557 lines
25 KiB
C#
557 lines
25 KiB
C#
//------------------------------------------------------------------------------
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// <copyright file="SqlColumnEncryptionCertificateStoreProvider.cs" company="Microsoft">
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// Copyright (c) Microsoft Corporation. All rights reserved.
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// </copyright>
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// <owner current="true" primary="true">balnee</owner>
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// <owner current="true" primary="false">krishnib</owner>
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//------------------------------------------------------------------------------
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namespace System.Data.SqlClient
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{
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using System;
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using System.Text;
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using System.Data.Common;
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using System.Diagnostics;
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using System.Globalization;
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using System.Security;
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using System.Security.Cryptography;
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using System.Security.Cryptography.X509Certificates;
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/// <summary>
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/// Certificate Key Store Provider class
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/// </summary>
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public class SqlColumnEncryptionCertificateStoreProvider : SqlColumnEncryptionKeyStoreProvider
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{
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// Constants
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//
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// Assumption: Certificate Locations (LocalMachine & CurrentUser), Certificate Store name "My"
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// Certificate provider name (CertificateStore) dont need to be localized.
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/// <summary>
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/// Name for the certificate key store provider.
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/// </summary>
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public const string ProviderName = @"MSSQL_CERTIFICATE_STORE";
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/// <summary>
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/// RSA_OAEP is the only algorithm supported for encrypting/decrypting column encryption keys.
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/// </summary>
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internal const string RSAEncryptionAlgorithmWithOAEP = @"RSA_OAEP";
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/// <summary>
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/// LocalMachine certificate store location. Valid certificate locations are LocalMachine and CurrentUser.
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/// </summary>
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private const string _certLocationLocalMachine = @"LocalMachine";
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/// <summary>
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/// CurrentUser certificate store location. Valid certificate locations are LocalMachine and CurrentUser.
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/// </summary>
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private const string _certLocationCurrentUser = @"CurrentUser";
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/// <summary>
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/// Valid certificate store
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/// </summary>
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private const string _myCertificateStore = @"My";
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/// <summary>
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/// Certificate path format. This is a custom format.
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/// </summary>
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private const string _certificatePathFormat = @"[LocalMachine|CurrentUser]/My/[Thumbprint]";
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/// <summary>
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/// Hashig algoirthm used for signing
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/// </summary>
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private const string _hashingAlgorithm = @"SHA256";
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/// <summary>
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/// Algorithm version
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/// </summary>
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private readonly byte[] _version = new byte[] { 0x01 };
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/// <summary>
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/// This function uses a certificate specified by the key path
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/// and decrypts an encrypted CEK with RSA encryption algorithm.
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/// </summary>
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/// <param name="masterKeyPath">Complete path of a certificate</param>
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/// <param name="encryptionAlgorithm">Asymmetric Key Encryption Algorithm</param>
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/// <param name="encryptedColumnEncryptionKey">Encrypted Column Encryption Key</param>
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/// <returns>Plain text column encryption key</returns>
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public override byte[] DecryptColumnEncryptionKey(string masterKeyPath, string encryptionAlgorithm, byte[] encryptedColumnEncryptionKey)
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{
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// Validate the input parameters
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ValidateNonEmptyCertificatePath(masterKeyPath, isSystemOp: true);
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if (null == encryptedColumnEncryptionKey)
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{
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throw SQL.NullEncryptedColumnEncryptionKey();
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}
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else if (0 == encryptedColumnEncryptionKey.Length)
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{
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throw SQL.EmptyEncryptedColumnEncryptionKey();
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}
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// Validate encryptionAlgorithm
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ValidateEncryptionAlgorithm(encryptionAlgorithm, isSystemOp: true);
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// Validate key path length
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ValidateCertificatePathLength(masterKeyPath, isSystemOp: true);
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// Parse the path and get the X509 cert
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X509Certificate2 certificate = GetCertificateByPath(masterKeyPath, isSystemOp: true);
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int keySizeInBytes = certificate.PublicKey.Key.KeySize / 8;
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// Validate and decrypt the EncryptedColumnEncryptionKey
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// Format is
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// version + keyPathLength + ciphertextLength + keyPath + ciphertext + signature
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//
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// keyPath is present in the encrypted column encryption key for identifying the original source of the asymmetric key pair and
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// we will not validate it against the data contained in the CMK metadata (masterKeyPath).
