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<?php |
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/* |
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* Copyright 2023 Google Inc. |
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* |
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* Licensed under the Apache License, Version 2.0 (the "License"); |
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* you may not use this file except in compliance with the License. |
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* You may obtain a copy of the License at |
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* |
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* http://www.apache.org/licenses/LICENSE-2.0 |
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* |
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* Unless required by applicable law or agreed to in writing, software |
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* distributed under the License is distributed on an "AS IS" BASIS, |
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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* See the License for the specific language governing permissions and |
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* limitations under the License. |
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*/ |
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|
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namespace Google\Auth\CredentialSource; |
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|
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use Google\Auth\ExternalAccountCredentialSourceInterface; |
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use Google\Auth\HttpHandler\HttpClientCache; |
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use Google\Auth\HttpHandler\HttpHandlerFactory; |
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use GuzzleHttp\Psr7\Request; |
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|
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/** |
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* Authenticates requests using AWS credentials. |
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*/ |
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class AwsNativeSource implements ExternalAccountCredentialSourceInterface |
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{ |
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private const CRED_VERIFICATION_QUERY = 'Action=GetCallerIdentity&Version=2011-06-15'; |
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private const ECS_CONTAINER_METADATA_URL = 'http://169.254.170.2'; |
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|
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private string $audience; |
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private string $regionalCredVerificationUrl; |
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private ?string $regionUrl; |
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private ?string $securityCredentialsUrl; |
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private ?string $imdsv2SessionTokenUrl; |
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|
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/** |
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* @param string $audience The audience for the credential. |
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* @param string $regionalCredVerificationUrl The regional AWS GetCallerIdentity action URL used to determine the |
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* AWS account ID and its roles. This is not called by this library, but |
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* is sent in the subject token to be called by the STS token server. |
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* @param string|null $regionUrl This URL should be used to determine the current AWS region needed for the signed |
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* request construction. |
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* @param string|null $securityCredentialsUrl The AWS metadata server URL used to retrieve the access key, secret |
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* key and security token needed to sign the GetCallerIdentity request. |
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* @param string|null $imdsv2SessionTokenUrl Presence of this URL enforces the auth libraries to fetch a Session |
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* Token from AWS. This field is required for EC2 instances using IMDSv2. |
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*/ |
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public function __construct( |
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string $audience, |
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string $regionalCredVerificationUrl, |
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?string $regionUrl = null, |
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?string $securityCredentialsUrl = null, |
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?string $imdsv2SessionTokenUrl = null |
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) { |
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$this->audience = $audience; |
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$this->regionalCredVerificationUrl = $regionalCredVerificationUrl; |
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$this->regionUrl = $regionUrl; |
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$this->securityCredentialsUrl = $securityCredentialsUrl; |
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$this->imdsv2SessionTokenUrl = $imdsv2SessionTokenUrl; |
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} |
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|
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public function fetchSubjectToken(?callable $httpHandler = null): string |
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{ |
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if (is_null($httpHandler)) { |
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$httpHandler = HttpHandlerFactory::build(HttpClientCache::getHttpClient()); |
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} |
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|
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$headers = []; |
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if ($this->imdsv2SessionTokenUrl) { |
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$headers = [ |
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'X-aws-ec2-metadata-token' => self::getImdsV2SessionToken($this->imdsv2SessionTokenUrl, $httpHandler) |
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]; |
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} |
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|
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$signingVars = self::getSigningVarsFromEnv() |
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?? self::getSigningVarsFromEcs($httpHandler); |
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|
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if (!$signingVars) { |
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if (!$this->securityCredentialsUrl) { |
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throw new \LogicException('Unable to get credentials from ENV, and no security credentials URL provided'); |
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} |
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$signingVars = self::getSigningVarsFromUrl( |
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$httpHandler, |
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$this->securityCredentialsUrl, |
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self::getRoleName($httpHandler, $this->securityCredentialsUrl, $headers), |
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$headers |
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); |
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} |
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|
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if (!$region = self::getRegionFromEnv()) { |
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if (!$this->regionUrl) { |
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throw new \LogicException('Unable to get region from ENV, and no region URL provided'); |
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} |
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$region = self::getRegionFromUrl($httpHandler, $this->regionUrl, $headers); |
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} |
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$url = str_replace('{region}', $region, $this->regionalCredVerificationUrl); |
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$host = parse_url($url)['host'] ?? ''; |
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|
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// From here we use the signing vars to create the signed request to receive a token |
