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| 1 | +/* |
| 2 | + * Copyright 2024, Google Inc. All rights reserved. |
| 3 | + * |
| 4 | + * Redistribution and use in source and binary forms, with or without |
| 5 | + * modification, are permitted provided that the following conditions are |
| 6 | + * met: |
| 7 | + * |
| 8 | + * * Redistributions of source code must retain the above copyright |
| 9 | + * notice, this list of conditions and the following disclaimer. |
| 10 | + * * Redistributions in binary form must reproduce the above |
| 11 | + * copyright notice, this list of conditions and the following disclaimer |
| 12 | + * in the documentation and/or other materials provided with the |
| 13 | + * distribution. |
| 14 | + * |
| 15 | + * * Neither the name of Google Inc. nor the names of its |
| 16 | + * contributors may be used to endorse or promote products derived from |
| 17 | + * this software without specific prior written permission. |
| 18 | + * |
| 19 | + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 20 | + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 21 | + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 22 | + * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 23 | + * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 24 | + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 25 | + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 26 | + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 27 | + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 28 | + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 29 | + * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 30 | + */ |
| 31 | +package com.google.auth.oauth2; |
| 32 | + |
| 33 | +import com.google.api.client.http.GenericUrl; |
| 34 | +import com.google.api.client.http.HttpBackOffIOExceptionHandler; |
| 35 | +import com.google.api.client.http.HttpBackOffUnsuccessfulResponseHandler; |
| 36 | +import com.google.api.client.http.HttpRequest; |
| 37 | +import com.google.api.client.http.HttpResponse; |
| 38 | +import com.google.api.client.json.JsonObjectParser; |
| 39 | +import com.google.api.client.util.ExponentialBackOff; |
| 40 | +import com.google.api.client.util.GenericData; |
| 41 | +import com.google.auth.http.HttpTransportFactory; |
| 42 | +import com.google.common.collect.Iterables; |
| 43 | +import com.google.errorprone.annotations.CanIgnoreReturnValue; |
| 44 | +import java.io.IOException; |
| 45 | +import java.io.InputStream; |
| 46 | +import java.util.Arrays; |
| 47 | +import java.util.HashSet; |
| 48 | +import java.util.ServiceLoader; |
| 49 | +import java.util.Set; |
| 50 | +import javax.annotation.concurrent.ThreadSafe; |
| 51 | + |
| 52 | +/** |
| 53 | + * Utilities to fetch the S2A (Secure Session Agent) address from the mTLS configuration. |
| 54 | + * |
| 55 | + * <p>mTLS configuration is queried from the MDS MTLS Autoconfiguration endpoint. See |
| 56 | + * https://google.aip.dev/auth/4115 for details. |
| 57 | + * |
| 58 | + * <p>This is an experimental utility. |
| 59 | + */ |
| 60 | +@ThreadSafe |
| 61 | +public class SecureSessionAgent { |
| 62 | + static final String S2A_PLAINTEXT_ADDRESS_JSON_KEY = "plaintext_address"; |
| 63 | + static final String S2A_MTLS_ADDRESS_JSON_KEY = "mtls_address"; |
| 64 | + static final String S2A_CONFIG_ENDPOINT_POSTFIX = |
| 65 | + "/computeMetadata/v1/instance/platform-security/auto-mtls-configuration"; |
