Repository: pyca/bcrypt

Issue:
Find a way to not use == in the README
I don't think it's actually exploitable as a timing attack (in fact I'm pretty sure it's not), but I think it'd be good hygeine to offer a check_password function or similar and use that, so we dont' have to expose a general purpose constant time comparison function.

Comments:

Patch:
diff --git a/.travis.yml b/.travis.yml
index 456aba7..bbcb336 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -30,6 +30,7 @@ matrix:
       env: TOXENV=pypy CC=clang
     - python: 2.7
       env: TOXENV=pep8
+    - env: TOXENV=packaging
     - python: 3.5
       env: TOXENV=py3pep8
     - language: generic
diff --git a/MANIFEST.in b/MANIFEST.in
index 622d66b..93a4480 100644
--- a/MANIFEST.in
+++ b/MANIFEST.in
@@ -1,3 +1,11 @@
 include LICENSE README.rst
+
+include tox.ini .coveragerc
 include src/build_bcrypt.py
+
 recursive-include src/_csrc *
+recursive-include tests *.py
+
+exclude requirements.txt tasks.py .travis.yml
+
+prune .travis
diff --git a/README.rst b/README.rst
index 0883286..3859bb8 100644
--- a/README.rst
+++ b/README.rst
@@ -40,6 +40,7 @@ Changelog
 3.1.0
 -----
 * Added support for ``checkpw`` as another method of verifying a password.
+* Ensure that you get a ``$2y$`` hash when you input a ``$2y$`` salt.
 
 3.0.0
 -----
@@ -104,7 +105,7 @@ the work factor merely pass the desired number of rounds to
     >>> hashed = bcrypt.hashpw(password, bcrypt.gensalt(14))
     >>> # Check that a unhashed password matches one that has previously been
     >>> #   hashed
-    >>> if bcrypt.hashpw(password, hashed) == hashed:
+    >>> if bcrypt.checkpw(password, hashed):
     ...     print("It Matches!")
     ... else:
     ...     print("It Does not Match :(")
diff --git a/src/bcrypt/__init__.py b/src/bcrypt/__init__.py
index d6acb84..abc9d75 100644
--- a/src/bcrypt/__init__.py
+++ b/src/bcrypt/__init__.py
@@ -39,10 +39,6 @@ __all__ = [
 _normalize_re = re.compile(b"^\$2y\$")
 
 
-def _normalize_prefix(salt):
-    return _normalize_re.sub(b"$2b$", salt)
-
-
 def gensalt(rounds=12, prefix=b"2b"):
     if prefix not in (b"2a", b"2b"):
         raise ValueError("Supported prefixes are b'2a' or b'2b'")
@@ -75,7 +71,13 @@ def hashpw(password, salt):
     # on $2a$, so we do it here to preserve compatibility with 2.0.0
     password = password[:72]
 
-    salt = _normalize_prefix(salt)
+    # When the original 8bit bug was found the original library we supported
+    # added a new prefix, $2y$, that fixes it. This prefix is exactly the same
+    # as the $2b$ prefix added by OpenBSD other than the name. Since the
+    # OpenBSD library does not support the $2y$ prefix, if the salt given to us
+    # is for the $2y$ prefix, we'll just mugne it so that it's a $2b$ prior to
+    # passing it into the C library.
+    original_salt, salt = salt, _normalize_re.sub(b"$2b$", salt)
 
     hashed = _bcrypt.ffi.new("unsigned char[]", 128)
     retval = _bcrypt.lib.bcrypt_hashpass(password, salt, hashed, len(hashed))
@@ -83,7 +85,13 @@ def hashpw(password, salt):
     if retval != 0:
         raise ValueError("Invalid salt")
 
-    return _bcrypt.ffi.string(hashed)
+    # Now that we've gotten our hashed password, we want to ensure that the
+    # prefix we return is the one that was passed in, so we'll use the prefix
+    # from the original salt and concatenate that with the return value (minus
+    # the return value's prefix). This will ensure that if someone passed in a
+    # salt with a $2y$ prefix, that they get back a hash with a $2y$ prefix
+    # even though we munged it to $2b$.
+    return original_salt[:4] + _bcrypt.ffi.string(hashed)[4:]
 
 
 def checkpw(password, hashed_password):
@@ -96,9 +104,6 @@ def checkpw(password, hashed_password):
             "password and hashed_password may not contain NUL bytes"
         )
 
-    # If the user supplies a $2y$ prefix we normalize to $2b$
-    hashed_password = _normalize_prefix(hashed_password)
-
     ret = hashpw(password, hashed_password)
 
     return _bcrypt.lib.timingsafe_bcmp(ret, hashed_password, len(ret)) == 0
diff --git a/tox.ini b/tox.ini
index abc6283..264d9aa 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,pypy,py33,py34,py35,pep8,py3pep8
+envlist = py26,py27,pypy,py33,py34,py35,pep8,py3pep8,packaging
 
 [testenv]
 # If you add a new dep here you probably need to add it in setup.py as well
@@ -27,6 +27,15 @@ deps =
 commands =
     flake8 .
 
+[testenv:packaging]
+deps =
+    check-manifest
+    readme_renderer
+commands =
+    check-manifest
+    python setup.py check --metadata --restructuredtext --strict
+
+
 [flake8]
 exclude = .tox,*.egg
 select = E,W,F,N,I


Test patch:
diff --git a/tests/test_bcrypt.py b/tests/test_bcrypt.py
index 47f315a..d9bde72 100644
--- a/tests/test_bcrypt.py
+++ b/tests/test_bcrypt.py
@@ -152,12 +152,12 @@ _2y_test_vectors = [
     (
         b"\xa3",
         b"$2y$05$/OK.fbVrR/bpIqNJ5ianF.Sa7shbm4.OzKpvFnX1pQLmQW96oUlCq",
-        b"$2b$05$/OK.fbVrR/bpIqNJ5ianF.Sa7shbm4.OzKpvFnX1pQLmQW96oUlCq",
+        b"$2y$05$/OK.fbVrR/bpIqNJ5ianF.Sa7shbm4.OzKpvFnX1pQLmQW96oUlCq",
     ),
     (
         b"\xff\xff\xa3",
         b"$2y$05$/OK.fbVrR/bpIqNJ5ianF.CE5elHaaO4EbggVDjb8P19RukzXSM3e",
-        b"$2b$05$/OK.fbVrR/bpIqNJ5ianF.CE5elHaaO4EbggVDjb8P19RukzXSM3e",
+        b"$2y$05$/OK.fbVrR/bpIqNJ5ianF.CE5elHaaO4EbggVDjb8P19RukzXSM3e",
     ),
 ]