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File fetchmail-add-contrib-fetchnmail-oauth2.py-token-acquisition-u.patch of Package fetchmail (Revision 2f28b12e70c661df3da9f584e9e8a330)

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From: Matthew Ogilvie <mmogilvi+fml@zoho.com>
Date: Thu, 1 Jun 2017 00:09:02 -0600
Subject: add contrib/fetchnmail-oauth2.py token acquisition utility
Git-repo: https://gitlab.com/fetchmail/fetchmail.git
Git-commit: c82625858682eb2396b6a49da79e403c6f2b018b

---
 contrib/README              |    6 
 contrib/fetchmail-oauth2.py |  567 ++++++++++++++++++++++++++++++++++++++++++++
 fetchmail.man               |    3 
 3 files changed, 575 insertions(+), 1 deletion(-)
 create mode 100755 contrib/fetchmail-oauth2.py

--- a/contrib/README
+++ b/contrib/README
@@ -181,6 +181,12 @@ sendmail 8.11.0 with multidrop.
 
 Watchdog script to check whether fetchmail is working in daemon mode.
 
+### fetchmail-oauth2.py
+
+Script to obtain oauth2 access tokens that "fetchmail --auth oauthbearer"
+expects in place of the password.  See --help and comments in the
+script, as well as fetchmail --auth documentation.
+
 ### mold-remover.py
 
 A short python script to remove old read mail from a pop3 mailserver.
--- /dev/null
+++ b/contrib/fetchmail-oauth2.py
@@ -0,0 +1,567 @@
+#!/usr/bin/python
+#
+# Updates: Copyright 2017 Matthew Ogilvie (mogilvie+fml at zoho.com)
+#  - Started with https://github.com/google/gmail-oauth2-tools.git
+#    commit 45c39795044c604ed126205806191a8473c0f671 dated
+#    2015-06-09.
+#  - Add file interaction (--refresh, --auto_refresh,
+#    --obtain_refresh_token_file and related options).
+#  - Support both python 2 and 3.
+#  - Keeping the same license (below).
+#
+# Copyright 2012 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+     # http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+###############
+# POSSIBLE IMPROVEMENTS:
+#
+# FUTURE: Explicitly track expiration time of access tokens,
+#   and base --auto_refresh on actual expiration time instead of
+#   simple age.
+# FUTURE: Add a mode that can print the access token by itself to
+#   stdout, presumably piped into fetchmail or similar (either both
+#   launched by a wrapper script, this launches fetchmail, or fetchmail
+#   launches this).
+# FUTURE: Mix old and new interfaces (or get rid of old interface):
+#   Support using a config file to supply some of the details
+#   for the original google modes of operation (--generate_oauth2_token,
+#   --generate_oauth2_string, --refresh_token, and --test_*).
+#   Also support providing sensative data on the command line instead
+#   of files for the new modes of operation, despite the lack
+#   of security (process listings, .bash_history files, etc).
+# FUTURE: Revise model for how to set permissions on updated files?
+#   Preserve existing?  Somehow allow setting UID/GID?  Warn if files
+#   are accessible by anyone but the current user?
+
+"""Performs client tasks for testing IMAP OAuth2 authentication.
+
+This documentation and examples is for gmail.  For other providers,
+you will likely need to track down appropriate non-default settings
+for auth_url, token_url, and scope.
+
+To use this script, you'll need to have registered with Google as an OAuth
+application and obtained an OAuth client ID and client secret.
+See https://developers.google.com/identity/protocols/OAuth2 and
+https://developers.google.com/identity/sign-in/web/devconsole-project
+for instructions on registering and for documentation of the APIs
+invoked by this code.
+
+This script has 2 main modes of operation.
+
+1. The first mode is used to generate and authorize an OAuth2 token, the
+first step in logging in via OAuth2.
