| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAF=yD-JwREKypTt5a2xEF7Fru19A4vzUbkpxz+my+bYe8gVL3g@mail.gmail.com>
Date: Thu, 4 Feb 2021 14:52:14 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Andreas Roeseler <andreas.a.roeseler@...il.com>
Cc: David Miller <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
Jakub Kicinski <kuba@...nel.org>,
Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH V2 net-next 5/5] icmp: add response to RFC 8335 PROBE messages
On Wed, Feb 3, 2021 at 6:30 PM Andreas Roeseler
<andreas.a.roeseler@...il.com> wrote:
>
> Modify the icmp_rcv function to check for PROBE messages and call
> icmp_echo if a PROBE request is detected.
>
> Modify the existing icmp_echo function to respond to both ping and PROBE
> requests.
>
> This was tested using a custom modification of the iputils package and
> wireshark. It supports IPV4 probing by name, ifindex, and probing by both IPV4 and IPV6
> addresses. It currently does not support responding to probes off the proxy node
> (See RFC 8335 Section 2).
>
>
> Signed-off-by: Andreas Roeseler <andreas.a.roeseler@...il.com>
> ---
> Changes since v1:
> - Reorder variable declarations to follow coding style
> - Switch to functions such as dev_get_by_name and ip_dev_find to lookup
> net devices
> ---
> net/ipv4/icmp.c | 98 ++++++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 88 insertions(+), 10 deletions(-)
>
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index 396b492c804f..18f9a2a3bf59 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -983,21 +983,85 @@ static bool icmp_redirect(struct sk_buff *skb)
>
> static bool icmp_echo(struct sk_buff *skb)
> {
> + struct icmp_bxm icmp_param;
> struct net *net;
> + struct net_device *dev;
> + struct icmp_extobj_hdr *extobj_hdr;
> + struct icmp_ext_ctype3_hdr *ctype3_hdr;
> + __u8 status;
nit: please maintain reverse christmas tree variable ordering
>
> net = dev_net(skb_dst(skb)->dev);
> - if (!net->ipv4.sysctl_icmp_echo_ignore_all) {
> - struct icmp_bxm icmp_param;
> + /* should there be an ICMP stat for ignored echos? */
> + if (net->ipv4.sysctl_icmp_echo_ignore_all)
> + return true;
> +
> + icmp_param.data.icmph = *icmp_hdr(skb);
> + icmp_param.skb = skb;
> + icmp_param.offset = 0;
> + icmp_param.data_len = skb->len;
> + icmp_param.head_len = sizeof(struct icmphdr);
>
> - icmp_param.data.icmph = *icmp_hdr(skb);
> + if (icmp_param.data.icmph.type == ICMP_ECHO) {
> icmp_param.data.icmph.type = ICMP_ECHOREPLY;
> - icmp_param.skb = skb;
> - icmp_param.offset = 0;
> - icmp_param.data_len = skb->len;
> - icmp_param.head_len = sizeof(struct icmphdr);
> - icmp_reply(&icmp_param, skb);
> + goto send_reply;
> }
> - /* should there be an ICMP stat for ignored echos? */
> + if (!net->ipv4.sysctl_icmp_echo_enable_probe)
> + return true;
> + /* We currently do not support probing off the proxy node */
> + if (!(ntohs(icmp_param.data.icmph.un.echo.sequence) & 1))
> + return true;
What does this comment mean?
And why does the sequence number need to be even?
> +
> + icmp_param.data.icmph.type = ICMP_EXT_ECHOREPLY;
> + icmp_param.data.icmph.un.echo.sequence &= htons(0xFF00);
Why this mask?
> + extobj_hdr = (struct icmp_extobj_hdr *)(skb->data + sizeof(struct icmp_ext_hdr));
> + ctype3_hdr = (struct icmp_ext_ctype3_hdr *)(extobj_hdr + 1);
It is not safe to trust the contents of unverified packets. We cannot
just cast to a string and call dev_get_by_name. Need to verify packet
length and data format.
Also below code just casts to the expected data type at some offset.
Can that be defined more formally as header structs? Like ctype3_hdr,
but for other headers, as well.
> + status = 0;
> + switch (extobj_hdr->class_type) {
> + case CTYPE_NAME:
> + dev = dev_get_by_name(net, (char *)(extobj_hdr + 1));
> + break;
> + case CTYPE_INDEX:
> + dev = dev_get_by_index(net, ntohl(*((uint32_t *)(extobj_hdr + 1))));
> + break;
> + case CTYPE_ADDR:
> + switch (ntohs(ctype3_hdr->afi)) {
> + case AFI_IP:
> + dev = ip_dev_find(net, *(__be32 *)(ctype3_hdr + 1));
> + break;
> + case AFI_IP6:
> + dev = ipv6_dev_find(net, (struct in6_addr *)(ctype3_hdr + 1), dev);
> + if(dev) dev_hold(dev);
> + break;
> + default:
> + icmp_param.data.icmph.code = ICMP_EXT_MAL_QUERY;
> + goto send_reply;
> + }
> + break;
> + default:
> + icmp_param.data.icmph.code = ICMP_EXT_MAL_QUERY;
> + goto send_reply;
> + }
> + if(!dev) {
> + icmp_param.data.icmph.code = ICMP_EXT_NO_IF;
> + goto send_reply;
> + }
> + /* RFC 8335: 3 the last 8 bits of the Extended Echo Reply Message
> + * are laid out as follows:
> + * +-+-+-+-+-+-+-+-+
> + * |State|Res|A|4|6|
> + * +-+-+-+-+-+-+-+-+
> + */
> + if (dev->flags & IFF_UP)
> + status |= EXT_ECHOREPLY_ACTIVE;
> + if (dev->ip_ptr->ifa_list)
> + status |= EXT_ECHOREPLY_IPV4;
> + if (!list_empty(&dev->ip6_ptr->addr_list))
> + status |= EXT_ECHOREPLY_IPV6;
> + dev_put(dev);
> + icmp_param.data.icmph.un.echo.sequence |= htons(status);
> +
> +send_reply:
> + icmp_reply(&icmp_param, skb);
> return true;
> }
Powered by blists - more mailing lists