#! @PYTHON@
### -*-python-*-
###
### Key management and distribution
###
### (c) 2006 Straylight/Edgeware
###

###----- Licensing notice ---------------------------------------------------
###
### This file is part of Trivial IP Encryption (TrIPE).
###
### TrIPE is free software; you can redistribute it and/or modify
### it under the terms of the GNU General Public License as published by
### the Free Software Foundation; either version 2 of the License, or
### (at your option) any later version.
###
### TrIPE is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU General Public License for more details.
###
### You should have received a copy of the GNU General Public License
### along with TrIPE; if not, write to the Free Software Foundation,
### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

###--------------------------------------------------------------------------
### External dependencies.

import catacomb as C
import os as OS
import sys as SYS
import re as RX
import getopt as O
import shutil as SH
import time as T
import filecmp as FC
from cStringIO import StringIO
from errno import *
from stat import *

###--------------------------------------------------------------------------
### Useful regular expressions

## Match a comment or blank line.
rx_comment = RX.compile(r'^\s*(#|$)')

## Match a KEY = VALUE assignment.
rx_keyval = RX.compile(r'^\s*([-\w]+)(?:\s+(?!=)|\s*=\s*)(|\S|\S.*\S)\s*$')

## Match a ${KEY} substitution.
rx_dollarsubst = RX.compile(r'\$\{([-\w]+)\}')

## Match a @TAG@ substitution.
rx_atsubst = RX.compile(r'@([-\w]+)@')

## Match a single non-alphanumeric character.
rx_nonalpha = RX.compile(r'\W')

## Match the literal string "<SEQ>".
rx_seq = RX.compile(r'\<SEQ\>')

## Match a shell metacharacter.
rx_shmeta = RX.compile('[\\s`!"#$&*()\\[\\];\'|<>?\\\\]')

## Match a character which needs escaping in a shell double-quoted string.
rx_shquote = RX.compile(r'["`$\\]')

###--------------------------------------------------------------------------
### Utility functions.

## Exceptions.
class SubprocessError (Exception): pass
class VerifyError (Exception): pass

## Program name and identification.
quis = OS.path.basename(SYS.argv[0])
PACKAGE = "@PACKAGE@"
VERSION = "@VERSION@"

def moan(msg):
  """Report MSG to standard error."""
  SYS.stderr.write('%s: %s\n' % (quis, msg))

def die(msg, rc = 1):
  """Report MSG to standard error, and exit with code RC."""
  moan(msg)
  SYS.exit(rc)

def subst(s, rx, map):
  """
  Substitute values into a string.

  Repeatedly match RX (a compiled regular expression) against the string S.
  For each match, extract group 1, and use it as a key to index the MAP;
  replace the match by the result.  Finally, return the fully-substituted
  string.
  """
  out = StringIO()
  i = 0
  for m in rx.finditer(s):
    out.write(s[i:m.start()] + map[m.group(1)])
    i = m.end()
  out.write(s[i:])
  return out.getvalue()

def shell_quotify(arg):
  """
  Quotify ARG to keep the shell happy.

  This isn't actually used for invoking commands, just for presentation
  purposes; but correctness is still nice.
  """
  if not rx_shmeta.search(arg):
    return arg
  elif arg.find("'") == -1:
    return "'%s'" % arg
  else:
    return '"%s"' % rx_shquote.sub(lambda m: '\\' + m.group(0), arg)

def rmtree(path):
  """Delete the directory tree given by PATH."""
  try:
    st = OS.lstat(path)
  except OSError, err:
    if err.errno == ENOENT:
      return
    raise
  if not S_ISDIR(st.st_mode):
    OS.unlink(path)
  else:
    cwd = OS.getcwd()
    try:
      OS.chdir(path)
      for i in OS.listdir('.'):
        rmtree(i)
    finally:
      OS.chdir(cwd)
    OS.rmdir(path)

def zap(file):
  """Delete the named FILE if it exists; otherwise do nothing."""
  try:
    OS.unlink(file)
  except OSError, err:
    if err.errno == ENOENT: return
    raise

def run(args):
  """
  Run a subprocess whose arguments are given by the string ARGS.

