Merge branch 'dubslow-master'

#
# Please enter a commit message to explain why this merge is necessary,
# especially if it merges an updated upstream into a topic branch.
#
# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.

2 files changed, 148 insertions, 82 deletions

diff --git a/toxencryptsave/toxencryptsave.c b/toxencryptsave/toxencryptsave.c
index 6567eb96..b6453a89 100644
--- a/toxencryptsave/toxencryptsave.c
+++ b/toxencryptsave/toxencryptsave.c
@@ -36,9 +36,9 @@
 #endif
 
 #define TOX_PASS_ENCRYPTION_EXTRA_LENGTH (crypto_box_MACBYTES + crypto_box_NONCEBYTES \
-           + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
+           + crypto_pwhash_scryptsalsa208sha256_SALTBYTES + TOX_ENC_SAVE_MAGIC_LENGTH)
 
-#define TOX_PASS_KEY_LENGTH (crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES)
+#define TOX_PASS_KEY_LENGTH (crypto_pwhash_scryptsalsa208sha256_SALTBYTES + crypto_box_KEYBYTES)
 
 int tox_pass_encryption_extra_length()
 {
@@ -50,6 +50,11 @@ int tox_pass_key_length()
     return TOX_PASS_KEY_LENGTH;
 }
 
+int tox_pass_salt_length()
+{
+    return 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.
@@ -59,7 +64,24 @@ int tox_pass_key_length()
 /*  return size of the messenger data (for encrypted saving). */
 uint32_t tox_encrypted_size(const Tox *tox)
 {
-    return tox_size(tox) + TOX_PASS_ENCRYPTION_EXTRA_LENGTH + TOX_ENC_SAVE_MAGIC_LENGTH;
+    return tox_size(tox) + TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
+}
+
+/* This retrieves the salt used to encrypt the given data, which can then be passed to
+ * derive_key_with_salt to produce the same key as was previously used. Any encrpyted
+ * data with this module can be used as input.
+ *
+ * returns -1 if the magic number is wrong
+ * returns 0 otherwise (no guarantee about validity of data)
+ */
+int tox_get_salt(uint8_t *data, uint8_t *salt)
+{
+    if (memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH) != 0)
+        return -1;
+
+    data += TOX_ENC_SAVE_MAGIC_LENGTH;
+    memcpy(salt, data, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
+    return 0;
 }
 
 /* Generates a secret symmetric key from the given passphrase. out_key must be at least
@@ -76,19 +98,28 @@ uint32_t tox_encrypted_size(const Tox *tox)
  */
 int tox_derive_key_from_pass(uint8_t *passphrase, uint32_t pplength, uint8_t *out_key)
 {
+    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
+    randombytes(salt, sizeof salt);
+    return tox_derive_key_with_salt(passphrase, pplength, salt, out_key);
+}
+
+/* Same as above, except with use the given salt for deterministic key derivation.
+ * The salt must be tox_salt_length() bytes in length.
+ */
+int tox_derive_key_with_salt(uint8_t *passphrase, uint32_t pplength, uint8_t *salt, uint8_t *out_key)
+{
     if (pplength == 0)
         return -1;
 
     uint8_t passkey[crypto_hash_sha256_BYTES];
     crypto_hash_sha256(passkey, passphrase, pplength);
-    /* First derive a key from the password */
+
+    uint8_t key[crypto_box_KEYBYTES];
+
+    /* Derive a key from the password */
     /* http://doc.libsodium.org/key_derivation/README.html */
     /* note that, according to the documentation, a generic pwhash interface will be created
      * once the pwhash competition (https://password-hashing.net/) is over */
-    uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
-    uint8_t key[crypto_box_KEYBYTES];
-    randombytes(salt, sizeof salt);
-
     if (crypto_pwhash_scryptsalsa208sha256(
                 key, sizeof(key), passkey, sizeof(passkey), salt,
                 crypto_pwhash_scryptsalsa208sha256_OPSLIMIT_INTERACTIVE * 2, /* slightly stronger */
@@ -123,13 +154,17 @@ int tox_pass_key_encrypt(const uint8_t *data, uint32_t data_len, const uint8_t *
      * need them to decrypt the data
      */
 
-    /* first add the prefix */
-    uint8_t nonce[crypto_box_NONCEBYTES];
-    random_nonce(nonce);
+    /* first add the magic number */
+    memcpy(out, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH);
+    out += TOX_ENC_SAVE_MAGIC_LENGTH;
 
