Source code for webtest.lint

# (c) 2005 Ian Bicking and contributors; written for Paste
# (http://pythonpaste.org)
# Licensed under the MIT license:
# http://www.opensource.org/licenses/mit-license.php Also licenced under the
# Apache License, 2.0: http://opensource.org/licenses/apache2.0.php Licensed to
# PSF under a Contributor Agreement

"""
Middleware to check for obedience to the WSGI specification.

Some of the things this checks:

* Signature of the application and start_response (including that
  keyword arguments are not used).

* Environment checks:

  - Environment is a dictionary (and not a subclass).

  - That all the required keys are in the environment: REQUEST_METHOD,
    SERVER_NAME, SERVER_PORT, wsgi.version, wsgi.input, wsgi.errors,
    wsgi.multithread, wsgi.multiprocess, wsgi.run_once

  - That HTTP_CONTENT_TYPE and HTTP_CONTENT_LENGTH are not in the
    environment (these headers should appear as CONTENT_LENGTH and
    CONTENT_TYPE).

  - Warns if QUERY_STRING is missing, as the cgi module acts
    unpredictably in that case.

  - That CGI-style variables (that don't contain a .) have
    (non-unicode) string values

  - That wsgi.version is a tuple

  - That wsgi.url_scheme is 'http' or 'https' (@@: is this too
    restrictive?)

  - Warns if the REQUEST_METHOD is not known (@@: probably too
    restrictive).

  - That SCRIPT_NAME and PATH_INFO are empty or start with /

  - That at least one of SCRIPT_NAME or PATH_INFO are set.

  - That CONTENT_LENGTH is a positive integer.

  - That SCRIPT_NAME is not '/' (it should be '', and PATH_INFO should
    be '/').

  - That wsgi.input has the methods read, readline, readlines, and
    __iter__

  - That wsgi.errors has the methods flush, write, writelines

* The status is a string, contains a space, starts with an integer,
  and that integer is in range (> 100).

* That the headers is a list (not a subclass, not another kind of
  sequence).

* That the items of the headers are tuples of 'native' strings (i.e.
  bytestrings in Python2, and unicode strings in Python3).

* That there is no 'status' header (that is used in CGI, but not in
  WSGI).

* That the headers don't contain newlines or colons, end in _ or -, or
  contain characters codes below 037.

* That Content-Type is given if there is content (CGI often has a
  default content type, but WSGI does not).

* That no Content-Type is given when there is no content (@@: is this
  too restrictive?)

* That the exc_info argument to start_response is a tuple or None.

* That all calls to the writer are with strings, and no other methods
  on the writer are accessed.

* That wsgi.input is used properly:

  - .read() is called with zero or one argument

  - That it returns a string

  - That readline, readlines, and __iter__ return strings

  - That .close() is not called

  - No other methods are provided

* That wsgi.errors is used properly:

  - .write() and .writelines() is called with a string, except
    with python3

  - That .close() is not called, and no other methods are provided.

* The response iterator:

  - That it is not a string (it should be a list of a single string; a
    string will work, but perform horribly).

  - That .next() returns a string

  - That the iterator is not iterated over until start_response has
    been called (that can signal either a server or application
    error).

  - That .close() is called (doesn't raise exception, only prints to
    sys.stderr, because we only know it isn't called when the object
    is garbage collected).

"""
from __future__ import unicode_literals

import re
import warnings
from six import PY3
from six import binary_type
from six import string_types
from six import text_type

from webtest.compat import Iterable

header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$')
bad_header_value_re = re.compile(r'[\000-\037]')

valid_methods = (
    'GET', 'HEAD', 'POST', 'OPTIONS', 'PUT', 'DELETE',
    'TRACE', 'PATCH',
)

METADATA_TYPE = PY3 and (str, binary_type) or (str,)

# PEP-3333 says that environment variables must be "native strings",
# i.e. str(), which however is something *different* in py2 and py3.
SLASH = str('/')


def to_string(value):
    if not isinstance(value, string_types):
        return value.decode('latin1')
    else:
        return value


class WSGIWarning(Warning):
    """
    Raised in response to WSGI-spec-related warnings
    """


