Steve, all,
here's another idea in draft stage. Please give me feedback before I
start working out the details.
In obj_xref.txt, we define
rsassaPss undef rsaEncryption
We add two components for pss to rsa_st
struct rsa_st
{
[...]
const EVP_MD *pssDigest; /* pointer ok or should we store the NID? */
int pssSaltlen;
};
and define a function to decode the parameters of the algorithm used in
the X.509 certificate
static int rsa_param_decode(EVP_PKEY *pkey, const unsigned char **pder, int
derlen)
{
/* TODO: parse and check paramters */
if (pkey && pkey->type == EVP_PKEY_RSA)
{
pkey->pkey.rsa->pssDigest = EVP_sha1();
pkey->pkey.rsa->pssSaltlen = 20;
}
return 1;
}
In ASN1_item_verify(), we use the EVP_DigestVerify...() API and call
the pkey's param_decode() method
...
if (pkey->ameth->param_decode)
{
/* TODO: pass real algorithm parameters */
pkey->ameth->param_decode(pkey, NULL, 0);
}
else printf("no param_decode method defined\n");
if (!EVP_DigestVerifyInit(&mctx,&pctx,md, NULL, pkey))
...
md may be NULL if message digest is undef is obj_xref.txt
(some low-level routines must be changed to get this result)
In do_sigver_init(), we check for type==NULL and set the pss parameters
in this case
...
}
else if (EVP_PKEY_sign_init(ctx->pctx) <= 0)
return 0;
}
if (type == NULL)
{
if (pkey && pkey->type == EVP_PKEY_RSA && pkey->pkey.rsa->pssDigest)
{
type = pkey->pkey.rsa->pssDigest;
EVP_PKEY_CTX_set_rsa_padding(ctx->pctx, RSA_PKCS1_PSS_PADDING);
EVP_PKEY_CTX_set_rsa_pss_saltlen(ctx->pctx,
pkey->pkey.rsa->pssSaltlen);
}
else
{
int def_nid;
if (EVP_PKEY_get_default_digest_nid(pkey, &def_nid) > 0)
type = EVP_get_digestbynid(def_nid);
}
}
if (type == NULL)
{
EVPerr(EVP_F_DO_SIGVER_INIT, EVP_R_NO_DEFAULT_DIGEST);
...
Does this approch look ok?
Best regards,
Martin
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