commit 621333f41bf594f8924fd1d71e002ac900a35153
author Gilles Peskine <Gilles.Peskine@arm.com> Wed Jul 07 21:08:28 2021 +0200
committer Mateusz Starzyk <mateusz.starzyk@mobica.com> Thu Aug 05 15:31:48 2021 +0200
tree 92bb5d2929209967a28b089d8c8fefa59ab98c84
parent 8d2b7aaeded52a95b2a389a6ca7eaeb66716aaac

Catch failures of AES or DES operations

A DES or AES block operation can fail in alternative implementations of
mbedtls_internal_aes_encrypt() (under MBEDTLS_AES_ENCRYPT_ALT),
mbedtls_internal_aes_decrypt() (under MBEDTLS_AES_DECRYPT_ALT),
mbedtls_des_crypt_ecb() (under MBEDTLS_DES_CRYPT_ECB_ALT),
mbedtls_des3_crypt_ecb() (under MBEDTLS_DES3_CRYPT_ECB_ALT).
A failure can happen if the accelerator peripheral is in a bad state.
Several block modes were not catching the error.

This commit does the following code changes:

* Fix DES and AES API calls which ignored the return values:
    * In library code: on failure, goto exit and return ret.
    * In pkey programs: goto exit.
    * In the benchmark program: exit (not ideal since there's no error
      message, but it's what the code currently does for failures).
    * In test code: TEST_ASSERT.
* Changelog entry.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Signed-off-by: Mateusz Starzyk <mateusz.starzyk@mobica.com>

library/aes.c

diff --git a/library/aes.c b/library/aes.c
index da0e5b6..af19a38 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -1082,6 +1082,7 @@
                     unsigned char *output )
 {
     int i;
+    int ret;
     unsigned char temp[16];
 
     AES_VALIDATE_RET( ctx != NULL );
@@ -1111,7 +1112,9 @@
         while( length > 0 )
         {
             memcpy( temp, input, 16 );
-            mbedtls_aes_crypt_ecb( ctx, mode, input, output );
+            ret = mbedtls_aes_crypt_ecb( ctx, mode, input, output );
+            if( ret != 0 )
+                goto exit;
 
             for( i = 0; i < 16; i++ )
                 output[i] = (unsigned char)( output[i] ^ iv[i] );
@@ -1130,7 +1133,9 @@
             for( i = 0; i < 16; i++ )
                 output[i] = (unsigned char)( input[i] ^ iv[i] );
 
-            mbedtls_aes_crypt_ecb( ctx, mode, output, output );
+            ret = mbedtls_aes_crypt_ecb( ctx, mode, output, output );
+            if( ret != 0 )
+                goto exit;
             memcpy( iv, output, 16 );
 
             input  += 16;
@@ -1138,8 +1143,10 @@
             length -= 16;
         }
     }
+    ret = 0;
 
-    return( 0 );
+exit:
+    return( ret );
 }
 #endif /* MBEDTLS_CIPHER_MODE_CBC */
 
@@ -1322,6 +1329,7 @@
                        unsigned char *output )
 {
     int c;
+    int ret;
     size_t n;
 
     AES_VALIDATE_RET( ctx != NULL );
@@ -1342,7 +1350,11 @@
         while( length-- )
         {
             if( n == 0 )
-                mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+            {
+                ret = mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+                if( ret != 0 )
+                    goto exit;
+            }
 
             c = *input++;
             *output++ = (unsigned char)( c ^ iv[n] );
@@ -1356,7 +1368,11 @@
         while( length-- )
         {
             if( n == 0 )
-                mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+            {
+                ret = mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+                if( ret != 0 )
+                    goto exit;
+            }
 
             iv[n] = *output++ = (unsigned char)( iv[n] ^ *input++ );
 
@@ -1365,8 +1381,10 @@
     }
 
     *iv_off = n;
+    ret = 0;
 
-    return( 0 );
+exit:
+    return( ret );
 }
 
 /*
@@ -1379,6 +1397,7 @@
                             const unsigned char *input,
                             unsigned char *output )
 {
+    int ret;
     unsigned char c;
     unsigned char ov[17];
 
@@ -1391,7 +1410,9 @@
     while( length-- )
     {
         memcpy( ov, iv, 16 );
-        mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+        ret = mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, iv, iv );
+        if( ret != 0 )
+            goto exit;
 
         if( mode == MBEDTLS_AES_DECRYPT )
             ov[16] = *input;
@@ -1403,8 +1424,10 @@
 
         memcpy( iv, ov + 1, 16 );
     }
+    ret = 0;
 
-    return( 0 );
+exit:
+    return( ret );
 }
 #endif /* MBEDTLS_CIPHER_MODE_CFB */
 
@@ -1466,6 +1489,7 @@
                        unsigned char *output )
 {
     int c, i;
+    int ret;
     size_t n;
 
     AES_VALIDATE_RET( ctx != NULL );
@@ -1483,7 +1507,9 @@
     while( length-- )
     {
         if( n == 0 ) {
-            mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, nonce_counter, stream_block );
+            ret = mbedtls_aes_crypt_ecb( ctx, MBEDTLS_AES_ENCRYPT, nonce_counter, stream_block );
+            if( ret != 0 )
+                goto exit;
 
             for( i = 16; i > 0; i-- )
                 if( ++nonce_counter[i - 1] != 0 )
@@ -1496,8 +1522,10 @@
     }
 
     *nc_off = n;
+    ret = 0;
 
-    return( 0 );
+exit:
+    return( ret );
 }
 #endif /* MBEDTLS_CIPHER_MODE_CTR */