| 1 | <?php
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| 2 | /*
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| 3 | * Copyright 2023 Google Inc.
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| 4 | *
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| 5 | * Licensed under the Apache License, Version 2.0 (the "License");
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| 6 | * you may not use this file except in compliance with the License.
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| 7 | * You may obtain a copy of the License at
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| 8 | *
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| 9 | * http://www.apache.org/licenses/LICENSE-2.0
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| 10 | *
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| 11 | * Unless required by applicable law or agreed to in writing, software
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| 12 | * distributed under the License is distributed on an "AS IS" BASIS,
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| 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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| 14 | * See the License for the specific language governing permissions and
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| 15 | * limitations under the License.
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| 16 | */
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| 17 |
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| 18 | namespace Google\Auth\CredentialSource;
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| 19 |
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| 20 | use Google\Auth\ExternalAccountCredentialSourceInterface;
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| 21 | use Google\Auth\HttpHandler\HttpClientCache;
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| 22 | use Google\Auth\HttpHandler\HttpHandlerFactory;
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| 23 | use GuzzleHttp\Psr7\Request;
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| 24 |
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| 25 | /**
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| 26 | * Authenticates requests using AWS credentials.
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| 27 | */
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| 28 | class AwsNativeSource implements ExternalAccountCredentialSourceInterface
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| 29 | {
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| 30 | private const CRED_VERIFICATION_QUERY = 'Action=GetCallerIdentity&Version=2011-06-15';
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| 31 |
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| 32 | private string $audience;
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| 33 | private string $regionalCredVerificationUrl;
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| 34 | private ?string $regionUrl;
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| 35 | private ?string $securityCredentialsUrl;
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| 36 | private ?string $imdsv2SessionTokenUrl;
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| 37 |
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| 38 | /**
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| 39 | * @param string $audience The audience for the credential.
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| 40 | * @param string $regionalCredVerificationUrl The regional AWS GetCallerIdentity action URL used to determine the
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| 41 | * AWS account ID and its roles. This is not called by this library, but
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| 42 | * is sent in the subject token to be called by the STS token server.
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| 43 | * @param string|null $regionUrl This URL should be used to determine the current AWS region needed for the signed
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| 44 | * request construction.
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| 45 | * @param string|null $securityCredentialsUrl The AWS metadata server URL used to retrieve the access key, secret
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| 46 | * key and security token needed to sign the GetCallerIdentity request.
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| 47 | * @param string|null $imdsv2SessionTokenUrl Presence of this URL enforces the auth libraries to fetch a Session
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| 48 | * Token from AWS. This field is required for EC2 instances using IMDSv2.
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| 49 | */
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| 50 | public function __construct(
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| 51 | string $audience,
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| 52 | string $regionalCredVerificationUrl,
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| 53 | ?string $regionUrl = null,
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| 54 | ?string $securityCredentialsUrl = null,
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| 55 | ?string $imdsv2SessionTokenUrl = null
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| 56 | ) {
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| 57 | $this->audience = $audience;
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| 58 | $this->regionalCredVerificationUrl = $regionalCredVerificationUrl;
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| 59 | $this->regionUrl = $regionUrl;
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| 60 | $this->securityCredentialsUrl = $securityCredentialsUrl;
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| 61 | $this->imdsv2SessionTokenUrl = $imdsv2SessionTokenUrl;
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| 62 | }
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| 63 |
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| 64 | public function fetchSubjectToken(?callable $httpHandler = null): string
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| 65 | {
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| 66 | if (is_null($httpHandler)) {
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| 67 | $httpHandler = HttpHandlerFactory::build(HttpClientCache::getHttpClient());
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| 68 | }
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| 69 |
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| 70 | $headers = [];
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| 71 | if ($this->imdsv2SessionTokenUrl) {
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| 72 | $headers = [
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| 73 | 'X-aws-ec2-metadata-token' => self::getImdsV2SessionToken($this->imdsv2SessionTokenUrl, $httpHandler)
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| 74 | ];
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| 75 | }
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| 76 |
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| 77 | if (!$signingVars = self::getSigningVarsFromEnv()) {
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| 78 | if (!$this->securityCredentialsUrl) {
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| 79 | throw new \LogicException('Unable to get credentials from ENV, and no security credentials URL provided');
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| 80 | }
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| 81 | $signingVars = self::getSigningVarsFromUrl(
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| 82 | $httpHandler,
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| 83 | $this->securityCredentialsUrl,
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| 84 | self::getRoleName($httpHandler, $this->securityCredentialsUrl, $headers),
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| 85 | $headers
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| 86 | );
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| 87 | }
