Make authentication mechanisms configurable
Added configuration option "auth_mechanisms" to the config file: it is a list of mechanisms that will be tried in the specified order. Author: Andreas Mack <andreas.mack@konsec.com> Signed-off-by: Eygene Ryabinkin <rea@codelabs.ru>
This commit is contained in:
Andreas Mack
Eygene Ryabinkin
parent
968d5520da
commit
e26827c1cb
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@ -19,6 +19,8 @@ WIP (add new stuff for the next release)
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* Support SASL PLAIN authentication method. (Andreas Mack)
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* Support transport-only tunnels that requre full IMAP authentication.
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(Steve Purcell)
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* Make the list of authentication mechanisms to be configurable.
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(Andreas Mack)
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OfflineIMAP v6.5.5-rc1 (2012-09-05)
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===================================
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@ -361,10 +361,24 @@ remoteuser = username
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# intact, but remote identity changes.
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#
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# Currently this variable is used only for SASL PLAIN authentication
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# mechanism.
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# mechanism, so consider using auth_mechanisms to prioritize PLAIN
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# or even make it the only mechanism to be tried.
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#
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# remote_identity = authzuser
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# Specify which authentication/authorization mechanisms we should try
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# and the order in which OfflineIMAP will try them. NOTE: any given
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# mechanism will be tried only if it is supported by the remote IMAP
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# server.
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#
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# Due to the technical limitations, if you're specifying GSSAPI
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# as the mechanism to try, it will be tried first, no matter where
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# it was specified in the list.
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#
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# Default value is
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# auth_mechanisms = GSSAPI, CRAM-MD5, PLAIN, LOGIN
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# ranged is from strongest to more weak ones.
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########## Passwords
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# There are six ways to specify the password for the IMAP server:
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@ -15,11 +15,12 @@
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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try:
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from ConfigParser import SafeConfigParser
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from ConfigParser import SafeConfigParser, Error, NoOptionError
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except ImportError: #python3
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from configparser import SafeConfigParser
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from configparser import SafeConfigParser, Error, NoOptionError
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from offlineimap.localeval import LocalEval
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import os
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import re
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class CustomConfigParser(SafeConfigParser):
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def getdefault(self, section, option, default, *args, **kwargs):
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@ -48,6 +49,25 @@ class CustomConfigParser(SafeConfigParser):
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else:
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return default
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def getlist(self, section, option, separator_re):
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"""
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Parses option as the list of values separated
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by the given regexp.
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"""
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try:
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val = self.get(section, option).strip()
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return re.split(separator_re, val)
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except re.error as e:
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raise Error("Bad split regexp '%s': %s" % \
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(separator_re, e))
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def getdefaultlist(self, section, option, default, separator_re):
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if self.has_option(section, option):
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return self.getlist(*(section, option, separator_re))
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else:
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return default
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def getmetadatadir(self):
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metadatadir = os.path.expanduser(self.getdefault("general", "metadata", "~/.offlineimap"))
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if not os.path.exists(metadatadir):
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@ -97,12 +117,14 @@ class ConfigHelperMixin:
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will then return the configuration values for the ConfigParser
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object in the specific section."""
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def _confighelper_runner(self, option, default, defaultfunc, mainfunc):
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def _confighelper_runner(self, option, default, defaultfunc, mainfunc, *args):
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"""Return config value for getsection()"""
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lst = [self.getsection(), option]
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if default == CustomConfigDefault:
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return mainfunc(*[self.getsection(), option])
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return mainfunc(*(lst + list(args)))
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else:
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return defaultfunc(*[self.getsection(), option, default])
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lst.append(default)
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return defaultfunc(*(lst + list(args)))
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def getconf(self, option,
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@ -125,3 +147,9 @@ class ConfigHelperMixin:
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return self._confighelper_runner(option, default,
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self.getconfig().getdefaultfloat,
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self.getconfig().getfloat)
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def getconflist(self, option, separator_re,
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default = CustomConfigDefault):
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return self._confighelper_runner(option, default,
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self.getconfig().getdefaultlist,
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self.getconfig().getlist, separator_re)
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@ -67,6 +67,7 @@ class IMAPServer:
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self.username = \
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None if self.preauth_tunnel else repos.getuser()
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self.user_identity = repos.get_remote_identity()
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self.authmechs = repos.get_auth_mechanisms()
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self.password = None
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self.passworderror = None
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self.goodpassword = None
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@ -195,6 +196,73 @@ class IMAPServer:
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return base64.b64decode(response)
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def _start_tls(self, imapobj):
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if 'STARTTLS' in imapobj.capabilities and not self.usessl:
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self.ui.debug('imap', 'Using STARTTLS connection')
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try:
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imapobj.starttls()
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except imapobj.error as e:
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raise OfflineImapError("Failed to start "
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"TLS connection: %s" % str(e),
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OfflineImapError.ERROR.REPO)
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## All _authn_* procedures are helpers that do authentication.
