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Fake responses for non-existent users (#5538)

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Bernd Schoolmann 2025-03-21 13:49:34 +01:00 committed by GitHub
parent 5016ece4ff
commit 77206b12a9
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
2 changed files with 45 additions and 16 deletions
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2
src/Core/Auth/Models/Api/Request/Opaque/OpaqueRegistrationStartRequest.cs
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@ -14,7 +14,7 @@ public class OpaqueRegistrationStartRequest
public class OpaqueKeyExchangeCipherConfiguration
{
static string OpaqueKe3Ristretto3DHArgonSuite = "OPAQUE_3_RISTRETTO255_OPRF_RISTRETTO255_KEGROUP_3DH_KEX_ARGON2ID13_KSF";
public static string OpaqueKe3Ristretto3DHArgonSuite = "OPAQUE_3_RISTRETTO255_OPRF_RISTRETTO255_KEGROUP_3DH_KEX_ARGON2ID13_KSF";
[Required]
public string CipherSuite { get; set; }

59
src/Core/Auth/Services/Implementations/OpaqueKeyExchangeService.cs
View File

@ -8,6 +8,7 @@ using Bit.Core.Auth.Repositories;
using Bit.Core.Auth.Utilities;
using Bit.Core.Entities;
using Bit.Core.Repositories;
using Bit.Core.Settings;
using Bit.Core.Utilities;
using Bitwarden.Opaque;
using Microsoft.Extensions.Caching.Distributed;
@ -25,6 +26,7 @@ public class OpaqueKeyExchangeService : IOpaqueKeyExchangeService
private readonly IUserRepository _userRepository;
private readonly ILogger<OpaqueKeyExchangeService> _logger;
private readonly DistributedCacheEntryOptions _distributedCacheEntryOptions;
private readonly byte[] _defaultKdfHmacKey = null;
const string REGISTRATION_SESSION_KEY = "opaque_register_session_{0}";
const string LOGIN_SESSION_KEY = "opaque_login_session_{0}";
@ -33,7 +35,8 @@ public class OpaqueKeyExchangeService : IOpaqueKeyExchangeService
IOpaqueKeyExchangeCredentialRepository opaqueKeyExchangeCredentialRepository,
IDistributedCache distributedCache,
IUserRepository userRepository,
ILogger<OpaqueKeyExchangeService> logger
ILogger<OpaqueKeyExchangeService> logger,
GlobalSettings globalSettings
)
{
_bitwardenOpaque = new BitwardenOpaqueServer();
@ -45,6 +48,14 @@ public class OpaqueKeyExchangeService : IOpaqueKeyExchangeService
{
AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(1)
};
if (CoreHelpers.SettingHasValue(globalSettings.KdfDefaultHashKey))
{
_defaultKdfHmacKey = Encoding.UTF8.GetBytes(globalSettings.KdfDefaultHashKey);
}
else
{
_defaultKdfHmacKey = new byte[32];
}
}
public async Task<OpaqueRegistrationStartResponse> StartRegistration(
@ -110,18 +121,39 @@ public class OpaqueKeyExchangeService : IOpaqueKeyExchangeService
{
try
{
// todo: don't allow user enumeration
var user = await _userRepository.GetByEmailAsync(email)
?? throw new InvalidOperationException("User not found");
var user = await _userRepository.GetByEmailAsync(email);
// Fake user to prevent user enumeration
user ??= new User() { Id = Guid.Empty };
// todo: generate fake credential
var credential = await _opaqueKeyExchangeCredentialRepository.GetByUserIdAsync(user.Id)
?? throw new InvalidOperationException("Credential not found");
var cipherConfiguration = JsonSerializer.Deserialize<OpaqueKeyExchangeCipherConfiguration>(credential.CipherConfiguration)!;
var credentialBlob = JsonSerializer.Deserialize<OpaqueKeyExchangeCredentialBlob>(credential.CredentialBlob)!;
var serverSetup = credentialBlob.ServerSetup;
var serverRegistration = credentialBlob.PasswordFile;
byte[] serverSetup = null;
byte[] serverRegistration = null;
OpaqueKeyExchangeCipherConfiguration cipherConfiguration;
var credential = await _opaqueKeyExchangeCredentialRepository.GetByUserIdAsync(user.Id);
if (credential != null)
{
cipherConfiguration = JsonSerializer.Deserialize<OpaqueKeyExchangeCipherConfiguration>(credential.CipherConfiguration)!;
var credentialBlob = JsonSerializer.Deserialize<OpaqueKeyExchangeCredentialBlob>(credential.CredentialBlob)!;
serverSetup = credentialBlob.ServerSetup;
serverRegistration = credentialBlob.PasswordFile;
}
else
{
// Generate a fake registration for non-existent users
cipherConfiguration = new OpaqueKeyExchangeCipherConfiguration()
{
CipherSuite = OpaqueKeyExchangeCipherConfiguration.OpaqueKe3Ristretto3DHArgonSuite,
Argon2Parameters = new Argon2KsfParameters()
{
Memory = 0,
Iterations = 0,
Parallelism = 0
}
};
var hmacMessage = Encoding.UTF8.GetBytes(email.Trim().ToLowerInvariant());
using var hmac = new System.Security.Cryptography.HMACSHA256(_defaultKdfHmacKey);
var hmacHash = hmac.ComputeHash(hmacMessage);
(serverSetup, serverRegistration) = _bitwardenOpaque.SeededFakeRegistration(hmacHash);
}
var loginResponse = _bitwardenOpaque.StartLogin(
cipherConfiguration.ToNativeConfiguration(), serverSetup, serverRegistration, request, user.Id.ToString());
@ -156,9 +188,6 @@ public class OpaqueKeyExchangeService : IOpaqueKeyExchangeService
?? throw new InvalidOperationException("Session not found");
var loginSession = JsonSerializer.Deserialize<OpaqueKeyExchangeLoginSession>(Encoding.ASCII.GetString(serializedLoginSession))!;
var credential = await _opaqueKeyExchangeCredentialRepository.GetByUserIdAsync(loginSession.UserId)
?? throw new InvalidOperationException("Credential not found");
var loginState = loginSession.LoginState;
var cipherConfiguration = loginSession.CipherConfiguration;
await ClearAuthenticationSession(sessionId);