static VALUE
ossl_pkey_sign(VALUE self, VALUE digest, VALUE data)
{
EVP_PKEY *pkey;
EVP_MD_CTX ctx;
unsigned int buf_len;
VALUE str;
if (rb_funcall(self, id_private_q, 0, NULL) != Qtrue) {
ossl_raise(rb_eArgError, "Private key is needed.");
}
GetPKey(self, pkey);
EVP_SignInit(&ctx, GetDigestPtr(digest));
StringValue(data);
EVP_SignUpdate(&ctx, RSTRING_PTR(data), RSTRING_LEN(data));
str = rb_str_new(0, EVP_PKEY_size(pkey)+16);
if (!EVP_SignFinal(&ctx, (unsigned char *)RSTRING_PTR(str), &buf_len, pkey))
ossl_raise(ePKeyError, NULL);
assert(buf_len <= RSTRING_LEN(str));
rb_str_set_len(str, buf_len);
return str;
}