hgweb: support Content Security Policy
Content-Security-Policy (CSP) is a web security feature that allows
servers to declare what loaded content is allowed to do. For example,
a policy can prevent loading of images, JavaScript, CSS, etc unless
the source of that content is whitelisted (by hostname, URI scheme,
hashes of content, etc). It's a nifty security feature that provides
extra mitigation against some attacks, notably XSS.
Mitigation against these attacks is important for Mercurial because
hgweb renders repository data, which is commonly untrusted. While we
make attempts to escape things, etc, there's the possibility that
malicious data could be injected into the site content. If this happens
today, the full power of the web browser is available to that
malicious content. A restrictive CSP policy (defined by the server
operator and sent in an HTTP header which is outside the control of
malicious content), could restrict browser capabilities and mitigate
security problems posed by malicious data.
CSP works by emitting an HTTP header declaring the policy that browsers
should apply. Ideally, this header would be emitted by a layer above
Mercurial (likely the HTTP server doing the WSGI "proxying"). This
works for some CSP policies, but not all.
For example, policies to allow inline JavaScript may require setting
a "nonce" attribute on <script>. This attribute value must be unique
and non-guessable. And, the value must be present in the HTTP header
and the HTML body. This means that coordinating the value between
Mercurial and another HTTP server could be difficult: it is much
easier to generate and emit the nonce in a central location.
This commit introduces support for emitting a
Content-Security-Policy header from hgweb. A config option defines
the header value. If present, the header is emitted. A special
"%nonce%" syntax in the value triggers generation of a nonce and
inclusion in <script> elements in templates. The inclusion of a
nonce does not occur unless "%nonce%" is present. This makes this
commit completely backwards compatible and the feature opt-in.
The nonce is a type 4 UUID, which is the flavor that is randomly
generated. It has 122 random bits, which should be plenty to satisfy
the guarantees of a nonce.
# hgweb/hgwebdir_mod.py - Web interface for a directory of repositories.
#
# Copyright 21 May 2005 - (c) 2005 Jake Edge <jake@edge2.net>
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
import os
import re
import time
from ..i18n import _
from .common import (
ErrorResponse,
HTTP_NOT_FOUND,
HTTP_OK,
HTTP_SERVER_ERROR,
cspvalues,
get_contact,
get_mtime,
ismember,
paritygen,
staticfile,
)
from .request import wsgirequest
from .. import (
encoding,
error,
hg,
profiling,
scmutil,
templater,
ui as uimod,
util,
)
from . import (
hgweb_mod,
webutil,
wsgicgi,
)
def cleannames(items):
return [(util.pconvert(name).strip('/'), path) for name, path in items]
def findrepos(paths):
repos = []
for prefix, root in cleannames(paths):
roothead, roottail = os.path.split(root)
# "foo = /bar/*" or "foo = /bar/**" lets every repo /bar/N in or below
# /bar/ be served as as foo/N .
# '*' will not search inside dirs with .hg (except .hg/patches),
# '**' will search inside dirs with .hg (and thus also find subrepos).
try:
recurse = {'*': False, '**': True}[roottail]
except KeyError:
repos.append((prefix, root))
continue
roothead = os.path.normpath(os.path.abspath(roothead))
paths = scmutil.walkrepos(roothead, followsym=True, recurse=recurse)
repos.extend(urlrepos(prefix, roothead, paths))
return repos
def urlrepos(prefix, roothead, paths):
"""yield url paths and filesystem paths from a list of repo paths
>>> conv = lambda seq: [(v, util.pconvert(p)) for v,p in seq]
>>> conv(urlrepos('hg', '/opt', ['/opt/r', '/opt/r/r', '/opt']))
[('hg/r', '/opt/r'), ('hg/r/r', '/opt/r/r'), ('hg', '/opt')]
>>> conv(urlrepos('', '/opt', ['/opt/r', '/opt/r/r', '/opt']))
[('r', '/opt/r'), ('r/r', '/opt/r/r'), ('', '/opt')]
"""
for path in paths:
path = os.path.normpath(path)
yield (prefix + '/' +
util.pconvert(path[len(roothead):]).lstrip('/')).strip('/'), path
def geturlcgivars(baseurl, port):
"""
Extract CGI variables from baseurl
>>> geturlcgivars("http://host.org/base", "80")
('host.org', '80', '/base')
>>> geturlcgivars("http://host.org:8000/base", "80")
('host.org', '8000', '/base')
>>> geturlcgivars('/base', 8000)
('', '8000', '/base')
>>> geturlcgivars("base", '8000')
('', '8000', '/base')
>>> geturlcgivars("http://host", '8000')
('host', '8000', '/')
>>> geturlcgivars("http://host/", '8000')
('host', '8000', '/')
"""
u = util.url(baseurl)
name = u.host or ''
if u.port:
port = u.port
path = u.path or ""
if not path.startswith('/'):
path = '/' + path
return name, str(port), path
class hgwebdir(object):
"""HTTP server for multiple repositories.
