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