c# - visual - strong name tool

Verificando un ensamble por un nombre fuerte

Question

¿Es posible verificar si un ensamble cargado dinámicamente ha sido firmado con un nombre fuerte específico?

¿Es suficiente / seguro comparar los valores devueltos del método AssemblyName.GetPublicKey () ?

Assembly loaded = Assembly.LoadFile(path);

byte[] evidenceKey = loaded.GetName().GetPublicKey();

if (evidenceKey != null)
{
    byte[] internalKey = Assembly.GetExecutingAssembly().GetName().GetPublicKey();

    if (evidenceKey.SequenceEqual(internalKey))
    {
        return extension;
    }
}

¿No puede ser falso? No estoy seguro de si el método SetPublicKey () tiene algún efecto en un ensamblado construido, pero incluso la documentación de MSDN muestra cómo puede usar esto en un ensamblaje generado dinámicamente (emitir reflejo), lo que significa que podría extraer la clave pública del la aplicación de host e inyectarlo en un ensamblado propio y ejecutar un código malicioso si lo anterior fue la protección de seguridad, o ¿me estoy perdiendo algo?

¿Hay un enfoque más correcto y seguro? Sé que si la situación revertida fuera el escenario, es decir, cuando quería asegurar que el ensamblado solo fuera llamado por los hosts firmados, entonces podría etiquetar el ensamblado con el atributo StrongNameIdentityPermission.

Answer 1

No hay una forma administrada de verificar la firma de un ensamblaje y comprobar que la clave pública lo deje vulnerable a la suplantación. Deberá usar P / Invoke y llamar a la función StrongNameSignatureVerificationEx para verificar la firma

[DllImport("mscoree.dll", CharSet=CharSet.Unicode)]
static extern bool StrongNameSignatureVerificationEx(string wszFilePath, bool fForceVerification, ref bool  pfWasVerified);

Answer 2

No tiene mucho sentido probar el nombre fuerte una vez que se haya cargado el ensamblaje. Un atacante podría simplemente inyectar un constructor de módulo en el ensamblado y ejecutar cualquier código deseado. La versión .NET 3.5 SP1 del framework hizo lo mismo y ya no está verificando el nombre fuerte de los ensamblados que se cargan desde las ubicaciones de confianza. Los tiempos de inicio mejoran en un 40%.

El punto clave es: una vez que un atacante pone en peligro la máquina hasta el punto en que puede inyectar un conjunto en la ruta de exploración de su aplicación, no se molestará en hacerlo de la manera difícil. Él simplemente reemplazaría tu archivo EXE.

Answer 3

Comprobar el nombre seguro mediante StrongNameSignatureVerificationEx de mscoree.dll está en desuso en .NET 4 de acuerdo con http://msdn.microsoft.com/pl-pl/library/ms232579.aspx .

La forma de hacerlo de .NET 4 es:

var clrStrongName = (IClrStrongName)RuntimeEnvironment.GetRuntimeInterfaceAsObject(new Guid("B79B0ACD-F5CD-409b-B5A5-A16244610B92"), new Guid("9FD93CCF-3280-4391-B3A9-96E1CDE77C8D"));
bool verificationForced;
int result = clrStrongName.StrongNameSignatureVerificationEx(@"PATH/TO/ASSEMBLY.DLL", true, out verificationForced);
if (result == 0)
{
    Console.WriteLine("Valid.");
}



