On Thu, Apr 17, 2014 at 10:47 AM, Simo Sorce <ssorce@xxxxxxxxxx> wrote: > On Thu, 2014-04-17 at 10:35 -0700, Andy Lutomirski wrote: >> On Thu, Apr 17, 2014 at 10:33 AM, Simo Sorce <ssorce@xxxxxxxxxx> wrote: >> > On Thu, 2014-04-17 at 10:26 -0700, Andy Lutomirski wrote: >> >> >> >> Not really. write(2) can't send SCM_CGROUP. Callers of sendmsg(2) >> >> who supply SCM_CGROUP are explicitly indicating that they want their >> >> cgroup associated with that message. Callers of write(2) and send(2) >> >> are simply indicating that they have some bytes that they want to >> >> shove into whatever's at the other end of the fd. >> > >> > But there is no attack vector that passes by tricking setuid binaries to >> > write to pre-opened file descriptors on sendmsg(), and for the other >> > cases (connected socket) journald can always cross check with >> > SO_PEERCGROUP, so why do we care again ? >> >> Because the proposed code does not do what I described, at least as >> far I as I can tell. > > You do realize that we have been speaking in hypothetical for a while > now ? > > Even without doing the SO_PEERCRED, you are not going to fool the log, > as it gathers a ton of other info about the process, and cgroup is just > one of the infos used to classify the log. > > There are also credentials, pid, and a lot of other things. > Even if a setuid binary could be tricked to send a message with an > "impostor" cgroup don't you think you'd see other things out of place ? > (wrong uid, wrong pid, etc...). Credentials and pid have much the same problem because SCM_CREDENTIALS is screwed up. That's not an excuse to screw up SCM_CGROUP in the same way. --Andy -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
