svn commit: r278479 - in head: etc sys/kern

[Rui Paulo]

On Feb 9, 2015, at 19:11, Don Lewis <truckman at FreeBSD.org> wrote:
> 
> On 10 Feb, Mateusz Guzik wrote:
>> On Mon, Feb 09, 2015 at 11:13:51PM +0000, Rui Paulo wrote:
>>> +notify 10 {
>>> +	match "system"          "kernel";
>>> +	match "subsystem"       "signal";
>>> +	match "type"            "coredump";
>>> +	action "logger $comm $core";
>>> +};
>>> +
>>> */
>>> 
>> [..]
>>> +	if (vn_fullpath_global(td, p->p_textvp, &fullpath, &freepath) != 0)
>>> +		goto out;
>>> +	snprintf(data, len, "comm=%s", fullpath);
>> 
>> I cannot test it right now, but it looks like immediate privilege
>> escalation.
>> 
>> Path is not sanitized in any way and devd passes it to 'sh -c'.
>> 
>> So a file named "a.out; /bin/id; meh" or so should result in execution
>> of aforementioned /bin/id.
> 
> Then there is the issue of a user-generated core file being fed into the
> crash analyzer, possibly exploiting bugs in the latter.

That's why there's a warning in devd.conf: devd will run the helper as root, so a proper written helper has to drop the privileges very early or be invoked by devd with lower privileges.  My helper just drops privileges to match the UID/GID of the generated core file before doing anything else.

--
Rui Paulo