  The ARGS are split at word boundaries, and then subjected to configuration
  variable substitution (see conf_subst).  Individual argument elements
  beginning with `!' are split again into multiple arguments at word
  boundaries.
  """
  args = map(conf_subst, args.split())
  nargs = []
  for a in args:
    if len(a) > 0 and a[0] != '!':
      nargs += [a]
    else:
      nargs += a[1:].split()
  args = nargs
  print '+ %s' % ' '.join([shell_quotify(arg) for arg in args])
  SYS.stdout.flush()
  rc = OS.spawnvp(OS.P_WAIT, args[0], args)
  if rc != 0:
    raise SubprocessError, rc

def hexhyphens(bytes):
  """
  Convert a byte string BYTES into hex, with hyphens at each 4-byte boundary.
  """
  out = StringIO()
  for i in xrange(0, len(bytes)):
    if i > 0 and i % 4 == 0: out.write('-')
    out.write('%02x' % ord(bytes[i]))
  return out.getvalue()

def fingerprint(kf, ktag):
  """
  Compute the fingerprint of a key, using the user's selected hash.

  KF is the name of a keyfile; KTAG is the tag of the key.
  """
  h = C.gchashes[conf['fingerprint-hash']]()
  k = C.KeyFile(kf)[ktag].fingerprint(h, '-secret')
  return h.done()

###--------------------------------------------------------------------------
### The configuration file.

## Exceptions.
class ConfigFileError (Exception): pass

## The configuration dictionary.
conf = {}

def conf_subst(s):
  """
  Apply configuration substitutions to S.

  That is, for each ${KEY} in S, replace it with the current value of the
  configuration variable KEY.
  """
  return subst(s, rx_dollarsubst, conf)

def conf_read(f):
  """
  Read the file F and insert assignments into the configuration dictionary.
  """
  lno = 0
  for line in file(f):
    lno += 1
    if rx_comment.match(line): continue
    if line[-1] == '\n': line = line[:-1]
    match = rx_keyval.match(line)
    if not match:
      raise ConfigFileError, "%s:%d: bad line `%s'" % (f, lno, line)
    k, v = match.groups()
    conf[k] = conf_subst(v)

def conf_defaults():
  """
  Apply defaults to the configuration dictionary.

  Fill in all the interesting configuration variables based on the existing
  contents, as described in the manual.
  """
  for k, v in [('repos-base', 'tripe-keys.tar.gz'),
               ('sig-base', 'tripe-keys.sig-<SEQ>'),
               ('repos-url', '${base-url}${repos-base}'),
               ('sig-url', '${base-url}${sig-base}'),
               ('sig-file', '${base-dir}${sig-base}'),
               ('repos-file', '${base-dir}${repos-base}'),
               ('conf-file', '${base-dir}tripe-keys.conf'),
               ('upload-hook', ': run upload hook'),
               ('kx', 'dh'),
               ('kx-param', lambda: {'dh': '-LS -b3072 -B256',
                                     'ec': '-Cnist-p256'}[conf['kx']]),
               ('kx-expire', 'now + 1 year'),
               ('kx-warn-days', '28'),
               ('cipher', 'rijndael-cbc'),
               ('hash', 'sha256'),
               ('master-keygen-flags', '-l'),
               ('mgf', '${hash}-mgf'),
               ('mac', lambda: '%s-hmac/%d' %
                         (conf['hash'],
                          C.gchashes[conf['hash']].hashsz * 4)),
               ('sig', lambda: {'dh': 'dsa', 'ec': 'ecdsa'}[conf['kx']]),
               ('sig-fresh', 'always'),
               ('sig-genalg', lambda: {'kcdsa': 'dh',
                                       'dsa': 'dsa',
                                       'rsapkcs1': 'rsa',
                                       'rsapss': 'rsa',
                                       'ecdsa': 'ec',
                                       'eckcdsa': 'ec'}[conf['sig']]),
               ('sig-param', lambda: {'dh': '-LS -b3072 -B256',
                                      'dsa': '-b3072 -B256',
                                      'ec': '-Cnist-p256',
                                      'rsa': '-b3072'}[conf['sig-genalg']]),
               ('sig-hash', '${hash}'),
               ('sig-expire', 'forever'),
               ('fingerprint-hash', '${hash}')]:
    try:
      if k in conf: continue
      if type(v) == str:
        conf[k] = conf_subst(v)
      else:
        conf[k] = v()
    except KeyError, exc:
      if len(exc.args) == 0: raise
      conf[k] = '<missing-var %s>' % exc.args[0]

