| # (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 strings. |
| |
| * 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 |
| |
| - 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). |
| """ |
| __all__ = ['validator'] |
| |
| |
| import re |
| import sys |
| from types import DictType, StringType, TupleType, ListType |
| import warnings |
| |
| header_re = re.compile(r'^[a-zA-Z][a-zA-Z0-9\-_]*$') |
| bad_header_value_re = re.compile(r'[\000-\037]') |
| |
| class WSGIWarning(Warning): |
| """ |
| Raised in response to WSGI-spec-related warnings |
| """ |
| |
| def assert_(cond, *args): |
| if not cond: |
| raise AssertionError(*args) |
| |
| def validator(application): |
| |
| """ |
| 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 raise 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 raise 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_(iterator is not None and iterator != False, |
| "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: |
| |
| 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 type("")) |
| return v |
| |
| def readline(self): |
| v = self.input.readline() |
| assert_(type(v) is type("")) |
| return v |
| |
| def readlines(self, *args): |
| assert_(len(args) <= 1) |
| lines = self.input.readlines(*args) |
| assert_(type(lines) is type([])) |
| for line in lines: |
| assert_(type(line) is 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") |
| |
| class ErrorWrapper: |
| |
| def __init__(self, wsgi_errors): |
| self.errors = wsgi_errors |
| |
| def write(self, s): |
| assert_(type(s) is 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: |
| |
| def __init__(self, wsgi_writer): |
| self.writer = wsgi_writer |
| |
| def __call__(self, s): |
| assert_(type(s) is type("")) |
| self.writer(s) |
| |
| class PartialIteratorWrapper: |
| |
| def __init__(self, wsgi_iterator): |
| self.iterator = wsgi_iterator |
| |
| def __iter__(self): |
| # We want to make sure __iter__ is called |
| return IteratorWrapper(self.iterator, None) |
| |
| class IteratorWrapper: |
| |
| 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 = self.iterator.next() |
| 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 |
| return v |
| |
| def close(self): |
| self.closed = True |
| if hasattr(self.original_iterator, 'close'): |
| self.original_iterator.close() |
| |
| def __del__(self): |
| if not self.closed: |
| sys.stderr.write( |
| "Iterator garbage collected without being closed") |
| assert_(self.closed, |
| "Iterator garbage collected without being closed") |
| |
| def check_environ(environ): |
| assert_(type(environ) is DictType, |
| "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.keys(): |
| if '.' in key: |
| # Extension, we don't care about its type |
| continue |
| assert_(type(environ[key]) is StringType, |
| "Environmental variable %s is not a string: %r (value: %r)" |
| % (key, type(environ[key]), environ[key])) |
| |
| assert_(type(environ['wsgi.version']) is TupleType, |
| "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 ( |
| 'GET', 'HEAD', 'POST', 'OPTIONS','PUT','DELETE','TRACE'): |
| warnings.warn( |
| "Unknown REQUEST_METHOD: %r" % environ['REQUEST_METHOD'], |
| WSGIWarning) |
| |
| assert_(not environ.get('SCRIPT_NAME') |
| or environ['SCRIPT_NAME'].startswith('/'), |
| "SCRIPT_NAME doesn't start with /: %r" % environ['SCRIPT_NAME']) |
| assert_(not environ.get('PATH_INFO') |
| or environ['PATH_INFO'].startswith('/'), |
| "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') != '/', |
| "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) is StringType, |
| "Status must be a string (not %r)" % status) |
| # Implicitly check that we can turn it into an integer: |
| status_code = status.split(None, 1)[0] |
| assert_(len(status_code) == 3, |
| "Status codes must be three characters: %r" % status_code) |
| status_int = int(status_code) |
| assert_(status_int >= 100, "Status code is invalid: %r" % status_int) |
| if len(status) < 4 or status[3] != ' ': |
| warnings.warn( |
| "The status string (%r) should be a three-digit integer " |
| "followed by a single space and a status explanation" |
| % status, WSGIWarning) |
| |
| def check_headers(headers): |
| assert_(type(headers) is ListType, |
| "Headers (%r) must be of type list: %r" |
| % (headers, type(headers))) |
| header_names = {} |
| for item in headers: |
| assert_(type(item) is TupleType, |
| "Individual headers (%r) must be of type tuple: %r" |
| % (item, type(item))) |
| assert_(len(item) == 2) |
| name, value = item |
| 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) |
| header_names[name.lower()] = None |
| 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) |
| if bad_header_value_re.search(value): |
| assert_(0, "Bad header value: %r (bad char: %r)" |
| % (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 = (204, 304) |
| for name, value in headers: |
| if name.lower() == 'content-type': |
| if code not in NO_MESSAGE_BODY: |
| return |
| assert_(0, ("Content-Type header found in a %s response, " |
| "which must not return content.") % code) |
| if code not in NO_MESSAGE_BODY: |
| 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 type(()), |
| "exc_info (%r) is not a tuple: %r" % (exc_info, type(exc_info))) |
| # More exc_info checks? |
| |
| def check_iterator(iterator): |
| # Technically a string 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, str), |
| "You should not return a string as your application iterator, " |
| "instead return a single-item list containing that string.") |
