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hmac check on rsa decrypt

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This commit is contained in:
Kyle Spearrin 2017-06-19 11:57:37 -04:00
parent 1e5883f028
commit 7823ec3fc8
4 changed files with 43 additions and 10 deletions
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4
src/App/Enums/EncryptionType.cs
View file

@ -6,6 +6,8 @@
AesCbc128_HmacSha256_B64 = 1,
AesCbc256_HmacSha256_B64 = 2,
Rsa2048_OaepSha256_B64 = 3,
Rsa2048_OaepSha1_B64 = 4
Rsa2048_OaepSha1_B64 = 4,
Rsa2048_OaepSha256_HmacSha256_B64 = 5,
Rsa2048_OaepSha1_HmacSha256_B64 = 6
}
}

9
src/App/Models/CipherString.cs
View file

@ -63,6 +63,15 @@ namespace Bit.App.Models
}
CipherText = encPieces[0];
break;
case EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64:
case EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64:
if(encPieces.Length != 2)
{
throw new ArgumentException("Malformed encPieces.");
}
CipherText = encPieces[0];
Mac = encPieces[1];
break;
default:
throw new ArgumentException("Unknown encType.");
}

11
src/App/Services/CryptoService.cs
View file

@ -323,13 +323,24 @@ namespace Bit.App.Services
throw new ArgumentNullException(nameof(privateKey));
}
if(EncKey?.MacKey != null && !string.IsNullOrWhiteSpace(encyptedValue.Mac))
{
var computedMacBytes = Crypto.ComputeMac(encyptedValue.CipherTextBytes, EncKey.MacKey);
if(!Crypto.MacsEqual(EncKey.MacKey, computedMacBytes, encyptedValue.MacBytes))
{
throw new InvalidOperationException("MAC failed.");
}
}
IAsymmetricKeyAlgorithmProvider provider = null;
switch(encyptedValue.EncryptionType)
{
case EncryptionType.Rsa2048_OaepSha256_B64:
case EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64:
provider = WinRTCrypto.AsymmetricKeyAlgorithmProvider.OpenAlgorithm(AsymmetricAlgorithm.RsaOaepSha256);
break;
case EncryptionType.Rsa2048_OaepSha1_B64:
case EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64:
provider = WinRTCrypto.AsymmetricKeyAlgorithmProvider.OpenAlgorithm(AsymmetricAlgorithm.RsaOaepSha1);
break;
default:

29
src/App/Utilities/Crypto.cs
View file

@ -1,6 +1,7 @@
using Bit.App.Models;
using PCLCrypto;
using System;
using System.Collections.Generic;
using System.Linq;
namespace Bit.App.Utilities
@ -63,19 +64,14 @@ namespace Bit.App.Utilities
return WinRTCrypto.CryptographicBuffer.GenerateRandom(length);
}
private static string ComputeMacBase64(byte[] ctBytes, byte[] ivBytes, byte[] macKey)
public static string ComputeMacBase64(byte[] ctBytes, byte[] ivBytes, byte[] macKey)
{
var mac = ComputeMac(ctBytes, ivBytes, macKey);
return Convert.ToBase64String(mac);
}
private static byte[] ComputeMac(byte[] ctBytes, byte[] ivBytes, byte[] macKey)
public static byte[] ComputeMac(byte[] ctBytes, byte[] ivBytes, byte[] macKey)
{
if(macKey == null)
{
throw new ArgumentNullException(nameof(macKey));
}
if(ctBytes == null)
{
throw new ArgumentNullException(nameof(ctBytes));
@ -86,16 +82,31 @@ namespace Bit.App.Utilities
throw new ArgumentNullException(nameof(ivBytes));
}
return ComputeMac(ivBytes.Concat(ctBytes), macKey);
}
public static byte[] ComputeMac(IEnumerable<byte> dataBytes, byte[] macKey)
{
if(macKey == null)
{
throw new ArgumentNullException(nameof(macKey));
}
if(dataBytes == null)
{
throw new ArgumentNullException(nameof(dataBytes));
}
var algorithm = WinRTCrypto.MacAlgorithmProvider.OpenAlgorithm(MacAlgorithm.HmacSha256);
var hasher = algorithm.CreateHash(macKey);
hasher.Append(ivBytes.Concat(ctBytes).ToArray());
hasher.Append(dataBytes.ToArray());
var mac = hasher.GetValueAndReset();
return mac;
}
// Safely compare two MACs in a way that protects against timing attacks (Double HMAC Verification).
// ref: https://www.nccgroup.trust/us/about-us/newsroom-and-events/blog/2011/february/double-hmac-verification/
private static bool MacsEqual(byte[] macKey, byte[] mac1, byte[] mac2)
public static bool MacsEqual(byte[] macKey, byte[] mac1, byte[] mac2)
{
var algorithm = WinRTCrypto.MacAlgorithmProvider.OpenAlgorithm(MacAlgorithm.HmacSha256);
var hasher = algorithm.CreateHash(macKey);