###--------------------------------------------------------------------------
### Key-management utilities.

def master_keys():
  """
  Iterate over the master keys.
  """
  if not OS.path.exists('master'):
    return
  for k in C.KeyFile('master').itervalues():
    if (k.type != 'tripe-keys-master' or
        k.expiredp or
        not k.tag.startswith('master-')):
      continue #??
    yield k

def master_sequence(k):
  """
  Return the sequence number of the given master key as an integer.

  No checking is done that K is really a master key.
  """
  return int(k.tag[7:])

def max_master_sequence():
  """
  Find the master key with the highest sequence number and return this
  sequence number.
  """
  seq = -1
  for k in master_keys():
    q = master_sequence(k)
    if q > seq: seq = q
  return seq

def seqsubst(x, q):
  """
  Return the value of the configuration variable X, with <SEQ> replaced by
  the value Q.
  """
  return rx_seq.sub(str(q), conf[x])

###--------------------------------------------------------------------------
### Commands: help [COMMAND...]

def version(fp = SYS.stdout):
  fp.write('%s, %s version %s\n' % (quis, PACKAGE, VERSION))

def usage(fp):
  fp.write('Usage: %s SUBCOMMAND [ARGS...]\n' % quis)

def cmd_help(args):
  if len(args) == 0:
    version(SYS.stdout)
    print
    usage(SYS.stdout)
    print """
Key management utility for TrIPE.

Options supported:

-h, --help              Show this help message.
-v, --version           Show the version number.
-u, --usage             Show pointlessly short usage string.

Subcommands available:
"""
    args = commands.keys()
    args.sort()
  for c in args:
    try: func, min, max, help = commands[c]
    except KeyError: die("unknown command `%s'" % c)
    print '%s%s%s' % (c, help and ' ', help)

###--------------------------------------------------------------------------
### Commands: newmaster

def cmd_newmaster(args):
  seq = max_master_sequence() + 1
  run('''key -kmaster add
    -a${sig-genalg} !${sig-param}
    -e${sig-expire} !${master-keygen-flags} -tmaster-%d tripe-keys-master
    sig=${sig} hash=${sig-hash}''' % seq)
  run('key -kmaster extract -f-secret repos/master.pub')

###--------------------------------------------------------------------------
### Commands: setup

def cmd_setup(args):
  OS.mkdir('repos')
  run('''key -krepos/param add
    -a${kx}-param !${kx-param}
    -eforever -tparam tripe-param
    kx-group=${kx} cipher=${cipher} hash=${hash} mac=${mac} mgf=${mgf}''')
  cmd_newmaster(args)

###--------------------------------------------------------------------------
### Commands: upload

def cmd_upload(args):

  ## Sanitize the repository directory
  umask = OS.umask(0); OS.umask(umask)
  mode = 0666 & ~umask
  for f in OS.listdir('repos'):
    ff = OS.path.join('repos', f)
    if (f.startswith('master') or f.startswith('peer-')) \
           and f.endswith('.old'):
      OS.unlink(ff)
      continue
    OS.chmod(ff, mode)

  rmtree('tmp')
  OS.mkdir('tmp')
  OS.symlink('../repos', 'tmp/repos')
  cwd = OS.getcwd()
  try:

