X509_get_X509_PUBKEY
z = i2d_X509_PUBKEY(X509_get_X509_PUBKEY(x), &d);
return SCT_CTX_set1_issuer_pubkey(sctx, X509_get_X509_PUBKEY(issuer));
X509_PUBKEY *X509_get_X509_PUBKEY(const X509 *x);