Hi all, I am working on providing a new Public Key method that will handle Composite Keys (i.e., multiple keys with different algos - e.g., one RSA and one EC) and Composite Signatures (i.e., multiple signatures generated with the corresponding Composite Keys). In particular, I would like to be able to add a method that will, in turn, call the methods supported by the different keys that form the COMPOSITE_PKEY structure.
I have looked around how to do it and I am a bit confused about how to
proceed as there are some conflicting implementations for different
algorithms.
Here's some high-level questions related to the EVP_PKEY interface, in
particular:
* *EVP_PKEY_ASN1_METHOD vs. EVP_PKEY_METHOD *- when these two
different types of methods are used? Shall both be implemented?
* *After providing the implementation for the ameth/pmeth, how does
the integration work with openssl?* In particular, should I add them
to the list of the default ameth/pmeth supported? Here's some more
specific questions:
o It seems there is an *app_method stack* of EVP_PKEY_ASN1_METHOD
- how do I add the method there (in case I will use a user-level
- i.e., not integrated into OpenSSL code - approach by using the
functions in the crypto/asn1/ameth_lib.c file). Will the
EVP_PKEY_asn1_add0() function call be sufficient?
o It seems there is an standard_methods stack of
EVP_PKEY_ASN1_METHOD - how do I add the method there if we need
to have a more tight integration with the core of the library
(in case we can not do our proof-of-concept without touching the
openssl's code / requiring a fork)
* *COMPOSITE_PKEY struct and COMPOSITE_PKEY_CTX struct.* I noticed
that, for example, both RSA and EC implement some form of _CTX and
_PKEY structures. Are these used only internally or should they be
implemented and integrated with the METHOD(s) ?
* *Given the above is implemented correctly - will this enable the use
of the method for processing signatures with the new
(pseudo-)algorithm for different structures (e.g., CRLs, X509,
X509_REQ, OCSP_REQ, OCSP_RESP, etc.)* ? I see that there is some
sort of different usages that can be implemented in the CTRL of the
ameth (e.g., rsa_pkey_ctrl), however this seems to be targeted to
the following operations:
ASN1_PKEY_CTRL_PKCS7_SIGN
ASN1_PKEY_CTRL_PKCS7_ENCRYPT
ASN1_PKEY_CTRL_CMS_SIGN
ASN1_PKEY_CTRL_CMS_ENVELOPE
ASN1_PKEY_CTRL_CMS_RI_TYPE
ASN1_PKEY_CTRL_DEFAULT_MD_NID
* Last but not least, since the EVP_PKEY has a union that points to
the internal key (i.e., crypto/internal/evp_int.h - evp_pkey_st)
where, besides the rsa, dsa, dh, and ec pointers, a void * ptr is
defined. Shall I use that pointer to reference the composite_pkey_st
(at least for the user-space implementation) ?
Thanks for any help for understanding all these details... :D
Cheers,
Max
--
Best Regards,
Massimiliano Pala, Ph.D.
OpenCA Labs Director
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