On Monday 01 February 2010 12:44:56 pm Jason Shaw wrote: > > Here is what I found. Using netlabelctl, I could successfully restrict all > > inbound/outbound network access to the system on a specific interface. I > > could then permit only SSH into the system via allow rules associated with > > the peer label assigned using netlabelctl unlbl.That worked great. In fact, > > I'm really excited to explore other possibilities using netlabelctl as it > > has many valuable possible uses. Great, glad to hear you got everything (well, almost) working; I apologize it took so long :) > > However, I found that my test app (with the allow rule below), could still > > read and display packet data coming in on any interface even with all > > interfaces assigned a unique peer_t using netlabelctl unlbl add. This was > > true when no explicit allow rules were added for the test app (running in > > myAPP_t). So while netlabelctl did require explicit allow rules for SSH to > > send/receive data (I beleive for sshd_t), an allow rule was not required to > > read raw data off of the interface for myAPP_t. > > > > allow myApp_t self:packet_socket { create read bind ioctl }; > > > > My understanding is that a packet socket is read at the device driver > > level. As such, is it possible that the packet socket is being read before > > netlabelctl enforcements are taking place? Hmm, yes, I think you've stumbled across a bug in the kernel where the LSM sock_rcv_skb() hook is not called for AF_PACKET. I need to take a look and verify the rest of the packet families and work up a fix. -- paul moore linux @ hp Description of problem:
I think this is a bug we need to pay attention too. Can not prevent raw_socket from certain packets.
Last I looked, SELinux only mediated IP packet send/recv. selinux_sock_rcv_skb bails immediately if not inet or inet6. Outbound netfilter hooks are for ipv4 and ipv6 only. packet socket is not the same thing as IP raw socket. So merely changing packet/af_packet.c:run_filter() to invoke sk_filter() [which calls security_sock_rcv_skb] wouldn't cause these packets to get mediated; the SELinux hook would immediately return.
To elaborate a bit on the issue I think Stephen is trying to make ... The real issue is that we likely can't rely on the packet already being parsed, i.e. skb_network_offset() isn't going to return anything useful, and without knowing that the packet is an IP packet we would have to parse the packet starting at the Ethernet header in order to get the IP information and the peer label (really only CIPSO and fallback, dealing with labeled IPsec packets here makes my head hurt due to the fact we would need to verify the AH/ESP header and then verify the SPI - basically a no-go). I'll look at this a bit more on Friday but I'm pretty sure this is just a limitation of non AF_INET[6] sockets.
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I'm moving this bug to be against 'rawhide' so that we don't keep getting the end-of-life bugzapper comments added. Is there any progress being made on this upstream ? Stephen, Paul ?
No one is actively pursuing adding SELinux per-packet controls for AF_PACKET sockets to my knowledge. SELinux can control what applications can create and use such sockets, but not per-packet send/recv based on peer information.
This bug appears to have been reported against 'rawhide' during the Fedora 19 development cycle. Changing version to '19'. (As we did not run this process for some time, it could affect also pre-Fedora 19 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 19 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora19