crypto: refactor code for dealing with AES cipher

The built-in and nettle cipher backends for AES maintain
two separate AES contexts, one for encryption and one for
decryption. This is going to be inconvenient for the future
code dealing with XTS, so wrap them up in a single struct
so there is just one pointer to pass around for both
encryption and decryption.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>

1 files changed, 29 insertions, 28 deletions

diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c
index 9b057fd6a3..ed08782c35 100644
--- a/crypto/cipher-nettle.c
+++ b/crypto/cipher-nettle.c
@@ -42,16 +42,23 @@ static nettle_cipher_func aes_decrypt_wrapper;
 static nettle_cipher_func des_encrypt_wrapper;
 static nettle_cipher_func des_decrypt_wrapper;
 
+typedef struct QCryptoNettleAES {
+    struct aes_ctx enc;
+    struct aes_ctx dec;
+} QCryptoNettleAES;
+
 static void aes_encrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length,
                                 uint8_t *dst, const uint8_t *src)
 {
-    aes_encrypt(ctx, length, dst, src);
+    const QCryptoNettleAES *aesctx = ctx;
+    aes_encrypt(&aesctx->enc, length, dst, src);
 }
 
 static void aes_decrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length,
                                 uint8_t *dst, const uint8_t *src)
 {
-    aes_decrypt(ctx, length, dst, src);
+    const QCryptoNettleAES *aesctx = ctx;
+    aes_decrypt(&aesctx->dec, length, dst, src);
 }
 
 static void des_encrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length,
@@ -104,8 +111,7 @@ static void twofish_decrypt_wrapper(cipher_ctx_t ctx, cipher_length_t length,
 
 typedef struct QCryptoCipherNettle QCryptoCipherNettle;
 struct QCryptoCipherNettle {
-    void *ctx_encrypt;
-    void *ctx_decrypt;
+    void *ctx;
     nettle_cipher_func *alg_encrypt;
     nettle_cipher_func *alg_decrypt;
     uint8_t *iv;
@@ -163,10 +169,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
 
     switch (alg) {
     case QCRYPTO_CIPHER_ALG_DES_RFB:
-        ctx->ctx_encrypt = g_new0(struct des_ctx, 1);
-        ctx->ctx_decrypt = NULL; /* 1 ctx can do both */
+        ctx->ctx = g_new0(struct des_ctx, 1);
         rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
-        des_set_key(ctx->ctx_encrypt, rfbkey);
+        des_set_key(ctx->ctx, rfbkey);
         g_free(rfbkey);
 
         ctx->alg_encrypt = des_encrypt_wrapper;
@@ -178,11 +183,10 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     case QCRYPTO_CIPHER_ALG_AES_128:
     case QCRYPTO_CIPHER_ALG_AES_192:
     case QCRYPTO_CIPHER_ALG_AES_256:
-        ctx->ctx_encrypt = g_new0(struct aes_ctx, 1);
-        ctx->ctx_decrypt = g_new0(struct aes_ctx, 1);
+        ctx->ctx = g_new0(QCryptoNettleAES, 1);
 
-        aes_set_encrypt_key(ctx->ctx_encrypt, nkey, key);
-        aes_set_decrypt_key(ctx->ctx_decrypt, nkey, key);
+        aes_set_encrypt_key(&((QCryptoNettleAES *)ctx->ctx)->enc, nkey, key);
+        aes_set_decrypt_key(&((QCryptoNettleAES *)ctx->ctx)->dec, nkey, key);
 
         ctx->alg_encrypt = aes_encrypt_wrapper;
         ctx->alg_decrypt = aes_decrypt_wrapper;
@@ -191,10 +195,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
         break;
 
     case QCRYPTO_CIPHER_ALG_CAST5_128:
-        ctx->ctx_encrypt = g_new0(struct cast128_ctx, 1);
-        ctx->ctx_decrypt = NULL; /* 1 ctx can do both */
+        ctx->ctx = g_new0(struct cast128_ctx, 1);
 
