mdw@git.distorted.org.uk Git - chopwood/blob - chpwd

   1 #! /usr/bin/python
   2 ###
   3 ### Password management
   4 ###
   5 ### (c) 2012 Mark Wooding
   6 ###
   7
   8 ###----- Licensing notice ---------------------------------------------------
   9 ###
  10 ### This file is part of Chopwood: a password-changing service.
  11 ###
  12 ### Chopwood is free software; you can redistribute it and/or modify
  13 ### it under the terms of the GNU Affero General Public License as
  14 ### published by the Free Software Foundation; either version 3 of the
  15 ### License, or (at your option) any later version.
  16 ###
  17 ### Chopwood is distributed in the hope that it will be useful,
  18 ### but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ### GNU Affero General Public License for more details.
  21 ###
  22 ### You should have received a copy of the GNU Affero General Public
  23 ### License along with Chopwood; if not, see
  24 ### <http://www.gnu.org/licenses/>.
  25
  26 from __future__ import with_statement
  27
  28 import contextlib as CTX
  29 import optparse as OP
  30 import os as OS; ENV = OS.environ
  31 import shlex as SL
  32 import sys as SYS
  33 import syslog as L
  34
  35 from auto import HOME, VERSION
  36 import cgi as CGI
  37 import cmdutil as CU
  38 import config as CONF; CFG = CONF.CFG
  39 import dbmaint as D
  40 import httpauth as HA
  41 import output as O; OUT = O.OUT
  42 import service as S
  43 import subcommand as SC
  44 import util as U
  45
  46 for i in ['admin', 'cgi', 'remote', 'user']:
  47   __import__('cmd-' + i)
  48
  49 ###--------------------------------------------------------------------------
  50 ### Parsing command-line options.
  51
  52 ## Command-line options parser.
  53 OPTPARSE = SC.SubcommandOptionParser(
  54   usage = '%prog SUBCOMMAND [ARGS ...]',
  55   version = '%%prog, verion %s' % VERSION,
  56   contexts = ['admin', 'userv', 'remote', 'cgi', 'cgi-query', 'cgi-noauth'],
  57   commands = SC.COMMANDS,
  58   description = """\
  59 Manage all of those annoying passwords.
  60
  61 This is free software, and you can redistribute it and/or modify it
  62 under the terms of the GNU Affero General Public License
  63 <http://www.gnu.org/licenses/agpl-3.0.html>.  For a `.tar.gz' file
  64 of the source code, use the `source' command.
  65 """)
  66
  67 OPTS = None
  68
  69 ## Set up the global options.
  70 for short, long, props in [
  71   ('-c', '--context', {
  72     'metavar': 'CONTEXT', 'dest': 'context', 'default': None,
  73     'help': 'run commands with the given CONTEXT' }),
  74   ('-f', '--config-file', {
  75     'metavar': 'FILE', 'dest': 'config',
  76     'default': ENV.get('CHPWD_CONFIG',
  77                        OS.path.join(HOME, 'chpwd.conf')),
  78     'help': 'read configuration from FILE.' }),
  79   ('-s', '--ssl', {
  80     'dest': 'sslp', 'action': 'store_true',
  81     'help': 'pretend CGI connection is carried over SSL/TLS' }),
  82   ('-u', '--user', {
  83     'metavar': 'USER', 'dest': 'user', 'default': None,
  84     'help': "impersonate USER, and default context to `userv'." })]:
  85   OPTPARSE.add_option(short, long, **props)
  86
  87 def parse_options():
  88   """
  89   Parse the main command-line options, returning the positional arguments.
  90   """
  91   global OPTS
  92   OPTS, args = OPTPARSE.parse_args()
  93   OPTPARSE.show_global_opts = False
  94   CFG.OPTS = OPTS
  95   ## It's tempting to load the configuration here.  Don't do that.  Some
  96   ## contexts will want to check that the command line was handled properly
  97   ## upstream before believing it for anything, such as executing arbitrary
  98   ## Python code.
  99   return args
 100
 101 ###--------------------------------------------------------------------------
 102 ### CGI dispatch.
 103
 104 ## The special variables, to be picked out by `cgiparse'.
