| # (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, 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 collections |
| import re |
| import warnings |
| from six import PY3 |
| from six import binary_type |
| from six import string_types |
| |
| 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 |
| """ |
| |
| |
| 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, collections.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_py3(string, message): |
| if PY3 and type(string) is str: |
| try: |
| string.encode('latin1') |
| except UnicodeEncodeError: |
| raise AssertionError(message) |
| |
| |
| 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_py3( |
| name, |
| "Headers values must be latin1 string or bytes." |
| "%r is not a valid latin1 string" % (value,) |
| ) |
| str_name = to_string(name) |
| assert str_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 str_name and ':' not in str_name, ( |
| "Header names may not contain ':' or '\\n': %r" % name) |
| assert header_re.search(str_name), "Bad header name: %r" % name |
| assert not str_name.endswith('-') and not str_name.endswith('_'), ( |
| "Names may not end in '-' or '_': %r" % name) |
| _assert_latin1_py3( |
| value, |
| "Headers values must be latin1 string or bytes." |
| "%r is not a valid latin1 string" % (value,) |
| ) |
| str_value = to_string(value) |
| assert not bad_header_value_re.search(str_value), ( |
| "Bad header value: %r (bad char: %r)" |
| % (str_value, bad_header_value_re.search(str_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: |
| str_name = to_string(name) |
| if str_name.lower() == 'content-length' and value.isdigit(): |
| length = int(value) |
| break |
| for name, value in headers: |
| str_name = to_string(name) |
| if str_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'] |
