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WPFアプリケーションでの資格情報の暗号化

WPFアプリケーションでは、資格情報を記憶し、次にアプリケーションが起動されたときにそれらを自動的に使用するための典型的な "Remember Me"オプションを提供したいと思います。

一方向ハッシュを使用 は明らかにオプションではありません。資格情報を保存することはできますが 分離ストレージに または レジストリに がありますが、資格情報を暗号化するときに処理する問題。

対称キー暗号化アルゴリズムを使用する場合、キーをどこかに保存する必要があります。たとえば、キーがメモリにハードコードされている場合、.NETアセンブリを分解して見つけるのは簡単だと思います。

.NETで資格情報を暗号化して安全に保ち、暗号化キーを完全に手の届かないところに保管するための最良の方法は何ですか？

c#wpfsecurityencryptioncredentials
28
Gigi

これが私のブログ投稿の概要です： Windowsにパスワードを保存する方法

データ保護APIとその.NET実装（ ProtectedData ）を使用してパスワードを暗号化できます。次に例を示します。

public static string Protect(string str)
{
    byte[] entropy = Encoding.ASCII.GetBytes(Assembly.GetExecutingAssembly().FullName);
    byte[] data = Encoding.ASCII.GetBytes(str);
    string protectedData = Convert.ToBase64String(ProtectedData.Protect(data, entropy, DataProtectionScope.CurrentUser));
    return protectedData;
}

public static string Unprotect(string str)
{
    byte[] protectedData = Convert.FromBase64String(str);
    byte[] entropy = Encoding.ASCII.GetBytes(Assembly.GetExecutingAssembly().FullName);
    string data = Encoding.ASCII.GetString(ProtectedData.Unprotect(protectedData, entropy, DataProtectionScope.CurrentUser));
    return data;
}

または、Windows資格情報マネージャーを使用することもできます（これは、アプリケーションにそのような機能がない場合でも、ユーザーが資格情報をバックアップ/復元/編集できるため、これが私が好む方法です）。 NuGetパッケージ Meziantou.Framework.Win32.CredentialManager を作成しました。どうやって使うのですか：

CredentialManager.WriteCredential("ApplicationName", "username", "Pa$$w0rd", CredentialPersistence.Session);

var cred = CredentialManager.ReadCredential("ApplicationName");
Assert.AreEqual("username", cred.UserName);
Assert.AreEqual("Pa$$w0rd", cred.Password);

CredentialManager.DeleteCredential("ApplicationName");

ネイティブAPIラッパーを使用した元の回答（これの最新バージョンは GitHubで利用可能 ）：

using System;
using System.Collections.Generic;
using System.Runtime.InteropServices;
using Microsoft.Win32.SafeHandles;
using System.Text;
using System.ComponentModel;

public static class CredentialManager
{
    public static Credential ReadCredential(string applicationName)
    {
        IntPtr nCredPtr;
        bool read = CredRead(applicationName, CredentialType.Generic, 0, out nCredPtr);
        if (read)
        {
            using (CriticalCredentialHandle critCred = new CriticalCredentialHandle(nCredPtr))
            {
                CREDENTIAL cred = critCred.GetCredential();
                return ReadCredential(cred);
            }
        }

        return null;
    }

    private static Credential ReadCredential(CREDENTIAL credential)
    {
        string applicationName = Marshal.PtrToStringUni(credential.TargetName);
        string userName = Marshal.PtrToStringUni(credential.UserName);
        string secret = null;
        if (credential.CredentialBlob != IntPtr.Zero)
        {
            secret = Marshal.PtrToStringUni(credential.CredentialBlob, (int)credential.CredentialBlobSize / 2);
        }

        return new Credential(credential.Type, applicationName, userName, secret);
    }

    public static int WriteCredential(string applicationName, string userName, string secret)
    {
        byte[] byteArray = Encoding.Unicode.GetBytes(secret);
        if (byteArray.Length > 512)
            throw new ArgumentOutOfRangeException("secret", "The secret message has exceeded 512 bytes.");

        CREDENTIAL credential = new CREDENTIAL();
        credential.AttributeCount = 0;
        credential.Attributes = IntPtr.Zero;
        credential.Comment = IntPtr.Zero;
        credential.TargetAlias = IntPtr.Zero;
        credential.Type = CredentialType.Generic;
        credential.Persist = (UInt32)CredentialPersistence.Session;
        credential.CredentialBlobSize = (UInt32)Encoding.Unicode.GetBytes(secret).Length;
        credential.TargetName = Marshal.StringToCoTaskMemUni(applicationName);
        credential.CredentialBlob = Marshal.StringToCoTaskMemUni(secret);
        credential.UserName = Marshal.StringToCoTaskMemUni(userName ?? Environment.UserName);

        bool written = CredWrite(ref credential, 0);
        int lastError = Marshal.GetLastWin32Error();