+
+First, after registering your "application" (above) you should setup a
+configuration file.  Use a text editor to do the command-line equivalent of:
+
+  sed 's/^ *//' > /path/to/oauth2Config.properties << EOF
+    client_id=1038[...].apps.googleusercontent.com
+    client_secret=VWFn8LIKAMC-MsjBMhJeOplZ
+    refresh_token_file=/home/path/to/refresh_token_file
+    access_token_file=/home/path/to/access_token_file
+EOF
+
+  chmod 600 /path/to/oauth2Config.properties
+
+Then run the following, and repeat any time the refresh token stops
+working, such as when you change your password.  This is interactive
+and requires a web browser to complete:
+
+  oauth2 -c /path/to/oauth2Config.properties --obtain_refresh_token_file
+
+The script will converse with Google and generate an oauth request
+token, then present you with a URL you should visit in your browser to
+authorize the token. Once you get the verification code from the Google
+website, enter it into the script, which will then save access and referesh
+tokens to the corresponding files for later use.
+
+Also, you'll usually need to configure fetchmail by
+including a section like the following in your .fetchmailrc:
+
+    poll imap.gmail.com protocol imap
+      auth oauthbearer username "USER@gmail.com"
+      passwordfile "/home/path/to/access_token_file"
+      is LOCALUSER here sslmode wrapped sslcertck
+
+Alternative for debugging: You can also use the original google
+script interface to obtain these tokens without involving files:
+
+  oauth2 \
+    --client_id=1038[...].apps.googleusercontent.com \
+    --client_secret=VWFn8LIKAMC-MsjBMhJeOplZ \
+    --generate_oauth2_token
+
+
+-----
+2. The script will generate new access tokens using a refresh token.
+
+This uses the same config file setup above.
+
+  oauth2 -c /path/to/oauth2Config.properties --auto_refresh
+  # Or force refresh by using --refresh instead of --auto_refresh.
+
+  fetchmail -s  # or other tools configured to use the access_token_file
+  # And/or call something to update outgoing MTA relay configuration,
+  # if necessary.
+
+You may put this sequence in a short shell script,
+and configure cron to call it a few times per hour.
+
+Alternative for debugging: You can also use the original google
+script interface to refresh the token without involving files:
+
+  oauth2 \
+    --client_id=1038[...].apps.googleusercontent.com \
+    --client_secret=VWFn8LIKAMC-MsjBMhJeOplZ \
+    --refresh_token=1/Yzm6MRy4q1xi7Dx2DuWXNgT6s37OrP_DW_IoyTum4YA
+
+-----
+Google's non-file script interface also supports a few other
+testing modes; see --help.
+"""
+
+from __future__ import print_function
+import base64
+import imaplib
+import json
+from optparse import OptionParser
+import smtplib
+import sys
+import os
+import time
+
+try:
+  import urllib.request as urlopen
+  import urllib.parse as urlparse
+except ImportError:
+  import urllib as urlopen
+  import urllib as urlparse
+
+try: input = raw_input
+except NameError: pass
+
+
+def SetupOptionParser():
+  # Usage message is the module's docstring.
+  parser = OptionParser(usage=__doc__)
+  parser.add_option('-c', '--config_file',
+                    default=None,
+                    help='Configuration file for --refresh '
+                                'and --obtain_refresh_token_file.\n'
+                         'The file should contain 4 (or more) settings, '
+                                'one per line, or they can also be overridden '
+                                'by the equivalent options:\n'
+                         ' client_id=...\n'
+                         ' client_secret=...\n'
+                         ' refresh_token_file=/path/to/...\n'
+                         ' access_token_file=/path/to/...\n'
+                         '  Also max_age_sec, scope, umask, auth_url, and'
+                         ' token_url have reasonable defaults for google.')
+  parser.add_option('--auto_refresh',
+                    action='store_const',
+                    default=None,
+                    const=1,
+                    dest='refresh',
+                    help='Automatically refresh access_token_file, '
+                         'if older than max_age_sec from '
+                         'required -c /file/ info.');
+  parser.add_option('--refresh',
+                    action='store_const',
+                    const=2,
+                    dest='refresh',
+                    help='Refresh access_token_file '
+                         'unconditionally.  Requires -c /file/ info.');
+  parser.add_option('--obtain_refresh_token_file',
+                    action='store_true',
+                    dest='obtain_refresh_token_file',
+                    default=None,
+                    help='Update refresh token in file.  This is '
+                         'interactive, and requires '
+                         'a web browser.  Also requires -c /file/ info.  '
+                         'This also saves an initial access_token_file.');
+  parser.add_option('--client_id',
+                    default=None,
+                    help='Client ID of the application that is authenticating. '
+                         'See OAuth2 documentation for details.')
