On 5/1/2015 1:36 AM, Tadeusz Struk wrote:
> This patch set introduces a Public Key Encryption API.
> What is proposed is a new crypto type called crypto_pke_type
> plus new struct pke_alg and struct pke_tfm together with number
> of helper functions to register pke type algorithms and allocate
> tfm instances. This is to make it similar to how the existing crypto
> API works for the ablkcipher, ahash, and aead types.
> The operations the new interface will allow to provide are:
>
> int (*sign)(struct pke_request *pkereq);
> int (*verify)(struct pke_request *pkereq);
> int (*encrypt)(struct pke_request *pkereq);
> int (*decrypt)(struct pke_request *pkereq);
Where would be the proper place for keygen operation?
>
> The benefits it gives comparing to the struct public_key_algorithm
> interface are:
> - drivers can add many implementations of RSA or DSA
> algorithms and user will allocate instances (tfms) of these, base on
> algorithm priority, in the same way as it is with the symmetric ciphers.
> - the new interface allows for asynchronous implementations that
> can use crypto hardware to offload the calculations to.
> - integrating it with linux crypto api allows using all its benefits
> i.e. managing algorithms using NETLINK_CRYPTO, monitoring implementations
> using /proc/crypto. etc
>
> New helper functions have been added to allocate pke_tfm instances
> and invoke the operations to make it easier to use.
> For instance to verify a public_signature against a public_key using
> the RSA algorithm a user would do:
>
> struct crypto_pke *tfm = crypto_alloc_pke("rsa", 0, 0);
> struct pke_request *req = pke_request_alloc(tfm, GFP_KERNEL);
> pke_request_set_crypt(req, pub_key, signature);
> int ret = crypto_pke_verify(req);
> pke_request_free(req);
> crypto_free_pke(tfm);
> return ret;
>
> Additionally existing public_key and rsa code have been reworked to
> use the new interface for verifying signed modules.
> As part of the rework the enum pkey_algo has been removed as the algorithm
> to allocate will be indicated by a string - for instance "rsa" or "dsa",
> similarly as it is with the symmetric algs e.g. "aes".
> It will also make it easier to extend in the future when new algorithms
> will be added.
AFAICT algorithms currently map to primitives + encoding methods, which
is not flexible. For e.g. current RSA implementation hardcodes the
PKCS1-v1_5 encoding method, making it hard to add OAEP(+) etc.
One solution would be to map algorithms to primitives only. Encoding
methods need to be abstracted somehow, maybe using templates to wrap the
algorithms.
Regards,
Horia
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