 105 CGI.SPECIAL['%act'] = None
 106 CGI.SPECIAL['%nonce'] = None
 107 CGI.SPECIAL['%user'] = None
 108
 109 ## We don't want to parse arguments until we've settled on a context; but
 110 ## issuing redirects in the early setup phase fails because we don't know
 111 ## the script name.  So package the setup here.
 112 def cgi_setup(ctx = 'cgi-noauth'):
 113   if OPTS: return
 114   OPTPARSE.context = ctx
 115   args = parse_options()
 116   if args: raise U.ExpectedError, (500, 'Unexpected arguments to CGI')
 117   CONF.loadconfig(OPTS.config)
 118   D.opendb()
 119
 120 def dispatch_cgi():
 121   """Examine the CGI request and invoke the appropriate command."""
 122
 123   ## Start by picking apart the request.
 124   CGI.cgiparse()
 125
 126   ## We'll be taking items off the trailing path.
 127   i, np = 0, len(CGI.PATH)
 128
 129   ## Sometimes, we want to run several actions out of the same form, so the
 130   ## subcommand name needs to be in the query string.  We use the special
 131   ## variable `%act' for this.  If it's not set, then we use the first elment
 132   ## of the path.
 133   act = CGI.SPECIAL['%act']
 134   if act is None:
 135     if i >= np:
 136       cgi_setup()
 137       CGI.redirect(CGI.action('login'))
 138       return
 139     act = CGI.PATH[i]
 140     i += 1
 141
 142   ## Figure out which context we're meant to be operating in, according to
 143   ## the requested action.  Unknown actions result in an error here; known
 144   ## actions where we don't have enough authorization send the user back to
 145   ## the login page.
 146   for ctx in ['cgi-noauth', 'cgi-query', 'cgi']:
 147     try:
 148       c = OPTPARSE.lookup_subcommand(act, exactp = True, context = ctx)
 149     except U.ExpectedError, e:
 150       if e.code != 404: raise
 151     else:
 152       break
 153   else:
 154     raise e
 155
 156   ## Parse the command line, and load configuration.
 157   cgi_setup(ctx)
 158
 159   ## Check whether we have enough authorization.  There's always enough for
 160   ## `cgi-noauth'.
 161   if ctx != 'cgi-noauth':
 162
 163     ## The next part of the URL should be the user name, so that caches don't
 164     ## cross things over.
 165     expuser = CGI.SPECIAL['%user']
 166     if expuser is None:
 167       if i >= np: raise U.ExpectedError, (404, 'Missing user name')
 168       expuser = CGI.PATH[i]
 169       i += 1
 170
 171     ## If there's no token cookie, then we have to bail.
 172     try: token = CGI.COOKIE['chpwd-token']
 173     except KeyError:
 174       CGI.redirect(CGI.action('login', why = 'NOAUTH'))
 175       return
 176
 177     ## If we only want read-only access, then the cookie is good enough.
 178     ## Otherwise we must check that a nonce was supplied, and that it is
 179     ## correct.
 180     if ctx == 'cgi-query':
 181       nonce = None
 182     else:
 183       nonce = CGI.SPECIAL['%nonce']
 184       if not nonce:
 185         CGI.redirect(CGI.action('login', why = 'NONONCE'))
 186         return
 187
 188     ## Verify the token and nonce.
 189     try:
 190       CU.USER = HA.check_auth(token, nonce)
 191     except HA.AuthenticationFailed, e:
 192       CGI.redirect(CGI.action('login', why = e.why))
 193       return
 194     if CU.USER != expuser: raise U.ExpectedError, (401, 'User mismatch')
 195     CGI.STATE.kw['user'] = CU.USER
 196
 197   ## Invoke the subcommand handler.
 198   c.cgi(CGI.PARAM, CGI.PATH[i:])
 199
 200 ###--------------------------------------------------------------------------
 201 ### Main dispatch.
 202
 203 @CTX.contextmanager
 204 def cli_errors():
 205   """Catch expected errors and report them in the traditional Unix style."""
 206   try:
 207     yield None
 208   except U.ExpectedError, e:
 209     SYS.stderr.write('%s: %s\n' % (OS.path.basename(SYS.argv[0]), e.msg))
 210     if 400 <= e.code < 500: SYS.exit(1)
 211     else: SYS.exit(2)
 212
 213 ### Main dispatch.
