###
# Copyright (c) 2015-2021, Valentin Lorentz
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
#
#   * Redistributions of source code must retain the above copyright notice,
#     this list of conditions, and the following disclaimer.
#   * Redistributions in binary form must reproduce the above copyright notice,
#     this list of conditions, and the following disclaimer in the
#     documentation and/or other materials provided with the distribution.
#   * Neither the name of the author of this software nor the name of
#     contributors to this software may be used to endorse or promote products
#     derived from this software without specific prior written consent.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

###

import re
import sys
import time
import uuid
import functools

import supybot.gpg as gpg
import supybot.conf as conf
import supybot.utils as utils
import supybot.ircdb as ircdb
from supybot.commands import *
import supybot.utils.minisix as minisix
import supybot.plugins as plugins
import supybot.commands as commands
import supybot.ircutils as ircutils
import supybot.callbacks as callbacks
if minisix.PY3:
    import http.client as http_client
else:
    import httplib as http_client
try:
    from supybot.i18n import PluginInternationalization
    _ = PluginInternationalization('GPG')
except ImportError:
    # Placeholder that allows to run the plugin on a bot
    # without the i18n module
    _ = lambda x: x

def check_gpg_available(f):
    if gpg.available:
        return f
    else:
        if not gpg.found_gnupg_lib:
            def newf(self, irc, *args):
                irc.error(_('gnupg features are not available because '
                    'the python-gnupg library is not installed.'))
        elif not gpg.found_gnupg_bin:
            def newf(self, irc, *args):
                irc.error(_('gnupg features are not available because '
                    'the gnupg executable is not installed.'))
        else:
            # This case should never happen.
            def newf(self, irc, *args):
                irc.error(_('gnupg features are not available.'))
        newf.__doc__ = f.__doc__
        newf.__name__ = f.__name__
        return newf

if hasattr(http_client, '_MAXHEADERS'):
    safe_getUrl = utils.web.getUrl
else:
    def safe_getUrl(url):
        try:
            return commands.process(utils.web.getUrl, url,
                    timeout=10, heap_size=10*1024*1024,
                    pn='GPG')
        except (commands.ProcessTimeoutError, MemoryError):
            raise utils.web.Error(_('Page is too big or the server took '
                    'too much time to answer the request.'))

class GPG(callbacks.Plugin):
    """Provides authentication based on GPG keys.

    First you must associate your GPG key with your Limnoria account. The gpg
    add command takes two arguments, key id and key server.

    My key is 0x0C207F07B2F32B67 and it's on keyserver pool.sks-keyservers.net
    so and now I add it to my bot::

        <Mikaela> +gpg add 0x0C207F07B2F32B67 pool.sks-keyservers.net
        <Yvzabevn> 1 key imported, 0 unchanged, 0 not imported.

    Now I can get token to sign so I can identify::

        <Guest45020> +gpg gettoken
        <Yvzabevn> Your token is: {03640620-97ea-4fdf-b0c3-ce8fb62f2dc5}. Please sign it with your GPG key, paste it somewhere, and call the 'auth' command with the URL to the (raw) file containing the signature.

    Then I follow the instructions and sign my token in terminal::

        echo "{03640620-97ea-4fdf-b0c3-ce8fb62f2dc5}"|gpg --clearsign|curl -F 'sprunge=<-' http://sprunge.us

    Note that I sent the output to curl with flags to directly send the
    clearsigned content to sprunge.us pastebin. Curl should be installed on
    most of distributions and comes with msysgit. If you remove the curl part,
    you get the output to terminal and can pastebin it to any pastebin of
    your choice. Sprunge.us has only plain text and is easy so I used it in
    this example.

    And last I give the bot link to the plain text signature::

        <Guest45020> +gpg auth http://sprunge.us/DUdd
        <Yvzabevn> You are now authenticated as Mikaela.
    """
    class key(callbacks.Commands):
        @check_gpg_available
        def add(self, irc, msg, args, user, keyid, keyserver):
            """<key id> <key server>

            Add a GPG key to your account."""
            if keyid in user.gpgkeys:
                irc.error(_('This key is already associated with your '
                    'account.'))
                return
            result = gpg.keyring.recv_keys(keyserver, keyid)
            reply = format(_('%n imported, %i unchanged, %i not imported.'),
                    (result.imported, _('key')),
                    result.unchanged,
                    result.not_imported,
                    [x['fingerprint'] for x in result.results])
            if result.imported == 1:
                user.gpgkeys.append(keyid)
                irc.reply(reply)
            else:
                irc.error(reply)
        add = wrap(add, ['user',
                         ('somethingWithoutSpaces',
                             _('You must give a valid key id')),
                         ('somethingWithoutSpaces',
                             _('You must give a valid key server'))])

