Sets the IV/nonce length of the Cipher. Normally block ciphers don’t allow
changing the IV length, but some make use of IV for ‘nonce’. You may
need this for interoperability with other applications.
static VALUE
ossl_cipher_set_iv_length(VALUE self, VALUE iv_length)
{
int len = NUM2INT(iv_length);
EVP_CIPHER_CTX *ctx;
GetCipher(self, ctx);
if (!(EVP_CIPHER_flags(EVP_CIPHER_CTX_cipher(ctx)) & EVP_CIPH_FLAG_AEAD_CIPHER))
ossl_raise(eCipherError, "cipher does not support AEAD");
if (!EVP_CIPHER_CTX_ctrl(ctx, EVP_CTRL_AEAD_SET_IVLEN, len, NULL))
ossl_raise(eCipherError, "unable to set IV length");
/*
* EVP_CIPHER_CTX_iv_length() returns the default length. So we need to save
* the length somewhere. Luckily currently we aren't using app_data.
*/
EVP_CIPHER_CTX_set_app_data(ctx, (void *)(VALUE)len);
return iv_length;
}