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Adds endpoints for creating and managing backup objects with ZK anonymous credentials.
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10 changes: 10 additions & 0 deletions
10
service/src/main/java/org/whispersystems/textsecuregcm/auth/AuthenticatedBackupUser.java
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| @@ -0,0 +1,10 @@ | ||
| /* | ||
| * Copyright 2023 Signal Messenger, LLC | ||
| * SPDX-License-Identifier: AGPL-3.0-only | ||
| */ | ||
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| package org.whispersystems.textsecuregcm.auth; | ||
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| import org.whispersystems.textsecuregcm.backup.BackupTier; | ||
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| public record AuthenticatedBackupUser(byte[] backupId, BackupTier backupTier) {} |
165 changes: 165 additions & 0 deletions
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service/src/main/java/org/whispersystems/textsecuregcm/backup/BackupAuthManager.java
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,165 @@ | ||
| /* | ||
| * Copyright 2023 Signal Messenger, LLC | ||
| * SPDX-License-Identifier: AGPL-3.0-only | ||
| */ | ||
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| package org.whispersystems.textsecuregcm.backup; | ||
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| import io.grpc.Status; | ||
| import java.security.MessageDigest; | ||
| import java.time.Clock; | ||
| import java.time.Duration; | ||
| import java.time.Instant; | ||
| import java.time.temporal.ChronoUnit; | ||
| import java.util.List; | ||
| import java.util.Optional; | ||
| import java.util.concurrent.CompletableFuture; | ||
| import java.util.stream.Stream; | ||
| import org.signal.libsignal.zkgroup.GenericServerSecretParams; | ||
| import org.signal.libsignal.zkgroup.InvalidInputException; | ||
| import org.signal.libsignal.zkgroup.backups.BackupAuthCredentialRequest; | ||
| import org.signal.libsignal.zkgroup.backups.BackupAuthCredentialResponse; | ||
| import org.whispersystems.textsecuregcm.configuration.dynamic.DynamicConfiguration; | ||
| import org.whispersystems.textsecuregcm.controllers.RateLimitExceededException; | ||
| import org.whispersystems.textsecuregcm.limits.RateLimiters; | ||
| import org.whispersystems.textsecuregcm.storage.Account; | ||
| import org.whispersystems.textsecuregcm.storage.AccountsManager; | ||
| import org.whispersystems.textsecuregcm.storage.DynamicConfigurationManager; | ||
| import org.whispersystems.textsecuregcm.util.Util; | ||
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| /** | ||
| * Issues ZK backup auth credentials for authenticated accounts | ||
| * <p> | ||
| * Authenticated callers can create ZK credentials that contain a blinded backup-id, so that they can later use that | ||
| * backup id without the verifier learning that the id is associated with this account. | ||
| * <p> | ||
| * First use {@link #commitBackupId} to provide a blinded backup-id. This is stored in durable storage. Then the caller | ||
| * can use {@link #getBackupAuthCredentials} to retrieve credentials that can subsequently be used to make anonymously | ||
| * authenticated requests against their backup-id. | ||
| */ | ||
| public class BackupAuthManager { | ||
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| private static final Duration MAX_REDEMPTION_DURATION = Duration.ofDays(7); | ||
| final static String BACKUP_EXPERIMENT_NAME = "backup"; | ||
| final static String BACKUP_MEDIA_EXPERIMENT_NAME = "backupMedia"; | ||
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| private final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager; | ||
| private final GenericServerSecretParams serverSecretParams; | ||
| private final Clock clock; | ||
| private final RateLimiters rateLimiters; | ||
| private final AccountsManager accountsManager; | ||
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| public BackupAuthManager( | ||
| final DynamicConfigurationManager<DynamicConfiguration> dynamicConfigurationManager, | ||
| final RateLimiters rateLimiters, | ||
| final AccountsManager accountsManager, | ||
| final GenericServerSecretParams serverSecretParams, | ||
| final Clock clock) { | ||
| this.dynamicConfigurationManager = dynamicConfigurationManager; | ||
| this.rateLimiters = rateLimiters; | ||
| this.accountsManager = accountsManager; | ||
| this.serverSecretParams = serverSecretParams; | ||
| this.clock = clock; | ||
| } | ||
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| /** | ||
| * Store a credential request containing a blinded backup-id for future use. | ||
| * | ||
| * @param account The account using the backup-id | ||
| * @param backupAuthCredentialRequest A request containing the blinded backup-id | ||
| * @return A future that completes when the credentialRequest has been stored | ||
| * @throws RateLimitExceededException If too many backup-ids have been committed | ||
| */ | ||
| public CompletableFuture<Void> commitBackupId(final Account account, | ||
