Re: private key not available for client_cert_cb

[George <whippet0@xxxxxxxxx>]

Hi,

   I've been looking at the code in the pppd EAP-TLS patch, but I can't seem to load the engine with the pkcs11 DLL. It is failing with the error:

error:2507606A:DSO support routines:WIN32_BIND_FUNC:could not bind to the requested symbol name

I've verified the path is correct.

I am using OpenSSL1.0.2u with the FIPS Object Module 2.0.16  in Windows 10. Do I need to do anything special to allow loading of DLLs in OpenSSL?

Here is what I am trying to do:

    char* engine_name = "C:\\Users\\whipp\\junk4\\ActivClient\\acpkcs211.dll";
    ENGINE_load_builtin_engines();
    ENGINE_register_all_complete();
    ENGINE *pkey_engine = ENGINE_by_id("dynamic");
    ENGINE_ctrl_cmd_string(pkey_engine, "SO_PATH", engine_name, 0);
    ENGINE_ctrl_cmd_string(pkey_engine, "ID", "pkcs11", 0);
    ENGINE_ctrl_cmd_string(pkey_engine, "LOAD", NULL, 0);

Do you see anything wrong with this?


Thanks,
George

On 2020-12-15 4:38 a.m., Jan Just Keijser wrote:

Hi,

On 14/12/20 21:01, George wrote:

Ok, so I am not actually going to populate EVP_PKEY with a private key in the callback function:
int (*client_cert_cb)(SSL *ssl, X509 **x509, EVP_PKEY **pkey)?

Instead, I will call
EVP_PKEY *ENGINE_load_private_key(ENGINE *e, const char *key_id, UI_METHOD *ui_method, void *callback_data);
to get the EVP_PKEY, which will be used by OpenSSL to access the Smart Card.

Once I get  the resulting EVP_PKEY using ENGINE_load_private_key(...), how do I assign it to pkey in the callback function?
If I had private key I would use something like
EVP_PKEY_assign_RSA(..)
Since I don't actually have a private key, should I use something else?

like Michael pointed out, my  eap-tls code is just an example of how you could handle a pkcs11 device; it does not us a callback at all, but my code loads the client cert+key upfront and avoids having to use a client callback altogether.

I guess you could also use a client callback for this (perhaps in combination with SSL_CTX_set_client_cert_engine()) . In that case you would get the (pseudo) key from the engine like this
   EVP_PKEY *engine_key = ENGINE_load_private_key(ENGINE *e, const char *key_id, UI_METHOD *ui_method, void *callback_data);
and then set
  pkey = &engine_key;
and see if that works.
Note that the ENGINE_load_private_key() function *does* return a EVP_PKEY struct but that does not mean the entire private key is contained in it; a private key consists of a modulus and a private part (exponent, prime1, prime2, exponent1, exponent2 etc). the ENGINE_load_private_key() call will return a struct containing the modulus but not the rest. You then use the engine to do the actual encryption and decryption.

HTH,

JJK