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[$accessKeyId, $secretAccessKey, $securityToken] = $signingVars; |
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$headers = self::getSignedRequestHeaders($region, $host, $accessKeyId, $secretAccessKey, $securityToken); |
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|
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// Inject x-goog-cloud-target-resource into header |
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$headers['x-goog-cloud-target-resource'] = $this->audience; |
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|
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// Format headers as they're expected in the subject token |
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$formattedHeaders = array_map( |
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fn ($k, $v) => ['key' => $k, 'value' => $v], |
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array_keys($headers), |
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$headers, |
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); |
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|
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$request = [ |
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'headers' => $formattedHeaders, |
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'method' => 'POST', |
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'url' => $url, |
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]; |
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|
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return urlencode(json_encode($request) ?: ''); |
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} |
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|
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/** |
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* @internal |
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*/ |
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public static function getImdsV2SessionToken(string $imdsV2Url, callable $httpHandler): string |
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{ |
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$headers = [ |
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'X-aws-ec2-metadata-token-ttl-seconds' => '21600' |
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]; |
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$request = new Request( |
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'PUT', |
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$imdsV2Url, |
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$headers |
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); |
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|
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$response = $httpHandler($request); |
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return (string) $response->getBody(); |
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} |
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|
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/** |
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* @see http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html |
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* |
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* @internal |
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* |
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* @return array<string, string> |
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*/ |
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public static function getSignedRequestHeaders( |
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string $region, |
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string $host, |
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string $accessKeyId, |
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string $secretAccessKey, |
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?string $securityToken |
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): array { |
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$service = 'sts'; |
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|
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# Create a date for headers and the credential string in ISO-8601 format |
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$amzdate = gmdate('Ymd\THis\Z'); |
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$datestamp = gmdate('Ymd'); # Date w/o time, used in credential scope |
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|
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# Create the canonical headers and signed headers. Header names |
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# must be trimmed and lowercase, and sorted in code point order from |
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# low to high. Note that there is a trailing \n. |
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$canonicalHeaders = sprintf("host:%s\nx-amz-date:%s\n", $host, $amzdate); |
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if ($securityToken) { |
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$canonicalHeaders .= sprintf("x-amz-security-token:%s\n", $securityToken); |
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} |
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|
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# Step 5: Create the list of signed headers. This lists the headers |
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# in the canonicalHeaders list, delimited with ";" and in alpha order. |
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# Note: The request can include any headers; $canonicalHeaders and |
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# $signedHeaders lists those that you want to be included in the |
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# hash of the request. "Host" and "x-amz-date" are always required. |
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$signedHeaders = 'host;x-amz-date'; |
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if ($securityToken) { |
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$signedHeaders .= ';x-amz-security-token'; |
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} |
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|
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# Step 6: Create payload hash (hash of the request body content). For GET |
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# requests, the payload is an empty string (""). |
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$payloadHash = hash('sha256', ''); |
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|
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# Step 7: Combine elements to create canonical request |
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$canonicalRequest = implode("\n", [ |
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'POST', // method |
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'/', // canonical URL |
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self::CRED_VERIFICATION_QUERY, // query string |
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$canonicalHeaders, |
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$signedHeaders, |
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$payloadHash |
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]); |
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|
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# ************* TASK 2: CREATE THE STRING TO SIGN************* |
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# Match the algorithm to the hashing algorithm you use, either SHA-1 or |
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# SHA-256 (recommended) |
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$algorithm = 'AWS4-HMAC-SHA256'; |
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$scope = implode('/', [$datestamp, $region, $service, 'aws4_request']); |
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$stringToSign = implode("\n", [$algorithm, $amzdate, $scope, hash('sha256', $canonicalRequest)]); |
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|
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# ************* TASK 3: CALCULATE THE SIGNATURE ************* |
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# Create the signing key using the function defined above. |
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// (done above) |
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$signingKey = self::getSignatureKey($secretAccessKey, $datestamp, $region, $service); |
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|
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# Sign the string_to_sign using the signing_key |
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$signature = bin2hex(self::hmacSign($signingKey, $stringToSign)); |
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|
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# ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST ************* |
