crypto: add CTR mode support

Introduce CTR mode support for the cipher APIs.
CTR mode uses a counter rather than a traditional IV.
The counter has additional properties, including a nonce
and initial counter block. We reuse the ctx->iv as
the counter for conveniences.

Both libgcrypt and nettle are support CTR mode, the
cipher-builtin doesn't support yet.

Signed-off-by: Gonglei <arei.gonglei@huawei.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 19 insertions, 6 deletions

diff --git a/crypto/cipher-gcrypt.c b/crypto/cipher-gcrypt.c
index 05026c0a0e..c550db9008 100644
--- a/crypto/cipher-gcrypt.c
+++ b/crypto/cipher-gcrypt.c
@@ -59,6 +59,7 @@ struct QCryptoCipherGcrypt {
     gcry_cipher_hd_t handle;
     gcry_cipher_hd_t tweakhandle;
     size_t blocksize;
+    /* Initialization vector or Counter */
     uint8_t *iv;
 };
 
@@ -80,6 +81,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     case QCRYPTO_CIPHER_MODE_CBC:
         gcrymode = GCRY_CIPHER_MODE_CBC;
         break;
+    case QCRYPTO_CIPHER_MODE_CTR:
+        gcrymode = GCRY_CIPHER_MODE_CTR;
+        break;
     default:
         error_setg(errp, "Unsupported cipher mode %s",
                    QCryptoCipherMode_lookup[mode]);
@@ -350,12 +354,21 @@ int qcrypto_cipher_setiv(QCryptoCipher *cipher,
     if (ctx->iv) {
         memcpy(ctx->iv, iv, niv);
     } else {
-        gcry_cipher_reset(ctx->handle);
-        err = gcry_cipher_setiv(ctx->handle, iv, niv);
-        if (err != 0) {
-            error_setg(errp, "Cannot set IV: %s",
-                   gcry_strerror(err));
-            return -1;
+        if (cipher->mode == QCRYPTO_CIPHER_MODE_CTR) {
+            err = gcry_cipher_setctr(ctx->handle, iv, niv);
+            if (err != 0) {
+                error_setg(errp, "Cannot set Counter: %s",
+                       gcry_strerror(err));
+                return -1;
+            }
+        } else {
+            gcry_cipher_reset(ctx->handle);
+            err = gcry_cipher_setiv(ctx->handle, iv, niv);
+            if (err != 0) {
+                error_setg(errp, "Cannot set IV: %s",
+                       gcry_strerror(err));
+                return -1;
+            }
         }
     }