We verified that the data block is properly sized modulo
AES_BLOCK_SIZE within qcrypto_builtin_cipher_{en,de}crypt.
Therefore we will never have to handle odd sized blocks.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 crypto/cipher-builtin.inc.c | 40 +++++++++++--------------------------
 1 file changed, 12 insertions(+), 28 deletions(-)

diff --git a/crypto/cipher-builtin.inc.c b/crypto/cipher-builtin.inc.c
index 1444139f36..e2ae5d090c 100644
--- a/crypto/cipher-builtin.inc.c
+++ b/crypto/cipher-builtin.inc.c
@@ -80,21 +80,13 @@ static void qcrypto_cipher_aes_ecb_encrypt(const AES_KEY *key,
 {
     const uint8_t *inptr = in;
     uint8_t *outptr = out;
+
+    /* We have already verified that len % AES_BLOCK_SIZE == 0. */
     while (len) {
-        if (len > AES_BLOCK_SIZE) {
-            AES_encrypt(inptr, outptr, key);
-            inptr += AES_BLOCK_SIZE;
-            outptr += AES_BLOCK_SIZE;
-            len -= AES_BLOCK_SIZE;
-        } else {
-            uint8_t tmp1[AES_BLOCK_SIZE], tmp2[AES_BLOCK_SIZE];
-            memcpy(tmp1, inptr, len);
-            /* Fill with 0 to avoid valgrind uninitialized reads */
-            memset(tmp1 + len, 0, sizeof(tmp1) - len);
-            AES_encrypt(tmp1, tmp2, key);
-            memcpy(outptr, tmp2, len);
-            len = 0;
-        }
+        AES_encrypt(inptr, outptr, key);
+        inptr += AES_BLOCK_SIZE;
+        outptr += AES_BLOCK_SIZE;
+        len -= AES_BLOCK_SIZE;
     }
 }
 
@@ -106,21 +98,13 @@ static void qcrypto_cipher_aes_ecb_decrypt(const AES_KEY *key,
 {
     const uint8_t *inptr = in;
     uint8_t *outptr = out;
+
+    /* We have already verified that len % AES_BLOCK_SIZE == 0. */
     while (len) {
-        if (len > AES_BLOCK_SIZE) {
-            AES_decrypt(inptr, outptr, key);
-            inptr += AES_BLOCK_SIZE;
-            outptr += AES_BLOCK_SIZE;
-            len -= AES_BLOCK_SIZE;
-        } else {
-            uint8_t tmp1[AES_BLOCK_SIZE], tmp2[AES_BLOCK_SIZE];
-            memcpy(tmp1, inptr, len);
-            /* Fill with 0 to avoid valgrind uninitialized reads */
-            memset(tmp1 + len, 0, sizeof(tmp1) - len);
-            AES_decrypt(tmp1, tmp2, key);
-            memcpy(outptr, tmp2, len);
-            len = 0;
-        }
+        AES_decrypt(inptr, outptr, key);
+        inptr += AES_BLOCK_SIZE;
+        outptr += AES_BLOCK_SIZE;
+        len -= AES_BLOCK_SIZE;
     }
 }
 
-- 
2.25.1

On Wed, Aug 12, 2020 at 08:25:31PM -0700, Richard Henderson wrote:
> We verified that the data block is properly sized modulo
> AES_BLOCK_SIZE within qcrypto_builtin_cipher_{en,de}crypt.
> Therefore we will never have to handle odd sized blocks.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  crypto/cipher-builtin.inc.c | 40 +++++++++++--------------------------
>  1 file changed, 12 insertions(+), 28 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>


Regards,
Daniel
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