1 files changed, 203 insertions, 0 deletions
diff --git a/oslo_middleware/basic_auth.py b/oslo_middleware/basic_auth.py
new file mode 100644
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+++ b/oslo_middleware/basic_auth.py
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+# Copyright 2012 OpenStack Foundation
+# All Rights Reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+import base64
+import binascii
+import logging
+
+import bcrypt
+import webob
+
+from oslo_config import cfg
+from oslo_middleware import base
+
+LOG = logging.getLogger(__name__)
+
+OPTS = [
+    cfg.StrOpt('http_basic_auth_user_file',
+               default='/etc/htpasswd',
+               help="HTTP basic auth password file.")
+]
+
+cfg.CONF.register_opts(OPTS, group='oslo_middleware')
+
+
+class ConfigInvalid(Exception):
+    def __init__(self, error_msg):
+        super().__init__(
+            'Invalid configuration file. %(error_msg)s')
+
+
+class BasicAuthMiddleware(base.ConfigurableMiddleware):
+    """Middleware which performs HTTP basic authentication on requests"""
+
+    def __init__(self, application, conf=None):
+        super().__init__(application, conf)
+        self.auth_file = cfg.CONF.oslo_middleware.http_basic_auth_user_file
+        validate_auth_file(self.auth_file)
+
+    def format_exception(self, e):
+        result = {'error': {'message': str(e), 'code': 401}}
+        headers = [('Content-Type', 'application/json')]
+        return webob.Response(content_type='application/json',
+                              status_code=401,
+                              json_body=result,
+                              headerlist=headers)
+
+    @webob.dec.wsgify
+    def __call__(self, req):
+        try:
+            token = parse_header(req.environ)
+            username, password = parse_token(token)
+            req.environ.update(authenticate(
+                self.auth_file, username, password))
+            return self.application
+        except Exception as e:
+            response = self.format_exception(e)
+            return self.process_response(response)
+
+
+def authenticate(auth_file, username, password):
+    """Finds username and password match in Apache style user auth file
+
+    The user auth file format is expected to comply with Apache
+    documentation[1] however the bcrypt password digest is the *only*
+    digest format supported.
+
+    [1] https://httpd.apache.org/docs/current/misc/password_encryptions.html
+
+    :param: auth_file: Path to user auth file
+    :param: username: Username to authenticate
+    :param: password: Password encoded as bytes
+    :returns: A dictionary of WSGI environment values to append to the request
+    :raises: HTTPUnauthorized, if no file entries match username/password
+    """
+
+    line_prefix = username + ':'
+    try:
+        with open(auth_file, 'r') as f:
+            for line in f:
+                entry = line.strip()
+                if entry and entry.startswith(line_prefix):
+                    return auth_entry(entry, password)
+    except OSError as exc:
+        LOG.error('Problem reading auth file: %s', exc)
+        raise webob.exc.HTTPBadRequest(
+            detail='Problem reading auth file')
+    # reached end of file with no matches
+    LOG.info('User %s not found', username)
+    raise webob.exc.HTTPUnauthorized()
+
+
+def auth_entry(entry, password):
+    """Compare a password with a single user auth file entry
+
+    :param: entry: Line from auth user file to use for authentication
+    :param: password: Password encoded as bytes
+    :returns: A dictionary of WSGI environment values to append to the request
+    :raises: HTTPUnauthorized, if the entry doesn't match supplied password or
+        if the entry is crypted with a method other than bcrypt
+    """
+
+    username, crypted = parse_entry(entry)
+    if not bcrypt.checkpw(password, crypted):
+        LOG.info('Password for %s does not match', username)
+        raise webob.exc.HTTPUnauthorized()
+    return {
+        'HTTP_X_USER': username,
+        'HTTP_X_USER_NAME': username
+    }
+
+
+def validate_auth_file(auth_file):
+    """Read the auth user file and validate its correctness
+
+    :param: auth_file: Path to user auth file
+    :raises: ConfigInvalid on validation error
+    """
+
+    try:
+        with open(auth_file, 'r') as f:
+            for line in f:
+                entry = line.strip()
+                if entry and ':' in entry:
+                    parse_entry(entry)
+    except OSError:
+        raise ConfigInvalid(error_msg='Problem reading auth user file')
+
+
+def parse_entry(entry):
+    """Extrace the username and crypted password from a user auth file entry
+
+    :param: entry: Line from auth user file to use for authentication
+    :returns: a tuple of username and crypted password
+    :raises: ConfigInvalid if the password is not in the supported bcrypt
+    format
+    """
+
+    username, crypted_str = entry.split(':', maxsplit=1)
+    crypted = crypted_str.encode('utf-8')
+    if crypted[:4] not in (b'$2y$', b'$2a$', b'$2b$'):
+        error_msg = ('Only bcrypt digested passwords are supported for '
+                     '%(username)s') % {'username': username}
+        raise webob.exc.HTTPBadRequest(detail=error_msg)
+    return username, crypted
+
+
+def parse_token(token):
+    """Parse the token portion of the Authentication header value
+
+    :param: token: Token value from basic authorization header
+    :returns: tuple of username, password
+    :raises: BadRequest, if username and password could not be parsed for any
+        reason
+    """
+
+    try:
+        if isinstance(token, str):
+            token = token.encode('utf-8')
+        auth_pair = base64.b64decode(token, validate=True)
+        (username, password) = auth_pair.split(b':', maxsplit=1)
+        return (username.decode('utf-8'), password)
+    except (TypeError, binascii.Error, ValueError) as exc:
+        LOG.info('Could not decode authorization token: %s', exc)
+        raise webob.exc.HTTPBadRequest(detail=(
+            'Could not decode authorization token'))
+
+
+def parse_header(env):
+    """Parse WSGI environment for Authorization header of type Basic
+
+    :param: env: WSGI environment to get header from
+    :returns: Token portion of the header value
+    :raises: HTTPUnauthorized, if header is missing or if the type is not Basic
+    """
+
+    try:
+        auth_header = env.pop('HTTP_AUTHORIZATION')
+    except KeyError:
+        LOG.info('No authorization token received')
+        raise webob.exc.HTTPUnauthorized()
+    try:
+        auth_type, token = auth_header.strip().split(maxsplit=1)
+    except (ValueError, AttributeError) as exc:
+        LOG.info('Could not parse Authorization header: %s', exc)
+        raise webob.exc.HTTPBadRequest(detail=(
+            'Could not parse Authorization header'))
+    if auth_type.lower() != 'basic':
+        error_msg = ('Unsupported authorization type "%s"') % auth_type
+        LOG.info(error_msg)
+        raise webob.exc.HTTPBadRequest(detail=error_msg)
+    return token