[docs]def middleware(application, global_conf=None): """ When applied between a WSGI server and a WSGI application, this middleware will check for WSGI compliancy on a number of levels. This middleware does not modify the request or response in any way, but will throw an AssertionError if anything seems off (except for a failure to close the application iterator, which will be printed to stderr -- there's no way to throw an exception at that point). """ def lint_app(*args, **kw): assert len(args) == 2, "Two arguments required" assert not kw, "No keyword arguments allowed" environ, start_response = args check_environ(environ) # We use this to check if the application returns without # calling start_response: start_response_started = [] def start_response_wrapper(*args, **kw): assert len(args) == 2 or len(args) == 3, ( "Invalid number of arguments: %s" % args) assert not kw, "No keyword arguments allowed" status = args[0] headers = args[1] if len(args) == 3: exc_info = args[2] else: exc_info = None check_status(status) check_headers(headers) check_content_type(status, headers) check_exc_info(exc_info) start_response_started.append(None) return WriteWrapper(start_response(*args)) environ['wsgi.input'] = InputWrapper(environ['wsgi.input']) environ['wsgi.errors'] = ErrorWrapper(environ['wsgi.errors']) iterator = application(environ, start_response_wrapper) assert isinstance(iterator, Iterable), ( "The application must return an iterator, if only an empty list") check_iterator(iterator) return IteratorWrapper(iterator, start_response_started) return lint_app
class InputWrapper(object): def __init__(self, wsgi_input): self.input = wsgi_input def read(self, *args): assert len(args) <= 1 v = self.input.read(*args) assert type(v) is binary_type return v def readline(self, *args): v = self.input.readline(*args) assert type(v) is binary_type return v def readlines(self, *args): assert len(args) <= 1 lines = self.input.readlines(*args) assert isinstance(lines, list) for line in lines: assert type(line) is binary_type return lines def __iter__(self): while 1: line = self.readline() if not line: return yield line def close(self): assert 0, "input.close() must not be called" def seek(self, *a, **kw): return self.input.seek(*a, **kw) class ErrorWrapper(object): def __init__(self, wsgi_errors): self.errors = wsgi_errors def write(self, s): if not PY3: assert type(s) is binary_type self.errors.write(s) def flush(self): self.errors.flush() def writelines(self, seq): for line in seq: self.write(line) def close(self): assert 0, "errors.close() must not be called" class WriteWrapper(object): def __init__(self, wsgi_writer): self.writer = wsgi_writer def __call__(self, s): assert type(s) is binary_type self.writer(s) class IteratorWrapper(object): def __init__(self, wsgi_iterator, check_start_response): self.original_iterator = wsgi_iterator self.iterator = iter(wsgi_iterator) self.closed = False self.check_start_response = check_start_response def __iter__(self): return self def next(self): assert not self.closed, ( "Iterator read after closed") v = next(self.iterator) if self.check_start_response is not None: assert self.check_start_response, ( "The application returns and we started iterating over its" " body, but start_response has not yet been called") self.check_start_response = None assert isinstance(v, binary_type), ( "Iterator %r returned a non-%r object: %r" % (self.iterator, binary_type, v)) return v __next__ = next def close(self): self.closed = True if hasattr(self.original_iterator, 'close'): self.original_iterator.close() def __del__(self): assert self.closed, ( "Iterator garbage collected without being closed") def check_environ(environ): assert type(environ) is dict, ( "Environment is not of the right type: %r (environment: %r)" % (type(environ), environ)) for key in ['REQUEST_METHOD', 'SERVER_NAME', 'SERVER_PORT', 'wsgi.version', 'wsgi.input', 'wsgi.errors', 'wsgi.multithread', 'wsgi.multiprocess', 'wsgi.run_once']: assert key in environ, ( "Environment missing required key: %r" % key) for key in ['HTTP_CONTENT_TYPE', 'HTTP_CONTENT_LENGTH']: assert key not in environ, ( "Environment should not have the key: %s " "(use %s instead)" % (key, key[5:])) if 'QUERY_STRING' not in environ: warnings.warn( 'QUERY_STRING is not in the WSGI environment; the cgi ' 'module will use sys.argv when this variable is missing, ' 'so application errors are more likely', WSGIWarning) for key in environ: if '.' in key: # Extension, we don't care about its type continue assert type(environ[key]) in METADATA_TYPE, ( "Environmental variable %s is not a string: %r (value: %r)" % (key, type(environ[key]), environ[key])) assert type(environ['wsgi.version']) is tuple, ( "wsgi.version should be a tuple (%r)" % environ['wsgi.version']) assert environ['wsgi.url_scheme'] in ('http', 'https'), ( "wsgi.url_scheme unknown: %r" % environ['wsgi.url_scheme']) check_input(environ['wsgi.input']) check_errors(environ['wsgi.errors']) # @@: these need filling out: if environ['REQUEST_METHOD'] not in valid_methods: warnings.warn( "Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'], WSGIWarning) assert (not environ.get('SCRIPT_NAME') or environ['SCRIPT_NAME'].startswith(SLASH)), ( "SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME']) assert (not environ.get('PATH_INFO') or environ['PATH_INFO'].startswith(SLASH)), ( "PATH_INFO doesn't start with /: %r" % environ['PATH_INFO']) if environ.get('CONTENT_LENGTH'): assert int(environ['CONTENT_LENGTH']) >= 0, ( "Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH']) if not environ.get('SCRIPT_NAME'): assert 'PATH_INFO' in environ, ( "One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO " "should at least be '/' if SCRIPT_NAME is empty)") assert environ.get('SCRIPT_NAME') != SLASH, ( "SCRIPT_NAME cannot be '/'; it should instead be '', and " "PATH_INFO should be '/'") def check_input(wsgi_input): for attr in ['read', 'readline', 'readlines', '__iter__']: assert hasattr(wsgi_input, attr), ( "wsgi.input (%r) doesn't have the attribute %s" % (wsgi_input, attr)) def check_errors(wsgi_errors): for attr in ['flush', 'write', 'writelines']: assert hasattr(wsgi_errors, attr), ( "wsgi.errors (%r) doesn't have the attribute %s" % (wsgi_errors, attr)) def check_status(status): assert type(status) in METADATA_TYPE, ( "Status must be a %s (not %r)" % (METADATA_TYPE, status)) status = to_string(status) assert len(status) > 5, ( "The status string (%r) should be a three-digit " "integer followed by a single space and a status explanation" ) % status assert status[:3].isdigit(), ( "The status string (%r) should start with" "three digits") % status status_int = int(status[:3]) assert status_int >= 100, ( "The status code must be greater or equal than " "100 (got %d)") % status_int assert status[3] == ' ', ( "The status string (%r) should start with three" "digits and a space (4th characters is not a space here)") % status def _assert_latin1_str(string, message): assert type(string) is str, message if type(string) is text_type: try: string.encode('latin1') except UnicodeEncodeError: raise AssertionError(message) return string def check_headers(headers): assert type(headers) is list, ( "Headers (%r) must be of type list: %r" % (headers, type(headers))) for item in headers: assert type(item) is tuple, ( "Individual headers (%r) must be of type tuple: %r" % (item, type(item))) assert len(item) == 2 name, value = item _assert_latin1_str( name, "Header names must be latin1 string " "(not Py2 unicode or Py3 bytes type). " "%r is not a valid latin1 string" % (name,) ) assert name.lower() != 'status', ( "The Status header cannot be used; it conflicts with CGI " "script, and HTTP status is not given through headers " "(value: %r)." % value) assert '\n' not in name and ':' not in name, ( "Header names may not contain ':' or '\\n': %r" % name) assert header_re.search(name), "Bad header name: %r" % name assert not name.endswith('-') and not name.endswith('_'), ( "Names may not end in '-' or '_': %r" % name) _assert_latin1_str( value, "Header values must be latin1 string " "(not Py2 unicode or Py3 bytes type)." "%r is not a valid latin1 string" % (value,) ) assert not bad_header_value_re.search(value), ( "Bad header value: %r (bad char: %r)" % (str_value, bad_header_value_re.search(value).group(0))) def check_content_type(status, headers): code = int(status.split(None, 1)[0]) # @@: need one more person to verify this interpretation of RFC 2616 # http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html NO_MESSAGE_BODY = (201, 204, 304) NO_MESSAGE_TYPE = (204, 304) length = None for name, value in headers: if name.lower() == 'content-length' and value.isdigit(): length = int(value) break for name, value in headers: if name.lower() == 'content-type': if code not in NO_MESSAGE_TYPE: return elif length == 0: warnings.warn(("Content-Type header found in a %s response, " "which not return content.") % code, WSGIWarning) return else: assert 0, (("Content-Type header found in a %s response, " "which must not return content.") % code) if code not in NO_MESSAGE_BODY and length is not None and length > 0: assert 0, "No Content-Type header found in headers (%s)" % headers def check_exc_info(exc_info): assert exc_info is None or type(exc_info) is tuple, ( "exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info))) # More exc_info checks? def check_iterator(iterator): valid_type = PY3 and bytes or str # Technically a bytes (str for py2.x) is legal, which is why it's a # really bad idea, because it may cause the response to be returned # character-by-character assert not isinstance(iterator, valid_type), ( "You should not return a bytes as your application iterator, " "instead return a single-item list containing that string.") __all__ = ['middleware']