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// Validate the version byte
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if (encryptedColumnEncryptionKey[0] != _version[0])
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{
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throw SQL.InvalidAlgorithmVersionInEncryptedCEK(encryptedColumnEncryptionKey[0], _version[0]);
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}
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// Get key path length
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int currentIndex = _version.Length;
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Int16 keyPathLength = BitConverter.ToInt16(encryptedColumnEncryptionKey, currentIndex);
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currentIndex += sizeof(Int16);
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// Get ciphertext length
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int cipherTextLength = BitConverter.ToInt16(encryptedColumnEncryptionKey, currentIndex);
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currentIndex += sizeof(Int16);
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// Skip KeyPath
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// KeyPath exists only for troubleshooting purposes and doesnt need validation.
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currentIndex += keyPathLength;
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// validate the ciphertext length
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if (cipherTextLength != keySizeInBytes)
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{
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throw SQL.InvalidCiphertextLengthInEncryptedCEK(cipherTextLength, keySizeInBytes, masterKeyPath);
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}
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// Validate the signature length
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// Signature length should be same as the key side for RSA PKCSv1.5
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int signatureLength = encryptedColumnEncryptionKey.Length - currentIndex - cipherTextLength;
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if (signatureLength != keySizeInBytes)
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{
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throw SQL.InvalidSignatureInEncryptedCEK(signatureLength, keySizeInBytes, masterKeyPath);
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}
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// Get ciphertext
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byte[] cipherText = new byte[cipherTextLength];
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Buffer.BlockCopy(encryptedColumnEncryptionKey, currentIndex, cipherText, 0, cipherText.Length);
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currentIndex += cipherTextLength;
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// Get signature
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byte[] signature = new byte[signatureLength];
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Buffer.BlockCopy(encryptedColumnEncryptionKey, currentIndex, signature, 0, signature.Length);
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// Compute the hash to validate the signature
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byte[] hash;
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using (SHA256Cng sha256 = new SHA256Cng())
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{
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sha256.TransformFinalBlock(encryptedColumnEncryptionKey, 0, encryptedColumnEncryptionKey.Length - signature.Length);
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hash = sha256.Hash;
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}
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Debug.Assert(hash != null, @"hash should not be null while decrypting encrypted column encryption key.");
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// Validate the signature
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if (!RSAVerifySignature(hash, signature, certificate))
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{
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throw SQL.InvalidCertificateSignature(masterKeyPath);
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}
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// Decrypt the CEK
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return RSADecrypt(cipherText, certificate);
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}
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/// <summary>
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/// This function uses a certificate specified by the key path
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/// and encrypts CEK with RSA encryption algorithm.