+  parser.add_option('--client_secret',
+                    default=None,
+                    help='Client secret of the application that is '
+                         'authenticating. See OAuth2 documentation for '
+                         'details.')
+  parser.add_option('--access_token_file',
+                    default=None,
+                    help='File name containing OAuth2 access token')
+  parser.add_option('--refresh_token_file',
+                    default=None,
+                    help='File name containing OAuth2 refresh token')
+  parser.add_option('--max_age_sec',
+                    default=None,  # manual default 3000
+                    help='default max file age for --auto_refresh.  '
+                         'Defaults to 3000 (10 minutes short of '
+                         'normal 3600 sec token expiration).')
+  parser.add_option('--umask',
+                    default=None,  # manual default 0077
+                    help='default umask for --auto_refresh and '
+                         '--obtain_refresh_token_file.  Defaults to 0077.')
+  parser.add_option('--scope',
+                    default=None,  # manual default='https://mail.google.com/'
+                    help='scope for the access token. Multiple scopes can be '
+                         'listed separated by spaces with the whole argument '
+                         'quoted.  Defaults to https://mail.google.com/')
+  parser.add_option('--auth_url',
+                    default=None,  # manual default...
+                    help='Permission URL for --obtain_refresh_token_file.  '
+                         'Defaults to https://accounts.google.com/o/oauth2/auth.')
+  parser.add_option('--token_url',
+                    default=None,  # manual default...
+                    help='Token URL for --obtain_refresh_token_file,'
+                         ' and --refresh.  '
+                         'Defaults to https://accounts.google.com/o/oauth2/token.')
+  parser.add_option('--generate_oauth2_token',
+                    action='store_true',
+                    dest='generate_oauth2_token',
+                    help='(OLD/testing) generates an OAuth2 token for testing.'
+                         '  Ignores all files.')
+  parser.add_option('--refresh_token',
+                    default=None,
+                    help='(OLD/testing) Generate a new access token using'
+                         ' this OAuth2 refresh token.  Ignores all files.')
+  parser.add_option('--user',
+                    default=None,
+                    help='(OLD/testing) email address of user whose account'
+                         ' is being accessed')
+  parser.add_option('--access_token',
+                    default=None,
+                    help='(OLD/testing) OAuth2 access token.')
+  parser.add_option('--generate_oauth2_string',
+                    action='store_true',
+                    dest='generate_oauth2_string',
+                    help='(OLD/testing) generates an initial client response'
+                         ' string for OAuth2.  Ignores all files.')
+  parser.add_option('--test_imap_authentication',
+                    action='store_true',
+                    dest='test_imap_authentication',
+                    help='(OLD/testing) attempts to authenticate to IMAP.  '
+                         'Ignores all files.')
+  parser.add_option('--test_smtp_authentication',
+                    action='store_true',
+                    dest='test_smtp_authentication',
+                    help='(OLD/testing) attempts to authenticate to SMTP.  '
+                         'Ignores all files.')
+  return parser
+
+
+# Hardcoded dummy redirect URI for non-web apps.
+REDIRECT_URI = 'urn:ietf:wg:oauth:2.0:oob'
+
+
+def UrlEscape(text):
+  # See OAUTH 5.1 for a definition of which characters need to be escaped.
+  return urlparse.quote(text, safe='~-._')
+
+
+def UrlUnescape(text):
+  # See OAUTH 5.1 for a definition of which characters need to be escaped.
+  return urlparse.unquote(text)
+
+
+def FormatUrlParams(params):
+  """Formats parameters into a URL query string.
+
+  Args:
+    params: A key-value map.
+
+  Returns:
+    A URL query string version of the given parameters.
+  """
+  param_fragments = []
+  for param in sorted(params.items(), key=lambda x: x[0]):
+    param_fragments.append('%s=%s' % (param[0], UrlEscape(param[1])))
+  return '&'.join(param_fragments)
+
+
+def GeneratePermissionUrl(client_id, scope, auth_url):
+  """Generates the URL for authorizing access.