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## They are class methods that take one parameter, IMAP object.
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##
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## Each function should return True if authentication was
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## successful and False if authentication wasn't even tried
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## for some reason (but not when IMAP has no such authentication
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## capability, calling code checks that).
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##
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## Functions can also raise exceptions; two types are special
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## and will be handled by the calling code:
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##
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## - imapobj.error means that there was some error that
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## comes from imaplib2;
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##
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## - OfflineImapError means that function detected some
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## problem by itself.
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def _authn_gssapi(self, imapobj):
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if not have_gss:
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return False
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self.connectionlock.acquire()
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try:
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imapobj.authenticate('GSSAPI', self.gssauth)
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return True
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except imapobj.error as e:
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self.gssapi = False
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raise
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else:
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self.gssapi = True
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kerberos.authGSSClientClean(self.gss_vc)
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self.gss_vc = None
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self.gss_step = self.GSS_STATE_STEP
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finally:
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self.connectionlock.release()
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def _authn_cram_md5(self, imapobj):
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imapobj.authenticate('CRAM-MD5', self.md5handler)
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return True
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def _authn_plain(self, imapobj):
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imapobj.authenticate('PLAIN', self.plainhandler)
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return True
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def _authn_login(self, imapobj):
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# Use LOGIN command, unless LOGINDISABLED is advertized
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# (per RFC 2595)
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if 'LOGINDISABLED' in imapobj.capabilities:
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raise OfflineImapError("IMAP LOGIN is "
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"disabled by server. Need to use SSL?",
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OfflineImapError.ERROR.REPO)
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else:
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self.loginauth(imapobj)
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return True
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def _authn_helper(self, imapobj):
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"""
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Authentication machinery for self.acquireconnection().
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@ -209,86 +277,56 @@ class IMAPServer:
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"""
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# Authentication routines, hash keyed by method name
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# with value that is a tuple with
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# - authentication function,
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# - tryTLS flag,
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# - check IMAP capability flag.
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auth_methods = {
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"GSSAPI": (self._authn_gssapi, False, True),
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"CRAM-MD5": (self._authn_cram_md5, True, True),
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"PLAIN": (self._authn_plain, True, True),
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"LOGIN": (self._authn_login, True, False),
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}
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# Stack stores pairs of (method name, exception)
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exc_stack = []
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tried_to_authn = False
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tried_tls = False
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mechs = self.authmechs
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# Try GSSAPI and continue if it fails
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if 'AUTH=GSSAPI' in imapobj.capabilities and have_gss:
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self.connectionlock.acquire()
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self.ui.debug('imap', 'Attempting GSSAPI authentication')
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tried_to_authn = True
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try:
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imapobj.authenticate('GSSAPI', self.gssauth)
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except imapobj.error as e:
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self.gssapi = False
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self.ui.warn('GSSAPI authentication failed: %s' % e)
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exc_stack.append(('GSSAPI', e))
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else:
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self.gssapi = True
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kerberos.authGSSClientClean(self.gss_vc)
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self.gss_vc = None
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self.gss_step = self.GSS_STATE_STEP
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#if we do self.password = None then the next attempt cannot try...
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#self.password = None
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return
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finally:
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self.connectionlock.release()
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# GSSAPI must be tried first: we will probably go TLS after it
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# and GSSAPI mustn't be tunneled over TLS.
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if "GSSAPI" in mechs:
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mechs.remove("GSSAPI")
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mechs.insert(0, "GSSAPI")
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# Fire up TLS if we can and asked to: gonna to authenticate
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# via plaintext or hashed schemes, so it is best to have
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# channel that is protected from eavesdropping.