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/// </summary>
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/// <param name="keyPath">Complete path of a certificate</param>
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/// <param name="encryptionAlgorithm">Asymmetric Key Encryption Algorithm</param>
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/// <param name="columnEncryptionKey">Plain text column encryption key</param>
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/// <returns>Encrypted column encryption key</returns>
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public override byte[] EncryptColumnEncryptionKey(string masterKeyPath, string encryptionAlgorithm, byte[] columnEncryptionKey)
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{
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// Validate the input parameters
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ValidateNonEmptyCertificatePath(masterKeyPath, isSystemOp: false);
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if (null == columnEncryptionKey)
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{
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throw SQL.NullColumnEncryptionKey();
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}
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else if (0 == columnEncryptionKey.Length)
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{
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throw SQL.EmptyColumnEncryptionKey();
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}
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// Validate encryptionAlgorithm
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ValidateEncryptionAlgorithm(encryptionAlgorithm, isSystemOp: false);
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// Validate masterKeyPath Length
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ValidateCertificatePathLength(masterKeyPath, isSystemOp: false);
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// Parse the certificate path and get the X509 cert
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X509Certificate2 certificate = GetCertificateByPath(masterKeyPath, isSystemOp: false);
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int keySizeInBytes = certificate.PublicKey.Key.KeySize / 8;
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// Construct the encryptedColumnEncryptionKey
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// Format is
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// version + keyPathLength + ciphertextLength + ciphertext + keyPath + signature
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//
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// We currently only support one version
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byte[] version = new byte[] { _version[0] };
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// Get the Unicode encoded bytes of cultureinvariant lower case masterKeyPath
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byte[] masterKeyPathBytes = Encoding.Unicode.GetBytes(masterKeyPath.ToLowerInvariant());
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byte[] keyPathLength = BitConverter.GetBytes((Int16)masterKeyPathBytes.Length);
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// Encrypt the plain text
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byte[] cipherText = RSAEncrypt(columnEncryptionKey, certificate);
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byte[] cipherTextLength = BitConverter.GetBytes((Int16)cipherText.Length);
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Debug.Assert(cipherText.Length == keySizeInBytes, @"cipherText length does not match the RSA key size");
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// Compute hash
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// SHA-2-256(version + keyPathLength + ciphertextLength + keyPath + ciphertext)
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byte[] hash;
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using (SHA256Cng sha256 = new SHA256Cng())
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{
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sha256.TransformBlock(version, 0, version.Length, version, 0);
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sha256.TransformBlock(keyPathLength, 0, keyPathLength.Length, keyPathLength, 0);
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sha256.TransformBlock(cipherTextLength, 0, cipherTextLength.Length, cipherTextLength, 0);
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sha256.TransformBlock(masterKeyPathBytes, 0, masterKeyPathBytes.Length, masterKeyPathBytes, 0);
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sha256.TransformFinalBlock(cipherText, 0, cipherText.Length);
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hash = sha256.Hash;
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}
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// Sign the hash
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byte[] signedHash = RSASignHashedData(hash, certificate);
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Debug.Assert(signedHash.Length == keySizeInBytes, @"signed hash length does not match the RSA key size");
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Debug.Assert(RSAVerifySignature(hash, signedHash, certificate), @"Invalid signature of the encrypted column encryption key computed.");
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// Construct the encrypted column encryption key
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// EncryptedColumnEncryptionKey = version + keyPathLength + ciphertextLength + keyPath + ciphertext + signature
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int encryptedColumnEncryptionKeyLength = version.Length + cipherTextLength.Length + keyPathLength.Length + cipherText.Length + masterKeyPathBytes.Length + signedHash.Length;
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byte[] encryptedColumnEncryptionKey = new byte[encryptedColumnEncryptionKeyLength];
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// Copy version byte
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int currentIndex = 0;
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Buffer.BlockCopy(version, 0, encryptedColumnEncryptionKey, currentIndex, version.Length);
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currentIndex += version.Length;
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// Copy key path length
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Buffer.BlockCopy(keyPathLength, 0, encryptedColumnEncryptionKey, currentIndex, keyPathLength.Length);
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currentIndex += keyPathLength.Length;
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// Copy ciphertext length
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Buffer.BlockCopy(cipherTextLength, 0, encryptedColumnEncryptionKey, currentIndex, cipherTextLength.Length);
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currentIndex += cipherTextLength.Length;
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// Copy key path
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Buffer.BlockCopy(masterKeyPathBytes, 0, encryptedColumnEncryptionKey, currentIndex, masterKeyPathBytes.Length);
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currentIndex += masterKeyPathBytes.Length;
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// Copy ciphertext
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Buffer.BlockCopy(cipherText, 0, encryptedColumnEncryptionKey, currentIndex, cipherText.Length);
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currentIndex += cipherText.Length;
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// copy the signature
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Buffer.BlockCopy(signedHash, 0, encryptedColumnEncryptionKey, currentIndex, signedHash.Length);
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return encryptedColumnEncryptionKey;
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}
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/// <summary>
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/// This function validates that the encryption algorithm is RSA_OAEP and if it is not,