| 66 | + |
| 67 | + static final String METADATA_FLAVOR = "Metadata-Flavor"; |
| 68 | + static final String GOOGLE = "Google"; |
| 69 | + private static final Set<Integer> RETRYABLE_STATUS_CODES = |
| 70 | + new HashSet<>(Arrays.asList(500, 502, 503)); |
| 71 | + private static final String PARSE_ERROR_S2A = "Error parsing S2A Config from MDS JSON response."; |
| 72 | + private static final String MDS_MTLS_ENDPOINT = |
| 73 | + ComputeEngineCredentials.getMetadataServerUrl() + S2A_CONFIG_ENDPOINT_POSTFIX; |
| 74 | + |
| 75 | + private transient HttpTransportFactory transportFactory; |
| 76 | + |
| 77 | + SecureSessionAgent(SecureSessionAgent.Builder builder) { |
| 78 | + this.transportFactory = builder.getHttpTransportFactory(); |
| 79 | + } |
| 80 | + |
| 81 | + /** |
| 82 | + * This method makes a network call to MDS to get the {@link SecureSessionAgentConfig} which |
| 83 | + * contains the plaintext and mtls address to reach the S2A (Secure Session Agent). |
| 84 | + * |
| 85 | + * @return a SecureSessionAgentConfig. |
| 86 | + */ |
| 87 | + public SecureSessionAgentConfig getConfig() { |
| 88 | + return getSecureSessionAgentConfigFromMDS(); |
| 89 | + } |
| 90 | + |
| 91 | + /** @return default instance of SecureSessionAgent */ |
| 92 | + public static SecureSessionAgent create() { |
| 93 | + return newBuilder().build(); |
| 94 | + } |
| 95 | + |
| 96 | + public static Builder newBuilder() { |
| 97 | + return new Builder(); |
| 98 | + } |
| 99 | + |
| 100 | + public static class Builder { |
| 101 | + private HttpTransportFactory transportFactory; |
| 102 | + |
| 103 | + protected Builder() {} |
| 104 | + |
| 105 | + @CanIgnoreReturnValue |
| 106 | + public Builder setHttpTransportFactory(HttpTransportFactory transportFactory) { |
| 107 | + this.transportFactory = transportFactory; |
| 108 | + return this; |
| 109 | + } |
| 110 | + |
| 111 | + public HttpTransportFactory getHttpTransportFactory() { |
| 112 | + return this.transportFactory; |
| 113 | + } |
| 114 | + |
| 115 | + public SecureSessionAgent build() { |
| 116 | + return new SecureSessionAgent(this); |
| 117 | + } |
| 118 | + } |
| 119 | + |
| 120 | + /** |
| 121 | + * Queries the MDS mTLS Autoconfiguration endpoint and returns the {@link |
| 122 | + * SecureSessionAgentConfig}. |
| 123 | + * |
| 124 | + * <p>Returns {@link SecureSessionAgentConfig}. If S2A is not running, or if any error occurs when |
| 125 | + * making the request to MDS / processing the response, {@link SecureSessionAgentConfig} will be |
| 126 | + * populated with empty addresses. |
| 127 | + * |
| 128 | + * <p>Users are expected to try to fetch the mTLS-S2A address first (via {@link |
| 129 | + * getMtlsS2AAddress}). If it is empty or they have some problem loading the mTLS-MDS credentials, |
| 130 | + * they should then fallback to fetching the plaintext-S2A address (via {@link |
| 131 | + * getPlaintextS2AAddress}). If the plaintext-S2A address is empty it means that an error occurred |
| 132 | + * when talking to the MDS / processing the response or that S2A is not running in the |
| 133 | + * environment; in either case this indicates S2A shouldn't be used. |
| 134 | + * |
| 135 | + * @return the {@link SecureSessionAgentConfig}. |
| 136 | + */ |
| 137 | + private SecureSessionAgentConfig getSecureSessionAgentConfigFromMDS() { |
| 138 | + if (transportFactory == null) { |