    ## Build the configuration file
    seq = max_master_sequence()
    v = {'MASTER-SEQUENCE': str(seq),
         'HK-MASTER': hexhyphens(fingerprint('repos/master.pub',
                                             'master-%d' % seq))}
    fin = file('tripe-keys.master')
    fout = file('tmp/tripe-keys.conf', 'w')
    for line in fin:
      fout.write(subst(line, rx_atsubst, v))
    fin.close(); fout.close()
    SH.copyfile('tmp/tripe-keys.conf', conf_subst('${conf-file}.new'))
    commit = [conf['repos-file'], conf['conf-file']]

    ## Make and sign the repository archive
    OS.chdir('tmp')
    run('tar chozf ${repos-file}.new .')
    OS.chdir(cwd)
    for k in master_keys():
      seq = master_sequence(k)
      sigfile = seqsubst('sig-file', seq)
      run('''catsign -kmaster sign -abdC -kmaster-%d
        -o%s.new ${repos-file}.new''' % (seq, sigfile))
      commit.append(sigfile)

    ## Commit the changes
    for base in commit:
      new = '%s.new' % base
      OS.rename(new, base)
  finally:
    OS.chdir(cwd)
    rmtree('tmp')
  run('sh -c ${upload-hook}')

###--------------------------------------------------------------------------
### Commands: rebuild

def cmd_rebuild(args):
  zap('keyring.pub')
  for i in OS.listdir('repos'):
    if i.startswith('peer-') and i.endswith('.pub'):
      run('key -kkeyring.pub merge %s' % OS.path.join('repos', i))

###--------------------------------------------------------------------------
### Commands: update

def cmd_update(args):
  cwd = OS.getcwd()
  rmtree('tmp')
  try:

    ## Fetch a new distribution
    OS.mkdir('tmp')
    OS.chdir('tmp')
    seq = int(conf['master-sequence'])
    run('curl -s -o tripe-keys.tar.gz ${repos-url}')
    run('curl -s -o tripe-keys.sig %s' % seqsubst('sig-url', seq))
    run('tar xfz tripe-keys.tar.gz')

    ## Verify the signature
    want = C.bytes(rx_nonalpha.sub('', conf['hk-master']))
    got = fingerprint('repos/master.pub', 'master-%d' % seq)
    if want != got: raise VerifyError
    run('''catsign -krepos/master.pub verify -avC -kmaster-%d
      -t${sig-fresh} tripe-keys.sig tripe-keys.tar.gz''' % seq)

    ## OK: update our copy
    OS.chdir(cwd)
    if OS.path.exists('repos'): OS.rename('repos', 'repos.old')
    OS.rename('tmp/repos', 'repos')
    if not FC.cmp('tmp/tripe-keys.conf', 'tripe-keys.conf'):
      moan('configuration file changed: recommend running another update')
      OS.rename('tmp/tripe-keys.conf', 'tripe-keys.conf')
    rmtree('repos.old')

  finally:
    OS.chdir(cwd)
    rmtree('tmp')
  cmd_rebuild(args)

###--------------------------------------------------------------------------
### Commands: generate TAG

def cmd_generate(args):
  tag, = args
  keyring_pub = 'peer-%s.pub' % tag
  zap('keyring'); zap(keyring_pub)
  run('key -kkeyring merge repos/param')
  run('key -kkeyring add -a${kx} -pparam -e${kx-expire} -t%s tripe' %
      tag)
  run('key -kkeyring extract -f-secret %s %s' % (keyring_pub, tag))

###--------------------------------------------------------------------------
### Commands: clean

def cmd_clean(args):
  rmtree('repos')
  rmtree('tmp')
  for i in OS.listdir('.'):
    r = i
    if r.endswith('.old'): r = r[:-4]
    if (r == 'master' or r == 'param' or
        r == 'keyring' or r == 'keyring.pub' or r.startswith('peer-')):
      zap(i)