[ComConversionLoss, Guid("9FD93CCF-3280-4391-B3A9-96E1CDE77C8D"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown), SecurityCritical]
[ComImport]
internal interface IClrStrongName
{
    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromAssemblyFile([MarshalAs(UnmanagedType.LPStr)] [In] string pszFilePath, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromAssemblyFileW([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromBlob([In] IntPtr pbBlob, [MarshalAs(UnmanagedType.U4)] [In] int cchBlob, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 4)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromFile([MarshalAs(UnmanagedType.LPStr)] [In] string pszFilePath, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromFileW([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int GetHashFromHandle([In] IntPtr hFile, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int piHashAlg, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbHash, [MarshalAs(UnmanagedType.U4)] [In] int cchHash, [MarshalAs(UnmanagedType.U4)] out int pchHash);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    [return: MarshalAs(UnmanagedType.U4)]
    int StrongNameCompareAssemblies([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzAssembly1, [MarshalAs(UnmanagedType.LPWStr)] [In] string pwzAssembly2, [MarshalAs(UnmanagedType.U4)] out int dwResult);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameFreeBuffer([In] IntPtr pbMemory);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameGetBlob([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] [Out] byte[] pbBlob, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int pcbBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameGetBlobFromImage([In] IntPtr pbBase, [MarshalAs(UnmanagedType.U4)] [In] int dwLength, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [Out] byte[] pbBlob, [MarshalAs(UnmanagedType.U4)] [In] [Out] ref int pcbBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameGetPublicKey([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] [In] byte[] pbKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbKeyBlob, out IntPtr ppbPublicKeyBlob, [MarshalAs(UnmanagedType.U4)] out int pcbPublicKeyBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    [return: MarshalAs(UnmanagedType.U4)]
    int StrongNameHashSize([MarshalAs(UnmanagedType.U4)] [In] int ulHashAlg, [MarshalAs(UnmanagedType.U4)] out int cbSize);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameKeyDelete([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameKeyGen([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer, [MarshalAs(UnmanagedType.U4)] [In] int dwFlags, out IntPtr ppbKeyBlob, [MarshalAs(UnmanagedType.U4)] out int pcbKeyBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameKeyGenEx([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer, [MarshalAs(UnmanagedType.U4)] [In] int dwFlags, [MarshalAs(UnmanagedType.U4)] [In] int dwKeySize, out IntPtr ppbKeyBlob, [MarshalAs(UnmanagedType.U4)] out int pcbKeyBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameKeyInstall([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 2)] [In] byte[] pbKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbKeyBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameSignatureGeneration([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.LPWStr)] [In] string pwzKeyContainer, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [In] byte[] pbKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbKeyBlob, [In] [Out] IntPtr ppbSignatureBlob, [MarshalAs(UnmanagedType.U4)] out int pcbSignatureBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameSignatureGenerationEx([MarshalAs(UnmanagedType.LPWStr)] [In] string wszFilePath, [MarshalAs(UnmanagedType.LPWStr)] [In] string wszKeyContainer, [MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 3)] [In] byte[] pbKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbKeyBlob, [In] [Out] IntPtr ppbSignatureBlob, [MarshalAs(UnmanagedType.U4)] out int pcbSignatureBlob, [MarshalAs(UnmanagedType.U4)] [In] int dwFlags);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameSignatureSize([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] [In] byte[] pbPublicKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbPublicKeyBlob, [MarshalAs(UnmanagedType.U4)] out int pcbSize);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    [return: MarshalAs(UnmanagedType.U4)]
    int StrongNameSignatureVerification([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.U4)] [In] int dwInFlags, [MarshalAs(UnmanagedType.U4)] out int dwOutFlags);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    [return: MarshalAs(UnmanagedType.U4)]
    int StrongNameSignatureVerificationEx([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, [MarshalAs(UnmanagedType.I1)] [In] bool fForceVerification, [MarshalAs(UnmanagedType.I1)] out bool fWasVerified);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    [return: MarshalAs(UnmanagedType.U4)]
    int StrongNameSignatureVerificationFromImage([In] IntPtr pbBase, [MarshalAs(UnmanagedType.U4)] [In] int dwLength, [MarshalAs(UnmanagedType.U4)] [In] int dwInFlags, [MarshalAs(UnmanagedType.U4)] out int dwOutFlags);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameTokenFromAssembly([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, out IntPtr ppbStrongNameToken, [MarshalAs(UnmanagedType.U4)] out int pcbStrongNameToken);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameTokenFromAssemblyEx([MarshalAs(UnmanagedType.LPWStr)] [In] string pwzFilePath, out IntPtr ppbStrongNameToken, [MarshalAs(UnmanagedType.U4)] out int pcbStrongNameToken, out IntPtr ppbPublicKeyBlob, [MarshalAs(UnmanagedType.U4)] out int pcbPublicKeyBlob);

    [MethodImpl(MethodImplOptions.PreserveSig | MethodImplOptions.InternalCall)]
    int StrongNameTokenFromPublicKey([MarshalAs(UnmanagedType.LPArray, SizeParamIndex = 1)] [In] byte[] pbPublicKeyBlob, [MarshalAs(UnmanagedType.U4)] [In] int cbPublicKeyBlob, out IntPtr ppbStrongNameToken, [MarshalAs(UnmanagedType.U4)] out int pcbStrongNameToken);
}