+    /* then add the rest prefix */
     memcpy(out, key, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
     key += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
     out += crypto_pwhash_scryptsalsa208sha256_SALTBYTES;
+
+    uint8_t nonce[crypto_box_NONCEBYTES];
+    random_nonce(nonce);
     memcpy(out, nonce, crypto_box_NONCEBYTES);
     out += crypto_box_NONCEBYTES;
 
@@ -172,11 +207,6 @@ 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);
 
-    /* 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;
-
     /* now encrypt */
     return tox_pass_encrypt(temp_data, temp_size, passphrase, pplength, data);
 }
@@ -194,11 +224,6 @@ int tox_encrypted_key_save(const Tox *tox, uint8_t *data, uint8_t *key)
     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;
-
     /* encrypt */
     return tox_pass_key_encrypt(temp_data, temp_size, key, data);
 }
@@ -211,9 +236,12 @@ int tox_encrypted_key_save(const Tox *tox, uint8_t *data, uint8_t *key)
  */
 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)
+    if (length <= TOX_PASS_ENCRYPTION_EXTRA_LENGTH
+            || 0 != memcmp(data, TOX_ENC_SAVE_MAGIC_NUMBER, TOX_ENC_SAVE_MAGIC_LENGTH))
         return -1;
 
+    data += TOX_ENC_SAVE_MAGIC_LENGTH;
+
     uint32_t decrypt_length = length - TOX_PASS_ENCRYPTION_EXTRA_LENGTH;
     //uint8_t salt[crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
     uint8_t nonce[crypto_box_NONCEBYTES];
@@ -241,12 +269,11 @@ int tox_pass_key_decrypt(const uint8_t *data, uint32_t length, const uint8_t *ke
  */
 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);
+    memcpy(salt, data + TOX_ENC_SAVE_MAGIC_LENGTH, crypto_pwhash_scryptsalsa208sha256_SALTBYTES);
 
     /* derive the key */
     uint8_t key[crypto_box_KEYBYTES + crypto_pwhash_scryptsalsa208sha256_SALTBYTES];
@@ -272,12 +299,6 @@ int tox_pass_decrypt(const uint8_t *data, uint32_t length, uint8_t *passphrase,
  */
 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];
 
@@ -295,12 +316,6 @@ int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *
  */
 int tox_encrypted_key_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *key)
 {
-    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];
 
@@ -316,10 +331,15 @@ int tox_encrypted_key_load(Tox *tox, const uint8_t *data, uint32_t length, uint8
  * returns 1 if it is encrypted
  * returns 0 otherwise
  */
-int tox_is_save_encrypted(const uint8_t *data)
+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;
 }
+
+int tox_is_save_encrypted(const uint8_t *data)
+{
+    return tox_is_data_encrypted(data);
+}
diff --git a/toxencryptsave/toxencryptsave.h b/toxencryptsave/toxencryptsave.h
index 14334ea7..169f736c 100644
--- a/toxencryptsave/toxencryptsave.h
+++ b/toxencryptsave/toxencryptsave.h
@@ -35,46 +35,44 @@ extern "C" {
 typedef struct Tox Tox;
 #endif
 
-// these two functions provide access to these defines in toxencryptsave.c, which
-//otherwise aren't actually available in clients...
+// these functions provide access to these defines in toxencryptsave.c, which
+// otherwise aren't actually available in clients...
 int tox_pass_encryption_extra_length();
 
 int tox_pass_key_length();
 
-/* 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.
- * Ditto if they forget their password, there is no way to recover the data.
- */
+int tox_pass_salt_length();
 