        Marshal.FreeCoTaskMem(credential.TargetName);
        Marshal.FreeCoTaskMem(credential.CredentialBlob);
        Marshal.FreeCoTaskMem(credential.UserName);

        if (written)
            return 0;

        throw new Exception(string.Format("CredWrite failed with the error code {0}.", lastError));
    }

    public static IReadOnlyList<Credential> EnumerateCrendentials()
    {
        List<Credential> result = new List<Credential>();

        int count;
        IntPtr pCredentials;
        bool ret = CredEnumerate(null, 0, out count, out pCredentials);
        if (ret)
        {
            for (int n = 0; n < count; n++)
            {
                IntPtr credential = Marshal.ReadIntPtr(pCredentials, n * Marshal.SizeOf(typeof(IntPtr)));
                result.Add(ReadCredential((CREDENTIAL)Marshal.PtrToStructure(credential, typeof(CREDENTIAL))));
            }
        }
        else
        {
            int lastError = Marshal.GetLastWin32Error();
            throw new Win32Exception(lastError);
        }

        return result;
    }

    [DllImport("Advapi32.dll", EntryPoint = "CredReadW", CharSet = CharSet.Unicode, SetLastError = true)]
    static extern bool CredRead(string target, CredentialType type, int reservedFlag, out IntPtr credentialPtr);

    [DllImport("Advapi32.dll", EntryPoint = "CredWriteW", CharSet = CharSet.Unicode, SetLastError = true)]
    static extern bool CredWrite([In] ref CREDENTIAL userCredential, [In] UInt32 flags);

    [DllImport("advapi32", SetLastError = true, CharSet = CharSet.Unicode)]
    static extern bool CredEnumerate(string filter, int flag, out int count, out IntPtr pCredentials);

    [DllImport("Advapi32.dll", EntryPoint = "CredFree", SetLastError = true)]
    static extern bool CredFree([In] IntPtr cred);



    private enum CredentialPersistence : uint
    {
        Session = 1,
        LocalMachine,
        Enterprise
    }

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    private struct CREDENTIAL
    {
        public UInt32 Flags;
        public CredentialType Type;
        public IntPtr TargetName;
        public IntPtr Comment;
        public System.Runtime.InteropServices.ComTypes.FILETIME LastWritten;
        public UInt32 CredentialBlobSize;
        public IntPtr CredentialBlob;
        public UInt32 Persist;
        public UInt32 AttributeCount;
        public IntPtr Attributes;
        public IntPtr TargetAlias;
        public IntPtr UserName;
    }

    sealed class CriticalCredentialHandle : CriticalHandleZeroOrMinusOneIsInvalid
    {
        public CriticalCredentialHandle(IntPtr preexistingHandle)
        {
            SetHandle(preexistingHandle);
        }

        public CREDENTIAL GetCredential()
        {
            if (!IsInvalid)
            {
                CREDENTIAL credential = (CREDENTIAL)Marshal.PtrToStructure(handle, typeof(CREDENTIAL));
                return credential;
            }

            throw new InvalidOperationException("Invalid CriticalHandle!");
        }

        protected override bool ReleaseHandle()
        {
            if (!IsInvalid)
            {
                CredFree(handle);
                SetHandleAsInvalid();
                return true;
            }

            return false;
        }
    }
}

public enum CredentialType
{
    Generic = 1,
    DomainPassword,
    DomainCertificate,
    DomainVisiblePassword,
    GenericCertificate,
    DomainExtended,
    Maximum,
    MaximumEx = Maximum + 1000,
}

public class Credential
{
    private readonly string _applicationName;
    private readonly string _userName;
    private readonly string _password;
    private readonly CredentialType _credentialType;

    public CredentialType CredentialType
    {
        get { return _credentialType; }
    }

    public string ApplicationName
    {
        get { return _applicationName; }
    }

    public string UserName
    {
        get { return _userName; }
    }

    public string Password
    {
        get { return _password; }
    }

    public Credential(CredentialType credentialType, string applicationName, string userName, string password)
    {
        _applicationName = applicationName;
        _userName = userName;
        _password = password;
        _credentialType = credentialType;
    }

    public override string ToString()
    {
        return string.Format("CredentialType: {0}, ApplicationName: {1}, UserName: {2}, Password: {3}", CredentialType, ApplicationName, UserName, Password);
    }
}

使用法：

WriteCredential("ApplicationName", "Meziantou", "Passw0rd");
Console.WriteLine(ReadCredential("Demo"));
36
meziantou