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Editing: fetchers.py
# -*- test-case-name: openid.test.test_fetchers -*- """ This module contains the HTTP fetcher interface and several implementations. """ __all__ = [ 'fetch', 'getDefaultFetcher', 'setDefaultFetcher', 'HTTPResponse', 'HTTPFetcher', 'createHTTPFetcher', 'HTTPFetchingError', 'HTTPError' ] import urllib.request import urllib.error import urllib.parse import http.client import time import io import sys import contextlib import openid import openid.urinorm # Try to import httplib2 for caching support # http://bitworking.org/projects/httplib2/ try: import httplib2 except ImportError: # httplib2 not available httplib2 = None # try to import pycurl, which will let us use CurlHTTPFetcher try: import pycurl except ImportError: pycurl = None USER_AGENT = "python-openid/%s (%s)" % (openid.__version__, sys.platform) MAX_RESPONSE_KB = 1024 def fetch(url, body=None, headers=None): """Invoke the fetch method on the default fetcher. Most users should need only this method. @raises Exception: any exceptions that may be raised by the default fetcher """ fetcher = getDefaultFetcher() return fetcher.fetch(url, body, headers) def createHTTPFetcher(): """Create a default HTTP fetcher instance prefers Curl to urllib2.""" if pycurl is None: fetcher = Urllib2Fetcher() else: fetcher = CurlHTTPFetcher() return fetcher # Contains the currently set HTTP fetcher. If it is set to None, the # library will call createHTTPFetcher() to set it. Do not access this # variable outside of this module. _default_fetcher = None def getDefaultFetcher(): """Return the default fetcher instance if no fetcher has been set, it will create a default fetcher. @return: the default fetcher @rtype: HTTPFetcher """ global _default_fetcher if _default_fetcher is None: setDefaultFetcher(createHTTPFetcher()) return _default_fetcher def setDefaultFetcher(fetcher, wrap_exceptions=True): """Set the default fetcher @param fetcher: The fetcher to use as the default HTTP fetcher @type fetcher: HTTPFetcher @param wrap_exceptions: Whether to wrap exceptions thrown by the fetcher wil HTTPFetchingError so that they may be caught easier. By default, exceptions will be wrapped. In general, unwrapped fetchers are useful for debugging of fetching errors or if your fetcher raises well-known exceptions that you would like to catch. @type wrap_exceptions: bool """ global _default_fetcher if fetcher is None or not wrap_exceptions: _default_fetcher = fetcher else: _default_fetcher = ExceptionWrappingFetcher(fetcher) def usingCurl(): """Whether the currently set HTTP fetcher is a Curl HTTP fetcher.""" fetcher = getDefaultFetcher() if isinstance(fetcher, ExceptionWrappingFetcher): fetcher = fetcher.fetcher return isinstance(fetcher, CurlHTTPFetcher) class HTTPResponse(object): """XXX document attributes""" headers = None status = None body = None final_url = None def __init__(self, final_url=None, status=None, headers=None, body=None): self.final_url = final_url self.status = status self.headers = headers self.body = body def __repr__(self): return "<%s status %s for %s>" % (self.__class__.__name__, self.status, self.final_url) class HTTPFetcher(object): """ This class is the interface for openid HTTP fetchers. This interface is only important if you need to write a new fetcher for some reason. """ def fetch(self, url, body=None, headers=None): """ This performs an HTTP POST or GET, following redirects along the way. If a body is specified, then the request will be a POST. Otherwise, it will be a GET. @param headers: HTTP headers to include with the request @type headers: {str:str} @return: An object representing the server's HTTP response. If there are network or protocol errors, an exception will be raised. HTTP error responses, like 404 or 500, do not cause exceptions. @rtype: L{HTTPResponse} @raise Exception: Different implementations will raise different errors based on the underlying HTTP library. """ raise NotImplementedError def _allowedURL(url): parsed = urllib.parse.urlparse(url) # scheme is the first item in the tuple return parsed[0] in ('http', 'https') class HTTPFetchingError(Exception): """Exception that is wrapped around all exceptions that are raised by the underlying fetcher when using the ExceptionWrappingFetcher @ivar why: The exception that caused this exception """ def __init__(self, why=None): Exception.__init__(self, why) self.why = why class ExceptionWrappingFetcher(HTTPFetcher): """Fetcher that wraps another fetcher, causing all exceptions @cvar uncaught_exceptions: Exceptions that should be exposed to the user if they are raised by the fetch call """ uncaught_exceptions = (SystemExit, KeyboardInterrupt, MemoryError) def __init__(self, fetcher): self.fetcher = fetcher def fetch(self, *args, **kwargs): try: return self.fetcher.fetch(*args, **kwargs) except self.uncaught_exceptions: raise except: exc_cls, exc_inst = sys.exc_info()[:2] if exc_inst is None: # string exceptions exc_inst = exc_cls raise HTTPFetchingError(why=exc_inst) class Urllib2Fetcher(HTTPFetcher): """An C{L{HTTPFetcher}} that uses urllib2. """ # Parameterized for the benefit of testing frameworks, see # http://trac.openidenabled.com/trac/ticket/85 urlopen = staticmethod(urllib.request.urlopen) def fetch(self, url, body=None, headers=None): if not _allowedURL(url): raise ValueError('Bad URL scheme: %r' % (url, )) if headers is None: headers = {} headers.setdefault('User-Agent', "%s Python-urllib/%s" % (USER_AGENT, urllib.request.__version__)) if isinstance(body, str): body = bytes(body, encoding="utf-8") req = urllib.request.Request(url, data=body, headers=headers) url_resource = None try: url_resource = self.urlopen(req) with contextlib.closing(url_resource): return self._makeResponse(url_resource) except urllib.error.HTTPError as why: with contextlib.closing(why): resp = self._makeResponse(why) return resp except (urllib.error.URLError, http.client.BadStatusLine) as why: raise except Exception as why: raise AssertionError(why) def _makeResponse(self, urllib2_response): ''' Construct an HTTPResponse from the the urllib response. Attempt to decode the response body from bytes to str if the necessary information is available. ''' resp = HTTPResponse() resp.body = urllib2_response.read(MAX_RESPONSE_KB * 1024) resp.final_url = urllib2_response.geturl() resp.headers = self._lowerCaseKeys( dict(list(urllib2_response.info().items()))) if hasattr(urllib2_response, 'code'): resp.status = urllib2_response.code else: resp.status = 200 _, extra_dict = self._parseHeaderValue( resp.headers.get("content-type", "")) # Try to decode the response body to a string, if there's a # charset known; fall back to ISO-8859-1 otherwise, since that's # what's suggested in HTTP/1.1 charset = extra_dict.get('charset', 'latin1') try: resp.body = resp.body.decode(charset) except Exception: pass return resp def _lowerCaseKeys(self, headers_dict): new_dict = {} for k, v in headers_dict.items(): new_dict[k.lower()] = v return new_dict def _parseHeaderValue(self, header_value): """ Parse out a complex header value (such as Content-Type, with a value like "text/html; charset=utf-8") into a main value and a dictionary of extra information (in this case, 'text/html' and {'charset': 'utf8'}). """ values = header_value.split(';', 1) if len(values) == 1: # There's no extra info -- return the main value and an empty dict return values[0], {} main_value, extra_values = values[0], values[1].split(';') extra_dict = {} for value_string in extra_values: try: key, value = value_string.split('=', 1) extra_dict[key.strip()] = value.strip() except ValueError: # Can't unpack it -- must be malformed. Ignore pass return main_value, extra_dict class HTTPError(HTTPFetchingError): """ This exception is raised by the C{L{CurlHTTPFetcher}} when it encounters an exceptional situation fetching a URL. """ pass # XXX: define what we mean by paranoid, and make sure it is. class CurlHTTPFetcher(HTTPFetcher): """ An C{L{HTTPFetcher}} that uses pycurl for fetching. See U{http://pycurl.sourceforge.net/}. """ ALLOWED_TIME = 20 # seconds def __init__(self): HTTPFetcher.__init__(self) if pycurl is None: raise RuntimeError('Cannot find pycurl library') def _parseHeaders(self, header_file): header_file.seek(0) # Remove all non "name: value" header lines from the input lines = [line.decode().strip() for line in header_file if b':' in line] headers = {} for line in lines: try: name, value = line.split(':', 1) except ValueError: raise HTTPError("Malformed HTTP header line in response: %r" % (line, )) value = value.strip() # HTTP headers are case-insensitive name = name.lower() headers[name] = value return headers def _checkURL(self, url): # XXX: document that this can be overridden to match desired policy # XXX: make sure url is well-formed and routeable return _allowedURL(url) def fetch(self, url, body=None, headers=None): stop = int(time.time()) + self.ALLOWED_TIME off = self.ALLOWED_TIME if headers is None: headers = {} headers.setdefault('User-Agent', "%s %s" % (USER_AGENT, pycurl.version, )) header_list = [] if headers is not None: for header_name, header_value in headers.items(): header = '%s: %s' % (header_name, header_value) header_list.append(header.encode()) c = pycurl.Curl() try: c.setopt(pycurl.NOSIGNAL, 1) if header_list: c.setopt(pycurl.HTTPHEADER, header_list) # Presence of a body indicates that we should do a POST if body is not None: c.setopt(pycurl.POST, 1) c.setopt(pycurl.POSTFIELDS, body) while off > 0: if not self._checkURL(url): raise HTTPError("Fetching URL not allowed: %r" % (url, )) data = io.BytesIO() def write_data(chunk): if data.tell() > (1024 * MAX_RESPONSE_KB): return 0 else: return data.write(chunk) response_header_data = io.BytesIO() c.setopt(pycurl.WRITEFUNCTION, write_data) c.setopt(pycurl.HEADERFUNCTION, response_header_data.write) c.setopt(pycurl.TIMEOUT, off) c.setopt(pycurl.URL, openid.urinorm.urinorm(url)) c.perform() response_headers = self._parseHeaders(response_header_data) code = c.getinfo(pycurl.RESPONSE_CODE) if code in [301, 302, 303, 307]: url = response_headers.get('location') if url is None: raise HTTPError( 'Redirect (%s) returned without a location' % code) # Redirects are always GETs c.setopt(pycurl.POST, 0) # There is no way to reset POSTFIELDS to empty and # reuse the connection, but we only use it once. else: resp = HTTPResponse() resp.headers = response_headers resp.status = code resp.final_url = url resp.body = data.getvalue().decode() return resp off = stop - int(time.time()) raise HTTPError("Timed out fetching: %r" % (url, )) finally: c.close() class HTTPLib2Fetcher(HTTPFetcher): """A fetcher that uses C{httplib2} for performing HTTP requests. This implementation supports HTTP caching. @see: http://bitworking.org/projects/httplib2/ """ def __init__(self, cache=None): """@param cache: An object suitable for use as an C{httplib2} cache. If a string is passed, it is assumed to be a directory name. """ if httplib2 is None: raise RuntimeError('Cannot find httplib2 library. ' 'See http://bitworking.org/projects/httplib2/') super(HTTPLib2Fetcher, self).__init__() # An instance of the httplib2 object that performs HTTP requests self.httplib2 = httplib2.Http(cache) # We want httplib2 to raise exceptions for errors, just like # the other fetchers. self.httplib2.force_exception_to_status_code = False def fetch(self, url, body=None, headers=None): """Perform an HTTP request @raises Exception: Any exception that can be raised by httplib2 @see: C{L{HTTPFetcher.fetch}} """ if body: method = 'POST' else: method = 'GET' if headers is None: headers = {} # httplib2 doesn't check to make sure that the URL's scheme is # 'http' so we do it here. if not (url.startswith('http://') or url.startswith('https://')): raise ValueError('URL is not a HTTP URL: %r' % (url, )) httplib2_response, content = self.httplib2.request( url, method, body=body, headers=headers) # Translate the httplib2 response to our HTTP response abstraction # When a 400 is returned, there is no "content-location" # header set. This seems like a bug to me. I can't think of a # case where we really care about the final URL when it is an # error response, but being careful about it can't hurt. try: final_url = httplib2_response['content-location'] except KeyError: # We're assuming that no redirects occurred assert not httplib2_response.previous # And this should never happen for a successful response assert httplib2_response.status != 200 final_url = url return HTTPResponse( body=content.decode(), # TODO Don't assume ASCII final_url=final_url, headers=dict(list(httplib2_response.items())), status=httplib2_response.status, )
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