72909 2002-08-06 00:38 /72 rader/ <secure@conectiva.com.br> Importerad: 2002-08-06 00:38 av Brevbäraren Extern mottagare: conectiva-updates@papaleguas.conectiva.com.br Mottagare: Bugtraq (import) <965> Ärende: [CLA-2002:514] Conectiva Linux Security Announcement - sendmail ------------------------------------------------------------ -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 - -------------------------------------------------------------------------- CONECTIVA LINUX SECURITY ANNOUNCEMENT - -------------------------------------------------------------------------- PACKAGE : sendmail SUMMARY : Local Denial of Service DATE : 2002-08-05 14:57 ID : CLA-:-1 RELEVANT RELEASES : 6.0, 7.0, 8 - ------------------------------------------------------------------------- DESCRIPTION Sendmail is a widely used Mail Transfer Agent (MTA). As publicized[1] by lumpy and reported in the sendmail website, a local user can stop the mail service (in the sense of "freezing" some operations) by holding an exclusive reading lock on some specific sendmail files (using a system call like flock()). In order to do that, the user must have permission to read the file. One example of such a file is /var/log/sendmail.st, which is world readable by default. By exploiting this vulnerability, a malicious local user can delay (for an undetermined amount of time) the e-mail delivery, thus characterizing a Denial of Service (DoS) attack. SOLUTION The current solution is to allow only root and users belonging to the mail group to read the files which are written by sendmail and its utilities (like newaliases). In order to do so, just run the following commands (as root user): chmod 0640 /etc/mail/*.db chmod 0640 /var/log/sendmail.st The given change does not affect the sendmail functionality and is the recommended procedure for all users. It is possible to obtain a list of users and programs which are acessing some file (and possibly locking it) with the lsof command, as seen in the example below: lsof /var/log/sendmail.st REFERENCES: 1.http://www.sendmail.org/LockingAdvisory.txt 2.http://distro.conectiva.com.br/bugzilla/show_bug.cgi?id=6350 - ------------------------------------------------------------------------- All our advisories and generic update instructions can be viewed at http://distro.conectiva.com.br/atualizacoes/?idioma=en - ------------------------------------------------------------------------- subscribe: conectiva-updates-subscribe@papaleguas.conectiva.com.br unsubscribe: conectiva-updates-unsubscribe@papaleguas.conectiva.com.br -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.7 (GNU/Linux) iD8DBQE9Tr5F42jd0JmAcZARAsuqAJ9pcuoM592BRwGkBDEizLsbXcdAxgCgwz1V 8XwS24aCWX8LVMdWYANMNLA= =GYjp -----END PGP SIGNATURE----- (72909) / <secure@conectiva.com.br>/----------------