*all* hashes now throw PasswordSizeError if password is larger than 4096 chars; to prevent DOS issues.

9 files changed, 62 insertions, 1 deletions

diff --git a/CHANGES b/CHANGES
index 7e79614..8fc1cc9 100644
--- a/CHANGES
+++ b/CHANGES
@@ -50,6 +50,14 @@ Release History
           that sometimes occurred on platforms with a deviant implementation
           of :func:`!os_crypt`.
 
+        * All hashes will now throw :exc:`~passlib.exc.PasswordSizeError`
+          if the provided password is larger than 4096 characters.
+
+          This limit should be above any reasonable password size,
+          and prevents various things including DOS abuse of hashes
+          that have an expensive password-length-dependant stage,
+          and for OS's which have a buggy :func:`!crypt.crypt` implementation.
+
     CryptContext
 
         .. currentmodule:: passlib.context
diff --git a/docs/lib/passlib.exc.rst b/docs/lib/passlib.exc.rst
index 263f754..b60ba63 100644
--- a/docs/lib/passlib.exc.rst
+++ b/docs/lib/passlib.exc.rst
@@ -11,6 +11,7 @@ may be raised by Passlib.
 Exceptions
 ==========
 .. autoexception:: MissingBackendError
+.. autoexception:: PasswordSizeError
 
 Warnings
 ========
diff --git a/passlib/exc.py b/passlib/exc.py
index cb158e7..44fadd4 100644
--- a/passlib/exc.py
+++ b/passlib/exc.py
@@ -14,6 +14,28 @@ class MissingBackendError(RuntimeError):
     from :class:`~passlib.utils.handlers.HasManyBackends`.
     """
 
+class PasswordSizeError(ValueError):
+    """Error raised if the password provided exceeds the limit set by Passlib.
+
+    Many password hashes take proportionately larger amounts of
+    time and/or memory depending on the size of the password provided.
+    This could present a potential denial of service (DOS) situation
+    if a maliciously large password was provided to the application.
+
+    Because of this, Passlib enforces a maximum of 4096 characters.
+    This error will be thrown if a password larger than
+    this is provided to any of the hashes in Passlib.
+
+    Applications wishing to use a different limit should set the
+    ``PASSLIB_MAX_PASSWORD_SIZE`` environmental variable before Passlib
+    is loaded.
+    """
+    def __init__(self):
+        ValueError.__init__(self, "password exceeds maximum allowed size")
+
+    # this also prevents a glibc crypt segfault issue, detailed here ...
+    # http://www.openwall.com/lists/oss-security/2011/11/15/1
+
 #==========================================================================
 # warnings
 #==========================================================================
diff --git a/passlib/handlers/misc.py b/passlib/handlers/misc.py
index 38b8c25..2fb3f13 100644
--- a/passlib/handlers/misc.py
+++ b/passlib/handlers/misc.py
@@ -170,6 +170,8 @@ class plaintext(object):
 
     @classmethod
     def encrypt(cls, secret):
+        if secret and len(secret) > uh.MAX_PASSWORD_SIZE:
+            raise uh.exc.PasswordSizeError()
         return to_native_str(secret, cls._hash_encoding, "secret")
 
     @classmethod
diff --git a/passlib/handlers/mssql.py b/passlib/handlers/mssql.py
index 36bff13..4bc7e24 100644
--- a/passlib/handlers/mssql.py
+++ b/passlib/handlers/mssql.py
@@ -160,6 +160,8 @@ class mssql2000(uh.HasRawSalt, uh.HasRawChecksum, uh.GenericHandler):
         chk = self.checksum
         if chk is None:
             raise uh.MissingDigestError(cls)
+        if secret and len(secret) > uh.MAX_PASSWORD_SIZE:
+            raise uh.exc.PasswordSizeError()
         secret = to_unicode(secret, 'utf-8', errname='secret')
         result = _raw_mssql(secret.upper(), self.salt)
         return consteq(result, chk[20:])
diff --git a/passlib/handlers/scram.py b/passlib/handlers/scram.py
index 5c9c65d..ab610c8 100644
--- a/passlib/handlers/scram.py
+++ b/passlib/handlers/scram.py
@@ -351,6 +351,8 @@ class scram(uh.HasRounds, uh.HasRawSalt, uh.HasRawChecksum, uh.GenericHandler):
 