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| 88 |
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| 89 | if (!$region = self::getRegionFromEnv()) {
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| 90 | if (!$this->regionUrl) {
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| 91 | throw new \LogicException('Unable to get region from ENV, and no region URL provided');
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| 92 | }
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| 93 | $region = self::getRegionFromUrl($httpHandler, $this->regionUrl, $headers);
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| 94 | }
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| 95 | $url = str_replace('{region}', $region, $this->regionalCredVerificationUrl);
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| 96 | $host = parse_url($url)['host'] ?? '';
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| 97 |
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| 98 | // From here we use the signing vars to create the signed request to receive a token
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| 99 | [$accessKeyId, $secretAccessKey, $securityToken] = $signingVars;
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| 100 | $headers = self::getSignedRequestHeaders($region, $host, $accessKeyId, $secretAccessKey, $securityToken);
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| 101 |
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| 102 | // Inject x-goog-cloud-target-resource into header
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| 103 | $headers['x-goog-cloud-target-resource'] = $this->audience;
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| 104 |
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| 105 | // Format headers as they're expected in the subject token
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| 106 | $formattedHeaders = array_map(
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| 107 | fn ($k, $v) => ['key' => $k, 'value' => $v],
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| 108 | array_keys($headers),
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| 109 | $headers,
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| 110 | );
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| 111 |
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| 112 | $request = [
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| 113 | 'headers' => $formattedHeaders,
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| 114 | 'method' => 'POST',
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| 115 | 'url' => $url,
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| 116 | ];
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| 117 |
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| 118 | return urlencode(json_encode($request) ?: '');
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| 119 | }
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| 120 |
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| 121 | /**
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| 122 | * @internal
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| 123 | */
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| 124 | public static function getImdsV2SessionToken(string $imdsV2Url, callable $httpHandler): string
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| 125 | {
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| 126 | $headers = [
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| 127 | 'X-aws-ec2-metadata-token-ttl-seconds' => '21600'
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| 128 | ];
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| 129 | $request = new Request(
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| 130 | 'PUT',
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| 131 | $imdsV2Url,
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| 132 | $headers
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| 133 | );
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| 134 |
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| 135 | $response = $httpHandler($request);
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| 136 | return (string) $response->getBody();
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| 137 | }
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| 138 |
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| 139 | /**
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| 140 | * @see http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
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| 141 | *
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| 142 | * @internal
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| 143 | *
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| 144 | * @return array<string, string>
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| 145 | */
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| 146 | public static function getSignedRequestHeaders(
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| 147 | string $region,
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| 148 | string $host,
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| 149 | string $accessKeyId,
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| 150 | string $secretAccessKey,
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| 151 | ?string $securityToken
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| 152 | ): array {
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| 153 | $service = 'sts';
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| 154 |
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| 155 | # Create a date for headers and the credential string in ISO-8601 format
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| 156 | $amzdate = gmdate('Ymd\THis\Z');
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| 157 | $datestamp = gmdate('Ymd'); # Date w/o time, used in credential scope
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| 158 |
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| 159 | # Create the canonical headers and signed headers. Header names
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| 160 | # must be trimmed and lowercase, and sorted in code point order from
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| 161 | # low to high. Note that there is a trailing \n.
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| 162 | $canonicalHeaders = sprintf("host:%s\nx-amz-date:%s\n", $host, $amzdate);
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| 163 | if ($securityToken) {
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| 164 | $canonicalHeaders .= sprintf("x-amz-security-token:%s\n", $securityToken);
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| 165 | }
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| 166 |
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| 167 | # Step 5: Create the list of signed headers. This lists the headers
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| 168 | # in the canonicalHeaders list, delimited with ";" and in alpha order.
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| 169 | # Note: The request can include any headers; $canonicalHeaders and
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| 170 | # $signedHeaders lists those that you want to be included in the
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| 171 | # hash of the request. "Host" and "x-amz-date" are always required.
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| 172 | $signedHeaders = 'host;x-amz-date';
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| 173 | if ($securityToken) {
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| 174 | $signedHeaders .= ';x-amz-security-token';
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| 175 | }
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| 176 |
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| 177 | # Step 6: Create payload hash (hash of the request body content). For GET
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| 178 | # requests, the payload is an empty string ("").