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/// then throws an exception
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/// </summary>
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/// <param name="encryptionAlgorithm">Asymmetric key encryptio algorithm</param>
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private void ValidateEncryptionAlgorithm(string encryptionAlgorithm, bool isSystemOp)
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{
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// This validates that the encryption algorithm is RSA_OAEP
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if (null == encryptionAlgorithm)
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{
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throw SQL.NullKeyEncryptionAlgorithm(isSystemOp);
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}
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if (string.Equals(encryptionAlgorithm, RSAEncryptionAlgorithmWithOAEP, StringComparison.OrdinalIgnoreCase) != true)
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{
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throw SQL.InvalidKeyEncryptionAlgorithm(encryptionAlgorithm, RSAEncryptionAlgorithmWithOAEP, isSystemOp);
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}
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}
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/// <summary>
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/// Certificate path length has to fit in two bytes, so check its value against Int16.MaxValue
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/// </summary>
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/// <param name="masterKeyPath"></param>
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/// <param name="isSystemOp"></param>
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private void ValidateCertificatePathLength(string masterKeyPath, bool isSystemOp)
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{
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if (masterKeyPath.Length >= Int16.MaxValue)
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{
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throw SQL.LargeCertificatePathLength(masterKeyPath.Length, Int16.MaxValue, isSystemOp);
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}
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}
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/// <summary>
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/// Gets a string array containing Valid certificate locations.
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/// </summary>
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private string[] GetValidCertificateLocations()
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{
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return new string[2] {_certLocationLocalMachine, _certLocationCurrentUser};
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}
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/// <summary>
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/// Checks if the certificate path is Empty or Null (and raises exception if they are).
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/// </summary>
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private void ValidateNonEmptyCertificatePath(string masterKeyPath, bool isSystemOp)
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{
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if (string.IsNullOrWhiteSpace(masterKeyPath))
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{
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if (null == masterKeyPath)
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{
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throw SQL.NullCertificatePath(GetValidCertificateLocations(), isSystemOp);
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}
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else
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{
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throw SQL.InvalidCertificatePath(masterKeyPath, GetValidCertificateLocations(), isSystemOp);
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}
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}
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}
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/// <summary>
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/// Parses the given certificate path, searches in certificate store and returns a matching certificate
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/// </summary>
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/// <param name="keyPath">
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/// Certificate key path. Format of the path is [LocalMachine|CurrentUser]/[storename]/thumbprint
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/// </param>
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/// <returns>Returns the certificate identified by the certificate path</returns>
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private X509Certificate2 GetCertificateByPath(string keyPath, bool isSystemOp)
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{
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Debug.Assert(!string.IsNullOrEmpty(keyPath));
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// Assign default values for omitted fields
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StoreLocation storeLocation = StoreLocation.LocalMachine; // Default to Local Machine
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StoreName storeName = StoreName.My;
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string[] certParts = keyPath.Split('/');
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// Validate certificate path
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// Certificate path should only contain 3 parts (Certificate Location, Certificate Store Name and Thumbprint)
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if (certParts.Length > 3)
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{
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throw SQL.InvalidCertificatePath(keyPath, GetValidCertificateLocations(), isSystemOp);
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}
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// Extract the store location where the cert is stored
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if (certParts.Length > 2)
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{
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if (string.Equals(certParts[0], _certLocationLocalMachine, StringComparison.OrdinalIgnoreCase) == true)
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{
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storeLocation = StoreLocation.LocalMachine;
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}
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else if (string.Equals(certParts[0], _certLocationCurrentUser, StringComparison.OrdinalIgnoreCase) == true)
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{
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storeLocation = StoreLocation.CurrentUser;
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}
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else
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{
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// throw an invalid certificate location exception
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throw SQL.InvalidCertificateLocation(certParts[0], keyPath, GetValidCertificateLocations(), isSystemOp);
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}
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}
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// Parse the certificate store name
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if (certParts.Length > 1)
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{
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if (string.Equals(certParts[certParts.Length - 2], _myCertificateStore, StringComparison.OrdinalIgnoreCase) == true)
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{
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storeName = StoreName.My;
