crypto: wire up XTS mode for cipher APIs
Introduce 'XTS' as a permitted mode for the cipher APIs.
With XTS the key provided must be twice the size of the
key normally required for any given algorithm. This is
because the key will be split into two pieces for use
in XTS mode.
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
diff --git a/crypto/cipher.c b/crypto/cipher.c
index 89fa5a2..5402d18 100644
--- a/crypto/cipher.c
+++ b/crypto/cipher.c
@@ -53,6 +53,7 @@
static bool mode_need_iv[QCRYPTO_CIPHER_MODE__MAX] = {
[QCRYPTO_CIPHER_MODE_ECB] = false,
[QCRYPTO_CIPHER_MODE_CBC] = true,
+ [QCRYPTO_CIPHER_MODE_XTS] = true,
};
@@ -93,6 +94,7 @@
static bool
qcrypto_cipher_validate_key_length(QCryptoCipherAlgorithm alg,
+ QCryptoCipherMode mode,
size_t nkey,
Error **errp)
{
@@ -102,10 +104,27 @@
return false;
}
- if (alg_key_len[alg] != nkey) {
- error_setg(errp, "Cipher key length %zu should be %zu",
- nkey, alg_key_len[alg]);
- return false;
+ if (mode == QCRYPTO_CIPHER_MODE_XTS) {
+ if (alg == QCRYPTO_CIPHER_ALG_DES_RFB) {
+ error_setg(errp, "XTS mode not compatible with DES-RFB");
+ return false;
+ }
+ if (nkey % 2) {
+ error_setg(errp, "XTS cipher key length should be a multiple of 2");
+ return false;
+ }
+
+ if (alg_key_len[alg] != (nkey / 2)) {
+ error_setg(errp, "Cipher key length %zu should be %zu",
+ nkey, alg_key_len[alg] * 2);
+ return false;
+ }
+ } else {
+ if (alg_key_len[alg] != nkey) {
+ error_setg(errp, "Cipher key length %zu should be %zu",
+ nkey, alg_key_len[alg]);
+ return false;
+ }
}
return true;
}