Merge branch 'master' of https://github.com/dubslow/toxcore

2 files changed, 177 insertions, 40 deletions

diff --git a/toxencryptsave/toxencryptsave.c b/toxencryptsave/toxencryptsave.c
index 070f0184..7efba089 100644
--- a/toxencryptsave/toxencryptsave.c
+++ b/toxencryptsave/toxencryptsave.c
@@ -44,17 +44,22 @@
 /*  return size of the messenger data (for encrypted saving). */
 uint32_t tox_encrypted_size(const Tox *tox)
 {
-    return tox_size(tox) + crypto_box_MACBYTES + crypto_box_NONCEBYTES
-           + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH;
+    return tox_size(tox) + TOX_PASS_ENCRYPTION_EXTRA_LENGTH + TOX_ENC_SAVE_MAGIC_LENGTH;
 }
 
-/* Save the messenger data encrypted with the given password.
- * data must be at least tox_encrypted_size().
+/* Generates a secret symmetric key from the given passphrase. out_key must be at least
+ * TOX_PASS_KEY_LENGTH bytes long.
+ * Be sure to not compromise the key! Only keep it in memory, do not write to disk.
+ * This function is fairly cheap, but irungentoo insists that you be allowed to
+ * cache the result if you want, to minimize computation for repeated encryptions.
+ * The password is zeroed after key derivation.
+ * The key should only be used with the other functions in this module, as it
+ * includes a salt.
  *
  * returns 0 on success
  * returns -1 on failure
  */
-int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint32_t pplength)
+int tox_derive_key_from_pass(uint8_t *passphrase, uint32_t pplength, uint8_t *out_key)
 {
     if (pplength == 0)
         return -1;
@@ -78,16 +83,27 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
     }
 
     sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
+    memcpy(out_key, salt, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
+    memcpy(out_key + crypto_pwhash_scryptsalsa208sha256_SALTBYTES, key, crypto_box_KEYBYTES);
+    return 0;
+}
 
-    /* next get plain save data */
-    uint32_t temp_size = tox_size(tox);
-    uint8_t temp_data[temp_size];
-    tox_save(tox, temp_data);
-
+/* Encrypt arbitrary with a key produced by tox_derive_key_from_pass. The output
+ * array must be at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
+ * key must be TOX_PASS_KEY_LENGTH bytes.
+ * If you already have a symmetric key from somewhere besides this module, simply
+ * call encrypt_data_symmetric in toxcore/crypto_core directly.
+ *
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_pass_key_encrypt(uint8_t *data, uint32_t data_len, const uint8_t *key, uint8_t *out)
+{
     /* the output data consists of, in order:
-     * magic number, salt, nonce, mac, enc_data
+     * salt, nonce, mac, enc_data
      * where the mac is automatically prepended by the encrypt()
-     * the magic+salt+nonce is called the prefix
+     * the 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
      */
@@ -96,56 +112,111 @@ int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint3
     uint8_t nonce[crypto_box_NONCEBYTES];
     random_nonce(nonce);
 
-    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;
+    memcpy(out, key, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
+    key += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+    out += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+    memcpy(out, nonce, crypto_box_NONCEBYTES);
+    out += crypto_box_NONCEBYTES;
 
     /* now encrypt */
-    if (encrypt_data_symmetric(key, nonce, temp_data, temp_size, data)
-            != temp_size + crypto_box_MACBYTES) {
+    if (encrypt_data_symmetric(key, nonce, data, data_len, out)
+            != data_len + crypto_box_MACBYTES) {
         return -1;
     }
 
     return 0;
 }
 
-/* Load the messenger from encrypted data of size length.
+/* Encrypts the given data with the given passphrase. The output array must be
+ * at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long. This delegates
+ * to tox_derive_key_from_pass and tox_pass_key_encrypt.
  *
  * returns 0 on success
  * returns -1 on failure
  */
-int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength)
+int tox_pass_encrypt(uint8_t *data, uint32_t data_len, uint8_t *passphrase, uint32_t pplength, uint8_t *out)
 {
-    if (length <= crypto_box_MACBYTES + crypto_box_NONCEBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES +
-            TOX_ENC_SAVE_MAGIC_LENGTH)
-        return -1;
+    uint8_t key[TOX_PASS_KEY_LENGTH];
 
