Date: Wed, 15 Jun 2011 09:48:50 -0400 (EDT) From: Josh Bressers <bressers@...hat.com> To: oss-security@...ts.openwall.com Cc: Tomas Mraz <tmraz@...hat.com>, "Steven M. Christey" <coley@...us.mitre.org>, Werner Koch <wk@...code.com> Subject: Re: CVE Request / Discussion -- dirmngr -- Improper dealing with blocking system calls, when verifying a certificate Please use CVE-2011-2207. Thanks. -- JB ----- Original Message ----- > Dear Jan, Gentlemen, > > thanks for caring about the issue, here is my input: > > Am Montag, 6. Juni 2011 19:42:10 schrieb Josh Bressers: > > > IOW was not able to reproduce the complete / indefinite > > > dirmngr-client > > > hang (thus blocking other clients from access). As noted in , > > > it is > > > true that during small time period running 'dirmngr' daemon > > > instance is > > > unresponsive also for '--ping' (dirmngr-client --ping) commands, > > > but > > > after finite time (~21 seconds in my test) the connection ends up > > > with > > > timeout. > > > > > > Though Bernard in: > > >  http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=627377#5 > > > > > > mentions "For example the KMail hung when trying to verify a > > > signature > > > which has the certificate in the chain." which would suggest there > > > may > > > exist clients / end-user application not able to recover from this > > > bug > > > properly. Bernhard, hopefully here, you could clarify / list such > > > applications and provide also time details, how long that hang of > > > such > > > applications took. > > For me the verification of the certiciate DTAG_Issuing_CA_i01.der > hangs for several minutes, e.g. just tested on Debian Lenny > for three minutes: > real 3m9.237s > user 0m0.000s > sys 0m0.004s > The time might depend on some network parameters or network timeouts > of the operating system. I have not changed these on my test system, > but I am also not very knowledgable about the various timeouts. > > Three minutes are way too much. People that use Kontact will > experience a > freeze of the application for that time and must assume their client > application to be hung or crashed. Given that Kontact is also a > calender > and contacts manager, this causes significant interruptions in a > typical > office. > > Applications affected are all applications that use dirmngr in a > blocking > way. Applications use dirmngr when they are trying to use the GnuPG > crypto > stack with CMS operations (aka X509 certificated, e.g. used with > S/MIME > emails or similar file crypto operations) and use of dirmngr is not > explicitely switched off. The default is to use dirmngr for > certification > revocation on all CMS operations that involve certificates. > > The application I have tested is KMail/Kontact which uses GnuPG via > the > library gpgme, which is the recommended way. Command line usage of > gpgsm is > also affected, which I have also verified. > > > > Based on your reply, this may not / may be worthy (in case there > > > are > > > such end-user applications) of an CVE identifier. > > > > Is this expected to only be used by end user applications? > > Gpgsm or gpgme can be used by system scripts, other scripts or system > applications as well. Dirmngr itself is a system service, so on a > multiuser > system all users are affected once one user tries a verification > waiting > for a network timeout. > > > It seems to me > > that if an attacker can DoS a client, it's not a security issue, > > especially > > when you consider the use (if a bad guy can interact with dirmngr, > > there > > are probably bigger potential issues). > > Two attack scenarios: > a) a local uses wants to block other users from using email or crypto > operations, like encrypting or verifying signatures to someone. This > user can > just initiate this verification with the system dirmngr. Any user of a > system > should be able to ask the system dirmngr for verifications. So all > users have > access. > > b) A remote user wants to cause interruptions and sends signed emails > or files > that causes an gpgsm to attempt to decrypt or verify with such a > certificate. > This will often be done automatically by the email clients for the > comfort of > the user. As gpgsm and thus dirmngr is needed to decide if a signature > is > good, attackers can assume that emails with such a signature will be > passed > to gpgsm who will pass the certificate to dirmngr and ask for > verification. > So it is a normal situation that outside data will reach dirmngr. > > Best Regards, > Bernhard Reiter > > -- > Managing Director - Owner: www.Intevation.net (Free Software Company) > FSFE.org: Founding GA Member. Kolabsys.com: Board Member > Intevation GmbH, Osnabrück, DE; Amtsgericht Osnabrück, HRB 18998 > Geschäftsführer Frank Koormann, Bernhard Reiter, Dr. Jan-Oliver Wagner
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