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}
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else
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{
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// We only support storing them in My certificate store
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throw SQL.InvalidCertificateStore(certParts[certParts.Length - 2], keyPath, _myCertificateStore, isSystemOp);
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}
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}
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// Get thumpbrint
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string thumbprint = certParts[certParts.Length - 1];
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if (string.IsNullOrEmpty(thumbprint))
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{
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// An empty thumbprint specified
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throw SQL.EmptyCertificateThumbprint(keyPath, isSystemOp);
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}
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// Find the certificate and return
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return GetCertificate(storeLocation, storeName, keyPath, thumbprint, isSystemOp);
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}
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/// <summary>
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/// Searches for a certificate in certificate store and returns the matching certificate
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/// </summary>
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/// <param name="storeLocation">Store Location: This can be one of LocalMachine or UserName</param>
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/// <param name="storeName">Store Location: Currently this can only be My store.</param>
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/// <param name="thumbprint">Certificate thumbprint</param>
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/// <returns>Matching certificate</returns>
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private X509Certificate2 GetCertificate(StoreLocation storeLocation, StoreName storeName, string masterKeyPath, string thumbprint, bool isSystemOp)
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{
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// Open specified certificate store
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X509Store certificateStore = null;
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try
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{
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certificateStore = new X509Store(storeName, storeLocation);
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certificateStore.Open(OpenFlags.ReadOnly | OpenFlags.OpenExistingOnly);
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// Search for the specified certificate
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X509Certificate2Collection matchingCertificates =
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certificateStore.Certificates.Find(X509FindType.FindByThumbprint,
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thumbprint,
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false);
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// Throw an exception if a cert with the specified thumbprint is not found
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if (matchingCertificates == null || matchingCertificates.Count == 0)
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{
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throw SQL.CertificateNotFound(thumbprint, storeName.ToString(), storeLocation.ToString(), isSystemOp);
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}
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X509Certificate2 certificate = matchingCertificates[0];
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if (!certificate.HasPrivateKey)
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{
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// ensure the certificate has private key
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throw SQL.CertificateWithNoPrivateKey(masterKeyPath, isSystemOp);
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}
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// return the matching certificate
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return certificate;
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}
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finally
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{
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// Close the certificate store
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if (certificateStore != null)
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{
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certificateStore.Close();
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}
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}
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}
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/// <summary>
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/// Encrypt the text using specified certificate.
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/// </summary>
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/// <param name="plaintext">Text to encrypt.</param>
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/// <param name="certificate">Certificate object.</param>
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/// <param name="masterKeyPath">Master key path that was used.</param>
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/// <returns>Returns an encrypted blob or throws an exception if there are any errors.</returns>
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private byte[] RSAEncrypt(byte[] plainText, X509Certificate2 certificate)
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{
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Debug.Assert(plainText != null);
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Debug.Assert(certificate != null);
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Debug.Assert(certificate.HasPrivateKey, "Attempting to encrypt with cert without privatekey");
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RSACryptoServiceProvider rscp = (RSACryptoServiceProvider)certificate.PublicKey.Key;
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return rscp.Encrypt(plainText, fOAEP: true);
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}
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/// <summary>
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/// Encrypt the text using specified certificate.
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/// </summary>
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/// <param name="plaintext">Text to decrypt.</param>
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/// <param name="certificate">Certificate object.</param>
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/// <param name="masterKeyPath">Master key path that was used.</param>
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private byte[] RSADecrypt(byte[] cipherText, X509Certificate2 certificate)
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{
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Debug.Assert((cipherText != null) && (cipherText.Length != 0));
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Debug.Assert(certificate != null);
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Debug.Assert(certificate.HasPrivateKey, "Attempting to decrypt with cert without privatekey");
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RSACryptoServiceProvider rscp = (RSACryptoServiceProvider)certificate.PrivateKey;
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return rscp.Decrypt(cipherText, fOAEP: true);
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}
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/// <summary>
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/// Generates signature based on RSA PKCS#v1.5 scheme using a specified certificate.