 214
 215 if __name__ == '__main__':
 216
 217   L.openlog(OS.path.basename(SYS.argv[0]), 0, L.LOG_AUTH)
 218
 219   if 'REQUEST_METHOD' in ENV:
 220     ## This looks like a CGI request.  The heavy lifting for authentication
 221     ## over HTTP is done in `dispatch_cgi'.
 222
 223     with OUT.redirect_to(CGI.HTTPOutput()):
 224       with U.Escape() as CGI.HEADER_DONE:
 225         with CGI.cgi_errors(cgi_setup):
 226           dispatch_cgi()
 227
 228   elif 'USERV_SERVICE' in ENV:
 229     ## This is a Userv request.  The caller's user name is helpfully in the
 230     ## `USERV_USER' environment variable.
 231
 232     with cli_errors():
 233       with OUT.redirect_to(O.FileOutput()):
 234         args = parse_options()
 235         if not args or args[0] != 'userv':
 236           raise U.ExpectedError, (500, 'missing userv token')
 237         CONF.loadconfig(OPTS.config)
 238         try: CU.set_user(ENV['USERV_USER'])
 239         except KeyError: raise ExpectedError, (500, 'USERV_USER unset')
 240         OPTPARSE.dispatch('userv', [ENV['USERV_SERVICE']] + args[1:])
 241
 242   elif 'SSH_ORIGINAL_COMMAND' in ENV:
 243     ## This looks like an SSH request; but we present two different
 244     ## interfaces over SSH.  We must distinguish them -- carefully: they have
 245     ## very different error-reporting conventions.
 246
 247     def ssh_setup():
 248       """Extract and parse the client's request from where SSH left it."""
 249       args = parse_options()
 250       CONF.loadconfig(OPTS.config)
 251       cmd = SL.split(ENV['SSH_ORIGINAL_COMMAND'])
 252       if args: raise U.ExpectedError, (500, 'Unexpected arguments via SSH')
 253       return cmd
 254
 255     if 'CHPWD_SSH_USER' in ENV:
 256       ## Setting `CHPWD_SSH_USER' to a user name is the administrator's way
 257       ## of telling us that this is a user request, so treat it like Userv.
 258
 259       with cli_errors():
 260         with OUT.redirect_to(O.FileOutput()):
 261           cmd = ssh_setup()
 262           CU.set_user(ENV['CHPWD_SSH_USER'])
 263           OPTPARSE.dispatch('userv', cmd)
 264
 265     elif 'CHPWD_SSH_MASTER' in ENV:
 266       ## Setting `CHPWD_SSH_MASTER' to anything tells us that the client is
 267       ## making a remote-service request.  We must turn on the protocol
 268       ## decoration machinery, but don't need to -- mustn't, indeed -- set up
 269       ## a user.
 270
 271       try:
 272         with OUT.redirect_to(O.RemoteOutput()):
 273           cmd = ssh_setup()
 274           OPTPARSE.dispatch('remote', map(CGI.urldecode, cmd))
 275       except U.ExpectedError, e:
 276         print 'ERR', e.code, e.msg
 277       else:
 278         print 'OK'
 279
 280     else:
 281       ## There's probably some strange botch in the `.ssh/authorized_keys'
 282       ## file, but we can't do much about it from here.
 283
 284       with cli_errors():
 285         raise U.ExpectedError, (400, "Unabled to determine SSH context")
 286
 287   else:
 288     ## Plain old command line, apparently.  We default to administration
 289     ## commands, but allow any kind, since this is useful for debugging, and
 290     ## this isn't a security problem since our caller is just as privileged
 291     ## as we are.
 292
 293     with cli_errors():
 294       with OUT.redirect_to(O.FileOutput()):
 295         args = parse_options()
 296         CONF.loadconfig(OPTS.config)
 297         CGI.SSLP = OPTS.sslp
 298         ctx = OPTS.context
 299         if OPTS.user:
 300           CU.set_user(OPTS.user)
 301           CGI.STATE.kw['user'] = OPTS.user
 302           if ctx is None: ctx = 'userv'
 303         else:
 304           D.opendb()
 305           if ctx is None:
 306             ctx = 'admin'
 307             OPTPARSE.show_global_opts = True
 308         OPTPARSE.dispatch(ctx, args)
 309
 310 ###----- That's all, folks --------------------------------------------------