1
# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
2
# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
3
# Also licenced under the Apache License, 2.0: http://opensource.org/licenses/apache2.0.php
4
# Licensed to PSF under a Contributor Agreement
6
Middleware to check for obedience to the WSGI specification.
8
Some of the things this checks:
10
* Signature of the application and start_response (including that
11
keyword arguments are not used).
15
- Environment is a dictionary (and not a subclass).
17
- That all the required keys are in the environment: REQUEST_METHOD,
18
SERVER_NAME, SERVER_PORT, wsgi.version, wsgi.input, wsgi.errors,
19
wsgi.multithread, wsgi.multiprocess, wsgi.run_once
21
- That HTTP_CONTENT_TYPE and HTTP_CONTENT_LENGTH are not in the
22
environment (these headers should appear as CONTENT_LENGTH and
25
- Warns if QUERY_STRING is missing, as the cgi module acts
26
unpredictably in that case.
28
- That CGI-style variables (that don't contain a .) have
29
(non-unicode) string values
31
- That wsgi.version is a tuple
33
- That wsgi.url_scheme is 'http' or 'https' (@@: is this too
36
- Warns if the REQUEST_METHOD is not known (@@: probably too
39
- That SCRIPT_NAME and PATH_INFO are empty or start with /
41
- That at least one of SCRIPT_NAME or PATH_INFO are set.
43
- That CONTENT_LENGTH is a positive integer.
45
- That SCRIPT_NAME is not '/' (it should be '', and PATH_INFO should
48
- That wsgi.input has the methods read, readline, readlines, and
51
- That wsgi.errors has the methods flush, write, writelines
53
* The status is a string, contains a space, starts with an integer,
54
and that integer is in range (> 100).
56
* That the headers is a list (not a subclass, not another kind of
59
* That the items of the headers are tuples of strings.
61
* That there is no 'status' header (that is used in CGI, but not in
64
* That the headers don't contain newlines or colons, end in _ or -, or
65
contain characters codes below 037.
67
* That Content-Type is given if there is content (CGI often has a
68
default content type, but WSGI does not).
70
* That no Content-Type is given when there is no content (@@: is this
73
* That the exc_info argument to start_response is a tuple or None.
75
* That all calls to the writer are with strings, and no other methods
76
on the writer are accessed.
78
* That wsgi.input is used properly:
80
- .read() is called with zero or one argument
82
- That it returns a string
84
- That readline, readlines, and __iter__ return strings
86
- That .close() is not called
88
- No other methods are provided
90
* That wsgi.errors is used properly:
92
- .write() and .writelines() is called with a string
94
- That .close() is not called, and no other methods are provided.
96
* The response iterator:
98
- That it is not a string (it should be a list of a single string; a
99
string will work, but perform horribly).
101
- That .next() returns a string
103
- That the iterator is not iterated over until start_response has
104
been called (that can signal either a server or application
107
- That .close() is called (doesn't raise exception, only prints to
108
sys.stderr, because we only know it isn't called when the object
109
is garbage collected).
111
__all__ = ['validator']
116
from types import DictType, StringType, TupleType, ListType
119
header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$')
120
bad_header_value_re = re.compile(r'[\000-\037]')
122
class WSGIWarning(Warning):
124
Raised in response to WSGI-spec-related warnings
127
def assert_(cond, *args):
129
raise AssertionError(*args)
131
def validator(application):
134
When applied between a WSGI server and a WSGI application, this
135
middleware will check for WSGI compliancy on a number of levels.