-        cast5_set_key(ctx->ctx_encrypt, nkey, key);
+        cast5_set_key(ctx->ctx, nkey, key);
 
         ctx->alg_encrypt = cast128_encrypt_wrapper;
         ctx->alg_decrypt = cast128_decrypt_wrapper;
@@ -205,10 +208,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     case QCRYPTO_CIPHER_ALG_SERPENT_128:
     case QCRYPTO_CIPHER_ALG_SERPENT_192:
     case QCRYPTO_CIPHER_ALG_SERPENT_256:
-        ctx->ctx_encrypt = g_new0(struct serpent_ctx, 1);
-        ctx->ctx_decrypt = NULL; /* 1 ctx can do both */
+        ctx->ctx = g_new0(struct serpent_ctx, 1);
 
-        serpent_set_key(ctx->ctx_encrypt, nkey, key);
+        serpent_set_key(ctx->ctx, nkey, key);
 
         ctx->alg_encrypt = serpent_encrypt_wrapper;
         ctx->alg_decrypt = serpent_decrypt_wrapper;
@@ -219,10 +221,9 @@ QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
     case QCRYPTO_CIPHER_ALG_TWOFISH_128:
     case QCRYPTO_CIPHER_ALG_TWOFISH_192:
     case QCRYPTO_CIPHER_ALG_TWOFISH_256:
-        ctx->ctx_encrypt = g_new0(struct twofish_ctx, 1);
-        ctx->ctx_decrypt = NULL; /* 1 ctx can do both */
+        ctx->ctx = g_new0(struct twofish_ctx, 1);
 
-        twofish_set_key(ctx->ctx_encrypt, nkey, key);
+        twofish_set_key(ctx->ctx, nkey, key);
 
         ctx->alg_encrypt = twofish_encrypt_wrapper;
         ctx->alg_decrypt = twofish_decrypt_wrapper;
@@ -257,8 +258,7 @@ void qcrypto_cipher_free(QCryptoCipher *cipher)
 
     ctx = cipher->opaque;
     g_free(ctx->iv);
-    g_free(ctx->ctx_encrypt);
-    g_free(ctx->ctx_decrypt);
+    g_free(ctx->ctx);
     g_free(ctx);
     g_free(cipher);
 }
@@ -280,14 +280,15 @@ int qcrypto_cipher_encrypt(QCryptoCipher *cipher,
 
     switch (cipher->mode) {
     case QCRYPTO_CIPHER_MODE_ECB:
-        ctx->alg_encrypt(ctx->ctx_encrypt, len, out, in);
+        ctx->alg_encrypt(ctx->ctx, len, out, in);
         break;
 
     case QCRYPTO_CIPHER_MODE_CBC:
-        cbc_encrypt(ctx->ctx_encrypt, ctx->alg_encrypt,
+        cbc_encrypt(ctx->ctx, ctx->alg_encrypt,
                     ctx->blocksize, ctx->iv,
                     len, out, in);
         break;
+
     default:
         error_setg(errp, "Unsupported cipher algorithm %d",
                    cipher->alg);
@@ -313,15 +314,15 @@ int qcrypto_cipher_decrypt(QCryptoCipher *cipher,
 
     switch (cipher->mode) {
     case QCRYPTO_CIPHER_MODE_ECB:
-        ctx->alg_decrypt(ctx->ctx_decrypt ? ctx->ctx_decrypt : ctx->ctx_encrypt,
-                         len, out, in);
+        ctx->alg_decrypt(ctx->ctx, len, out, in);
         break;
 
     case QCRYPTO_CIPHER_MODE_CBC:
-        cbc_decrypt(ctx->ctx_decrypt ? ctx->ctx_decrypt : ctx->ctx_encrypt,
-                    ctx->alg_decrypt, ctx->blocksize, ctx->iv,
+        cbc_decrypt(ctx->ctx, ctx->alg_decrypt,
+                    ctx->blocksize, ctx->iv,
                     len, out, in);
         break;
+
     default:
         error_setg(errp, "Unsupported cipher algorithm %d",
                    cipher->alg);