+
+  This uses the "OAuth2 for Installed Applications" flow described at
+  https://developers.google.com/accounts/docs/OAuth2InstalledApp
+
+  Args:
+    client_id: Client ID obtained by registering your app.
+    scope: scope for access token, e.g. 'https://mail.google.com'
+  Returns:
+    A URL that the user should visit in their browser.
+  """
+  if not scope:
+    scope = 'https://mail.google.com/'
+  if not auth_url:
+    auth_url = 'https://accounts.google.com/o/oauth2/auth'
+  params = {}
+  params['client_id'] = client_id
+  params['redirect_uri'] = REDIRECT_URI
+  params['scope'] = scope
+  params['response_type'] = 'code'
+  return '%s?%s' % (auth_url, FormatUrlParams(params))
+
+
+def AuthorizeTokens(client_id, client_secret, authorization_code, token_url):
+  """Obtains OAuth access token and refresh token.
+
+  This uses the application portion of the "OAuth2 for Installed Applications"
+  flow at https://developers.google.com/accounts/docs/OAuth2InstalledApp#handlingtheresponse
+
+  Args:
+    client_id: Client ID obtained by registering your app.
+    client_secret: Client secret obtained by registering your app.
+    authorization_code: code generated by Google Accounts after user grants
+        permission.
+  Returns:
+    The decoded response from the Google Accounts server, as a dict. Expected
+    fields include 'access_token', 'expires_in', and 'refresh_token'.
+  """
+  params = {}
+  params['client_id'] = client_id
+  params['client_secret'] = client_secret
+  params['code'] = authorization_code
+  params['redirect_uri'] = REDIRECT_URI
+  params['grant_type'] = 'authorization_code'
+  if not token_url:
+    token_url = 'https://accounts.google.com/o/oauth2/token'
+
+  response = urlopen.urlopen(token_url,
+                             urlparse.urlencode(params).encode('ascii')).read()
+  return json.loads(response.decode("utf-8"))
+
+
+def RefreshToken(client_id, client_secret, refresh_token, token_url):
+  """Obtains a new token given a refresh token.
+
+  See https://developers.google.com/accounts/docs/OAuth2InstalledApp#refresh
+
+  Args:
+    client_id: Client ID obtained by registering your app.
+    client_secret: Client secret obtained by registering your app.
+    refresh_token: A previously-obtained refresh token.
+  Returns:
+    The decoded response from the Google Accounts server, as a dict. Expected
+    fields include 'access_token', 'expires_in', and 'refresh_token'.
+  """
+  params = {}
+  params['client_id'] = client_id
+  params['client_secret'] = client_secret
+  params['refresh_token'] = refresh_token
+  params['grant_type'] = 'refresh_token'
+  if not token_url:
+    token_url = 'https://accounts.google.com/o/oauth2/token'
+
+  response = urlopen.urlopen(token_url,
+                             urlparse.urlencode(params).encode('ascii')).read()
+  return json.loads(response.decode("utf-8"))
+
+
+def GenerateOAuth2String(username, access_token, base64_encode=True):
+  """Generates an IMAP OAuth2 authentication string.
+
+  See https://developers.google.com/google-apps/gmail/oauth2_overview
+
+  Args:
+    username: the username (email address) of the account to authenticate
+    access_token: An OAuth2 access token.
+    base64_encode: Whether to base64-encode the output.
+
+  Returns:
+    The SASL argument for the OAuth2 mechanism.
+  """
+  auth_string = 'user=%s\1auth=Bearer %s\1\1' % (username, access_token)
+  if base64_encode:
+    auth_string = base64.b64encode(auth_string)
+  return auth_string
+
+
+def TestImapAuthentication(user, auth_string):
+  """Authenticates to IMAP with the given auth_string.
+
+  Prints a debug trace of the attempted IMAP connection.
+
+  Args:
+    user: The Gmail username (full email address)
+    auth_string: A valid OAuth2 string, as returned by GenerateOAuth2String.
+        Must not be base64-encoded, since imaplib does its own base64-encoding.
