*/
private static final String TOKEN = "Token";
private final SdkClock clock;
/**
* Whether expired credentials can be returned if the credential service is down or returns expired credentials
*/
private final boolean allowExpiredCredentials;
private final String providerName;
/** The current instance profile credentials */
private volatile AWSCredentials credentials;
/** The expiration for the current instance profile credentials */
private volatile Date credentialsExpiration;
/** The time at which we will refresh the credentials because they are about to expire */
private volatile Date credentialExpirationRefreshTime;
/** The time of the last attempt to check for new credentials */
protected volatile Date lastInstanceProfileCheck;
protected BaseCredentialsFetcher(SdkClock clock, boolean allowExpiredCredentials) {
this(clock, allowExpiredCredentials, null);
}
protected BaseCredentialsFetcher(SdkClock clock, boolean allowExpiredCredentials, String providerName) {
this.clock = clock;
this.allowExpiredCredentials = allowExpiredCredentials;
this.providerName = providerName;
}
public AWSCredentials getCredentials() {
if (needsToLoadCredentials())
fetchCredentials();
if (!allowExpiredCredentials && expired()) {
throw new SdkClientException(
"The credentials received have been expired");
}
return credentials;
}
/**
* Returns true if credentials are null, credentials are within expiration or
* if the last attempt to refresh credentials is beyond the refresh threshold.
*/
boolean needsToLoadCredentials() {
return credentials == null || isExpiring() || noRecentInstanceProfileCheck();
}
/**
* Returns true if the credential expiration refresh time is in the past.
*/
private boolean isExpiring() {
return credentialExpirationRefreshTime != null &&
credentialExpirationRefreshTime.getTime() <= clock.currentTimeMillis();
}
/**
* Returns true if it has been REFRESH_THRESHOLD millis since we last refreshed the credentials from IMDS.
*/
private boolean noRecentInstanceProfileCheck() {
return lastInstanceProfileCheck != null &&
lastInstanceProfileCheck.getTime() + REFRESH_THRESHOLD <= clock.currentTimeMillis();
}
/**
* @return the raw credential response string from the local endpoint.
*/
abstract String getCredentialsResponse();
/**
* Fetches the credentials from the endpoint.
*/
private synchronized void fetchCredentials() {
if (!needsToLoadCredentials()) return;
if (LOG.isDebugEnabled()) {
if (credentialsExpiration != null) {
LOG.debug("Updating credentials, because currently-cached credentials expire on " + credentialsExpiration);
} else {
LOG.debug("Retrieving credentials.");
}
}
JsonNode accessKey;
JsonNode secretKey;
JsonNode node;
JsonNode token;
try {
lastInstanceProfileCheck = new Date();
String credentialsResponse = getCredentialsResponse();
node = Jackson.fromSensitiveJsonString(credentialsResponse, JsonNode.class);
accessKey = node.get(ACCESS_KEY_ID);
secretKey = node.get(SECRET_ACCESS_KEY);
token = node.get(TOKEN);
if (null == accessKey || null == secretKey) {
throw new SdkClientException("Unable to load credentials. Access key or secret key are null.");
}
if (null != token) {
credentials = new BasicSessionCredentials(accessKey.asText(),
secretKey.asText(),
token.asText(),
null,
providerName);
} else {
credentials = new BasicAWSCredentials(accessKey.asText(),
secretKey.asText(),
null,
providerName);
}
JsonNode expirationJsonNode = node.get("Expiration");
if (null != expirationJsonNode) {
/*
* TODO: The expiration string comes in a different format
* than what we deal with in other parts of the SDK, so we
* have to convert it to the ISO8601 syntax we expect.
*/
String expiration = expirationJsonNode.asText();
expiration = expiration.replaceAll("\\+0000$", "Z");
try {
credentialsExpiration = DateUtils.parseISO8601Date(expiration);
credentialExpirationRefreshTime = new Date(credentialsExpiration.getTime() - EXPIRATION_THRESHOLD);
LOG.debug("Successfully retrieved credentials with expiration " + expiration);
} catch(Exception ex) {
handleError("Unable to parse credentials expiration date from Amazon EC2 instance", ex);
}
}
} catch (Exception e) {
handleError("Unable to load credentials from service endpoint", e);
} finally {
if (allowExpiredCredentials && credentials != null && isExpiring()) {
// Try again in 50-70 seconds
long now = clock.currentTimeMillis();
long waitUntilNextRefresh = 50 * 1000 + JITTER.nextInt(20 * 1000 + 1);
long nextRefreshTime = now + waitUntilNextRefresh;
// Log if our next refresh will be after the credentials have expired. We want to treat the credentials as
// expiring a little earlier than the actual expiration time, since the request may take a few seconds.
long effectiveExpiration = credentialsExpiration.getTime() - 15 * 1000;
if (nextRefreshTime > effectiveExpiration) {
LOG.warn("Credential expiration has been extended due to a credential service availability " +
"issue. A refresh of these credentials will be attempted again in " + waitUntilNextRefresh + " ms.");
}
this.credentialExpirationRefreshTime = new Date(nextRefreshTime);
}
}
}
/**
* Handles reporting or throwing an error encountered while requesting
* credentials from the Amazon EC2 endpoint. The Service could be
* briefly unavailable for a number of reasons, so
* we need to gracefully handle falling back to valid credentials if they're
* available, and only throw exceptions if we really can't recover.
*
* @param errorMessage
* A human readable description of the error.
* @param e
* The error that occurred.
*/
private void handleError(String errorMessage, Exception e) {
// If we don't have any valid credentials to fall back on, then throw an exception
if (credentials == null || (!allowExpiredCredentials && expired())) {
if (e instanceof SdkClientException) {
throw (SdkClientException) e;
}
throw new SdkClientException(errorMessage, e);
}
// Otherwise, just log the error and continuing using the current credentials
LOG.warn(errorMessage, e);
}
public void refresh() {
credentials = null;
}
private boolean expired() {
if (credentialsExpiration == null) {
return false;
}
if (credentialsExpiration.getTime() > clock.currentTimeMillis()) {
return false;
}
return true;
}
Date getCredentialsExpiration() {
return credentialsExpiration;
}
@Override
public String toString() {
return "BaseCredentialsFetcher";
}
}