-    if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
+    if (tox_derive_key_from_pass(passphrase, pplength, key) == -1)
         return -1;
 
+    return tox_pass_key_encrypt(data, data_len, key, out);
+}
+
+/* Save the messenger data encrypted with the given password.
+ * data must be at least tox_encrypted_size().
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint32_t pplength)
+{
+    /* first get plain save data */
+    uint32_t temp_size = tox_size(tox);
+    uint8_t temp_data[temp_size];
+    tox_save(tox, temp_data);
+
+    /* the output data consists of, in order: magic number, enc_data */
+    /* first add the magic number */
+    memcpy(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
     data += TOX_ENC_SAVE_MAGIC_LENGTH;
 
-    uint32_t decrypt_length = length - crypto_box_MACBYTES - crypto_box_NONCEBYTES
-                              - crypto_pwhash_scryptsalsa208sha256_SALTBYTES - TOX_ENC_SAVE_MAGIC_LENGTH;
-    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
+    /* now encrypt */
+    return tox_pass_encrypt(temp_data, temp_size, passphrase, pplength, data);
+}
+
+/* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
+ * tox_derive_key_from_pass.
+ *
+ * returns the length of the output data (== data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH) on success
+ * returns -1 on failure
+ */
+int tox_pass_key_decrypt(const uint8_t *data, uint32_t length, const uint8_t *key, uint8_t *out)
+{
+    if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH)
+        return -1;
+
+    uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
+    //uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
     uint8_t nonce[crypto_box_NONCEBYTES];
 
+    //memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
+    key += crypto_pwhash_scryptsalsa208sha256_SALTBYTES; // ignore the salt, which is only needed for kdf
+    data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+    memcpy(nonce, data, crypto_box_NONCEBYTES);
+    data += crypto_box_NONCEBYTES;
+
+    /* decrypt the data */
+    if (decrypt_data_symmetric(key, nonce, data, decrypt_length + crypto_box_MACBYTES, out)
+            != decrypt_length) {
+        return -1;
+    }
+
+    return decrypt_length;
+}
+
+/* Decrypts the given data with the given passphrase. The output array must be
+ * at least data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
+ *
+ * returns the length of the output data (== data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH) on success
+ * returns -1 on failure
+ */
+int tox_pass_decrypt(const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength, uint8_t *out)
+{
+
     uint8_t passkey[crypto_hash_sha256_BYTES];
     crypto_hash_sha256(passkey, passphrase, pplength);
 
+    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
     memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
-    data += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
-    memcpy(nonce, data, crypto_box_NONCEBYTES);
-    data += crypto_box_NONCEBYTES;
 
     /* derive the key */
-    uint8_t key[crypto_box_KEYBYTES];
+    uint8_t key[crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
 
     if (crypto_pwhash_scryptsalsa208sha256(
-                key, sizeof(key), passkey, sizeof(passkey), salt,
+                key + crypto_pwhash_scryptsalsa208sha256_SALTBYTES,
+                crypto_box_KEYBYTES, passkey, sizeof(passkey), salt,
                 crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
                 crypto_pwhash_scryptsalsa208sha256_MEMLIMIT_INTERACTIVE) != 0) {
         /* out of memory most likely */
@@ -154,13 +225,28 @@ int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *
 
     sodium_memzero(passkey, crypto_hash_sha256_BYTES); /* wipe plaintext pw */
 
-    /* decrypt the data */
+    return tox_pass_key_decrypt(data, length, key, out);
+}
+
+/* Load the messenger from encrypted data of size length.
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength)
+{
+    if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
+        return -1;
+
+    data += TOX_ENC_SAVE_MAGIC_LENGTH;
+    length -= TOX_ENC_SAVE_MAGIC_LENGTH;
+
+    uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
     uint8_t temp_data[decrypt_length];
 
-    if (decrypt_data_symmetric(key, nonce, data, decrypt_length + crypto_box_MACBYTES, temp_data)
-            != decrypt_length) {
+    if (tox_pass_decrypt(data, length, passphrase, pplength, temp_data)
+            != decrypt_length)
         return -1;
-    }
 
     return tox_load(tox, temp_data, decrypt_length);
 }
@@ -170,7 +256,7 @@ int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *
  * returns 1 if it is encrypted
  * returns 0 otherwise
  */
-int tox_is_data_encrypted(const uint8_t *data)
+int tox_is_save_encrypted(const uint8_t *data)
 {
     if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) == 0)
         return 1;
diff --git a/toxencryptsave/toxencryptsave.h b/toxencryptsave/toxencryptsave.h
index 75094a2b..527578a5 100644
--- a/toxencryptsave/toxencryptsave.h
+++ b/toxencryptsave/toxencryptsave.h
@@ -35,6 +35,10 @@ extern "C" {
 typedef struct Tox Tox;
 #endif
 
+#define TOX_PASS_ENCRYPTION_EXTRA_LENGTH (crypto_box_MACBYTES + crypto_box_NONCEBYTES \
+           + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
+
+#define TOX_PASS_KEY_LENGTH (crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
 
 /* This "module" provides functions analogous to tox_load and tox_save in toxcore
  * Clients should consider alerting their users that, unlike plain data, if even one bit
@@ -45,6 +49,43 @@ typedef struct Tox Tox;
 /*  return size of the messenger data (for encrypted saving). */
 uint32_t tox_encrypted_size(const Tox *tox);
 
+/* Generates a secret symmetric key from the given passphrase. out_key must be at least
+ * TOX_PASS_KEY_LENGTH bytes long.
+ * Be sure to not compromise the key! Only keep it in memory, do not write to disk.
+ * This function is fairly cheap, but irungentoo insists that you be allowed to
+ * cache the result if you want, to minimize computation for repeated encryptions.
+ * The password is zeroed after key derivation.
+ * The key should only be used with the other functions in this module, as it
+ * includes a salt.
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_derive_key_from_pass(uint8_t *passphrase, uint32_t pplength, uint8_t *out_key);
+
+/* Encrypt arbitrary with a key produced by tox_derive_key_from_pass. The output
+ * array must be at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
+ * key must be TOX_PASS_KEY_LENGTH bytes.
+ * If you already have a symmetric key from somewhere besides this module, simply
+ * call encrypt_data_symmetric in toxcore/crypto_core directly.
+ *
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_pass_key_encrypt(uint8_t *data, uint32_t data_len, const uint8_t *key, uint8_t *out);
+
+/* Encrypts the given data with the given passphrase. The output array must be
+ * at least data_len + TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long. This delegates
+ * to tox_derive_key_from_pass and tox_pass_key_encrypt.
+ *
+ * tox_encrypted_save() is a good example of how to use this function.
+ *
+ * returns 0 on success
+ * returns -1 on failure
+ */
+int tox_pass_encrypt(uint8_t *data, uint32_t data_len, uint8_t *passphrase, uint32_t pplength, uint8_t *out);
+
 /* Save the messenger data encrypted with the given password.
  * data must be at least tox_encrypted_size().
  *
@@ -53,6 +94,16 @@ uint32_t tox_encrypted_size(const Tox *tox);
  */
 int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint32_t pplength);
 
+/* Decrypts the given data with the given passphrase. The output array must be
+ * at least data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH bytes long.
+ *
+ * tox_encrypted_load() is a good example of how to use this function.
+ *
+ * returns the length of the output data (== data_len - TOX_PASS_ENCRYPTION_EXTRA_LENGTH) on success
+ * returns -1 on failure
+ */
+int tox_pass_decrypt(const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength, uint8_t *out);
+
 /* Load the messenger from encrypted data of size length.
  *
  * returns 0 on success
@@ -65,7 +116,7 @@ int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *
  * returns 1 if it is encrypted
  * returns 0 otherwise
  */
-int tox_is_data_encrypted(const uint8_t *data);
+int tox_is_save_encrypted(const uint8_t *data);
 
 #ifdef __cplusplus
 }