mercurial_keyring.py

# -*- coding: utf-8 -*-
#
# mercurial_keyring: save passwords in password database
#
# Copyright 2009 Marcin Kasperski <[e-mail]>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.

"""
=================
mercurial_keyring
=================

Mercurial extension to securely save HTTP authentication passwords
in password databases (Gnome Keyring, KDE KWallet, OSXKeyChain, 
specific solutions for Win32 and command line). Uses and wraps
services of the keyring_ library.

.. _keyring: http://pypi.python.org/pypi/keyring

How does it work
================

The extension prompts for the password on the first pull/push as it is
done by default, but saves the given password (keyed by the
combination of username and remote repository url) in the password
database. On the next run it checks for the username in ``.hg/hgrc``,
then for suitable password in the password database, and uses those
credentials if found.

In case password turns out incorrect (either because it was invalid,
or because it was changed on the server) it just prompts the user
again.

Installation
============

Install keyring library:

::

    easy_install keyring

(or ``pip keyring``)

Either save mercurial_keyring.py anywhere and put the following
in ~/.hgrc (or /etc/mercurial/hgrc):

::

    [extensions]
    hgext.mercurial_keyring = /path/to/mercurial_keyring.py

or save mercurial_keyring.py to mercurial/hgext directory and use

::

    [extensions]
    hgext.mercurial_keyring = 

Password backend configuration
==============================

The library should usually pick the most appropriate password backend
without configuration. Still, if necessary, it can be configured using
``~/keyringrc.cfg`` file (``keyringrc.cfg`` in the home directory of
the current user). Refer to keyring_ docs for more details.

*I considered handling similar options in hgrc, but decided that
single person may use more than one keyring-based script. Still, I am
open to suggestions.*

Repository configuration
========================

Edit repository-local ``.hg/hgrc`` and save there the remote repository
path and the username, but do not save the password. For example:

::

    [paths]
    myremote = https://my.server.com/hgrepo/someproject

    [auth]
    myremote.schemes = http https
    myremote.prefix = my.server.com/hgrepo
    myremote.username = mekk

Simpler form with url-embedded name can also be used:

::

    [paths]
    bitbucket = https://[e-mail]/User/project_name/

Note: if both username and password are given in ``.hg/hgrc``, extension
will use them without using the password database. If username is not
given, extension will prompt for credentials every time, also without
saving the password. 

Usage
=====

Configure the repository as above, then just pull and push.
You should be asked for the password only once (per every
username+remote_repository_url combination).

Implementation details
======================

The extension is monkey-patching the mercurial passwordmgr class
to replace the find_user_password method. 

"""

from mercurial import hg, repo, util
from mercurial.i18n import _
try:
	from mercurial.url import passwordmgr
except:
	from mercurial.httprepo import passwordmgr
from mercurial.httprepo import httprepository

import keyring
import getpass
from urlparse import urlparse
import urllib2

KEYRING_SERVICE = "Mercurial"

############################################################

def monkeypatch_method(cls):
    def decorator(func):
        setattr(cls, func.__name__, func)
        return func
    return decorator

############################################################

class PasswordStore(object):
    """
    Helper object handling keyring usage (password save&restore,
    the way passwords are keyed in the keyring).
    """
    def __init__(self):
        self.cache = dict()
    def get_password(self, url, username):
        return keyring.get_password(KEYRING_SERVICE,
                                    self._format_key(url, username))
    def set_password(self, url, username, password):
        keyring.set_password(KEYRING_SERVICE,
                             self._format_key(url, username),
                             password)
    def clear_password(self, url, username):
        self.set_password(url, username, "")
    def _format_key(self, url, username):
        return "%s@@%s" % (username, url)

password_store = PasswordStore()

############################################################

class PasswordHandler(object):
    """
    Actual implementation of password handling (user prompting,
    configuration file searching, keyring save&restore).

    Object of this class is bound as passwordmgr attribute.
    """
    def __init__(self):
        self.pwd_cache = {}
        self.last_reply = None

    def find_auth(self, pwmgr, realm, authuri):
        """
        Actual implementation of find_user_password - different
        ways of obtaining the username and password.
        """
        ui = pwmgr.ui

        # If we are called again just after identical previous
        # request, then the previously returned auth must have been
        # wrong. So we note this to force password prompt (and avoid
        # reusing bad password indifinitely).
        after_bad_auth = (self.last_reply \
           and (self.last_reply['realm'] == realm) \
           and (self.last_reply['authuri'] == authuri))
           
        # Strip arguments to get actual remote repository url.
        base_url = self.canonical_url(authuri)

        # Extracting possible username (or password)
        # stored directly in repository url
        user, pwd = urllib2.HTTPPasswordMgrWithDefaultRealm.find_user_password(pwmgr, realm, authuri)
        if user and pwd:
           self._debug_reply(ui, _("Auth data found in repository URL"), base_url, user, pwd)
           self.last_reply = dict(realm=realm,authuri=authuri,user=user)
           return user, pwd

