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   ## It's tempting to load the configuration here.  Don't do that.  Some
  95   ## contexts will want to check that the command line was handled properly
  96   ## upstream before believing it for anything, such as executing arbitrary
  97   ## Python code.
  98   return args
  99
 100 ###--------------------------------------------------------------------------
 101 ### CGI dispatch.
 102
 103 ## The special variables, to be picked out by `cgiparse'.
 104 CGI.SPECIAL['%act'] = None
 105 CGI.SPECIAL['%nonce'] = None
 106 CGI.SPECIAL['%user'] = None
 107
 108 ## We don't want to parse arguments until we've settled on a context; but
 109 ## issuing redirects in the early setup phase fails because we don't know
 110 ## the script name.  So package the setup here.
 111 def cgi_setup(ctx = 'cgi-noauth'):
 112   if OPTS: return
 113   OPTPARSE.context = ctx
 114   args = parse_options()
 115   if args: raise U.ExpectedError, (500, 'Unexpected arguments to CGI')
 116   CONF.loadconfig(OPTS.config)
 117   D.opendb()
 118
 119 def dispatch_cgi():
 120   """Examine the CGI request and invoke the appropriate command."""
 121
 122   ## Start by picking apart the request.
 123   CGI.cgiparse()
 124
 125   ## We'll be taking items off the trailing path.
 126   i, np = 0, len(CGI.PATH)
 127
 128   ## Sometimes, we want to run several actions out of the same form, so the
 129   ## subcommand name needs to be in the query string.  We use the special
 130   ## variable `%act' for this.  If it's not set, then we use the first elment
 131   ## of the path.
 132   act = CGI.SPECIAL['%act']
 133   if act is None:
 134     if i >= np:
 135       cgi_setup()
 136       CGI.redirect(CGI.action('login'))
 137       return
 138     act = CGI.PATH[i]
 139     i += 1
 140
 141   ## Figure out which context we're meant to be operating in, according to
 142   ## the requested action.  Unknown actions result in an error here; known
 143   ## actions where we don't have enough authorization send the user back to
 144   ## the login page.
 145   for ctx in ['cgi-noauth', 'cgi-query', 'cgi']:
 146     try:
 147       c = OPTPARSE.lookup_subcommand(act, exactp = True, context = ctx)
 148     except U.ExpectedError, e:
 149       if e.code != 404: raise
 150     else:
 151       break
 152   else:
 153     raise e
 154
 155   ## Parse the command line, and load configuration.
 156   cgi_setup(ctx)
 157
 158   ## Check whether we have enough authorization.  There's always enough for
 159   ## `cgi-noauth'.
 160   if ctx != 'cgi-noauth':
 161
 162     ## The next part of the URL should be the user name, so that caches don't
 163     ## cross things over.
 164     expuser = CGI.SPECIAL['%user']
 165     if expuser is None:
 166       if i >= np: raise U.ExpectedError, (404, 'Missing user name')
 167       expuser = CGI.PATH[i]
 168       i += 1
 169
 170     ## If there's no token cookie, then we have to bail.
 171     try: token = CGI.COOKIE['chpwd-token']
 172     except KeyError:
 173       CGI.redirect(CGI.action('login', why = 'NOAUTH'))
 174       return
 175
 176     ## If we only want read-only access, then the cookie is good enough.
 177     ## Otherwise we must check that a nonce was supplied, and that it is
 178     ## correct.
 179     if ctx == 'cgi-query':
 180       nonce = None
 181     else:
 182       nonce = CGI.SPECIAL['%nonce']
 183       if not nonce:
 184         CGI.redirect(CGI.action('login', why = 'NONONCE'))
 185         return
 186
 187     ## Verify the token and nonce.
 188     try:
 189       CU.USER = HA.check_auth(token, nonce)
 190     except HA.AuthenticationFailed, e:
 191       CGI.redirect(CGI.action('login', why = e.why))
 192       return
 193     if CU.USER != expuser: raise U.ExpectedError, (401, 'User mismatch')
 194     CGI.STATE.kw['user'] = CU.USER
 195
 196   ## Invoke the subcommand handler.
 197   c.cgi(CGI.PARAM, CGI.PATH[i:])
 198
 199 ###--------------------------------------------------------------------------
 200 ### Main dispatch.
 201
 202 @CTX.contextmanager
 203 def cli_errors():
 204   """Catch expected errors and report them in the traditional Unix style."""
