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: NEric Blake <eblake@redhat.com>
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

crypto/cipher-builtin.c

@@ -22,10 +22,14 @@
 #include "crypto/aes.h"
 #include "crypto/desrfb.h"
 
+typedef struct QCryptoCipherBuiltinAESContext QCryptoCipherBuiltinAESContext;
+struct QCryptoCipherBuiltinAESContext {
+    AES_KEY enc;
+    AES_KEY dec;
+};
 typedef struct QCryptoCipherBuiltinAES QCryptoCipherBuiltinAES;
 struct QCryptoCipherBuiltinAES {
-    AES_KEY encrypt_key;
-    AES_KEY decrypt_key;
+    QCryptoCipherBuiltinAESContext key;
     uint8_t iv[AES_BLOCK_SIZE];
 };
 typedef struct QCryptoCipherBuiltinDESRFB QCryptoCipherBuiltinDESRFB;
@@ -67,20 +71,16 @@ static void qcrypto_cipher_free_aes(QCryptoCipher *cipher)
 }
 
 
-static int qcrypto_cipher_encrypt_aes(QCryptoCipher *cipher,
+static void qcrypto_cipher_aes_ecb_encrypt(AES_KEY *key,
                                            const void *in,
                                            void *out,
-                                      size_t len,
-                                      Error **errp)
+                                           size_t len)
 {
-    QCryptoCipherBuiltin *ctxt = cipher->opaque;
-
-    if (cipher->mode == QCRYPTO_CIPHER_MODE_ECB) {
     const uint8_t *inptr = in;
     uint8_t *outptr = out;
     while (len) {
         if (len > AES_BLOCK_SIZE) {
-                AES_encrypt(inptr, outptr, &ctxt->state.aes.encrypt_key);
+            AES_encrypt(inptr, outptr, key);
             inptr += AES_BLOCK_SIZE;
             outptr += AES_BLOCK_SIZE;
             len -= AES_BLOCK_SIZE;
@@ -89,35 +89,24 @@ static int qcrypto_cipher_encrypt_aes(QCryptoCipher *cipher,
             memcpy(tmp1, inptr, len);
             /* Fill with 0 to avoid valgrind uninitialized reads */
             memset(tmp1 + len, 0, sizeof(tmp1) - len);
-                AES_encrypt(tmp1, tmp2, &ctxt->state.aes.encrypt_key);
+            AES_encrypt(tmp1, tmp2, key);
             memcpy(outptr, tmp2, len);
             len = 0;
         }
     }
-    } else {
-        AES_cbc_encrypt(in, out, len,
-                        &ctxt->state.aes.encrypt_key,
-                        ctxt->state.aes.iv, 1);
-    }
-
-    return 0;
 }
 
 
-static int qcrypto_cipher_decrypt_aes(QCryptoCipher *cipher,
+static void qcrypto_cipher_aes_ecb_decrypt(AES_KEY *key,
                                            const void *in,
                                            void *out,
-                                      size_t len,
-                                      Error **errp)
+                                           size_t len)
 {
-    QCryptoCipherBuiltin *ctxt = cipher->opaque;
-
-    if (cipher->mode == QCRYPTO_CIPHER_MODE_ECB) {
     const uint8_t *inptr = in;
     uint8_t *outptr = out;
     while (len) {
         if (len > AES_BLOCK_SIZE) {
-                AES_decrypt(inptr, outptr, &ctxt->state.aes.decrypt_key);
+            AES_decrypt(inptr, outptr, key);
             inptr += AES_BLOCK_SIZE;
             outptr += AES_BLOCK_SIZE;
             len -= AES_BLOCK_SIZE;
@@ -126,15 +115,60 @@ static int qcrypto_cipher_decrypt_aes(QCryptoCipher *cipher,
             memcpy(tmp1, inptr, len);
             /* Fill with 0 to avoid valgrind uninitialized reads */
             memset(tmp1 + len, 0, sizeof(tmp1) - len);
-                AES_decrypt(tmp1, tmp2, &ctxt->state.aes.decrypt_key);
+            AES_decrypt(tmp1, tmp2, key);
             memcpy(outptr, tmp2, len);
             len = 0;
         }
     }
-    } else {
+}
+
+
+static int qcrypto_cipher_encrypt_aes(QCryptoCipher *cipher,
+                                      const void *in,
+                                      void *out,
+                                      size_t len,
+                                      Error **errp)
+{
+    QCryptoCipherBuiltin *ctxt = cipher->opaque;
+
+    switch (cipher->mode) {
+    case QCRYPTO_CIPHER_MODE_ECB:
+        qcrypto_cipher_aes_ecb_encrypt(&ctxt->state.aes.key.enc,
+                                       in, out, len);
+        break;
+    case QCRYPTO_CIPHER_MODE_CBC:
         AES_cbc_encrypt(in, out, len,
-                        &ctxt->state.aes.decrypt_key,
+                        &ctxt->state.aes.key.enc,
+                        ctxt->state.aes.iv, 1);
+        break;
+    default:
+        g_assert_not_reached();
+    }
+
+    return 0;
+}
+
+
+static int qcrypto_cipher_decrypt_aes(QCryptoCipher *cipher,
+                                      const void *in,
+                                      void *out,
+                                      size_t len,
+                                      Error **errp)
+{
+    QCryptoCipherBuiltin *ctxt = cipher->opaque;
+
+    switch (cipher->mode) {
+    case QCRYPTO_CIPHER_MODE_ECB:
+        qcrypto_cipher_aes_ecb_decrypt(&ctxt->state.aes.key.dec,
+                                       in, out, len);
+        break;
+    case QCRYPTO_CIPHER_MODE_CBC:
+        AES_cbc_encrypt(in, out, len,
+                        &ctxt->state.aes.key.dec,
                         ctxt->state.aes.iv, 0);
+        break;
+    default:
+        g_assert_not_reached();
     }
 
     return 0;
@@ -173,12 +207,12 @@ static int qcrypto_cipher_init_aes(QCryptoCipher *cipher,
 
     ctxt = g_new0(QCryptoCipherBuiltin, 1);
 
-    if (AES_set_encrypt_key(key, nkey * 8, &ctxt->state.aes.encrypt_key) != 0) {
+    if (AES_set_encrypt_key(key, nkey * 8, &ctxt->state.aes.key.enc) != 0) {
         error_setg(errp, "Failed to set encryption key");
         goto error;
     }
 
-    if (AES_set_decrypt_key(key, nkey * 8, &ctxt->state.aes.decrypt_key) != 0) {
+    if (AES_set_decrypt_key(key, nkey * 8, &ctxt->state.aes.key.dec) != 0) {
         error_setg(errp, "Failed to set decryption key");
         goto error;
     }

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);