Sets the length of the authentication tag to be generated or to be given
for AEAD ciphers that
requires it as in input parameter. Note that not all AEAD ciphers support this method.
In OCB mode, the length must be supplied both when encrypting and when
decrypting, and must be before specifying an IV.
static VALUE
ossl_cipher_set_auth_tag_len(VALUE self, VALUE vlen)
{
int tag_len = NUM2INT(vlen);
EVP_CIPHER_CTX *ctx;
GetCipher(self, ctx);
if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
ossl_raise(eCipherError, "AEAD not supported by this cipher");
if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_TAG, tag_len, NULL))
ossl_raise(eCipherError, "unable to set authentication tag length");
/* for #auth_tag */
rb_ivar_set(self, id_auth_tag_len, INT2NUM(tag_len));
return vlen;
}