Given a configuration, different repositories will be served depending
on the request path.
Instances are typically used as WSGI applications.
"""
def __init__(self, conf, baseui=None):
self.conf = conf
self.baseui = baseui
self.ui = None
self.lastrefresh = 0
self.motd = None
self.refresh()
def refresh(self):
refreshinterval = 20
if self.ui:
refreshinterval = self.ui.configint('web', 'refreshinterval',
refreshinterval)
# refreshinterval <= 0 means to always refresh.
if (refreshinterval > 0 and
self.lastrefresh + refreshinterval > time.time()):
return
if self.baseui:
u = self.baseui.copy()
else:
u = uimod.ui.load()
u.setconfig('ui', 'report_untrusted', 'off', 'hgwebdir')
u.setconfig('ui', 'nontty', 'true', 'hgwebdir')
# displaying bundling progress bar while serving feels wrong and may
# break some wsgi implementations.
u.setconfig('progress', 'disable', 'true', 'hgweb')
if not isinstance(self.conf, (dict, list, tuple)):
map = {'paths': 'hgweb-paths'}
if not os.path.exists(self.conf):
raise error.Abort(_('config file %s not found!') % self.conf)
u.readconfig(self.conf, remap=map, trust=True)
paths = []
for name, ignored in u.configitems('hgweb-paths'):
for path in u.configlist('hgweb-paths', name):
paths.append((name, path))
elif isinstance(self.conf, (list, tuple)):
paths = self.conf
elif isinstance(self.conf, dict):
paths = self.conf.items()
repos = findrepos(paths)
for prefix, root in u.configitems('collections'):
prefix = util.pconvert(prefix)
for path in scmutil.walkrepos(root, followsym=True):
repo = os.path.normpath(path)
name = util.pconvert(repo)
if name.startswith(prefix):
name = name[len(prefix):]
repos.append((name.lstrip('/'), repo))
self.repos = repos
self.ui = u
encoding.encoding = self.ui.config('web', 'encoding',
encoding.encoding)
self.style = self.ui.config('web', 'style', 'paper')
self.templatepath = self.ui.config('web', 'templates', None)
self.stripecount = self.ui.config('web', 'stripes', 1)
if self.stripecount:
self.stripecount = int(self.stripecount)
self._baseurl = self.ui.config('web', 'baseurl')
prefix = self.ui.config('web', 'prefix', '')
if prefix.startswith('/'):
prefix = prefix[1:]
if prefix.endswith('/'):
prefix = prefix[:-1]
self.prefix = prefix
self.lastrefresh = time.time()
def run(self):
if not encoding.environ.get('GATEWAY_INTERFACE',
'').startswith("CGI/1."):
raise RuntimeError("This function is only intended to be "
"called while running as a CGI script.")
wsgicgi.launch(self)
def __call__(self, env, respond):
req = wsgirequest(env, respond)
return self.run_wsgi(req)
def read_allowed(self, ui, req):
"""Check allow_read and deny_read config options of a repo's ui object
to determine user permissions. By default, with neither option set (or
both empty), allow all users to read the repo. There are two ways a
user can be denied read access: (1) deny_read is not empty, and the
user is unauthenticated or deny_read contains user (or *), and (2)
allow_read is not empty and the user is not in allow_read. Return True
if user is allowed to read the repo, else return False."""
user = req.env.get('REMOTE_USER')
deny_read = ui.configlist('web', 'deny_read', untrusted=True)
if deny_read and (not user or ismember(ui, user, deny_read)):
return False
allow_read = ui.configlist('web', 'allow_read', untrusted=True)
# by default, allow reading if no allow_read option has been set
if (not allow_read) or ismember(ui, user, allow_read):
return True
return False
def run_wsgi(self, req):
with profiling.maybeprofile(self.ui):
for r in self._runwsgi(req):
yield r
def _runwsgi(self, req):
try:
self.refresh()
csp, nonce = cspvalues(self.ui)
if csp:
req.headers.append(('Content-Security-Policy', csp))
virtual = req.env.get("PATH_INFO", "").strip('/')
tmpl = self.templater(req, nonce)
ctype = tmpl('mimetype', encoding=encoding.encoding)
ctype = templater.stringify(ctype)
# a static file
if virtual.startswith('static/') or 'static' in req.form:
if virtual.startswith('static/'):
fname = virtual[7:]
else:
fname = req.form['static'][0]
static = self.ui.config("web", "static", None,
untrusted=False)
if not static:
tp = self.templatepath or templater.templatepaths()
if isinstance(tp, str):
tp = [tp]
static = [os.path.join(p, 'static') for p in tp]
staticfile(static, fname, req)
return []
# top-level index
elif not virtual:
req.respond(HTTP_OK, ctype)
return self.makeindex(req, tmpl)
# nested indexes and hgwebs
repos = dict(self.repos)
virtualrepo = virtual
while virtualrepo:
real = repos.get(virtualrepo)
if real:
req.env['REPO_NAME'] = virtualrepo
try:
# ensure caller gets private copy of ui
repo = hg.repository(self.ui.copy(), real)
return hgweb_mod.hgweb(repo).run_wsgi(req)
except IOError as inst:
msg = inst.strerror
raise ErrorResponse(HTTP_SERVER_ERROR, msg)
except error.RepoError as inst:
raise ErrorResponse(HTTP_SERVER_ERROR, str(inst))
up = virtualrepo.rfind('/')
if up < 0:
break
virtualrepo = virtualrepo[:up]
# browse subdirectories
subdir = virtual + '/'
if [r for r in repos if r.startswith(subdir)]:
req.respond(HTTP_OK, ctype)
return self.makeindex(req, tmpl, subdir)
# prefixes not found
req.respond(HTTP_NOT_FOUND, ctype)
return tmpl("notfound", repo=virtual)
except ErrorResponse as err:
req.respond(err, ctype)
return tmpl('error', error=err.message or '')
finally:
tmpl = None
def makeindex(self, req, tmpl, subdir=""):
def archivelist(ui, nodeid, url):
allowed = ui.configlist("web", "allow_archive", untrusted=True)
archives = []
for typ, spec in hgweb_mod.archivespecs.iteritems():
if typ in allowed or ui.configbool("web", "allow" + typ,
untrusted=True):
archives.append({"type" : typ, "extension": spec[2],
"node": nodeid, "url": url})
return archives
def rawentries(subdir="", **map):
descend = self.ui.configbool('web', 'descend', True)
collapse = self.ui.configbool('web', 'collapse', False)
seenrepos = set()
seendirs = set()
for name, path in self.repos:
if not name.startswith(subdir):
continue
name = name[len(subdir):]
directory = False
if '/' in name:
if not descend:
continue
nameparts = name.split('/')
rootname = nameparts[0]
if not collapse:
pass
elif rootname in seendirs:
continue
elif rootname in seenrepos:
pass
else:
directory = True
name = rootname
# redefine the path to refer to the directory
discarded = '/'.join(nameparts[1:])
# remove name parts plus accompanying slash
path = path[:-len(discarded) - 1]
try:
r = hg.repository(self.ui, path)
directory = False
except (IOError, error.RepoError):
pass
parts = [name]
if 'PATH_INFO' in req.env:
parts.insert(0, req.env['PATH_INFO'].rstrip('/'))
if req.env['SCRIPT_NAME']:
parts.insert(0, req.env['SCRIPT_NAME'])
url = re.sub(r'/+', '/', '/'.join(parts) + '/')
# show either a directory entry or a repository
if directory:
# get the directory's time information
try:
d = (get_mtime(path), util.makedate()[1])
except OSError:
continue
# add '/' to the name to make it obvious that
# the entry is a directory, not a regular repository
row = {'contact': "",
'contact_sort': "",
'name': name + '/',
'name_sort': name,
'url': url,
'description': "",
'description_sort': "",
'lastchange': d,
'lastchange_sort': d[1]-d[0],
'archives': [],
'isdirectory': True,
'labels': [],
}
seendirs.add(name)
yield row
continue
u = self.ui.copy()
try:
u.readconfig(os.path.join(path, '.hg', 'hgrc'))
except Exception as e:
u.warn(_('error reading %s/.hg/hgrc: %s\n') % (path, e))
continue
def get(section, name, default=None):
return u.config(section, name, default, untrusted=True)
if u.configbool("web", "hidden", untrusted=True):
continue
if not self.read_allowed(u, req):
continue
# update time with local timezone
try:
r = hg.repository(self.ui, path)
except IOError:
u.warn(_('error accessing repository at %s\n') % path)
continue
except error.RepoError:
u.warn(_('error accessing repository at %s\n') % path)
continue
try:
d = (get_mtime(r.spath), util.makedate()[1])
except OSError:
continue
contact = get_contact(get)
description = get("web", "description", "")
seenrepos.add(name)
name = get("web", "name", name)
row = {'contact': contact or "unknown",
'contact_sort': contact.upper() or "unknown",
'name': name,
'name_sort': name,
'url': url,
'description': description or "unknown",
'description_sort': description.upper() or "unknown",
'lastchange': d,
'lastchange_sort': d[1]-d[0],
'archives': archivelist(u, "tip", url),
'isdirectory': None,
'labels': u.configlist('web', 'labels', untrusted=True),
}
yield row
sortdefault = None, False
def entries(sortcolumn="", descending=False, subdir="", **map):
rows = rawentries(subdir=subdir, **map)
if sortcolumn and sortdefault != (sortcolumn, descending):
sortkey = '%s_sort' % sortcolumn
rows = sorted(rows, key=lambda x: x[sortkey],
reverse=descending)
for row, parity in zip(rows, paritygen(self.stripecount)):
row['parity'] = parity
yield row
self.refresh()
sortable = ["name", "description", "contact", "lastchange"]
sortcolumn, descending = sortdefault
if 'sort' in req.form:
sortcolumn = req.form['sort'][0]
descending = sortcolumn.startswith('-')
if descending:
sortcolumn = sortcolumn[1:]
if sortcolumn not in sortable:
sortcolumn = ""
sort = [("sort_%s" % column,
"%s%s" % ((not descending and column == sortcolumn)
and "-" or "", column))
for column in sortable]
self.refresh()
self.updatereqenv(req.env)
return tmpl("index", entries=entries, subdir=subdir,
pathdef=hgweb_mod.makebreadcrumb('/' + subdir, self.prefix),
sortcolumn=sortcolumn, descending=descending,
**dict(sort))
def templater(self, req, nonce):
def motd(**map):
if self.motd is not None:
yield self.motd
else:
yield config('web', 'motd', '')
def config(section, name, default=None, untrusted=True):
return self.ui.config(section, name, default, untrusted)
self.updatereqenv(req.env)
url = req.env.get('SCRIPT_NAME', '')
if not url.endswith('/'):
url += '/'
vars = {}
styles = (
req.form.get('style', [None])[0],
config('web', 'style'),
'paper'
)
style, mapfile = templater.stylemap(styles, self.templatepath)
if style == styles[0]:
vars['style'] = style
start = url[-1] == '?' and '&' or '?'
sessionvars = webutil.sessionvars(vars, start)
logourl = config('web', 'logourl', 'https://mercurial-scm.org/')
logoimg = config('web', 'logoimg', 'hglogo.png')
staticurl = config('web', 'staticurl') or url + 'static/'
if not staticurl.endswith('/'):
staticurl += '/'
defaults = {
"encoding": encoding.encoding,
"motd": motd,
"url": url,
"logourl": logourl,
"logoimg": logoimg,
"staticurl": staticurl,
"sessionvars": sessionvars,
"style": style,
"nonce": nonce,
}
tmpl = templater.templater.frommapfile(mapfile, defaults=defaults)
return tmpl
def updatereqenv(self, env):
if self._baseurl is not None:
name, port, path = geturlcgivars(self._baseurl, env['SERVER_PORT'])
env['SERVER_NAME'] = name
env['SERVER_PORT'] = port
env['SCRIPT_NAME'] = path