Mailman 3 Warning about ISessionSetEnv interface - Twisted

24 May 2022

      I'm setting up a manhole with twisted.conch.manhole, and it works, but gives this warning:

Can't handle environment variables for SSH avatar
<twisted.conch.manhole_ssh.TerminalUser object at 0x7fef33174f60>:
<twisted.conch.manhole_ssh.TerminalSession object at
0x7fef33174fd0> does not provide ISessionSetEnv interface. It
should be decorated with @implementer(ISession, ISessionSetEnv) to
support env variables.

I've looked at the release notes about #9315 <https://twistedmatrix.com/trac/ticket/9315>, but can't see where in my code to add @implementer. Here's the code:

def create_shell_server(inputs):
    import pwd
    # The manhole service
    from twisted.conch import manhole, manhole_ssh
    from twisted.conch.checkers import IAuthorizedKeysDB, SSHPublicKeyChecker, readAuthorizedKeyFile
    from twisted.conch.ssh import keys
    from twisted.cred import portal
    from twisted.python.filepath import FilePath
    from zope.interface import implementer
    # pylint: disable=no-name-in-module
    from twisted.application.internet import TCPServer
    # pylint: enable=no-name-in-module

    @implementer(IAuthorizedKeysDB)
    class RunbenchAuthorizedKeysFiles(object):
        """Object that provides SSH public keys.

        There is a central file readable only by services that run as
        users who have permissions to read it, and users are allowed
        to provide their own file for use during development. The
        files have fixed names and are not overrideable by inputs or
        the environment, because that would make it harder to see
        which files a service was actually using.
        """
        def getAuthorizedKeys(self, username):
            try:
                passwd = pwd.getpwnam(bytes_to_native_str(username))
            except KeyError:
                return ()

            def read_keys(filepaths):
                for fp in filepaths:
                    if fp.exists():
                        try:
                            with fp.open() as f:
                                for key in readAuthorizedKeyFile(f, keys.Key.fromString):
                                    yield key
                        except (IOError, OSError):
                            pass
            return read_keys([
                FilePath(passwd.pw_dir).child('.ssh').child(b'runbench_manhole.pub'),
                FilePath(rb_site.runbench.keydir).child(b'manhole_authkeys')
            ])

    checker = SSHPublicKeyChecker(RunbenchAuthorizedKeysFiles())
    import gc
    from pprint import pprint
    namespace = {'sys': sys, 'time': time, 'datetime': datetime,
                 'gc': gc, 'os': os, 'reactor': reactor,
                 'runbench': runbench, 'execute': execute,
                 'pprint': pprint, 'inputs': inputs}
    class PF(ServerProtocol):
        # pylint: disable=E0202
        def protocolFactory(self, *a, **kw):
            return manhole.Manhole(namespace)

    realm = manhole_ssh.TerminalRealm()
    realm.chainedProtocolFactory = PF
    mh_portal = portal.Portal(realm)
    mh_portal.registerChecker(checker)

    cf = manhole_ssh.ConchFactory(mh_portal)
    public, private = get_rsa_keys(os.path.join(os.path.dirname(__file__), 'rb_host_rsa'))
    cf.publicKeys = {b'ssh-rsa': public}
    cf.privateKeys = {b'ssh-rsa': private}

    manhole_service = TCPServer(0, cf)
    manhole_service.startService()
    print('Started manhole service on port', manhole_service._port._realPortNumber)

What do I need to change to make this work?

Peter.

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Peter Westlake

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