convert PEM encoded RSA private key to AsymmetricKeyParameter

Question

I am trying (but failing) to create a method that constructs an AsymmetricKeyParameter from a PEM encoded private key. How can I complete this method?

It seems that an older version of BouncyCastle had a pemReader.ReadObject() method whose results could be casted, but that no longer exists.

I have tried various combinations of using PrivateKeyFactory, PrivateKeyInfo, Asn1Object and perhaps 10 other types, but all are throwing an exception at some point.

static AsymmetricKeyParameter ReadPrivateKeyFromPemEncodedString(string pemEncodedKey)
{
    AsymmetricKeyParameter result = null;
    using (var stringReader = new StringReader(pemEncodedKey))
    {
        var pemReader = new PemReader(stringReader);
        var pemObject = pemReader.ReadPemObject();
        // WHAT NEXT???
    }            

    return result;
}

Here is the PEM-encoded key I am testing with:

Actually, Org.BouncyCastle.OpenSsl.PemReader still exists, and its ReadObject() can still do what you need here I think. Perhaps the addition of Org.BouncyCastle.Utilities.IO.Pem.PemReader is causing confusion? — Peter Dettman, Jun 09 '17 at 04:28
big sigh. yeah, that was the confusion. thanks so much. Would you mind posting your comment as the answer so I can accept and upvote? I edited my post with the solution. It baffles me that folks think that having two public classes of the same name in the same project is a good idea. These classes should be renamed to OpenSslPemReader and UtilityPemReader so that it's 100% obvious from the name what it does and why it's qualified and you don't have to lean on reading the using directives. Anyways, I doubt that will change based on the maturity of this project. — Suraj, Jun 09 '17 at 13:49
@PeterDettman - can you help with this one... https://stackoverflow.com/questions/44459497/convert-pem-encoded-rsa-public-key-to-asymmetrickeyparameter — Suraj, Jun 09 '17 at 13:53
I agree the PemReader name-sharing is less than ideal. We have in other places chosen to include namespace-specific prefixes on classes. There is sometimes (not here) a tension arising from wanting names to exactly match structures in standards documents, which can work against this. I will look into deprecating/duplicating the openssl one in favour of, say OpenSslReader, as the other one is already appropriately named. Unfortunately we must allow for the extensive "external documentation" on sites such as this, using existing class names. — Peter Dettman, Jun 10 '17 at 04:51
@PeterDettman - Thanks for considering the rename. I'm just now seeing that PemReader extends PemReader =) so I like the idea of an OpenSslReader that extends a PemReader. I think that OpenSslPemReader would be a slightly better name. I favor using base class names in derived classes so that the "is a kind of" relationship is super clear. OpenSslPemReader is a kind of PemReader. Anyways, just my $.02. — Suraj, Jun 11 '17 at 19:00

score 2 · Accepted Answer · answered Jun 11 '17 at 18:35

Here's a working solution:

using Org.BouncyCastle.OpenSsl;

private static AsymmetricKeyParameter ReadPrivateKeyFromPemEncodedString(string pemEncodedKey)
{
    AsymmetricKeyParameter result;
    using (var stringReader = new StringReader(pemEncodedKey))
    {
        var pemReader = new PemReader(stringReader);
        var pemObject = pemReader.ReadObject();
        result = ((AsymmetricCipherKeyPair)pemObject).Private;
    }

    return result;
}

convert PEM encoded RSA private key to AsymmetricKeyParameter

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