| final BackupAuthCredentialRequest backupAuthCredentialRequest) throws RateLimitExceededException { | ||
| if (receiptLevel(account).isEmpty()) { | ||
| throw Status.PERMISSION_DENIED.withDescription("Backups not allowed on account").asRuntimeException(); | ||
| } | ||
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| byte[] serializedRequest = backupAuthCredentialRequest.serialize(); | ||
| byte[] existingRequest = account.getBackupCredentialRequest(); | ||
| if (existingRequest != null && MessageDigest.isEqual(serializedRequest, existingRequest)) { | ||
| // No need to update or enforce rate limits, this is the credential that the user has already | ||
| // committed to. | ||
| return CompletableFuture.completedFuture(null); | ||
| } | ||
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| rateLimiters.forDescriptor(RateLimiters.For.SET_BACKUP_ID).validate(account.getUuid()); | ||
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| return this.accountsManager | ||
| .updateAsync(account, acc -> acc.setBackupCredentialRequest(serializedRequest)) | ||
| .thenRun(Util.NOOP); | ||
| } | ||
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| public record Credential(BackupAuthCredentialResponse credential, Instant redemptionTime) {} | ||
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| /** | ||
| * Create a credential for every day between redemptionStart and redemptionEnd | ||
| * <p> | ||
| * This uses a {@link BackupAuthCredentialRequest} previous stored via {@link this#commitBackupId} to generate the | ||
| * credentials. | ||
| * | ||
| * @param account The account to create the credentials for | ||
| * @param redemptionStart The day (must be truncated to a day boundary) the first credential should be valid | ||
| * @param redemptionEnd The day (must be truncated to a day boundary) the last credential should be valid | ||
| * @return Credentials and the day on which they may be redeemed | ||
| */ | ||
| public CompletableFuture<List<Credential>> getBackupAuthCredentials( | ||
| final Account account, | ||
| final Instant redemptionStart, | ||
| final Instant redemptionEnd) { | ||
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| final long receiptLevel = receiptLevel(account).orElseThrow( | ||
| () -> Status.PERMISSION_DENIED.withDescription("Backups not allowed on account").asRuntimeException()); | ||
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| final Instant startOfDay = clock.instant().truncatedTo(ChronoUnit.DAYS); | ||
| if (redemptionStart.isAfter(redemptionEnd) || | ||
| redemptionStart.isBefore(startOfDay) || | ||
| redemptionEnd.isAfter(startOfDay.plus(MAX_REDEMPTION_DURATION)) || | ||
| !redemptionStart.equals(redemptionStart.truncatedTo(ChronoUnit.DAYS)) || | ||
| !redemptionEnd.equals(redemptionEnd.truncatedTo(ChronoUnit.DAYS))) { | ||
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| throw Status.INVALID_ARGUMENT.withDescription("invalid redemption window").asRuntimeException(); | ||
| } | ||
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| // fetch the blinded backup-id the account should have previously committed to | ||
| final byte[] committedBytes = account.getBackupCredentialRequest(); | ||
| if (committedBytes == null) { | ||
| throw Status.NOT_FOUND.withDescription("No blinded backup-id has been added to the account").asRuntimeException(); | ||
| } | ||
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| try { | ||
| // create a credential for every day in the requested period | ||
| final BackupAuthCredentialRequest credentialReq = new BackupAuthCredentialRequest(committedBytes); | ||
| return CompletableFuture.completedFuture(Stream | ||
| .iterate(redemptionStart, curr -> curr.plus(Duration.ofDays(1))) | ||
| .takeWhile(redemptionTime -> !redemptionTime.isAfter(redemptionEnd)) | ||
| .map(redemption -> new Credential( | ||
| credentialReq.issueCredential(redemption, receiptLevel, serverSecretParams), | ||
| redemption)) | ||
| .toList()); | ||
| } catch (InvalidInputException e) { | ||
| throw Status.INTERNAL | ||
| .withDescription("Could not deserialize stored request credential") | ||
| .withCause(e) | ||
| .asRuntimeException(); | ||
| } | ||
| } | ||
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| private Optional<Long> receiptLevel(final Account account) { | ||
| if (inExperiment(BACKUP_MEDIA_EXPERIMENT_NAME, account)) { | ||
| return Optional.of(BackupTier.MEDIA.getReceiptLevel()); | ||
| } | ||
| if (inExperiment(BACKUP_EXPERIMENT_NAME, account)) { | ||
| return Optional.of(BackupTier.MESSAGES.getReceiptLevel()); | ||
| } | ||
| return Optional.empty(); | ||
| } | ||
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| private boolean inExperiment(final String experimentName, final Account account) { | ||
| return dynamicConfigurationManager.getConfiguration() | ||
| .getExperimentEnrollmentConfiguration(experimentName) | ||
| .map(config -> config.getEnrolledUuids().contains(account.getUuid())) | ||
| .orElse(false); | ||
| } | ||
| } |
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