X509V3_set_issuer_pkey
if (!X509V3_set_issuer_pkey(&ext_ctx, pkey))
if (!X509V3_set_issuer_pkey(&ext_ctx, issuer_key))
if (!X509V3_set_issuer_pkey(&ext_ctx, privkey))
int X509V3_set_issuer_pkey(X509V3_CTX *ctx, EVP_PKEY *pkey);