        # Checking the memory cache (there may be many http calls per command)
        cache_key = (realm, base_url)
        if not after_bad_auth:
           cached_auth = self.pwd_cache.get(cache_key)
           if cached_auth:
              user, pwd = cached_auth
              self._debug_reply(ui, _("Cached auth data found"), base_url, user, pwd)
              self.last_reply = dict(realm=realm,authuri=authuri,user=user)
              return user, pwd

        # Loading username and maybe password from [auth] in .hg/hgrc
        nuser, pwd = self.load_hgrc_auth(ui, base_url)
        if nuser:
           if user:
              raise util.Abort(_('mercurial_keyring: username for %s specified both in repository path (%s) and in .hg/hgrc/[auth] (%s). Please, leave only one of those' % (base_url, user, nuser)))
           user = nuser
           if pwd:
              self.pwd_cache[cache_key] = user, pwd
              self._debug_reply(ui, _("Auth data set in .hg/hgrc"), base_url, user, pwd)
              self.last_reply = dict(realm=realm,authuri=authuri,user=user)
              return user, pwd
           else:
              ui.debug(_("Username found in .hg/hgrc: %s\n" % user))

        # Loading password from keyring. 
        # Only if username is known (so we know the key) and we are not after failure (so
        # we don't reuse the bad password).
        if user and not after_bad_auth:
           pwd = password_store.get_password(base_url, user)
           if pwd:
              self.pwd_cache[cache_key] = user, pwd
              self._debug_reply(ui, _("Keyring password found"), base_url, user, pwd)
              self.last_reply = dict(realm=realm,authuri=authuri,user=user)
              return user, pwd
        
        # Is the username permanently set?
        fixed_user = (user and True or False)

        # Last resort: interactive prompt
        if not ui.interactive():
           raise util.Abort(_('mercurial_keyring: http authorization required'))
        ui.write(_("http authorization required\n"))
        ui.status(_("realm: %s\n") % realm)
        if fixed_user:
           ui.write(_("user: %s (fixed in .hg/hgrc)\n" % user))
        else:
           user = ui.prompt(_("user:"), default=None)
        pwd = ui.getpass(_("password: "))

        if fixed_user:
           # Saving password to the keyring.
           # It is done only if username is fixed. Otherwise we won't
           # be able to find the password so it does not make much sense to 
           # preserve it
           ui.debug("Saving password for %s to keyring\n" % user)
           password_store.set_password(base_url, user, pwd)

        # Saving password to the memory cache
        self.pwd_cache[cache_key] = user, pwd

        self._debug_reply(ui, _("Manually entered password"), base_url, user, pwd)
        self.last_reply = dict(realm=realm,authuri=authuri,user=user)
        return user, pwd

    def load_hgrc_auth(self, ui, base_url):
        """
        Loading username and possibly password from [auth] in local
        repo .hgrc
        """
        # Theoretically 3 lines below should do. 
        #
        # Unfortunately they do not work, readauthtoken always return
        # None. Why? Because ui (self.ui of passwordmgr) describes the
        # *remote* repository, so does *not* contain any option from
        # local .hg/hgrc.

        #auth_token = self.readauthtoken(base_url)
        #if auth_token:
        #   user, pwd = auth.get('username'), auth.get('password')
     
        # Workaround: we recreate the repository object
        repo_root = ui.config("bundle", "mainreporoot")
        if repo_root:
           from mercurial.ui import ui as _ui
           import os
           local_ui = _ui(ui)
           local_ui.readconfig(os.path.join(repo_root, ".hg", "hgrc"))
           local_passwordmgr = passwordmgr(local_ui)
           auth_token = local_passwordmgr.readauthtoken(base_url)
           if auth_token:
              return auth_token.get('username'), auth_token.get('password')
        return None, None


    def canonical_url(self, authuri):
        """
        Strips query params from url. Used to convert
        https://repo.machine.com/repos/apps/module?pairs=0000000000000000000000000000000000000000-0000000000000000000000000000000000000000&cmd=between
        to
        https://repo.machine.com/repos/apps/module
        """
        parsed_url = urlparse(authuri)
        return "%s://%s%s" % (parsed_url.scheme, parsed_url.netloc, parsed_url.path)

    def _debug_reply(self, ui, msg, url, user, pwd):
        ui.debug("%s. Url: %s, user: %s, passwd: %s\n" % (msg, url, user, pwd and '*' * len(pwd) or 'not set'))

############################################################

@monkeypatch_method(passwordmgr)
def find_user_password(self, realm, authuri):
    """
    keyring-based implementation of username/password query

    Passwords are saved in gnome keyring, OSX/Chain or other platform
    specific storage and keyed by the repository url
    """
    # Extend object attributes
    if not hasattr(self, '_pwd_handler'):
       self._pwd_handler = PasswordHandler()

    return self._pwd_handler.find_auth(self, realm, authuri)