+  """
+  print()
+  imap_conn = imaplib.IMAP4_SSL('imap.gmail.com')
+  imap_conn.debug = 4
+  imap_conn.authenticate('XOAUTH2', lambda x: auth_string)
+  imap_conn.select('INBOX')
+
+
+def TestSmtpAuthentication(user, auth_string):
+  """Authenticates to SMTP with the given auth_string.
+
+  Args:
+    user: The Gmail username (full email address)
+    auth_string: A valid OAuth2 string, not base64-encoded, as returned by
+        GenerateOAuth2String.
+  """
+  print()
+  smtp_conn = smtplib.SMTP('smtp.gmail.com', 587)
+  smtp_conn.set_debuglevel(True)
+  smtp_conn.ehlo('test')
+  smtp_conn.starttls()
+  smtp_conn.docmd('AUTH', 'XOAUTH2 ' + base64.b64encode(auth_string))
+
+
+def RequireOptions(options, *args):
+  missing = [arg for arg in args if getattr(options, arg) is None]
+  if missing:
+    print('Missing options: %s' % ' '.join(missing))
+    sys.exit(-1)
+
+def parseConfigFile(options):
+  if options.config_file:
+    cfg = dict(line.strip().split('=',1) for line in open(options.config_file))
+  else:
+    cfg = { }
+  # defaults:
+  if not 'scope' in cfg:
+    cfg['scope'] = 'https://mail.google.com/'
+  if not 'max_age_sec' in cfg:
+    cfg['max_age_sec'] = '3000'
+  if not 'umask' in cfg:
+    cfg['umask'] = '0077'
+  if not 'auth_url' in cfg:
+    cfg['auth_url'] = 'https://accounts.google.com/o/oauth2/auth'
+  if not 'token_url' in cfg:
+    cfg['token_url'] = 'https://accounts.google.com/o/oauth2/token'
+  # overrides (from command line):
+  for arg in [ 'scope', 'client_id', 'client_secret', 'umask',
+               'max_age_sec', 'access_token_file', 'refresh_token_file',
+               'auth_url', 'token_url' ]:
+    if getattr(options,arg):
+      cfg[arg] = getattr(options,arg)
+  return cfg
+
+def requireConfig(cfg, *args):
+  missing = [arg for arg in args if not arg in cfg]
+  if missing:
+    print('Missing options: %s' % ' '.join(missing))
+    sys.exit(-1)
+
+
+def main(argv):
+  options_parser = SetupOptionParser()
+  (options, args) = options_parser.parse_args()
+  if options.refresh:
+    cfg = parseConfigFile(options)
+    requireConfig(cfg, 'refresh_token_file', 'access_token_file',
+                  'client_id', 'client_secret', 'umask')
+    st = os.stat(cfg['access_token_file'])
+    if options.refresh < 2:
+       requireConfig(cfg, 'max_age_sec')
+       if time.time()-st.st_mtime < int(cfg['max_age_sec']):
+         return
+    with open(cfg['refresh_token_file'],"r") as f:
+      reftok = f.readline().rstrip()
+    if len(reftok) == 0:
+      print('refresh token is empty')
+      sys.exit(-1)
+    response = RefreshToken(cfg['client_id'],cfg['client_secret'],reftok,
+                            cfg['token_url'])
+    newTok = response['access_token']
+    if len(newTok) == 0:
+      print('failed to obtain access token: it is empty')
+      sys.exit(-1)
+    savedUmask = os.umask(int(cfg['umask'],8))
+    try:
+      with open(cfg['access_token_file']+".tmp","w") as f:
+        f.write(newTok)
+        f.write('\n')
+      os.rename(cfg['access_token_file']+".tmp",cfg['access_token_file'])
+    finally:
+      os.umask(savedUmask)
+  elif options.obtain_refresh_token_file:
+    cfg = parseConfigFile(options)
+    requireConfig(cfg, 'refresh_token_file', 'access_token_file',
+                  'client_id', 'client_secret', 'umask')
+    print('To authorize token, visit this url and follow the directions:')
+    print('  %s' % GeneratePermissionUrl(cfg['client_id'], cfg['scope'],
+                                         cfg['auth_url']))
+    authorization_code = input('Enter verification code: ')
+    response = AuthorizeTokens(cfg['client_id'], cfg['client_secret'],
+                               authorization_code, cfg['token_url'])
+    newRefTok = response['refresh_token']
+    if len(newRefTok) == 0:
+      print('failed to obtain refresh token: it is empty')
+      sys.exit(-1)
+    newTok = response['access_token']
+    if len(newTok) == 0:
+      print('failed to obtain corresponding access token: it is empty')
+      sys.exit(-1)
+    savedUmask = os.umask(int(cfg['umask'],8))
+    try:
+      with open(cfg['refresh_token_file']+".tmp","w") as f:
+        f.write(newRefTok)
+        f.write('\n')
+      os.rename(cfg['refresh_token_file']+".tmp",cfg['refresh_token_file'])
+      with open(cfg['access_token_file']+".tmp","w") as f:
+        f.write(newTok)
+        f.write('\n')
+      print("Refresh token saved to '%s'" % cfg['refresh_token_file'])
+      print("Initial access token saved to '%s'" % cfg['access_token_file'])
+      print('Access Token Expiration Seconds: %s' % response['expires_in'])
+      os.rename(cfg['access_token_file']+".tmp",cfg['access_token_file'])
+    finally:
+      os.umask(savedUmask)
+
+  ##### (OLD/testing options)
+
+  elif options.refresh_token:
+    RequireOptions(options, 'client_id', 'client_secret')
+    response = RefreshToken(options.client_id, options.client_secret,
+                            options.refresh_token, options.token_url)
+    print('Access Token: %s' % response['access_token'])
+    print('Access Token Expiration Seconds: %s' % response['expires_in'])
+  elif options.generate_oauth2_string:
+    RequireOptions(options, 'user', 'access_token')
+    print ('OAuth2 argument:\n' +
+           GenerateOAuth2String(options.user, options.access_token))
+  elif options.generate_oauth2_token:
+    RequireOptions(options, 'client_id', 'client_secret')
+    print('To authorize token, visit this url and follow the directions:')
+    print('  %s' % GeneratePermissionUrl(options.client_id, options.scope,
+                                         options.auth_url))
+    authorization_code = input('Enter verification code: ')
+    response = AuthorizeTokens(options.client_id, options.client_secret,
+                                authorization_code, options.token_url)
+    print('Refresh Token: %s' % response['refresh_token'])
+    print('Access Token: %s' % response['access_token'])
+    print('Access Token Expiration Seconds: %s' % response['expires_in'])
+  elif options.test_imap_authentication:
+    RequireOptions(options, 'user', 'access_token')
+    TestImapAuthentication(options.user,
+        GenerateOAuth2String(options.user, options.access_token,
+                             base64_encode=False))
+  elif options.test_smtp_authentication:
+    RequireOptions(options, 'user', 'access_token')
+    TestSmtpAuthentication(options.user,
+        GenerateOAuth2String(options.user, options.access_token,
+                             base64_encode=False))
+  else:
+    options_parser.print_help()
+    print('Nothing to do, exiting.')
+    return
+
+
+if __name__ == '__main__':
+  main(sys.argv)
--- a/fetchmail.man
+++ b/fetchmail.man
@@ -1062,7 +1062,8 @@ External tools are necessary to obtain
 such tokens.  Access tokens often expire fairly quickly (e.g. 1 hour),
 and new ones need to be generated from renewal tokens, so the
 "passwordfile", "passwordfd", or "pwmd_*" options may be useful.  See the
-oauth2.py script from
+contrib/fetchmail-oauth2.py script from the fetchmail source code, which
+was derived from code associated with
 .URL https://github.com/google/gmail-oauth2-tools/wiki/OAuth2DotPyRunThrough "Google's Oauth2 Run Through" ,
 and other oauth2 documentation.  For services like gmail, an "App Password"
 is probably preferable if available, because it has roughly the same

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File fetchmail-add-contrib-fetchnmail-oauth2.py-token-acquisition-u.patch of Package fetchmail (Revision 2f28b12e70c661df3da9f584e9e8a330)

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