136
This middleware does not modify the request or response in any
137
way, but will throw an AssertionError if anything seems off
138
(except for a failure to close the application iterator, which
139
will be printed to stderr -- there's no way to throw an exception
143
def lint_app(*args, **kw):
144
assert_(len(args) == 2, "Two arguments required")
145
assert_(not kw, "No keyword arguments allowed")
146
environ, start_response = args
148
check_environ(environ)
150
# We use this to check if the application returns without
151
# calling start_response:
152
start_response_started = []
154
def start_response_wrapper(*args, **kw):
155
assert_(len(args) == 2 or len(args) == 3, (
156
"Invalid number of arguments: %s" % (args,)))
157
assert_(not kw, "No keyword arguments allowed")
166
check_headers(headers)
167
check_content_type(status, headers)
168
check_exc_info(exc_info)
170
start_response_started.append(None)
171
return WriteWrapper(start_response(*args))
173
environ['wsgi.input'] = InputWrapper(environ['wsgi.input'])
174
environ['wsgi.errors'] = ErrorWrapper(environ['wsgi.errors'])
176
iterator = application(environ, start_response_wrapper)
177
assert_(iterator is not None and iterator != False,
178
"The application must return an iterator, if only an empty list")
180
check_iterator(iterator)
182
return IteratorWrapper(iterator, start_response_started)
188
def __init__(self, wsgi_input):
189
self.input = wsgi_input
191
def read(self, *args):
192
assert_(len(args) <= 1)
193
v = self.input.read(*args)
194
assert_(type(v) is type(""))
198
v = self.input.readline()
199
assert_(type(v) is type(""))
202
def readlines(self, *args):
203
assert_(len(args) <= 1)
204
lines = self.input.readlines(*args)
205
assert_(type(lines) is type([]))
207
assert_(type(line) is type(""))
212
line = self.readline()
218
assert_(0, "input.close() must not be called")
222
def __init__(self, wsgi_errors):
223
self.errors = wsgi_errors
226
assert_(type(s) is type(""))
232
def writelines(self, seq):
237
assert_(0, "errors.close() must not be called")
241
def __init__(self, wsgi_writer):
242
self.writer = wsgi_writer
244
def __call__(self, s):
245
assert_(type(s) is type(""))
248
class PartialIteratorWrapper:
250
def __init__(self, wsgi_iterator):
251
self.iterator = wsgi_iterator
254
# We want to make sure __iter__ is called
255
return IteratorWrapper(self.iterator, None)
257
class IteratorWrapper:
259
def __init__(self, wsgi_iterator, check_start_response):
260
self.original_iterator = wsgi_iterator
261
self.iterator = iter(wsgi_iterator)
263
self.check_start_response = check_start_response
269
assert_(not self.closed,
270
"Iterator read after closed")
271
v = self.iterator.next()
272
if self.check_start_response is not None:
273
assert_(self.check_start_response,
274
"The application returns and we started iterating over its body, but start_response has not yet been called")
275
self.check_start_response = None
280
if hasattr(self.original_iterator, 'close'):
281
self.original_iterator.close()
286
"Iterator garbage collected without being closed")
288
"Iterator garbage collected without being closed")
290
def check_environ(environ):
291
assert_(type(environ) is DictType,
292
"Environment is not of the right type: %r (environment: %r)"
293
% (type(environ), environ))
295
for key in ['REQUEST_METHOD', 'SERVER_NAME', 'SERVER_PORT',
296
'wsgi.version', 'wsgi.input', 'wsgi.errors',
297
'wsgi.multithread', 'wsgi.multiprocess',
299
assert_(key in environ,
300
"Environment missing required key: %r" % (key,))
302
for key in ['HTTP_CONTENT_TYPE', 'HTTP_CONTENT_LENGTH']:
303
assert_(key not in environ,
304
"Environment should not have the key: %s "
305
"(use %s instead)" % (key, key[5:]))
307
if 'QUERY_STRING' not in environ:
309
'QUERY_STRING is not in the WSGI environment; the cgi '
310
'module will use sys.argv when this variable is missing, '
311
'so application errors are more likely',
314
for key in environ.keys():
316
# Extension, we don't care about its type
318
assert_(type(environ[key]) is StringType,
319
"Environmental variable %s is not a string: %r (value: %r)"
320
% (key, type(environ[key]), environ[key]))
322
assert_(type(environ['wsgi.version']) is TupleType,
323
"wsgi.version should be a tuple (%r)" % (environ['wsgi.version'],))
324
