Thanks Kent. I was able to modify create_tpm_key.c in the TPM engine project to set the PCR's for the new key. Tested fine using openssl s_server, then I extended one of the PCR's used to seal the key and tried s_server again, and it correctly failed to load the private key when attempting to accept an incoming connection.
The TPM Engine uses Tspi_Data_Unbind for the RSA decryption during the handshake, which is perfect for what I'm doing. Jonathan On Mar 4, 2013, at 7:29 AM, Kent Yoder wrote: > On Sat, Mar 2, 2013 at 10:36 PM, Jonathan Buhacoff > <jonat...@buhacoff.net> wrote: >> Hi, >> >> I have a school project to make use of a TPM to store the server's RSA >> private key for use with openssl. Specifically, that private key would be >> sealed to certain PCR values that are also encoded in the X509 certificate >> so that, when clients make a TLS connection to the server, clients trusting >> that particular X509 certificate know that a connection can only be >> established if the server's state corresponds to the what is on the >> certificate. >> >> When a server needs to decrypt the client challenge in order to prepare the >> server-verify message, instead of loading its private key from disk and >> performing an RSA decryption, in this project the server would use the >> trousers library to pass the material to be decrypted to the TPM and get the >> results. Everything before and after this step should stay the same. >> >> I think the relevant code is in ssl3_get_client_key_exchange, because it >> calls RSA_private_decrypt. >> >> My question is - should I be writing a patch for the default engine to >> allow this option to keep the private key in the TPM? or should I be >> writing a new engine that is essentially a copy of the default engine except >> for this one change? What makes more sense if I'm going to contribute the >> code after my project is done? > > We have a TPM engine available on the trousers site: > > https://sourceforge.net/projects/trousers/files/OpenSSL%20TPM%20Engine/0.4.2/ > > We may not have a utility that lets you generate a key with PCRs > though. You can find lots of sample code in the testsuite, available > in git: > > git://trousers.git.sourceforge.net/gitroot/trousers/testsuite > > Kent > >> A related consideration is that the configuration would need to accommodate >> this option, either by allowing another format for the private key file >> option or by creating a new custom option. >> >> All opinions welcome... >> >> Thanks, >> >> Jonathan >> >> >> ______________________________________________________________________ >> OpenSSL Project http://www.openssl.org >> Development Mailing List openssl-dev@openssl.org >> Automated List Manager majord...@openssl.org > ______________________________________________________________________ > OpenSSL Project http://www.openssl.org > Development Mailing List openssl-dev@openssl.org > Automated List Manager majord...@openssl.org