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| 179 | $payloadHash = hash('sha256', '');
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| 180 |
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| 181 | # Step 7: Combine elements to create canonical request
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| 182 | $canonicalRequest = implode("\n", [
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| 183 | 'POST', // method
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| 184 | '/', // canonical URL
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| 185 | self::CRED_VERIFICATION_QUERY, // query string
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| 186 | $canonicalHeaders,
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| 187 | $signedHeaders,
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| 188 | $payloadHash
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| 189 | ]);
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| 190 |
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| 191 | # ************* TASK 2: CREATE THE STRING TO SIGN*************
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| 192 | # Match the algorithm to the hashing algorithm you use, either SHA-1 or
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| 193 | # SHA-256 (recommended)
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| 194 | $algorithm = 'AWS4-HMAC-SHA256';
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| 195 | $scope = implode('/', [$datestamp, $region, $service, 'aws4_request']);
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| 196 | $stringToSign = implode("\n", [$algorithm, $amzdate, $scope, hash('sha256', $canonicalRequest)]);
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| 197 |
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| 198 | # ************* TASK 3: CALCULATE THE SIGNATURE *************
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| 199 | # Create the signing key using the function defined above.
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| 200 | // (done above)
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| 201 | $signingKey = self::getSignatureKey($secretAccessKey, $datestamp, $region, $service);
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| 202 |
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| 203 | # Sign the string_to_sign using the signing_key
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| 204 | $signature = bin2hex(self::hmacSign($signingKey, $stringToSign));
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| 205 |
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| 206 | # ************* TASK 4: ADD SIGNING INFORMATION TO THE REQUEST *************
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| 207 | # The signing information can be either in a query string value or in
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| 208 | # a header named Authorization. This code shows how to use a header.
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| 209 | # Create authorization header and add to request headers
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| 210 | $authorizationHeader = sprintf(
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| 211 | '%s Credential=%s/%s, SignedHeaders=%s, Signature=%s',
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| 212 | $algorithm,
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| 213 | $accessKeyId,
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| 214 | $scope,
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| 215 | $signedHeaders,
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| 216 | $signature
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| 217 | );
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| 218 |
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| 219 | # The request can include any headers, but MUST include "host", "x-amz-date",
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| 220 | # and (for this scenario) "Authorization". "host" and "x-amz-date" must
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| 221 | # be included in the canonical_headers and signed_headers, as noted
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| 222 | # earlier. Order here is not significant.
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| 223 | $headers = [
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| 224 | 'host' => $host,
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| 225 | 'x-amz-date' => $amzdate,
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| 226 | 'Authorization' => $authorizationHeader,
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| 227 | ];
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| 228 | if ($securityToken) {
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| 229 | $headers['x-amz-security-token'] = $securityToken;
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| 230 | }
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| 231 |
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| 232 | return $headers;
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| 233 | }
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| 234 |
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| 235 | /**
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| 236 | * @internal
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| 237 | */
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| 238 | public static function getRegionFromEnv(): ?string
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| 239 | {
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| 240 | $region = getenv('AWS_REGION');
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| 241 | if (empty($region)) {
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| 242 | $region = getenv('AWS_DEFAULT_REGION');
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| 243 | }
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| 244 | return $region ?: null;
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| 245 | }
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| 246 |
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| 247 | /**
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| 248 | * @internal
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| 249 | *
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| 250 | * @param callable $httpHandler
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| 251 | * @param string $regionUrl
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| 252 | * @param array<string, string|string[]> $headers Request headers to send in with the request.
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| 253 | */
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| 254 | public static function getRegionFromUrl(callable $httpHandler, string $regionUrl, array $headers): string
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| 255 | {
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| 256 | // get the region/zone from the region URL
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| 257 | $regionRequest = new Request('GET', $regionUrl, $headers);
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| 258 | $regionResponse = $httpHandler($regionRequest);
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| 259 |
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| 260 | // Remove last character. For example, if us-east-2b is returned,
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| 261 | // the region would be us-east-2.
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| 262 | return substr((string) $regionResponse->getBody(), 0, -1);
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| 263 | }
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| 264 |
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| 265 | /**
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| 266 | * @internal
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| 267 | *
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| 268 | * @param callable $httpHandler
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| 269 | * @param string $securityCredentialsUrl
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| 270 | * @param array<string, string|string[]> $headers Request headers to send in with the request.
