From 8b3f5a8ad7434850804a4a664d2b07c6ffa9b1c7 Mon Sep 17 00:00:00 2001
From: Amaury Pouly <amaury.pouly@gmail.com>
Date: Tue, 3 Jan 2017 13:56:48 +0100
Subject: imxtools/sbtools: switch AES implementation to Crypto++

Instead of having our own copy of the AES code, use a good library to do that.
Crypto++ is well-maintained, supports a lot of ciphers, works on many OSes, and
is optimized for many architectures.

Change-Id: I7d7d24b47993206d7338c5f9bac8bbdd3915a667
---
 utils/imxtools/sbtools/crypto.cpp | 83 ++++++++++++++++++++++++++++++++++++---
 1 file changed, 77 insertions(+), 6 deletions(-)

(limited to 'utils/imxtools/sbtools/crypto.cpp')

diff --git a/utils/imxtools/sbtools/crypto.cpp b/utils/imxtools/sbtools/crypto.cpp
index 35068c3e7d..5ccde27fdd 100644
--- a/utils/imxtools/sbtools/crypto.cpp
+++ b/utils/imxtools/sbtools/crypto.cpp
@@ -20,9 +20,81 @@
  ****************************************************************************/
 #include "crypto.h"
 #include "misc.h"
+#include <cryptopp/modes.h>
+#include <cryptopp/aes.h>
 
-static enum crypto_method_t g_cur_method = CRYPTO_NONE;
-static byte g_key[16];
+using namespace CryptoPP;
+
+namespace
+{
+
+enum crypto_method_t g_cur_method = CRYPTO_NONE;
+byte g_key[16];
+CBC_Mode<AES>::Encryption g_aes_enc;
+CBC_Mode<AES>::Decryption g_aes_dec;
+bool g_aes_enc_key_dirty; /* true of g_aes_enc key needs to be updated */
+bool g_aes_dec_key_dirty; /* same for g_aes_dec */
+
+int cbc_mac2(
+    const byte *in_data, /* Input data */
+    byte *out_data, /* Output data (or NULL) */
+    int nr_blocks, /* Number of blocks to encrypt/decrypt (one block=16 bytes) */
+    byte key[16], /* Key */
+    byte iv[16], /* Initialisation Vector */
+    byte (*out_cbc_mac)[16], /* CBC-MAC of the result (or NULL) */
+    bool encrypt /* 1 to encrypt, 0 to decrypt */
+    )
+{
+    /* encrypt */
+    if(encrypt)
+    {
+        /* update keys if neeeded */
+        if(g_aes_enc_key_dirty)
+        {
+            /* we need to provide an IV with the key, although we change it
+             * everytime we run the cipher anyway */
+            g_aes_enc.SetKeyWithIV(g_key, 16, iv, 16);
+            g_aes_enc_key_dirty = false;
+        }
+        g_aes_enc.Resynchronize(iv, 16);
+        byte tmp[16];
+        /* we need some output buffer, either a temporary one if we are CBC-MACing
+         * only, or use output buffer if available */
+        byte *out_ptr = (out_data == NULL) ? tmp : out_data;
+        while(nr_blocks-- > 0)
+        {
+            g_aes_enc.ProcessData(out_ptr, in_data, 16);
+            /* if this is the last block, copy CBC-MAC */
+            if(nr_blocks == 0 && out_cbc_mac)
+                memcpy(out_cbc_mac, out_ptr, 16);
+            /* if we are writing data to the output buffer, advance output pointer */
+            if(out_data != NULL)
+                out_ptr += 16;
+            in_data += 16;
+        }
+        return CRYPTO_ERROR_SUCCESS;
+    }
+    /* decrypt */
+    else
+    {
+        /* update keys if neeeded */
+        if(g_aes_dec_key_dirty)
+        {
+            /* we need to provide an IV with the key, although we change it
+             * everytime we run the cipher anyway */
+            g_aes_dec.SetKeyWithIV(g_key, 16, iv, 16);
+            g_aes_dec_key_dirty = false;
+        }
+        /* we cannot produce a CBC-MAC in decrypt mode, output buffer exists */
+        if(out_cbc_mac || out_data == NULL)
+            return CRYPTO_ERROR_INVALID_OP;
+        g_aes_dec.Resynchronize(iv, 16);
+        g_aes_dec.ProcessData(out_data, in_data, nr_blocks * 16);
+        return CRYPTO_ERROR_SUCCESS;
+    }
+}
+
+}
 
 int crypto_setup(struct crypto_key_t *key)
 {
@@ -31,6 +103,8 @@ int crypto_setup(struct crypto_key_t *key)
     {
         case CRYPTO_KEY:
             memcpy(g_key, key->u.key, 16);
+            g_aes_dec_key_dirty = true;
+            g_aes_enc_key_dirty = true;
             return CRYPTO_ERROR_SUCCESS;
         default:
             return CRYPTO_ERROR_BADSETUP;
@@ -46,10 +120,7 @@ int crypto_apply(
     bool encrypt)
 {
     if(g_cur_method == CRYPTO_KEY)
-    {
-        cbc_mac(in_data, out_data, nr_blocks, g_key, iv, out_cbc_mac, encrypt);
-        return CRYPTO_ERROR_SUCCESS;
-    }
+        return cbc_mac2(in_data, out_data, nr_blocks, g_key, iv, out_cbc_mac, encrypt);
     else
         return CRYPTO_ERROR_BADSETUP;
 }
-- 
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