assert_(environ['wsgi.url_scheme'] in ('http', 'https'),
325
"wsgi.url_scheme unknown: %r" % environ['wsgi.url_scheme'])
327
check_input(environ['wsgi.input'])
328
check_errors(environ['wsgi.errors'])
330
# @@: these need filling out:
331
if environ['REQUEST_METHOD'] not in (
332
'GET', 'HEAD', 'POST', 'OPTIONS','PUT','DELETE','TRACE'):
334
"Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'],
337
assert_(not environ.get('SCRIPT_NAME')
338
or environ['SCRIPT_NAME'].startswith('/'),
339
"SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME'])
340
assert_(not environ.get('PATH_INFO')
341
or environ['PATH_INFO'].startswith('/'),
342
"PATH_INFO doesn't start with /: %r" % environ['PATH_INFO'])
343
if environ.get('CONTENT_LENGTH'):
344
assert_(int(environ['CONTENT_LENGTH']) >= 0,
345
"Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH'])
347
if not environ.get('SCRIPT_NAME'):
348
assert_(environ.has_key('PATH_INFO'),
349
"One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO "
350
"should at least be '/' if SCRIPT_NAME is empty)")
351
assert_(environ.get('SCRIPT_NAME') != '/',
352
"SCRIPT_NAME cannot be '/'; it should instead be '', and "
353
"PATH_INFO should be '/'")
355
def check_input(wsgi_input):
356
for attr in ['read', 'readline', 'readlines', '__iter__']:
357
assert_(hasattr(wsgi_input, attr),
358
"wsgi.input (%r) doesn't have the attribute %s"
359
% (wsgi_input, attr))
361
def check_errors(wsgi_errors):
362
for attr in ['flush', 'write', 'writelines']:
363
assert_(hasattr(wsgi_errors, attr),
364
"wsgi.errors (%r) doesn't have the attribute %s"
365
% (wsgi_errors, attr))
367
def check_status(status):
368
assert_(type(status) is StringType,
369
"Status must be a string (not %r)" % status)
370
# Implicitly check that we can turn it into an integer:
371
status_code = status.split(None, 1)[0]
372
assert_(len(status_code) == 3,
373
"Status codes must be three characters: %r" % status_code)
374
status_int = int(status_code)
375
assert_(status_int >= 100, "Status code is invalid: %r" % status_int)
376
if len(status) < 4 or status[3] != ' ':
378
"The status string (%r) should be a three-digit integer "
379
"followed by a single space and a status explanation"
380
% status, WSGIWarning)
382
def check_headers(headers):
383
assert_(type(headers) is ListType,
384
"Headers (%r) must be of type list: %r"
385
% (headers, type(headers)))
388
assert_(type(item) is TupleType,
389
"Individual headers (%r) must be of type tuple: %r"
390
% (item, type(item)))
391
assert_(len(item) == 2)
393
assert_(name.lower() != 'status',
394
"The Status header cannot be used; it conflicts with CGI "
395
"script, and HTTP status is not given through headers "
396
"(value: %r)." % value)
397
header_names[name.lower()] = None
398
assert_('\n' not in name and ':' not in name,
399
"Header names may not contain ':' or '\\n': %r" % name)
400
assert_(header_re.search(name), "Bad header name: %r" % name)
401
assert_(not name.endswith('-') and not name.endswith('_'),
402
"Names may not end in '-' or '_': %r" % name)
403
if bad_header_value_re.search(value):
404
assert_(0, "Bad header value: %r (bad char: %r)"
405
% (value, bad_header_value_re.search(value).group(0)))
407
def check_content_type(status, headers):
408
code = int(status.split(None, 1)[0])
409
# @@: need one more person to verify this interpretation of RFC 2616
410
# http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
411
NO_MESSAGE_BODY = (204, 304)
412
for name, value in headers:
413
if name.lower() == 'content-type':
414
if code not in NO_MESSAGE_BODY:
416
assert_(0, ("Content-Type header found in a %s response, "
417
"which must not return content.") % code)
418
if code not in NO_MESSAGE_BODY:
419
assert_(0, "No Content-Type header found in headers (%s)" % headers)
421
def check_exc_info(exc_info):
422
assert_(exc_info is None or type(exc_info) is type(()),
423
"exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info)))
424
# More exc_info checks?
426
def check_iterator(iterator):
427
# Technically a string is legal, which is why it's a really bad
428
# idea, because it may cause the response to be returned
429
# character-by-character
430
assert_(not isinstance(iterator, str),
431
"You should not return a string as your application iterator, "
432
"instead return a single-item list containing that string.")