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/// </summary>
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/// <param name="dataToSign">Text to sign.</param>
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/// <param name="certificate">Certificate object.</param>
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/// <returns>Signature</returns>
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private byte[] RSASignHashedData(byte[] dataToSign, X509Certificate2 certificate)
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{
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Debug.Assert((dataToSign != null) && (dataToSign.Length != 0));
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Debug.Assert(certificate != null);
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Debug.Assert(certificate.HasPrivateKey, "Attempting to sign with cert without privatekey");
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// Prepare RSACryptoServiceProvider from certificate's private key
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RSACryptoServiceProvider rscp = GetCSPFromCertificatePrivateKey(certificate);
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// Prepare RSAPKCS1SignatureFormatter for signing the passed in hash
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RSAPKCS1SignatureFormatter rsaFormatter = new RSAPKCS1SignatureFormatter(rscp);
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//Set the hash algorithm to SHA256.
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rsaFormatter.SetHashAlgorithm(_hashingAlgorithm);
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//Create a signature for HashValue and return it.
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return rsaFormatter.CreateSignature(dataToSign);
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}
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/// <summary>
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/// Verifies the given RSA PKCSv1.5 signature.
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/// </summary>
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/// <param name="dataToVerify"></param>
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/// <param name="signature"></param>
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/// <param name="certificate"></param>
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/// <returns>true if signature is valid, false if it is not valid</returns>
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private bool RSAVerifySignature(byte[] dataToVerify, byte[] signature, X509Certificate2 certificate)
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{
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Debug.Assert((dataToVerify != null) && (dataToVerify.Length != 0));
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Debug.Assert((signature != null) && (signature.Length != 0));
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Debug.Assert(certificate != null);
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Debug.Assert(certificate.HasPrivateKey, "Attempting to sign with cert without privatekey");
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// Prepare RSACryptoServiceProvider from certificate's private key
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RSACryptoServiceProvider rscp = GetCSPFromCertificatePrivateKey(certificate);
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// Prepare RSAPKCS1SignatureFormatter for signing the passed in hash
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RSAPKCS1SignatureDeformatter rsaDeFormatter = new RSAPKCS1SignatureDeformatter(rscp);
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//Set the hash algorithm to SHA256.
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rsaDeFormatter.SetHashAlgorithm(_hashingAlgorithm);
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//Create a signature for HashValue and return it.
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return rsaDeFormatter.VerifySignature(dataToVerify, signature);
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}
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/// <summary>
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/// Prepares RSACryptoServiceProvider from a given certificate's private key
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/// </summary>
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/// <param name="certificate"></param>
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/// <returns></returns>
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private RSACryptoServiceProvider GetCSPFromCertificatePrivateKey(X509Certificate2 certificate)
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{
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const int rsaAesProviderType = 24;
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CspParameters privateKeyParams = new CspParameters();
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privateKeyParams = new CspParameters();
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privateKeyParams.KeyContainerName = ((RSACryptoServiceProvider)certificate.PrivateKey).CspKeyContainerInfo.KeyContainerName;
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privateKeyParams.ProviderType = rsaAesProviderType /*PROV_RSA_AES*/;
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privateKeyParams.KeyNumber = (int)((RSACryptoServiceProvider)certificate.PrivateKey).CspKeyContainerInfo.KeyNumber;
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// For CurrentUser store, use UseExistingKey
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// For LocalMachine store, use UseMachineKeyStore
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// CspKeyContainerInfo.MachineKeyStore already contains the appropriate information so just use it.
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if (((RSACryptoServiceProvider)certificate.PrivateKey).CspKeyContainerInfo.MachineKeyStore)
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{
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privateKeyParams.Flags = CspProviderFlags.UseMachineKeyStore;
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}
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else
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{
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privateKeyParams.Flags = CspProviderFlags.UseExistingKey;
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}
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return new RSACryptoServiceProvider(privateKeyParams);
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}
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}
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}
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