Red Hat Bugzilla – Bug 102466
netdump server overly trusts client root
Last modified: 2014-06-18 04:28:32 EDT
Description of problem:
I'm not sure if this bug should be severity security or enhancement.
In normal operation, the netdump client copies its session cookie to the server
using ssh on startup. The /var/crash/.ssh/authorized_keys2 file doesn't limit
the commands the client can run on the server over ssh. Therefore, root on a
compromised but trusted netdump client can run *any* command on the server as
user netdump without a password.
Version-Release number of selected component (if applicable):
How to reproduce:
1. Set up a netdump server (10.0.0.1 below) and a client that crash dumps to it.
2. Run the following command on the client as root:
ssh -i /etc/sysconfig/netdump_id_dsa email@example.com cat /etc/passwd
3. The server's /etc/password file is displayed to stdout.
Restrict the /var/crash/.ssh/authorized_keys2 file to only allow the cookie
distribution command by starting each key entry with a command option:
command="echo "$MAGIC2$MAGIC1" \> /var/crash/magic/$LOCALADDR"
Steve -- thanks for the report.
I guess I've never seen an authorized_keys entry with a command restriction.
Can you suggest how would that be properly scripted in the netdump init script?
Here's what it does now:
# propagate netdump ssh public key to the crashdump server
cat /etc/sysconfig/netdump_id_dsa.pub | \
ssh -x netdump@$NETDUMPADDR cat '>>' /var/crash/.ssh/authorized_keys2
Damn -- the MAGIC numbers are only calculated at each boot time
registration; the "propagate" command is a one-time only operation.
Even though we can't encode the MAGIC numbers into the conditional
we can submit that information via standard input. I suggest we
format the authorized entry like this:
command="cat /var/crash/magic/$LOCALADDR",no-port-forwarding $KEY
... and do:
echo "$MAGIC2$MAGIC1" | ssh -x -i /etc/... netdump@NETDUMPADDR