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if 'STARTTLS' in imapobj.capabilities and not self.usessl:
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self.ui.debug('imap', 'Using STARTTLS connection')
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try:
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imapobj.starttls()
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except imapobj.error as e:
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raise OfflineImapError("Failed to start "
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"TLS connection: %s" % str(e),
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OfflineImapError.ERROR.REPO)
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for m in mechs:
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if m not in auth_methods:
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raise Exception("Bad authentication method %s, "
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"please, file OfflineIMAP bug" % m)
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func, tryTLS, check_cap = auth_methods[m]
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# TLS must be initiated before checking capabilities:
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# they could have been changed after STARTTLS.
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if tryTLS and not tried_tls:
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tried_tls = True
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self._start_tls(imapobj)
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if check_cap:
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cap = "AUTH=" + m
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if cap not in imapobj.capabilities:
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continue
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# Hashed authenticators come first: they don't reveal
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# passwords.
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if 'AUTH=CRAM-MD5' in imapobj.capabilities:
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tried_to_authn = True
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self.ui.debug('imap', 'Attempting '
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'CRAM-MD5 authentication')
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'%s authentication' % m)
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try:
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imapobj.authenticate('CRAM-MD5', self.md5handler)
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return
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except imapobj.error as e:
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self.ui.warn('CRAM-MD5 authentication failed: %s' % e)
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exc_stack.append(('CRAM-MD5', e))
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# Try plaintext authenticators.
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if 'AUTH=PLAIN' in imapobj.capabilities:
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tried_to_authn = True
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self.ui.debug('imap', 'Attempting '
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'PLAIN authentication')
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try:
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imapobj.authenticate('PLAIN', self.plainhandler)
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return
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except imapobj.error as e:
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self.ui.warn('PLAIN authentication failed: %s' % e)
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exc_stack.append(('PLAIN', e))
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# Last resort: use LOGIN command,
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# unless LOGINDISABLED is advertized (RFC 2595)
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if 'LOGINDISABLED' in imapobj.capabilities:
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e = OfflineImapError("IMAP LOGIN is "
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"disabled by server. Need to use SSL?",
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OfflineImapError.ERROR.REPO)
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exc_stack.append(('IMAP LOGIN', e))
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else:
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tried_to_authn = True
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self.ui.debug('imap', 'Attempting '
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'IMAP LOGIN authentication')
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try:
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self.loginauth(imapobj)
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return
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except imapobj.error as e:
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self.ui.warn('IMAP LOGIN authentication failed: %s' % e)
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exc_stack.append(('IMAP LOGIN', e))
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if func(imapobj):
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return
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except (imapobj.error, OfflineImapError) as e:
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self.ui.warn('%s authentication failed: %s' % (m, e))
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exc_stack.append((m, e))
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if len(exc_stack):
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msg = "\n\t".join(map(
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@ -303,9 +341,10 @@ class IMAPServer:
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lambda x: x[5:], filter(lambda x: x[0:5] == "AUTH=",
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imapobj.capabilities)
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))
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raise OfflineImapError("No supported "
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"authentication mechanisms found; "
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"server advertises %s" % methods,
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raise OfflineImapError("Repository %s: no supported "
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"authentication mechanisms found; configured %s, "
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"server advertises %s" % (self.repos,
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", ".join(self.authmechs), methods),
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OfflineImapError.ERROR.REPO)
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@ -126,6 +126,26 @@ class IMAPRepository(BaseRepository):
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return self.getconf('remote_identity', default=None)
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def get_auth_mechanisms(self):
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supported = ["GSSAPI", "CRAM-MD5", "PLAIN", "LOGIN"]
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# Mechanisms are ranged from the strongest to the
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# weakest ones.
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# TODO: we need DIGEST-MD5, it must come before CRAM-MD5
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# TODO: due to the chosen-plaintext resistance.
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default = ["GSSAPI", "CRAM-MD5", "PLAIN", "LOGIN"]
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mechs = self.getconflist('auth_mechanisms', r',\s*',
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default)
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for m in mechs:
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if m not in supported:
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raise OfflineImapError("Repository %s: " % self + \
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"unknown authentication mechanism '%s'" % m,
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OfflineImapError.ERROR.REPO)
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self.ui.debug('imap', "Using authentication mechanisms %s" % mechs)
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return mechs
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def getuser(self):
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user = None
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