| 139 | + transportFactory = |
| 140 | + Iterables.getFirst( |
| 141 | + ServiceLoader.load(HttpTransportFactory.class), OAuth2Utils.HTTP_TRANSPORT_FACTORY); |
| 142 | + } |
| 143 | + |
| 144 | + HttpRequest request = null; |
| 145 | + GenericUrl genericUrl = new GenericUrl(MDS_MTLS_ENDPOINT); |
| 146 | + try { |
| 147 | + request = transportFactory.create().createRequestFactory().buildGetRequest(genericUrl); |
| 148 | + } catch (IOException ignore) { |
| 149 | + /* |
| 150 | + * Return empty addresses in {@link SecureSessionAgentConfig} if error building the GET request. |
| 151 | + */ |
| 152 | + return SecureSessionAgentConfig.createBuilder().build(); |
| 153 | + } |
| 154 | + |
| 155 | + request.setParser(new JsonObjectParser(OAuth2Utils.JSON_FACTORY)); |
| 156 | + request.getHeaders().set(METADATA_FLAVOR, GOOGLE); |
| 157 | + request.setThrowExceptionOnExecuteError(false); |
| 158 | + request.setNumberOfRetries(OAuth2Utils.DEFAULT_NUMBER_OF_RETRIES); |
| 159 | + |
| 160 | + ExponentialBackOff backoff = |
| 161 | + new ExponentialBackOff.Builder() |
| 162 | + .setInitialIntervalMillis(OAuth2Utils.INITIAL_RETRY_INTERVAL_MILLIS) |
| 163 | + .setRandomizationFactor(OAuth2Utils.RETRY_RANDOMIZATION_FACTOR) |
| 164 | + .setMultiplier(OAuth2Utils.RETRY_MULTIPLIER) |
| 165 | + .build(); |
| 166 | + |
| 167 | + // Retry on 5xx status codes. |
| 168 | + request.setUnsuccessfulResponseHandler( |
| 169 | + new HttpBackOffUnsuccessfulResponseHandler(backoff) |
| 170 | + .setBackOffRequired( |
| 171 | + response -> RETRYABLE_STATUS_CODES.contains(response.getStatusCode()))); |
| 172 | + request.setIOExceptionHandler(new HttpBackOffIOExceptionHandler(backoff)); |
| 173 | + |
| 174 | + GenericData responseData = null; |
| 175 | + try { |
| 176 | + HttpResponse response = request.execute(); |
| 177 | + InputStream content = response.getContent(); |
| 178 | + if (content == null) { |
| 179 | + return SecureSessionAgentConfig.createBuilder().build(); |
| 180 | + } |
| 181 | + responseData = response.parseAs(GenericData.class); |
| 182 | + } catch (IOException ignore) { |
| 183 | + /* |
| 184 | + * Return empty addresses in {@link SecureSessionAgentConfig} once all retries have been exhausted. |
| 185 | + */ |
| 186 | + return SecureSessionAgentConfig.createBuilder().build(); |
| 187 | + } |
| 188 | + |
| 189 | + String plaintextS2AAddress = ""; |
| 190 | + String mtlsS2AAddress = ""; |
| 191 | + try { |
| 192 | + plaintextS2AAddress = |
| 193 | + OAuth2Utils.validateString(responseData, S2A_PLAINTEXT_ADDRESS_JSON_KEY, PARSE_ERROR_S2A); |
| 194 | + } catch (IOException ignore) { |
| 195 | + /* |
| 196 | + * Do not throw error because of parsing error, just leave the address as empty in {@link SecureSessionAgentConfig}. |
| 197 | + */ |
| 198 | + } |
| 199 | + try { |
| 200 | + mtlsS2AAddress = |
| 201 | + OAuth2Utils.validateString(responseData, S2A_MTLS_ADDRESS_JSON_KEY, PARSE_ERROR_S2A); |
| 202 | + } catch (IOException ignore) { |
| 203 | + /* |
| 204 | + * Do not throw error because of parsing error, just leave the address as empty in {@link SecureSessionAgentConfig}. |
| 205 | + */ |
| 206 | + } |
| 207 | + |
| 208 | + return SecureSessionAgentConfig.createBuilder() |
| 209 | + .setPlaintextAddress(plaintextS2AAddress) |
| 210 | + .setMtlsAddress(mtlsS2AAddress) |
| 211 | + .build(); |
| 212 | + } |
| 213 | +} |
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