EVP_PKEY_CTX_ctrl_str
rv = EVP_PKEY_CTX_ctrl_str(ctx, stmp, vtmp);
if (EVP_PKEY_CTX_ctrl_str(ctx, opt, passwd) <= 0) {
int EVP_PKEY_CTX_ctrl_str(EVP_PKEY_CTX *ctx, const char *type,
rv = EVP_PKEY_CTX_ctrl_str(pctx, tmpval, p);
rv = EVP_PKEY_CTX_ctrl_str(pctx, tmpval, p);