I believe I have found a security vulnerability in dump, which, under the
right conditions, allows any user with shell-access to gain root-privileges.
When dumping to a file, dump writes this file chmod 644. When the
root-partition is being backed-up, this leaves the dump-file vulnerable to
scanning by unprivileged users for the duration of the dump.
I tested this, and, as a non-privileged user, was able to extract the
root-password from the dump-file using a simple regex:
"(/root:(.*?):0:0::0:0:Superuser:/)". This, of course, based on the fact
that /etc/master.passwd also becomes part of the dump-file.
As to how high to rank this exploitability, I am not sure. Certain
conditions need to be met. The dump must be made to file, and the
unprivileged user must, naturally, know the name of the dump-file; and the
dump, of course, must be made in multi-user mode.
Still, I would feel a lot better if the FreeBSD development team made a
small adjustment to dump, writing its dump-file chmod 600, which would
immediately solve any and all exploitability.
If people deem it serious enough, I will file a report.
Thanks for listening.
P.S. I understand, of course, that the dump-file, when written to a
directory to which non-privileged users have no access, would still be safe.
But I deem it best to make dump safe on its own, and not have its safety
depend on external factors.
- Mark
System Administrator Asarian-host.org
---
"If you were supposed to understand it,
we wouldn't call it code." - FedEx
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