        @check_gpg_available
        def remove(self, irc, msg, args, user, fingerprint):
            """<fingerprint>

            Remove a GPG key from your account."""
            try:
                keyids = [x['keyid'] for x in gpg.keyring.list_keys()
                        if x['fingerprint'] == fingerprint]
                if len(keyids) == 0:
                    raise ValueError
                for keyid in keyids:
                    try:
                        user.gpgkeys.remove(keyid)
                    except ValueError:
                        user.gpgkeys.remove('0x' + keyid)
                gpg.keyring.delete_keys(fingerprint)
                irc.replySuccess()
            except ValueError:
                irc.error(_('GPG key not associated with your account.'))
        remove = wrap(remove, ['user', 'somethingWithoutSpaces'])

        @check_gpg_available
        def list(self, irc, msg, args, user):
            """takes no arguments

            List your GPG keys."""
            keyids = user.gpgkeys
            if len(keyids) == 0:
                irc.reply(_('No key is associated with your account.'))
            else:
                irc.reply(format('%L', keyids))
        list = wrap(list, ['user'])

    class signing(callbacks.Commands):
        def __init__(self, *args):
            super(GPG.signing, self).__init__(*args)
            self._tokens = {}

        def _expire_tokens(self):
            now = time.time()
            self._tokens = dict(filter(lambda x_y: x_y[1][1]>now,
                self._tokens.items()))

        @check_gpg_available
        def gettoken(self, irc, msg, args):
            """takes no arguments

            Send you a token that you'll have to sign with your key."""
            self._expire_tokens()
            token = '{%s}' % str(uuid.uuid4())
            lifetime = conf.supybot.plugins.GPG.auth.sign.TokenTimeout()
            self._tokens.update({token: (msg.prefix, time.time()+lifetime)})
            irc.reply(_('Your token is: %s. Please sign it with your '
                'GPG key, paste it somewhere, and call the \'auth\' '
                'command with the URL to the (raw) file containing the '
                'signature.') % token)
        gettoken = wrap(gettoken, [])

        _auth_re = re.compile(r'-----BEGIN PGP SIGNED MESSAGE-----\r?\n'
                r'Hash: .*\r?\n\r?\n'
                r'\s*({[0-9a-z-]+})\s*\r?\n'
                r'-----BEGIN PGP SIGNATURE-----\r?\n.*'
                r'\r?\n-----END PGP SIGNATURE-----',
                re.S)
        
        @check_gpg_available
        def auth(self, irc, msg, args, url):
            """<url>

            Check the GPG signature at the <url> and authenticates you if
            the key used is associated to a user."""
            self._expire_tokens()
            content = safe_getUrl(url)
            if minisix.PY3 and isinstance(content, bytes):
                content = content.decode()
            match = self._auth_re.search(content)
            if not match:
                irc.error(_('Signature or token not found.'), Raise=True)
            data = match.group(0)
            token = match.group(1)
            if token not in self._tokens:
                irc.error(_('Unknown token. It may have expired before you '
                    'submit it.'), Raise=True)
            if self._tokens[token][0] != msg.prefix:
                irc.error(_('Your hostname/nick changed in the process. '
                    'Authentication aborted.'), Raise=True)
            verified = gpg.keyring.verify(data)
            if verified and verified.valid:
                keyid = verified.pubkey_fingerprint[-16:]
                prefix, expiry = self._tokens.pop(token)
                found = False
                for (id, user) in ircdb.users.items():
                    if keyid in [x[-len(keyid):] for x in user.gpgkeys]:
                        try:
                            user.addAuth(msg.prefix)
                        except ValueError:
                            irc.error(_('Your secure flag is true and your '
                                      'hostmask doesn\'t match any of your '
                                      'known hostmasks.'), Raise=True)
                        ircdb.users.setUser(user, flush=False)
                        irc.reply(_('You are now authenticated as %s.') %
                                user.name)
                        return
                irc.error(_('Unknown GPG key.'), Raise=True)
            else:
                irc.error(_('Signature could not be verified. Make sure '
                    'this is a valid GPG signature and the URL is valid.'))
        auth = wrap(auth, ['url'])


Class = GPG


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