#!/usr/bin/env python
#
# Copyright 2008 LShift Ltd
# Copyright 2005-2007 by Intevation GmbH <intevation@intevation.de>
# Author(s):
# Paul Crowley <paul@lshift.net>
# Thomas Arendsen Hein <thomas@intevation.de>
# with ideas from  Mathieu PASQUET <kiorky@cryptelium.net>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

"""
hg-ssh - limit access to hg repositories reached via ssh.  Part of
hg-admin-tools.

This script is called by hg-ssh-wrapper with two arguments:

hg-ssh <rulefile> <keyname>

It expects to find the command the SSH user was trying to run in the
environment variable SSH_ORIGINAL_COMMAND, and uses it to determine
what the user was trying to do and to what repository, and then checks
each rule in the rule file in turn for a matching rule which decides
what to do, defaulting to disallowing the action.
"""

# enable importing on demand to reduce startup time
from mercurial import demandimport; demandimport.enable()

from mercurial import dispatch

import sys, os, re

def fail(message):
    #logfile.write("Fail: %s\n" % message)
    sys.stderr.write(message + "\n")
    sys.exit(-1)

# Note that this currently disallows dots in path components - if you change it
# to allow them ensure that "." and ".." are disallowed in path components.
allowedchars = "A-Za-z0-9_-"
goodpathre = re.compile("([%s]+/)*[%s]+$" % (allowedchars, allowedchars))
def goodpath(path):
    if goodpathre.match(path) is None:
        fail("Disallowing path: %s" % path)

# Don't put anything except *A-Za-z0-9_- in rule globs or
# you'll probably break security.  No regexp metachars, not even .
# We may fix this later.
goodglobre = re.compile("[*/%s]+$" % allowedchars)
def globmatch(pattern, match):
    if goodglobre.match(pattern) is None:
        fail("Bad glob pattern in auth config: %s" % pattern)
    pattern = pattern.replace(".", r'\.')
    pattern = pattern.replace("*", "[%s]*" % allowedchars)
    return re.compile(pattern + "$").match(match) is not None

def testrule(rulefile, keyname, path, applicable):
    goodpath(keyname)
    goodpath(path)
    f = open(rulefile)
    try:
        for l in f:
            l = l.strip()
            if l == "" or l.startswith("#"):
                continue
            rule, rk, rp = l.split()
            if globmatch(rk, keyname) and globmatch(rp, path):
                #logfile.write("Used rule: %s\n" % l)
                return rule in applicable
    finally:
        f.close()
    return False

def get_cmd(rulefile, keyname, cmd):
    if cmd.startswith('hg -R ') and cmd.endswith(' serve --stdio'):
        path = cmd[6:-14]
        if testrule(rulefile, keyname, path, set(["allow", "init"])):
            return ['-R', path, 'serve', '--stdio']
    elif cmd.startswith('hg init '):
        path = cmd[8:]
        if testrule(rulefile, keyname, path, set(["init"])):
            return ['init', path]
    fail("Illegal command %r" % cmd)

#logfile = open("/tmp/hg-ssh.%d.txt" % os.getpid(), "w")
#logfile.write("Started: %s\n" % sys.argv)

if len(sys.argv) != 3:
    fail("hg-ssh must have exactly two arguments (%s)" 
        % sys.argv)

rulefile = sys.argv[1]
keyname = sys.argv[2]
todispatch = get_cmd(rulefile, keyname, 
    os.environ.get('SSH_ORIGINAL_COMMAND', '?'))
dispatch.dispatch(todispatch)