-/*  return size of the messenger data (for encrypted saving). */
+/*  return size of the messenger data (for encrypted Messenger 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.
+/* This "module" provides functions analogous to tox_load and tox_save in toxcore,
+ * as well as functions for encryption of arbitrary client data (e.g. chat logs).
  *
- * 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.
+ * It is conceptually organized into two parts. The first part are the functions
+ * with "key" in the name. To use these functions, first derive an encryption key
+ * from a password with tox_derive_key_from_pass, and use the returned key to
+ * encrypt the data. The second part takes the password itself instead of the key,
+ * and then delegates to the first part to derive the key before de/encryption,
+ * which can simplify client code; however, key derivation is very expensive
+ * compared to the actual encryption, so clients that do a lot of encryption should
+ * favor using the first part intead of the second part.
  *
+ * The encrypted data is prepended with a magic number, to aid validity checking
+ * (no guarantees are made of course).
  *
- * returns 0 on success
- * returns -1 on failure
+ * Clients should consider alerting their users that, unlike plain data, if even one bit
+ * becomes corrupted, the data will be entirely unrecoverable.
+ * Ditto if they forget their password, there is no way to recover the data.
+ */
+
+
+/******************************* BEGIN PART 2 *******************************
+ * For simplicty, the second part of the module is presented first. The API for
+ * the first part is analgous, with some extra functions for key handling. If
+ * your code spends too much time using these functions, consider using the part
+ * 1 functions instead.
  */
-int tox_pass_key_encrypt(const 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
@@ -95,39 +93,86 @@ int tox_pass_encrypt(const uint8_t *data, uint32_t data_len, uint8_t *passphrase
  */
 int tox_encrypted_save(const Tox *tox, uint8_t *data, uint8_t *passphrase, uint32_t pplength);
 
-/* Save the messenger data encrypted with the given key from tox_derive_key.
- * data must be at least tox_encrypted_size().
+/* Decrypts 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_pass_key_decrypt.
+ *
+ * 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
  * returns -1 on failure
  */
-int tox_encrypted_key_save(const Tox *tox, uint8_t *data, uint8_t *key);
+int tox_encrypted_load(Tox *tox, const uint8_t *data, uint32_t length, uint8_t *passphrase, uint32_t pplength);
 
-/* This is the inverse of tox_pass_key_encrypt, also using only keys produced by
- * tox_derive_key_from_pass.
+
+/******************************* BEGIN PART 1 *******************************
+ * And now part "1", which does the actual encryption, and is rather less cpu
+ * intensive than part one. The first 3 functions are for key handling.
+ */
+
+/* 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.
+ * 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.
+ * Note that this function is not deterministic; to derive the same key from a
+ * password, you also must know the random salt that was used. See below.
  *
- * returns the length of the output data (== data_len - tox_pass_encryption_extra_length()) on success
+ * returns 0 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);
+int tox_derive_key_from_pass(uint8_t *passphrase, uint32_t pplength, uint8_t *out_key);
 
-/* Decrypts 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_pass_key_decrypt.
+/* Same as above, except with use the given salt for deterministic key derivation.
+ * The salt must be tox_salt_length() bytes in length.
+ */
+int tox_derive_key_with_salt(uint8_t *passphrase, uint32_t pplength, uint8_t *salt, uint8_t *out_key);
+
+/* This retrieves the salt used to encrypt the given data, which can then be passed to
+ * derive_key_with_salt to produce the same key as was previously used. Any encrpyted
+ * data with this module can be used as input.
  *
- * tox_encrypted_load() is a good example of how to use this function.
+ * returns -1 if the magic number is wrong
+ * returns 0 otherwise (no guarantee about validity of data)
+ */
+int tox_get_salt(uint8_t *data, uint8_t *salt);
+
+/* Now come the functions that are analogous to the part 2 functions. */
+
+/* Encrypt arbitrary with a key produced by tox_derive_key_. 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 the length of the output data (== data_len - tox_pass_encryption_extra_length()) on success
+ * returns 0 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);
+int tox_pass_key_encrypt(const uint8_t *data, uint32_t data_len, const uint8_t *key, uint8_t *out);
 
-/* Load the messenger from encrypted data of size length.
+/* Save the messenger data encrypted with the given key from tox_derive_key.
+ * data must be at least tox_encrypted_size().
  *
  * 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_encrypted_key_save(const Tox *tox, uint8_t *data, uint8_t *key);
+
+/* 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);
 
 /* Load the messenger from encrypted data of size length, with key from tox_derive_key.
  *
@@ -141,7 +186,8 @@ int tox_encrypted_key_load(Tox *tox, const uint8_t *data, uint32_t length, uint8
  * returns 1 if it is encrypted
  * returns 0 otherwise
  */
-int tox_is_save_encrypted(const uint8_t *data);
+int tox_is_data_encrypted(const uint8_t *data);
+int tox_is_save_encrypted(const uint8_t *data); // poorly-named alias for backwards compat (oh irony...)
 
 #ifdef __cplusplus
 }