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Allow use of the token returned with spam challenges as auth for the …
…challenge verification request
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12 changes: 12 additions & 0 deletions
12
.../src/main/java/org/whispersystems/textsecuregcm/configuration/ChallengeConfiguration.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,12 @@ | ||
| /* | ||
| * Copyright 2021-2022 Signal Messenger, LLC | ||
| * SPDX-License-Identifier: AGPL-3.0-only | ||
| */ | ||
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| package org.whispersystems.textsecuregcm.configuration; | ||
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| import java.time.Duration; | ||
| import org.whispersystems.textsecuregcm.configuration.secrets.SecretBytes; | ||
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| public record ChallengeConfiguration(SecretBytes blindingSecret, Duration tokenTtl) { | ||
| } |
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109 changes: 109 additions & 0 deletions
109
service/src/main/java/org/whispersystems/textsecuregcm/util/ChallengeTokenBlinder.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,109 @@ | ||
| /* | ||
| * Copyright 2023 Signal Messenger, LLC | ||
| * SPDX-License-Identifier: AGPL-3.0-only | ||
| */ | ||
|
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| package org.whispersystems.textsecuregcm.util; | ||
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| import com.fasterxml.jackson.databind.ObjectMapper; | ||
| import com.fasterxml.jackson.core.JsonProcessingException; | ||
| import java.io.IOException; | ||
| import java.nio.ByteBuffer; | ||
| import java.security.GeneralSecurityException; | ||
| import java.security.ProviderException; | ||
| import java.security.SecureRandom; | ||
| import java.time.Clock; | ||
| import java.time.Duration; | ||
| import java.time.Instant; | ||
| import java.util.Base64; | ||
| import java.util.Optional; | ||
| import java.util.UUID; | ||
| import javax.crypto.AEADBadTagException; | ||
| import javax.crypto.Cipher; | ||
| import javax.crypto.SecretKey; | ||
| import javax.crypto.spec.GCMParameterSpec; | ||
| import javax.crypto.spec.SecretKeySpec; | ||
| import org.whispersystems.textsecuregcm.configuration.ChallengeConfiguration; | ||
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| public class ChallengeTokenBlinder { | ||
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| private record Token( | ||
| UUID uuid, | ||
| Instant timestamp) { | ||
| } | ||
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| private static final ObjectMapper mapper = SystemMapper.jsonMapper(); | ||
| private final Clock clock; | ||
| private final Duration tokenTtl; | ||
| private final SecureRandom secureRandom = new SecureRandom(); | ||
| private final SecretKey blindingKey; | ||
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| public ChallengeTokenBlinder(final ChallengeConfiguration config, final Clock clock) { | ||
| this.blindingKey = new SecretKeySpec(config.blindingSecret().value(), "AES"); | ||
| this.tokenTtl = config.tokenTtl(); | ||
| this.clock = clock; | ||
| } | ||
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| public String generateBlindedAccountToken(UUID aci) { | ||
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| final Token token = new Token(aci, clock.instant()); | ||
| final byte[] serializedToken; | ||
| try { | ||
| serializedToken = mapper.writeValueAsBytes(token); | ||
| } catch (IOException e) { // should really, really never happen | ||
| throw new IllegalArgumentException(); | ||
| } | ||
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| final byte[] iv = new byte[12]; | ||
| secureRandom.nextBytes(iv); | ||
| final GCMParameterSpec parameterSpec = new GCMParameterSpec(128, iv); | ||
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| try { | ||
| final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); | ||
| cipher.init(Cipher.ENCRYPT_MODE, blindingKey, parameterSpec); | ||
| final byte[] ciphertext = cipher.doFinal(serializedToken); | ||
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| final ByteBuffer byteBuffer = ByteBuffer.allocate(iv.length + ciphertext.length); | ||
| byteBuffer.put(iv); | ||
| byteBuffer.put(ciphertext); | ||
| return Base64.getUrlEncoder().withoutPadding().encodeToString(byteBuffer.array()); | ||
| } catch (GeneralSecurityException e) { | ||
| throw new IllegalArgumentException(e); | ||
| } | ||
| } | ||
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| public Optional<UUID> unblindAccountToken(String token) { | ||
| final byte[] ciphertext; | ||
| try { | ||
| ciphertext = Base64.getUrlDecoder().decode(token); | ||
| } catch (IllegalArgumentException e) { | ||
| return Optional.empty(); | ||
| } | ||
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| final Token parsedToken; | ||
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| try { | ||
| final Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding"); | ||
| final GCMParameterSpec parameterSpec = new GCMParameterSpec(128, ciphertext, 0, 12); | ||
| cipher.init(Cipher.DECRYPT_MODE, blindingKey, parameterSpec); | ||
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| parsedToken = mapper.readValue(cipher.doFinal(ciphertext, 12, ciphertext.length - 12), Token.class); | ||
| } catch (ProviderException | AEADBadTagException | JsonProcessingException e) { | ||
| // the token doesn't successfully decrypt with this key, it's bogus (or from an older server version or before a key rotation) | ||
| return Optional.empty(); | ||
| } catch (IOException | GeneralSecurityException e) { // should never happen | ||
| throw new IllegalArgumentException(); | ||
| } | ||
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| Instant now = clock.instant(); | ||
| Instant intervalStart = now.minus(tokenTtl); | ||
| Instant tokenTime = parsedToken.timestamp(); | ||
| if (tokenTime.isAfter(now) || tokenTime.isBefore(intervalStart)) { | ||
| // expired or fraudulently-future token | ||
| return Optional.empty(); | ||
| } | ||
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| return Optional.of(parsedToken.uuid()); | ||
| } | ||
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| } |
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