The nagios daemon should create its PID file before dropping
privileges. This represents a minor security issue; additional factors
are needed to make it exploitable.
Description
The purpose of the PID file is to hold the PID of the running daemon,
so that later it can be stopped, restarted, or otherwise signalled
(many daemons reload their configurations in response to a SIGHUP).
To fulfill that purpose, the contents of the PID file need to be
trustworthy. If the PID file is writable by a non-root user, then he
can replace its contents with the PID of a root process. Afterwards,
any attempt to signal the PID contained in the PID file will instead
signal a root process chosen by the non-root user (a vulnerability).
This is commonly exploitable by init scripts that are run as root and
which blindly trust the contents of their PID files. If one daemon
flushes its cache in response to SIGUSR2 and another daemon drops all
connections in response to SIGUSR2, it is not hard to imagine a
denial-of-service by the user of the first daemon against the second.
Exploitation
There is only a risk of exploitation when some other user relies on
the data in the PID file. But you have to wonder, what's the point of
the PID file if not to provide the PID to other people? Any situation
where the PID file is used is therefore suspicious.
The init script daemon-init.in that ships with nagios itself relies on the PID file to
e.g. reload the nagios configuration.
The text was updated successfully, but these errors were encountered:
@hedenface Thanks for the fast response. I can push this patch live on Gentoo for testing, but first I see a problem with one of the ./configure defaults. Now that the PID file is owned by root, it won't be writable by the nagios user (good!). But in configure.ac, we still have
dnl User can override lock file location
AC_ARG_WITH(lockfile,
AC_HELP_STRING([--with-lockfile=<path>],
[sets path and file name for lock file]),
lockfile=$withval,
lockfile=$localstatedir/nagios.lock
)
I think the default should be /run instead, or at least something outside of $localstatedir. The problem with $localstatedir is that it needs to be owned by the nagios user, who can then delete the existing root-owned PID file and replace it with his own.
And now that the PID file will be created as root, there won't be a problem writing to e.g. /run/nagios.lock.
Summary
The nagios daemon should create its PID file before dropping
privileges. This represents a minor security issue; additional factors
are needed to make it exploitable.
Description
The purpose of the PID file is to hold the PID of the running daemon,
so that later it can be stopped, restarted, or otherwise signalled
(many daemons reload their configurations in response to a SIGHUP).
To fulfill that purpose, the contents of the PID file need to be
trustworthy. If the PID file is writable by a non-root user, then he
can replace its contents with the PID of a root process. Afterwards,
any attempt to signal the PID contained in the PID file will instead
signal a root process chosen by the non-root user (a vulnerability).
This is commonly exploitable by init scripts that are run as root and
which blindly trust the contents of their PID files. If one daemon
flushes its cache in response to SIGUSR2 and another daemon drops all
connections in response to SIGUSR2, it is not hard to imagine a
denial-of-service by the user of the first daemon against the second.
Exploitation
There is only a risk of exploitation when some other user relies on
the data in the PID file. But you have to wonder, what's the point of
the PID file if not to provide the PID to other people? Any situation
where the PID file is used is therefore suspicious.
The init script
daemon-init.inthat ships with nagios itself relies on the PID file toe.g. reload the nagios configuration.
The text was updated successfully, but these errors were encountered: