re-refactor to separate pass->key and key->encryption

1 files changed, 30 insertions, 1 deletions

diff --git a/toxencryptsave/toxencryptsave.h b/toxencryptsave/toxencryptsave.h
index e3f998af..b85d945c 100644
--- a/toxencryptsave/toxencryptsave.h
+++ b/toxencryptsave/toxencryptsave.h
@@ -38,6 +38,8 @@ typedef struct Tox Tox;
 #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
  * becomes corrupted, the data will be entirely unrecoverable.
@@ -47,8 +49,35 @@ 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.
+ * 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.
  *