X509Certificate2.Verify() returns false always

Question

Facing a really strange issue X509Certificate2.Verify() returning false for a valid certificate. Maybe some has already faced this strange scenario before and can shine some light on it. I am using openssl to generate client certificates for testing purposes. I create a Root CA and generate a client certificate based on that Root CA and add the Root CA to its chain. I load the Root CA and the Client Cert to the local certificate store and it seems ok there but when I load it from my NUnit code to test X509Certificate2.Verify() always returns false. Here is the code to load the Cert from the store: ``` X509Store store = new X509Store(StoreName.My); string thumbprint = "60 d1 38 95 ee 3a 73 1e 7e 0d 70 68 0f 2d d0 69 1e 9a eb 72"; store.Open(OpenFlags.ReadOnly); var mCert = store.Certificates.Find( X509FindType.FindByThumbprint, thumbprint, true ).OfType<System.Security.Cryptography.X509Certificates.X509Certificate>().FirstOrDefault(); if(mCert != null) { var testClientCert = new X509Ce…

Accepted Answer

According to the X509Certificate2.Verify documentation

This method builds a simple chain for the certificate and applies the base policy to that chain. If you need more information about a failure, validate the certificate directly using the X509Chain object.

Therefore I would try to build chain using this code (replace Log method with your own implementation, I was using Console.Writeline)

```
X509Chain chain = new X509Chain();

try
{
    var chainBuilt = chain.Build(testClientCert );
    Log(string.Format("Chain building status: {0}", chainBuilt));

if (chainBuilt == false)
        foreach (X509ChainStatus chainStatus in chain.ChainStatus)
            Log(string.Format("Chain error: {0} {1}", chainStatus.Status, chainStatus.StatusInformation));
}
catch (Exception ex)
{
    Log(ex.ToString());
}
```

This code will tell you the reason why the certificate could not be verified. If you need to adjust chain policy then set `chain.ChainPolicy` property i.e.

```
chain.ChainPolicy = new X509ChainPolicy()
{
    RevocationMode = X509RevocationMode.NoCheck,
    VerificationFlags = X509VerificationFlags.IgnoreNotTimeValid,
    UrlRetrievalTimeout = new TimeSpan(0, 1, 0)
};
```

X509Certificate2.Verify() returns false always

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