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# The signing information can be either in a query string value or in |
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# a header named Authorization. This code shows how to use a header. |
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# Create authorization header and add to request headers |
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$authorizationHeader = sprintf( |
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'%s Credential=%s/%s, SignedHeaders=%s, Signature=%s', |
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$algorithm, |
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$accessKeyId, |
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$scope, |
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$signedHeaders, |
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$signature |
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); |
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|
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# The request can include any headers, but MUST include "host", "x-amz-date", |
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# and (for this scenario) "Authorization". "host" and "x-amz-date" must |
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# be included in the canonical_headers and signed_headers, as noted |
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# earlier. Order here is not significant. |
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$headers = [ |
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'host' => $host, |
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'x-amz-date' => $amzdate, |
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'Authorization' => $authorizationHeader, |
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]; |
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if ($securityToken) { |
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$headers['x-amz-security-token'] = $securityToken; |
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} |
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|
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return $headers; |
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} |
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|
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/** |
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* @internal |
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*/ |
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public static function getRegionFromEnv(): ?string |
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{ |
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$region = getenv('AWS_REGION'); |
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if (empty($region)) { |
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$region = getenv('AWS_DEFAULT_REGION'); |
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} |
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return $region ?: null; |
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} |
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|
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/** |
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* @internal |
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* |
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* @param callable $httpHandler |
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* @param string $regionUrl |
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* @param array<string, string|string[]> $headers Request headers to send in with the request. |
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*/ |
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public static function getRegionFromUrl(callable $httpHandler, string $regionUrl, array $headers): string |
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{ |
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// get the region/zone from the region URL |
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$regionRequest = new Request('GET', $regionUrl, $headers); |
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$regionResponse = $httpHandler($regionRequest); |
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|
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// Remove last character. For example, if us-east-2b is returned, |
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// the region would be us-east-2. |
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return substr((string) $regionResponse->getBody(), 0, -1); |
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} |
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|
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/** |
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* @internal |
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* |
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* @param callable $httpHandler |
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* @param string $securityCredentialsUrl |
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* @param array<string, string|string[]> $headers Request headers to send in with the request. |
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*/ |
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public static function getRoleName(callable $httpHandler, string $securityCredentialsUrl, array $headers): string |
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{ |
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// Get the AWS role name |
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$roleRequest = new Request('GET', $securityCredentialsUrl, $headers); |
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$roleResponse = $httpHandler($roleRequest); |
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$roleName = (string) $roleResponse->getBody(); |
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|
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return $roleName; |
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} |
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|
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/** |
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* @internal |
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* |
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* @param callable $httpHandler |
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* @param string $securityCredentialsUrl |
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* @param array<string, string|string[]> $headers Request headers to send in with the request. |
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* @return array{string, string, ?string} |
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*/ |
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public static function getSigningVarsFromUrl( |
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callable $httpHandler, |
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string $securityCredentialsUrl, |
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string $roleName, |
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array $headers |
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): array { |
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// Get the AWS credentials |
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$credsRequest = new Request( |
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'GET', |
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$securityCredentialsUrl . '/' . $roleName, |
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$headers |
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); |
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$credsResponse = $httpHandler($credsRequest); |
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$awsCreds = json_decode((string) $credsResponse->getBody(), true); |
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return [ |
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$awsCreds['AccessKeyId'], // accessKeyId |
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$awsCreds['SecretAccessKey'], // secretAccessKey |
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$awsCreds['Token'], // token |
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]; |
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} |
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|
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/** |
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* @internal |
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* |
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* @param callable $httpHandler |
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* @return array{string, string, ?string}|null |
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*/ |
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public static function getSigningVarsFromEcs(callable $httpHandler): ?array |
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{ |
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// Load the environment variables defined by AWS for the ECS/EKS container metadata. |