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| 271 | */
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| 272 | public static function getRoleName(callable $httpHandler, string $securityCredentialsUrl, array $headers): string
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| 273 | {
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| 274 | // Get the AWS role name
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| 275 | $roleRequest = new Request('GET', $securityCredentialsUrl, $headers);
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| 276 | $roleResponse = $httpHandler($roleRequest);
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| 277 | $roleName = (string) $roleResponse->getBody();
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| 278 |
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| 279 | return $roleName;
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| 280 | }
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| 281 |
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| 282 | /**
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| 283 | * @internal
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| 284 | *
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| 285 | * @param callable $httpHandler
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| 286 | * @param string $securityCredentialsUrl
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| 287 | * @param array<string, string|string[]> $headers Request headers to send in with the request.
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| 288 | * @return array{string, string, ?string}
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| 289 | */
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| 290 | public static function getSigningVarsFromUrl(
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| 291 | callable $httpHandler,
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| 292 | string $securityCredentialsUrl,
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| 293 | string $roleName,
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| 294 | array $headers
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| 295 | ): array {
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| 296 | // Get the AWS credentials
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| 297 | $credsRequest = new Request(
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| 298 | 'GET',
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| 299 | $securityCredentialsUrl . '/' . $roleName,
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| 300 | $headers
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| 301 | );
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| 302 | $credsResponse = $httpHandler($credsRequest);
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| 303 | $awsCreds = json_decode((string) $credsResponse->getBody(), true);
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| 304 | return [
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| 305 | $awsCreds['AccessKeyId'], // accessKeyId
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| 306 | $awsCreds['SecretAccessKey'], // secretAccessKey
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| 307 | $awsCreds['Token'], // token
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| 308 | ];
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| 309 | }
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| 310 |
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| 311 | /**
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| 312 | * @internal
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| 313 | *
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| 314 | * @return array{string, string, ?string}
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| 315 | */
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| 316 | public static function getSigningVarsFromEnv(): ?array
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| 317 | {
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| 318 | $accessKeyId = getenv('AWS_ACCESS_KEY_ID');
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| 319 | $secretAccessKey = getenv('AWS_SECRET_ACCESS_KEY');
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| 320 | if ($accessKeyId && $secretAccessKey) {
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| 321 | return [
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| 322 | $accessKeyId,
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| 323 | $secretAccessKey,
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| 324 | getenv('AWS_SESSION_TOKEN') ?: null, // session token (can be null)
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| 325 | ];
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| 326 | }
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| 327 |
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| 328 | return null;
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| 329 | }
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| 330 |
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| 331 | /**
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| 332 | * Gets the unique key for caching
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| 333 | * For AwsNativeSource the values are:
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| 334 | * Imdsv2SessionTokenUrl.SecurityCredentialsUrl.RegionUrl.RegionalCredVerificationUrl
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| 335 | *
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| 336 | * @return string
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| 337 | */
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| 338 | public function getCacheKey(): string
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| 339 | {
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| 340 | return ($this->imdsv2SessionTokenUrl ?? '') .
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| 341 | '.' . ($this->securityCredentialsUrl ?? '') .
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| 342 | '.' . $this->regionUrl .
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| 343 | '.' . $this->regionalCredVerificationUrl;
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| 344 | }
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| 345 |
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| 346 | /**
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| 347 | * Return HMAC hash in binary string
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| 348 | */
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| 349 | private static function hmacSign(string $key, string $msg): string
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| 350 | {
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| 351 | return hash_hmac('sha256', self::utf8Encode($msg), $key, true);
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| 352 | }
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| 353 |
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| 354 | /**
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| 355 | * @TODO add a fallback when mbstring is not available
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| 356 | */
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| 357 | private static function utf8Encode(string $string): string
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| 358 | {
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| 359 | return mb_convert_encoding($string, 'UTF-8', 'ISO-8859-1');
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| 360 | }
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| 361 |
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| 362 | private static function getSignatureKey(
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| 363 | string $key,
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| 364 | string $dateStamp,
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| 365 | string $regionName,
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| 366 | string $serviceName
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| 367 | ): string {
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| 368 | $kDate = self::hmacSign(self::utf8Encode('AWS4' . $key), $dateStamp);
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| 369 | $kRegion = self::hmacSign($kDate, $regionName);
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| 370 | $kService = self::hmacSign($kRegion, $serviceName);
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| 371 | $kSigning = self::hmacSign($kService, 'aws4_request');
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| 372 |
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| 373 | return $kSigning;
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| 374 | }
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| 375 | }
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