server/users: harden password hashes

- Changed password setup to use libsodium and argon2id (regular SHA256
  hashing for passwords is inadequate as modern GPU's can hash generate
  billions of hashes per second).
- Added code to auto migrate old passwords to the new password_hash if
  the existing password_hash matches either of the legacy password
  generation schemes (SHA1 or SHA256).
- Added migration to support new password_hash format length
- Added column password_revision. This field will default to 0, which
  all passwords will have till they're updated. After that each password
  hash method has a revision.

1 files changed, 36 insertions, 12 deletions

diff --git a/server/szurubooru/func/auth.py b/server/szurubooru/func/auth.py
index 25c991c..c9740fe 100644
--- a/server/szurubooru/func/auth.py
+++ b/server/szurubooru/func/auth.py
@@ -1,7 +1,10 @@
+from typing import Tuple
 import hashlib
 import random
 from collections import OrderedDict
-from szurubooru import config, model, errors
+from nacl import pwhash
+from nacl.exceptions import InvalidkeyError
+from szurubooru import config, model, errors, db
 from szurubooru.func import util
 
 
@@ -16,22 +19,29 @@ RANK_MAP = OrderedDict([
 ])
 
 
-def get_password_hash(salt: str, password: str) -> str:
-    ''' Retrieve new-style password hash. '''
+def get_password_hash(salt: str, password: str) -> Tuple[str, int]:
+    ''' Retrieve argon2id password hash. '''
+    return pwhash.argon2id.str(
+        (config.config['secret'] + salt + password).encode('utf8')
+    ).decode('utf8'), 3
+
+
+def get_sha256_legacy_password_hash(salt: str, password: str) -> Tuple[str, int]:
+    ''' Retrieve old-style sha256 password hash. '''
     digest = hashlib.sha256()
     digest.update(config.config['secret'].encode('utf8'))
     digest.update(salt.encode('utf8'))
     digest.update(password.encode('utf8'))
-    return digest.hexdigest()
+    return digest.hexdigest(), 2
 
 
-def get_legacy_password_hash(salt: str, password: str) -> str:
-    ''' Retrieve old-style password hash. '''
+def get_sha1_legacy_password_hash(salt: str, password: str) -> Tuple[str, int]:
+    ''' Retrieve old-style sha1 password hash. '''
     digest = hashlib.sha1()
     digest.update(b'1A2/$_4xVa')
     digest.update(salt.encode('utf8'))
     digest.update(password.encode('utf8'))
-    return digest.hexdigest()
+    return digest.hexdigest(), 1
 
 
 def create_password() -> str:
@@ -47,11 +57,25 @@ def create_password() -> str:
 def is_valid_password(user: model.User, password: str) -> bool:
     assert user
     salt, valid_hash = user.password_salt, user.password_hash
-    possible_hashes = [
-        get_password_hash(salt, password),
-        get_legacy_password_hash(salt, password)
-    ]
-    return valid_hash in possible_hashes
+
+    try:
+        return pwhash.verify(
+            user.password_hash.encode('utf8'),
+            (config.config['secret'] + salt + password).encode('utf8'))
+    except InvalidkeyError:
+        possible_hashes = [
+            get_sha256_legacy_password_hash(salt, password)[0],
+            get_sha1_legacy_password_hash(salt, password)[0]
+        ]
+        if valid_hash in possible_hashes:
+            # Convert the user password hash to the new hash
+            new_hash, revision = get_password_hash(salt, password)
+            user.password_hash = new_hash
+            user.password_revision = revision
+            db.session.commit()
+            return True
+
+    return False
 
 
 def has_privilege(user: model.User, privilege_name: str) -> bool: