"""Functions for builtin CherryPy tools."""
import logging
try:
# Python 2.5+
from hashlib import md5
except ImportError:
from md5 import new
import re
import cherrypy
from cherrypy.lib import http
# Conditional HTTP request support #
def validate_etags(autotags=False):
"""Validate the current ETag against If-Match, If-None-Match headers.
If autotags is True, an ETag response-header value will be provided
from an MD5 hash of the response body (unless some other code has
already provided an ETag header). If False (the default), the ETag
will not be automatic.
WARNING: the autotags feature is not designed for URL's which allow
methods other than GET. For example, if a POST to the same URL returns
no content, the automatic ETag will be incorrect, breaking a fundamental
use for entity tags in a possibly destructive fashion. Likewise, if you
raise 304 Not Modified, the response body will be empty, the ETag hash
will be incorrect, and your application will break.
See http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.24
"""
response = cherrypy.response
# Guard against being run twice.
if hasattr(response, "ETag"):
return
status, reason, msg = _http.valid_status(response.status)
etag = response.headers.get('ETag')
# Automatic ETag generation. See warning in docstring.
if (not etag) and autotags:
if status == 200:
etag = response.collapse_body()
etag = '"%s"' % md5(etag).hexdigest()
response.headers['ETag'] = etag
response.ETag = etag
# "If the request would, without the If-Match header field, result in
# anything other than a 2xx or 412 status, then the If-Match header
# MUST be ignored."
if status >= 200 and status <= 299:
request = cherrypy.request
conditions = request.headers.elements('If-Match') or []
conditions = [str(x) for x in conditions]
if conditions and not (conditions == ["*"] or etag in conditions):
raise cherrypy.HTTPError(412, "If-Match failed: ETag %r did "
"not match %r" % (etag, conditions))
conditions = request.headers.elements('If-None-Match') or []
conditions = [str(x) for x in conditions]
if conditions == ["*"] or etag in conditions:
if request.method in ("GET", "HEAD"):
raise cherrypy.HTTPRedirect([], 304)
else:
raise cherrypy.HTTPError(412, "If-None-Match failed: ETag %r "
"matched %r" % (etag, conditions))
def validate_since():
"""Validate the current Last-Modified against If-Modified-Since headers.
If no code has set the Last-Modified response header, then no validation
will be performed.
"""
response = cherrypy.response
lastmod = response.headers.get('Last-Modified')
if lastmod:
status, reason, msg = _http.valid_status(response.status)
request = cherrypy.request
since = request.headers.get('If-Unmodified-Since')
if since and since != lastmod:
if (status >= 200 and status <= 299) or status == 412:
raise cherrypy.HTTPError(412)
since = request.headers.get('If-Modified-Since')
if since and since == lastmod:
if (status >= 200 and status <= 299) or status == 304:
if request.method in ("GET", "HEAD"):
raise cherrypy.HTTPRedirect([], 304)
else:
raise cherrypy.HTTPError(412)
# Tool code #
def proxy(base=None, local='X-Forwarded-Host', remote='X-Forwarded-For',
scheme='X-Forwarded-Proto'):
"""Change the base URL (scheme://host[:port][/path]).
For running a CP server behind Apache, lighttpd, or other HTTP server.
If you want the new request.base to include path info (not just the host),
you must explicitly set base to the full base path, and ALSO set 'local'
to '', so that the X-Forwarded-Host request header (which never includes
path info) does not override it.
cherrypy.request.remote.ip (the IP address of the client) will be
rewritten if the header specified by the 'remote' arg is valid.
By default, 'remote' is set to 'X-Forwarded-For'. If you do not
want to rewrite remote.ip, set the 'remote' arg to an empty string.
"""
request = cherrypy.request
if scheme:
s = request.headers.get(scheme, None)
if s == 'on' and 'ssl' in scheme.lower():
# This handles e.g. webfaction's 'X-Forwarded-Ssl: on' header
scheme = 'https'
else:
# This is for lighttpd/pound/Mongrel's 'X-Forwarded-Proto: https'
scheme = s
if not scheme:
scheme = request.base[:request.base.find("://")]
if local:
base = request.headers.get(local, base)
if not base:
port = cherrypy.request.local.port
if port == 80:
base = '127.0.0.1'
else:
base = '127.0.0.1:%s' % port
if base.find("://") == -1:
# add http:// or https:// if needed
base = scheme + "://" + base
request.base = base
if remote:
xff = request.headers.get(remote)
if xff:
if remote == 'X-Forwarded-For':
# See http://bob.pythonmac.org/archives/2005/09/23/apache-x-forwarded-for-caveat/
xff = xff.split(',')[-1].strip()
request.remote.ip = xff
def ignore_headers(headers=('Range',)):
"""Delete request headers whose field names are included in 'headers'.
This is a useful tool for working behind certain HTTP servers;
for example, Apache duplicates the work that CP does for 'Range'
headers, and will doubly-truncate the response.
"""
request = cherrypy.request
for name in headers:
if name in request.headers:
del request.headers[name]
def response_headers(headers=None):
"""Set headers on the response."""
for name, value in (headers or []):
cherrypy.response.headers[name] = value
response_headers.failsafe = True
def referer(pattern, accept=True, accept_missing=False, error=403,
message='Forbidden Referer header.'):
"""Raise HTTPError if Referer header does/does not match the given pattern.
pattern: a regular expression pattern to test against the Referer.
accept: if True, the Referer must match the pattern; if False,
the Referer must NOT match the pattern.
accept_missing: if True, permit requests with no Referer header.
error: the HTTP error code to return to the client on failure.
message: a string to include in the response body on failure.
"""
try:
match = bool(re.match(pattern, cherrypy.request.headers['Referer']))
if accept == match:
return
except KeyError:
if accept_missing:
return
raise cherrypy.HTTPError(error, message)
class SessionAuth(object):
"""Assert that the user is logged in."""
session_key = "username"
def check_username_and_password(self, username, password):
pass
def anonymous(self):
"""Provide a temporary user name for anonymous users."""
pass
def on_login(self, username):
pass
def on_logout(self, username):
pass
def on_check(self, username):
pass
def login_screen(self, from_page='..', username='', error_msg='', **kwargs):
return """<html><body>
Message: %(error_msg)s
<form method="post" action="do_login">
Login: <input type="text" name="username" value="%(username)s" size="10" /><br />
Password: <input type="password" name="password" size="10" /><br />
<input type="hidden" name="from_page" value="%(from_page)s" /><br />
<input type="submit" />
</form>
</body></html>""" % {'from_page': from_page, 'username': username,
'error_msg': error_msg}
def do_login(self, username, password, from_page='..', **kwargs):
"""Login. May raise redirect, or return True if request handled."""
error_msg = self.check_username_and_password(username, password)
if error_msg:
body = self.login_screen(from_page, username, error_msg)
cherrypy.response.body = body
if cherrypy.response.headers.has_key("Content-Length"):
# Delete Content-Length header so finalize() recalcs it.
del cherrypy.response.headers["Content-Length"]
return True
else:
cherrypy.session[self.session_key] = cherrypy.request.login = username
self.on_login(username)
raise cherrypy.HTTPRedirect(from_page or "/")
def do_logout(self, from_page='..', **kwargs):
"""Logout. May raise redirect, or return True if request handled."""
sess = cherrypy.session
username = sess.get(self.session_key)
sess[self.session_key] = None
if username:
cherrypy.request.login = None
self.on_logout(username)
raise cherrypy.HTTPRedirect(from_page)
def do_check(self):
"""Assert username. May raise redirect, or return True if request handled."""
sess = cherrypy.session
request = cherrypy.request
username = sess.get(self.session_key)
if not username:
sess[self.session_key] = username = self.anonymous()
if not username:
cherrypy.response.body = self.login_screen(cherrypy.url(qs=request.query_string))
if cherrypy.response.headers.has_key("Content-Length"):
# Delete Content-Length header so finalize() recalcs it.
del cherrypy.response.headers["Content-Length"]
return True
cherrypy.request.login = username
self.on_check(username)
def run(self):
request = cherrypy.request
path = request.path_info
if path.endswith('login_screen'):
return self.login_screen(**request.params)
elif path.endswith('do_login'):
return self.do_login(**request.params)
elif path.endswith('do_logout'):
return self.do_logout(**request.params)
else:
return self.do_check()
def session_auth(**kwargs):
sa = SessionAuth()
for k, v in kwargs.iteritems():
setattr(sa, k, v)
return sa.run()
session_auth.__doc__ = """Session authentication hook.
Any attribute of the SessionAuth class may be overridden via a keyword arg
to this function:
""" + "\n".join(["%s: %s" % (k, type(getattr(SessionAuth, k)).__name__)
for k in dir(SessionAuth) if not k.startswith("__")])
def log_traceback(severity=logging.DEBUG):
"""Write the last error's traceback to the cherrypy error log."""
cherrypy.log("", "HTTP", severity=severity, traceback=True)
def log_request_headers():
"""Write request headers to the cherrypy error log."""
h = [" %s: %s" % (k, v) for k, v in cherrypy.request.header_list]
cherrypy.log('\nRequest Headers:\n' + '\n'.join(h), "HTTP")
def log_hooks():
"""Write request.hooks to the cherrypy error log."""
msg = []
# Sort by the standard points if possible.
from cherrypy import _cprequest
points = _cprequest.hookpoints
for k in cherrypy.request.hooks.keys():
if k not in points:
points.append(k)
for k in points:
msg.append(" %s:" % k)
v = cherrypy.request.hooks.get(k, [])
v.sort()
for h in v:
msg.append(" %r" % h)
cherrypy.log('\nRequest Hooks for ' + cherrypy.url() +
':\n' + '\n'.join(msg), "HTTP")
def redirect(url='', internal=True):
"""Raise InternalRedirect or HTTPRedirect to the given url."""
if internal:
raise cherrypy.InternalRedirect(url)
else:
raise cherrypy.HTTPRedirect(url)
def trailing_slash(missing=True, extra=False):
"""Redirect if path_info has (missing|extra) trailing slash."""
request = cherrypy.request
pi = request.path_info
if request.is_index is True:
if missing:
if not pi.endswith('/'):
new_url = cherrypy.url(pi + '/', request.query_string)
raise cherrypy.HTTPRedirect(new_url)
elif request.is_index is False:
if extra:
# If pi == '/', don't redirect to ''!
if pi.endswith('/') and pi != '/':
new_url = cherrypy.url(pi[:-1], request.query_string)
raise cherrypy.HTTPRedirect(new_url)
def flatten():
"""Wrap response.body in a generator that recursively iterates over body.
This allows cherrypy.response.body to consist of 'nested generators';
that is, a set of generators that yield generators.
"""
import types
def flattener(input):
for x in input:
if not isinstance(x, types.GeneratorType):
yield x
else:
for y in flattener(x):
yield y
response = cherrypy.response
response.body = flattener(response.body)
def accept(media=None):
"""Return the client's preferred media-type (from the given Content-Types).
If 'media' is None (the default), no test will be performed.
If 'media' is provided, it should be the Content-Type value (as a string)
or values (as a list or tuple of strings) which the current request
can emit. The client's acceptable media ranges (as declared in the
Accept request header) will be matched in order to these Content-Type
values; the first such string is returned. That is, the return value
will always be one of the strings provided in the 'media' arg (or None
if 'media' is None).
If no match is found, then HTTPError 406 (Not Acceptable) is raised.
Note that most web browsers send */* as a (low-quality) acceptable
media range, which should match any Content-Type. In addition, "...if
no Accept header field is present, then it is assumed that the client
accepts all media types."
Matching types are checked in order of client preference first,
and then in the order of the given 'media' values.
Note that this function does not honor accept-params (other than "q").
"""
if not media:
return
if isinstance(media, basestring):
media = [media]
# Parse the Accept request header, and try to match one
# of the requested media-ranges (in order of preference).
ranges = cherrypy.request.headers.elements('Accept')
if not ranges:
# Any media type is acceptable.
return media[0]
else:
# Note that 'ranges' is sorted in order of preference
for element in ranges:
if element.qvalue > 0:
if element.value == "*/*":
# Matches any type or subtype
return media[0]
elif element.value.endswith("/*"):
# Matches any subtype
mtype = element.value[:-1] # Keep the slash
for m in media:
if m.startswith(mtype):
return m
else:
# Matches exact value
if element.value in media:
return element.value
# No suitable media-range found.
ah = cherrypy.request.headers.get('Accept')
if ah is None:
msg = "Your client did not send an Accept header."
else:
msg = "Your client sent this Accept header: %s." % ah
msg += (" But this resource only emits these media types: %s." %
", ".join(media))
raise cherrypy.HTTPError(406, msg)
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