 205   try:
 206     yield None
 207   except U.ExpectedError, e:
 208     SYS.stderr.write('%s: %s\n' % (OS.path.basename(SYS.argv[0]), e.msg))
 209     if 400 <= e.code < 500: SYS.exit(1)
 210     else: SYS.exit(2)
 211
 212 ### Main dispatch.
 213
 214 if __name__ == '__main__':
 215
 216   L.openlog(OS.path.basename(SYS.argv[0]), 0, L.LOG_AUTH)
 217
 218   if 'REQUEST_METHOD' in ENV:
 219     ## This looks like a CGI request.  The heavy lifting for authentication
 220     ## over HTTP is done in `dispatch_cgi'.
 221
 222     with OUT.redirect_to(CGI.HTTPOutput()):
 223       with U.Escape() as CGI.HEADER_DONE:
 224         with CGI.cgi_errors(cgi_setup):
 225           dispatch_cgi()
 226
 227   elif 'USERV_SERVICE' in ENV:
 228     ## This is a Userv request.  The caller's user name is helpfully in the
 229     ## `USERV_USER' environment variable.
 230
 231     with cli_errors():
 232       args = parse_options()
 233       if not args or args[0] != 'userv':
 234         raise U.ExpectedError, (500, 'missing userv token')
 235       CONF.loadconfig(OPTS.config)
 236       try: CU.set_user(ENV['USERV_USER'])
 237       except KeyError: raise ExpectedError, (500, 'USERV_USER unset')
 238       with OUT.redirect_to(O.FileOutput()):
 239         OPTPARSE.dispatch('userv', [ENV['USERV_SERVICE']] + args[1:])
 240
 241   elif 'SSH_ORIGINAL_COMMAND' in ENV:
 242     ## This looks like an SSH request; but we present two different
 243     ## interfaces over SSH.  We must distinguish them -- carefully: they have
 244     ## very different error-reporting conventions.
 245
 246     def ssh_setup():
 247       """Extract and parse the client's request from where SSH left it."""
 248       args = parse_options()
 249       CONF.loadconfig(OPTS.config)
 250       cmd = SL.split(ENV['SSH_ORIGINAL_COMMAND'])
 251       if args: raise U.ExpectedError, (500, 'Unexpected arguments via SSH')
 252       return cmd
 253
 254     if 'CHPWD_SSH_USER' in ENV:
 255       ## Setting `CHPWD_SSH_USER' to a user name is the administrator's way
 256       ## of telling us that this is a user request, so treat it like Userv.
 257
 258       with cli_errors():
 259         cmd = ssh_setup()
 260         CU.set_user(ENV['CHPWD_SSH_USER'])
 261         with OUT.redirect_to(O.FileOutput()):
 262           OPTPARSE.dispatch('userv', cmd)
 263
 264     elif 'CHPWD_SSH_MASTER' in ENV:
 265       ## Setting `CHPWD_SSH_MASTER' to anything tells us that the client is
 266       ## making a remote-service request.  We must turn on the protocol
 267       ## decoration machinery, but don't need to -- mustn't, indeed -- set up
 268       ## a user.
 269
 270       try:
 271         cmd = ssh_setup()
 272         with OUT.redirect_to(O.RemoteOutput()):
 273           OPTPARSE.dispatch('remote', map(CGI.urldecode, cmd))
 274       except U.ExpectedError, e:
 275         print 'ERR', e.code, e.msg
 276       else:
 277         print 'OK'
 278
 279     else:
 280       ## There's probably some strange botch in the `.ssh/authorized_keys'
 281       ## file, but we can't do much about it from here.
 282
 283       with cli_errors():
 284         raise U.ExpectedError, (400, "Unabled to determine SSH context")
 285
 286   else:
 287     ## Plain old command line, apparently.  We default to administration
 288     ## commands, but allow any kind, since this is useful for debugging, and
 289     ## this isn't a security problem since our caller is just as privileged
 290     ## as we are.
 291
 292     with cli_errors():
 293       args = parse_options()
 294       CONF.loadconfig(OPTS.config)
 295       CGI.SSLP = OPTS.sslp
 296       ctx = OPTS.context
 297       if OPTS.user:
 298         CU.set_user(OPTS.user)
 299         CGI.STATE.kw['user'] = OPTS.user
 300         if ctx is None: ctx = 'userv'
 301       else:
 302         D.opendb()
 303         if ctx is None:
 304           ctx = 'admin'
 305           OPTPARSE.show_global_opts = True
 306       with OUT.redirect_to(O.FileOutput()):
 307         OPTPARSE.dispatch(ctx, args)
 308
 309 ###----- That's all, folks --------------------------------------------------