     @classmethod
     def verify(cls, secret, hash, full=False):
+        if secret and len(secret) > uh.MAX_PASSWORD_SIZE:
+            raise uh.exc.PasswordSizeError()
         self = cls.from_string(hash)
         chkmap = self.checksum
         if not chkmap:
diff --git a/passlib/tests/utils.py b/passlib/tests/utils.py
index b3ce550..7c79975 100644
--- a/passlib/tests/utils.py
+++ b/passlib/tests/utils.py
@@ -1231,6 +1231,19 @@ class HandlerCase(TestCase):
         self.assertRaises(TypeError, self.do_genhash, None, hash)
         self.assertRaises(TypeError, self.do_verify, None, hash)
 
+    def test_63_max_password_size(self):
+        "test MAX_PASSWORD_SIZE is enforced"
+        if self.is_disabled_handler:
+            raise self.skipTest("not applicable")
+        from passlib.exc import PasswordSizeError
+        from passlib.utils import MAX_PASSWORD_SIZE
+        secret = '.' * (1+MAX_PASSWORD_SIZE)
+        config = self.do_genconfig()
+        hash = self.get_sample_hash()[1]
+        self.assertRaises(PasswordSizeError, self.do_genhash, secret, config)
+        self.assertRaises(PasswordSizeError, self.do_encrypt, secret)
+        self.assertRaises(PasswordSizeError, self.do_verify, secret, hash)
+
     #==============================================================
     # check identify(), verify(), genhash() against test vectors
     #==============================================================
diff --git a/passlib/utils/__init__.py b/passlib/utils/__init__.py
index 24173f7..e8e5b27 100644
--- a/passlib/utils/__init__.py
+++ b/passlib/utils/__init__.py
@@ -105,6 +105,9 @@ _BEMPTY = b('')
 _UEMPTY = u("")
 _USPACE = u(" ")
 
+# maximum password size which passlib will allow; see exc.PasswordSizeError
+MAX_PASSWORD_SIZE = int(os.environ.get("PASSLIB_MAX_PASSWORD_SIZE") or 4096)
+
 #=================================================================================
 #decorators and meta helpers
 #=================================================================================
diff --git a/passlib/utils/handlers.py b/passlib/utils/handlers.py
index 2d283c5..7c8b747 100644
--- a/passlib/utils/handlers.py
+++ b/passlib/utils/handlers.py
@@ -13,12 +13,14 @@ import os
 from warnings import warn
 # site
 # pkg
+import passlib.exc as exc
 from passlib.exc import MissingBackendError, PasslibConfigWarning, \
                         PasslibHashWarning
 from passlib.registry import get_crypt_handler
 from passlib.utils import classproperty, consteq, getrandstr, getrandbytes,\
                           BASE64_CHARS, HASH64_CHARS, rng, to_native_str, \
-                          is_crypt_handler, deprecated_function, to_unicode
+                          is_crypt_handler, deprecated_function, to_unicode, \
+                          MAX_PASSWORD_SIZE
 from passlib.utils.compat import b, join_byte_values, bytes, irange, u, \
                                  uascii_to_str, join_unicode, unicode, str_to_uascii
 # local
@@ -442,6 +444,8 @@ class GenericHandler(object):
 
     @classmethod
     def genhash(cls, secret, config, **context):
+        if secret and len(secret) > MAX_PASSWORD_SIZE:
+            raise exc.PasswordSizeError()
         self = cls.from_string(config, **context)
         self.checksum = self._calc_checksum(secret)
         return self.to_string()
@@ -458,6 +462,8 @@ class GenericHandler(object):
     #=========================================================
     @classmethod
     def encrypt(cls, secret, **kwds):
+        if secret and len(secret) > MAX_PASSWORD_SIZE:
+            raise exc.PasswordSizeError()
         self = cls(use_defaults=True, **kwds)
         self.checksum = self._calc_checksum(secret)
         return self.to_string()
@@ -467,6 +473,8 @@ class GenericHandler(object):
         # NOTE: classes with multiple checksum encodings should either
         # override this method, or ensure that from_string() / _norm_checksum()
         # ensures .checksum always uses a single canonical representation.
+        if secret and len(secret) > MAX_PASSWORD_SIZE:
+            raise exc.PasswordSizeError()
         self = cls.from_string(hash, **context)
         chk = self.checksum
         if chk is None: