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hgweb: fail if an invalid command was supplied in url path (issue4071)...
hgweb: fail if an invalid command was supplied in url path (issue4071) Traditionally, the way to specify a command for hgweb was to use url query arguments (e.g. "?cmd=batch"). If the command is unknown to hgweb, it gives an error (e.g. "400 no such method: badcmd"). But there's also another way to specify a command: as a url path fragment (e.g. "/graph"). Before, hgweb was made forgiving (looks like it was made in 44c5157474e7) and user could put any unknown command in the url. If hgweb couldn't understand it, it would just silently fall back to the default command, which depends on the actual style (e.g. for paper it's shortlog, for monoblue it's summary). This was inconsistent and was breaking some tools that rely on http status codes (as noted in the issue4071). So this patch changes that behavior to the more consistent one, i.e. hgweb will now return "400 no such method: badcmd". So if some tool was relying on having an invalid command return http status code 200 and also have some information, then it will stop working. That is, if somebody typed foobar when they really meant shortlog (and the user was lucky enough to choose a style where the default command is shortlog too), that fact will now be revealed. Code-wise, the changed if block is only relevant when there's no "?cmd" query parameter (i.e. only when command is specified as a url path fragment), and looks like the removed else branch was there only for falling back to default command. With that removed, the rest of the code works as expected: it looks at the command, and if it's not known, raises a proper ErrorResponse exception with an appropriate message. Evidently, there were no tests that required the old behavior. But, frankly, I don't know any way to tell if anyone actually exploited such forgiving behavior in some in-house tool.

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commandserver.py
251 lines | 7.1 KiB | text/x-python | PythonLexer
# commandserver.py - communicate with Mercurial's API over a pipe
#
# Copyright 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 i18n import _
import struct
import sys, os
import dispatch, encoding, util
logfile = None
def log(*args):
if not logfile:
return
for a in args:
logfile.write(str(a))
logfile.flush()
class channeledoutput(object):
"""
Write data from in_ to out in the following format:
data length (unsigned int),
data
"""
def __init__(self, in_, out, channel):
self.in_ = in_
self.out = out
self.channel = channel
def write(self, data):
if not data:
return
self.out.write(struct.pack('>cI', self.channel, len(data)))
self.out.write(data)
self.out.flush()
def __getattr__(self, attr):
if attr in ('isatty', 'fileno'):
raise AttributeError(attr)
return getattr(self.in_, attr)
class channeledinput(object):
"""
Read data from in_.
Requests for input are written to out in the following format:
channel identifier - 'I' for plain input, 'L' line based (1 byte)
how many bytes to send at most (unsigned int),
The client replies with:
data length (unsigned int), 0 meaning EOF
data
"""
maxchunksize = 4 * 1024
def __init__(self, in_, out, channel):
self.in_ = in_
self.out = out
self.channel = channel
def read(self, size=-1):
if size < 0:
# if we need to consume all the clients input, ask for 4k chunks
# so the pipe doesn't fill up risking a deadlock
size = self.maxchunksize
s = self._read(size, self.channel)
buf = s
while s:
s = self._read(size, self.channel)
buf += s
return buf
else:
return self._read(size, self.channel)
def _read(self, size, channel):
if not size:
return ''
assert size > 0
# tell the client we need at most size bytes
self.out.write(struct.pack('>cI', channel, size))
self.out.flush()
length = self.in_.read(4)
length = struct.unpack('>I', length)[0]
if not length:
return ''
else:
return self.in_.read(length)
def readline(self, size=-1):
if size < 0:
size = self.maxchunksize
s = self._read(size, 'L')
buf = s
# keep asking for more until there's either no more or
# we got a full line
while s and s[-1] != '\n':
s = self._read(size, 'L')
buf += s
return buf
else:
return self._read(size, 'L')
def __iter__(self):
return self
def next(self):
l = self.readline()
if not l:
raise StopIteration
return l
def __getattr__(self, attr):
if attr in ('isatty', 'fileno'):
raise AttributeError(attr)
return getattr(self.in_, attr)
class server(object):
"""
Listens for commands on stdin, runs them and writes the output on a channel
based stream to stdout.
"""
def __init__(self, ui, repo, mode):
self.cwd = os.getcwd()
logpath = ui.config("cmdserver", "log", None)
if logpath:
global logfile
if logpath == '-':
# write log on a special 'd' (debug) channel
logfile = channeledoutput(sys.stdout, sys.stdout, 'd')
else:
logfile = open(logpath, 'a')
if repo:
# the ui here is really the repo ui so take its baseui so we don't
# end up with its local configuration
self.ui = repo.baseui
self.repo = repo
self.repoui = repo.ui
else:
self.ui = ui
self.repo = self.repoui = None
if mode == 'pipe':
self.cerr = channeledoutput(sys.stderr, sys.stdout, 'e')
self.cout = channeledoutput(sys.stdout, sys.stdout, 'o')
self.cin = channeledinput(sys.stdin, sys.stdout, 'I')
self.cresult = channeledoutput(sys.stdout, sys.stdout, 'r')
self.client = sys.stdin
else:
raise util.Abort(_('unknown mode %s') % mode)
def _read(self, size):
if not size:
return ''
data = self.client.read(size)
# is the other end closed?
if not data:
raise EOFError
return data
def runcommand(self):
""" reads a list of \0 terminated arguments, executes
and writes the return code to the result channel """
length = struct.unpack('>I', self._read(4))[0]
if not length:
args = []
else:
args = self._read(length).split('\0')
# copy the uis so changes (e.g. --config or --verbose) don't
# persist between requests
copiedui = self.ui.copy()
uis = [copiedui]
if self.repo:
self.repo.baseui = copiedui
# clone ui without using ui.copy because this is protected
repoui = self.repoui.__class__(self.repoui)
repoui.copy = copiedui.copy # redo copy protection
uis.append(repoui)
self.repo.ui = self.repo.dirstate._ui = repoui
self.repo.invalidateall()
for ui in uis:
# any kind of interaction must use server channels
ui.setconfig('ui', 'nontty', 'true', 'commandserver')
req = dispatch.request(args[:], copiedui, self.repo, self.cin,
self.cout, self.cerr)
ret = (dispatch.dispatch(req) or 0) & 255 # might return None
# restore old cwd
if '--cwd' in args:
os.chdir(self.cwd)
self.cresult.write(struct.pack('>i', int(ret)))
def getencoding(self):
""" writes the current encoding to the result channel """
self.cresult.write(encoding.encoding)
def serveone(self):
cmd = self.client.readline()[:-1]
if cmd:
handler = self.capabilities.get(cmd)
if handler:
handler(self)
else:
# clients are expected to check what commands are supported by
# looking at the servers capabilities
raise util.Abort(_('unknown command %s') % cmd)
return cmd != ''
capabilities = {'runcommand' : runcommand,
'getencoding' : getencoding}
def serve(self):
hellomsg = 'capabilities: ' + ' '.join(sorted(self.capabilities))
hellomsg += '\n'
hellomsg += 'encoding: ' + encoding.encoding
# write the hello msg in -one- chunk
self.cout.write(hellomsg)
try:
while self.serveone():
pass
except EOFError:
# we'll get here if the client disconnected while we were reading
# its request
return 1
return 0