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using System;
using System.Security.Cryptography;
using System.Text;
namespace PKISharp.WACS.Services.Serialization
{
/// <summary>
/// Wrapper to handle string encryption and encoding
/// Strings can be in three forms:
/// - Clear, prefixed by ClearPrefix
/// - Base64 encoded, without any prefix
/// - Base64 encoded *with* encryption, prefixed by EncryptedPrefix
/// </summary>
public class ProtectedString
{
/// <summary>
/// Indicates encryption
/// </summary>
internal const string EncryptedPrefix = "enc-";
/// <summary>
/// Indicates clear text
/// </summary>
internal const string ClearPrefix = "clear-";
/// <summary>
/// Logging service, used only by the JsonConverter
/// </summary>
private readonly ILogService _log;
/// <summary>
/// Indicates if there was an error decoding or decrypting the string
/// </summary>
public bool Error { get; private set; } = false;
/// <summary>
/// Clear value, should be used for operations
/// </summary>
public string Value { get; private set; }
/// <summary>
/// Value to save to disk, based on the setting
/// </summary>
public string DiskValue
{
get
{
return Properties.Settings.Default.EncryptConfig? ProtectedValue : EncodedValue;
}
}
/// <summary>
/// Constructor for user input, always starting with clear text
/// </summary>
/// <param name="clearValue"></param>
public ProtectedString(string clearValue)
{
Value = clearValue;
}
/// <summary>
/// Constructor for deserialisation, may be any format
/// </summary>
/// <param name="rawValue"></param>
/// <param name="log"></param>
public ProtectedString(string rawValue, ILogService log)
{
_log = log;
Value = rawValue;
if (!string.IsNullOrEmpty(rawValue))
{
if (rawValue.StartsWith(EncryptedPrefix))
{
// Sure to be encrypted
try
{
Value = Unprotect(rawValue.Substring(EncryptedPrefix.Length));
}
catch
{
_log.Error("Unable to decrypt configuration value, may have been written by a different machine.");
Error = true;
}
}
else if (rawValue.StartsWith(ClearPrefix))
{
// Sure to be clear/unencoded
Value = rawValue.Substring(ClearPrefix.Length);
}
else
{
// Should be Base64
try
{
var clearBytes = Convert.FromBase64String(rawValue);
Value = Encoding.UTF8.GetString(clearBytes);
}
catch
{
_log.Error("Unable to decode configuration value, use the prefix {prefix} to input clear text", ClearPrefix);
Error = true;
}
}
}
}
/// <summary>
/// Encrypted value should be used when the "EncryptConfig" setting is true
/// </summary>
internal string ProtectedValue
{
get
{
if (string.IsNullOrEmpty(Value) || Error)
{
return Value;
}
else
{
return EncryptedPrefix + Protect(Value);
}
}
}
/// <summary>
/// Encoded value should be used when the "EncryptConfig" setting is false
/// </summary>
internal string EncodedValue
{
get
{
if (string.IsNullOrEmpty(Value) || Error)
{
return Value;
}
else
{
return Encode(Value);
}
}
}
/// <summary>
/// Base64 encode a string
/// </summary>
/// <param name="clearText"></param>
/// <returns></returns>
private string Encode(string clearText)
{
byte[] clearBytes = Encoding.UTF8.GetBytes(clearText);
return Convert.ToBase64String(clearBytes);
}
/// <summary>
/// Encrypt and Base64-encode a string
/// </summary>
/// <param name="clearText"></param>
/// <param name="optionalEntropy"></param>
/// <param name="scope"></param>
/// <returns></returns>
private string Protect(string clearText, string optionalEntropy = null, DataProtectionScope scope = DataProtectionScope.LocalMachine)
{
byte[] clearBytes = Encoding.UTF8.GetBytes(clearText);
byte[] entropyBytes = string.IsNullOrEmpty(optionalEntropy)
? null
: Encoding.UTF8.GetBytes(optionalEntropy);
byte[] encryptedBytes = ProtectedData.Protect(clearBytes, entropyBytes, scope);
return Convert.ToBase64String(encryptedBytes);
}
/// <summary>
/// Base64-decode and decrypt a string
/// </summary>
/// <param name="clearText"></param>
/// <param name="optionalEntropy"></param>
/// <param name="scope"></param>
/// <returns></returns>
private string Unprotect(string encryptedText, string optionalEntropy = null, DataProtectionScope scope = DataProtectionScope.LocalMachine)
{
if (encryptedText == null)
{
return null;
}
byte[] clearBytes = null;
byte[] encryptedBytes = Convert.FromBase64String(encryptedText);
byte[] entropyBytes = string.IsNullOrEmpty(optionalEntropy)
? null
: Encoding.UTF8.GetBytes(optionalEntropy);
clearBytes = ProtectedData.Unprotect(encryptedBytes, entropyBytes, scope);
return Encoding.UTF8.GetString(clearBytes);
}
}
}
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