Add magic number, auto tests still required

2 files changed, 44 insertions, 16 deletions

diff --git a/toxencryptsave/toxencryptsave.c b/toxencryptsave/toxencryptsave.c
index 1f5aae35..390a5e5d 100644
--- a/toxencryptsave/toxencryptsave.c
+++ b/toxencryptsave/toxencryptsave.c
@@ -43,7 +43,7 @@
 uint32_t tox_encrypted_size(const Tox *tox)
 {
     return tox_size(tox) + crypto_box_MACBYTES + crypto_box_NONCEBYTES
-            + crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+            + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH;
 }
 
 /* Save the messenger data encrypted with the given password.
@@ -79,27 +79,30 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
     uint8_t temp_data[temp_size];
     tox_save(tox, temp_data);
     
-    /* now encrypt.
-     * the output data consists of, in order:
-     * salt, nonce, mac, enc_data
+    /* the output data consists of, in order:
+     * magic number, salt, nonce, mac, enc_data
      * where the mac is automatically prepended by the encrypt()
-     * the salt+nonce is called the prefix
+     * the magic+salt+nonce is called the prefix
      * I'm not sure what else I'm supposed to do with the salt and nonce, since we
      * need them to decrypt the data
      */
-    uint32_t prefix_size = crypto_box_NONCEBYTES+crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
 
+    /* first add the prefix */
     uint8_t nonce[crypto_box_NONCEBYTES];
     random_nonce(nonce);
 
-    if (encrypt_data_symmetric(key, nonce, temp_data, temp_size, data + prefix_size)
+    memcpy(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
+    data += TOX_ENC_SAVE_MAGIC_LENGTH;
+    memcpy(data, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
+    data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+    memcpy(data, nonce, crypto_box_NONCEBYTES);
+    data += crypto_box_NONCEBYTES;
+
+    /* now encrypt */
+    if (encrypt_data_symmetric(key, nonce, temp_data, temp_size, data)
            != temp_size + crypto_box_MACBYTES) {
         return -1;
     }
-    
-    /* add the prefix */
-    memcpy(data, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
-    memcpy(data + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, nonce, crypto_box_NONCEBYTES);
 
     return 0;
 }
@@ -111,16 +114,22 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
  */
 int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength)
 {
-    if (length <= crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
+    if (length <= crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH)
+        return -1;
+
+    if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
         return -1;
+    data += TOX_ENC_SAVE_MAGIC_LENGTH;
 
     uint32_t decrypt_length = length - crypto_box_MACBYTES - crypto_box_NONCEBYTES
-                                    - crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+                              - crypto_pwhash_scryptsalsa208sha256_SALTBYTES - TOX_ENC_SAVE_MAGIC_LENGTH;
     uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
     uint8_t nonce[crypto_box_NONCEBYTES];
     
     memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
-    memcpy(nonce, data + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, crypto_box_NONCEBYTES);
+    data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+    memcpy(nonce, data, crypto_box_NONCEBYTES);
+    data += crypto_box_NONCEBYTES;
     
     /* derive the key */
     uint8_t key[crypto_box_KEYBYTES];
@@ -135,11 +144,23 @@ int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *
 
     /* decrypt the data */
     uint8_t temp_data[decrypt_length];
-    if (decrypt_data_symmetric(key, nonce, data+crypto_pwhash_scryptsalsa208sha256_SALTBYTES+crypto_box_NONCEBYTES,
-            decrypt_length + crypto_box_MACBYTES, temp_data)
+    if (decrypt_data_symmetric(key, nonce, data, decrypt_length + crypto_box_MACBYTES, temp_data)
             != decrypt_length) {
         return -1;
     }
 
     return tox_load(tox, temp_data, decrypt_length);
 }
+
+/* Determines whether or not the given data is encrypted (by checking the magic number)
+ *
+ * returns 1 if it is encrypted
+ * returns 0 otherwise
+ */
+int tox_is_data_encrypted(const uint8_t *data)
+{
+    if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0)
+        return 1;
+    else
+        return 0;
+}
diff --git a/toxencryptsave/toxencryptsave.h b/toxencryptsave/toxencryptsave.h
index c32716f8..64617b27 100644
--- a/toxencryptsave/toxencryptsave.h
+++ b/toxencryptsave/toxencryptsave.h
@@ -54,6 +54,13 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
  */
 int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength);
 
+/* Determines whether or not the given data is encrypted (by checking the magic number)
+ *
+ * returns 1 if it is encrypted
+ * returns 0 otherwise
+ */
+int tox_is_data_encrypted(const uint8_t *data);
+
 #ifdef __cplusplus
 }
 #endif