Hello everyone,
I think I'm in a little too deep with something I'm playing around
with so I was wondering if anyone could help me out.
I'm playing around with making openssh use my Cyberflex Access for
authentication. Right now I'm just testing out my understanding of the
smartcard and openssh so I'm writing a little test that gets the
smartcard ready then attempts to decrypt a challenge.
I start by creating the challenge as a BIGNUM.
Next I call openssh's rsa_public_encrypt just like it would call in
sshconnect. It expects a BIGNUM to encrypt and the public key. The
problem here is that inside rsa_public_encrypt they call the openssl
RSA functions to encrypt with PKCS1 padding which apparently is quite
popular.
Now I use the smartcard to decrypt using the ssp-lite call
CSP_CK_Decrypt. Everything here seems to go alright, however I'm not
sure if there is any way to specify padding when decrypting with the
smartcard. I haven't found anything in the Cyberflex Programming
reference.
Anyway, so I go along my merry way and attempt to look at the output
by converting the binary buffer back to a BIGNUM. When I print it out
in hex I always get similar results. I get a long number that always
has 02 at the beginning and whatever my initial challenge was at the
end with a bunch of junk in between.
So then I started looking at padding and that's where I am now. I was
wondering if I could check the padding after I decrypt with the
smartcard with RSA_padding_check_PKCS1_type2 type functions in openssl
and if I can how do I use them?
Any tips would be appreciated.
Stephen Pellicer
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Linux Smart Card Developers - M.U.S.C.L.E.
(Movement for the Use of Smart Cards in a Linux Environment)
http://www.linuxnet.com/smartcard/index.html
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