###--------------------------------------------------------------------------
### Commands: check

def check_key(k):
  now = T.time()
  thresh = int(conf['kx-warn-days']) * 86400
  if k.exptime == C.KEXP_FOREVER: return None
  elif k.exptime == C.KEXP_EXPIRE: left = -1
  else: left = k.exptime - now
  if left < 0:
    return "key `%s' HAS EXPIRED" % k.tag
  elif left < thresh:
    if left >= 86400: n, u, uu = left // 86400, 'day', 'days'
    else: n, u, uu = left // 3600, 'hour', 'hours'
    return "key `%s' EXPIRES in %d %s" % (k.tag, n, n == 1 and u or uu)
  else:
    return None

def cmd_check(args):
  if OS.path.exists('keyring.pub'):
    for k in C.KeyFile('keyring.pub').itervalues():
      whinge = check_key(k)
      if whinge is not None: print whinge
  if OS.path.exists('master'):
    whinges = []
    for k in C.KeyFile('master').itervalues():
      whinge = check_key(k)
      if whinge is None: break
      whinges.append(whinge)
    else:
      for whinge in whinges: print whinge

###--------------------------------------------------------------------------
### Commands: mtu

def cmd_mtu(args):
  mtu, = (lambda mtu = '1500': (mtu,))(*args)
  mtu = int(mtu)

  blksz = C.gcciphers[conf['cipher']].blksz

  index = conf['mac'].find('/')
  if index == -1:
    tagsz = C.gcmacs[conf['mac']].tagsz
  else:
    tagsz = int(conf['mac'][index + 1:])/8

  mtu -= 20                             # Minimum IP header
  mtu -= 8                              # UDP header
  mtu -= 1                              # TrIPE packet type octet
  mtu -= tagsz                          # MAC tag
  mtu -= 4                              # Sequence number
  mtu -= blksz                          # Initialization vector

  print mtu

###--------------------------------------------------------------------------
### Main driver.

commands = {'help': (cmd_help, 0, 1, ''),
            'newmaster': (cmd_newmaster, 0, 0, ''),
            'setup': (cmd_setup, 0, 0, ''),
            'upload': (cmd_upload, 0, 0, ''),
            'update': (cmd_update, 0, 0, ''),
            'clean': (cmd_clean, 0, 0, ''),
            'mtu': (cmd_mtu, 0, 1, '[PATH-MTU]'),
            'check': (cmd_check, 0, 0, ''),
            'generate': (cmd_generate, 1, 1, 'TAG'),
            'rebuild': (cmd_rebuild, 0, 0, '')}

def init():
  """
  Load the appropriate configuration file and set up the configuration
  dictionary.
  """
  for f in ['tripe-keys.master', 'tripe-keys.conf']:
    if OS.path.exists(f):
      conf_read(f)
      break
  conf_defaults()

def main(argv):
  """
  Main program: parse options and dispatch to appropriate command handler.
  """
  try:
    opts, args = O.getopt(argv[1:], 'hvu',
                          ['help', 'version', 'usage'])
  except O.GetoptError, exc:
    moan(exc)
    usage(SYS.stderr)
    SYS.exit(1)
  for o, v in opts:
    if o in ('-h', '--help'):
      cmd_help([])
      SYS.exit(0)
    elif o in ('-v', '--version'):
      version(SYS.stdout)
      SYS.exit(0)
    elif o in ('-u', '--usage'):
      usage(SYS.stdout)
      SYS.exit(0)
  if len(argv) < 2:
    cmd_help([])
  else:
    c = argv[1]
    try: func, min, max, help = commands[c]
    except KeyError: die("unknown command `%s'" % c)
    args = argv[2:]
    if len(args) < min or (max is not None and len(args) > max):
      SYS.stderr.write('Usage: %s %s%s%s\n' % (quis, c, help and ' ', help))
      SYS.exit(1)
    func(args)

###----- That's all, folks --------------------------------------------------

if __name__ == '__main__':
  init()
  main(SYS.argv)