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$ecsContainerCredentialsRelativeUri = getenv('AWS_CONTAINER_CREDENTIALS_RELATIVE_URI'); |
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$ecsContainerCredentialsFullUri = getenv('AWS_CONTAINER_CREDENTIALS_FULL_URI'); |
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$ecsContainerAuthorizationToken = getenv('AWS_CONTAINER_AUTHORIZATION_TOKEN'); |
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$ecsContainerAuthorizationTokenFile = getenv('AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE'); |
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|
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$credentialsUrl = ''; |
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// The full URI takes precedence over the relative URI if both are defined. |
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if ($ecsContainerCredentialsFullUri) { |
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$credentialsUrl = $ecsContainerCredentialsFullUri; |
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} elseif ($ecsContainerCredentialsRelativeUri) { |
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// The relative URI is appended to the default ECS Task Metadata Endpoint. |
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$credentialsUrl = self::ECS_CONTAINER_METADATA_URL . $ecsContainerCredentialsRelativeUri; |
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} else { |
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// Not running in an ECS environment, or metadata is not enabled. |
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return null; |
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} |
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|
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$headers = []; |
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// The authorization token file takes precedence over the direct token variable. |
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if ($ecsContainerAuthorizationTokenFile) { |
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if (is_readable($ecsContainerAuthorizationTokenFile)) { |
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$headers['Authorization'] = trim((string) file_get_contents($ecsContainerAuthorizationTokenFile)); |
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} else { |
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throw new \RuntimeException( |
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sprintf('Token file %s is not readable', $ecsContainerAuthorizationTokenFile) |
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); |
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} |
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} elseif ($ecsContainerAuthorizationToken) { |
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$headers['Authorization'] = $ecsContainerAuthorizationToken; |
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} |
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|
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// Fetch the temporary AWS credentials from the resolved metadata endpoint. |
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$credsRequest = new Request('GET', $credentialsUrl, $headers); |
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$credsResponse = $httpHandler($credsRequest); |
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$awsCreds = json_decode((string) $credsResponse->getBody(), true); |
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|
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// Ensure the response has the minimum required credential fields. |
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if (!is_array($awsCreds) || !isset($awsCreds['AccessKeyId']) || !isset($awsCreds['SecretAccessKey'])) { |
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throw new \UnexpectedValueException('Invalid or missing ECS credentials in response'); |
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} |
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|
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return [ |
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$awsCreds['AccessKeyId'], |
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$awsCreds['SecretAccessKey'], |
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$awsCreds['Token'] ?? null, |
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]; |
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} |
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|
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/** |
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* @internal |
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* |
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* @return array{string, string, ?string} |
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*/ |
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public static function getSigningVarsFromEnv(): ?array |
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{ |
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$accessKeyId = getenv('AWS_ACCESS_KEY_ID'); |
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$secretAccessKey = getenv('AWS_SECRET_ACCESS_KEY'); |
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if ($accessKeyId && $secretAccessKey) { |
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return [ |
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$accessKeyId, |
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$secretAccessKey, |
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getenv('AWS_SESSION_TOKEN') ?: null, // session token (can be null) |
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]; |
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} |
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|
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return null; |
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} |
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|
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/** |
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* Gets the unique key for caching |
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* For AwsNativeSource the values are: |
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* Imdsv2SessionTokenUrl.SecurityCredentialsUrl.RegionUrl.RegionalCredVerificationUrl |
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* |
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* @return string |
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*/ |
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public function getCacheKey(): string |
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{ |
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return ($this->imdsv2SessionTokenUrl ?? '') . |
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'.' . ($this->securityCredentialsUrl ?? '') . |
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'.' . $this->regionUrl . |
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'.' . $this->regionalCredVerificationUrl; |
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} |
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|
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/** |
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* Return HMAC hash in binary string |
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*/ |
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private static function hmacSign(string $key, string $msg): string |
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{ |
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return hash_hmac('sha256', self::utf8Encode($msg), $key, true); |
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} |
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|
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/** |
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* @TODO add a fallback when mbstring is not available |
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*/ |
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private static function utf8Encode(string $string): string |
| 419 |
{ |
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return (string) mb_convert_encoding($string, 'UTF-8', 'ISO-8859-1'); |
| 421 |
} |
| 422 |
|
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private static function getSignatureKey( |
| 424 |
string $key, |
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string $dateStamp, |
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string $regionName, |
| 427 |
string $serviceName |
| 428 |
): string { |
| 429 |
$kDate = self::hmacSign(self::utf8Encode('AWS4' . $key), $dateStamp); |
| 430 |
$kRegion = self::hmacSign($kDate, $regionName); |
| 431 |
$kService = self::hmacSign($kRegion, $serviceName); |
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$kSigning = self::hmacSign($kService, 'aws4_request'); |
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|
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return $kSigning; |
| 435 |
} |
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} |
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|
