* [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
@ 2021-06-10 14:23 Phil Sutter
2021-06-10 17:43 ` Pablo Neira Ayuso
0 siblings, 1 reply; 6+ messages in thread
From: Phil Sutter @ 2021-06-10 14:23 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel, Florian Westphal
Since user space does not generate a payload dependency, plain sctp
chunk matches cause searching in non-SCTP packets, too. Avoid this
potential mis-interpretation of packet data by checking pkt->tprot.
Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
Signed-off-by: Phil Sutter <phil@nwl.cc>
---
net/netfilter/nft_exthdr.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
index 7f705b5c09de8..1093bb83f8aeb 100644
--- a/net/netfilter/nft_exthdr.c
+++ b/net/netfilter/nft_exthdr.c
@@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
const struct sctp_chunkhdr *sch;
struct sctp_chunkhdr _sch;
+ if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
+ goto err;
+
do {
sch = skb_header_pointer(pkt->skb, offset, sizeof(_sch), &_sch);
if (!sch || !sch->length)
@@ -334,7 +337,7 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
}
offset += SCTP_PAD4(ntohs(sch->length));
} while (offset < pkt->skb->len);
-
+err:
if (priv->flags & NFT_EXTHDR_F_PRESENT)
nft_reg_store8(dest, false);
else
--
2.31.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
2021-06-10 14:23 [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only Phil Sutter
@ 2021-06-10 17:43 ` Pablo Neira Ayuso
2021-06-11 10:26 ` Phil Sutter
0 siblings, 1 reply; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-10 17:43 UTC (permalink / raw)
To: Phil Sutter; +Cc: netfilter-devel, Florian Westphal
Hi Phil,
On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote:
> Since user space does not generate a payload dependency, plain sctp
> chunk matches cause searching in non-SCTP packets, too. Avoid this
> potential mis-interpretation of packet data by checking pkt->tprot.
>
> Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> Signed-off-by: Phil Sutter <phil@nwl.cc>
> ---
> net/netfilter/nft_exthdr.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> index 7f705b5c09de8..1093bb83f8aeb 100644
> --- a/net/netfilter/nft_exthdr.c
> +++ b/net/netfilter/nft_exthdr.c
> @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> const struct sctp_chunkhdr *sch;
> struct sctp_chunkhdr _sch;
>
> + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
> + goto err;
nft_set_pktinfo_unspec() already initializes pkt->tprot to zero.
I think it's safe to simplify this to:
if (pkt->tprot != IPPROTO_SCTP)
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
2021-06-10 17:43 ` Pablo Neira Ayuso
@ 2021-06-11 10:26 ` Phil Sutter
2021-06-11 11:56 ` Pablo Neira Ayuso
0 siblings, 1 reply; 6+ messages in thread
From: Phil Sutter @ 2021-06-11 10:26 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel, Florian Westphal
On Thu, Jun 10, 2021 at 07:43:34PM +0200, Pablo Neira Ayuso wrote:
> On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote:
> > Since user space does not generate a payload dependency, plain sctp
> > chunk matches cause searching in non-SCTP packets, too. Avoid this
> > potential mis-interpretation of packet data by checking pkt->tprot.
> >
> > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > ---
> > net/netfilter/nft_exthdr.c | 5 ++++-
> > 1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > index 7f705b5c09de8..1093bb83f8aeb 100644
> > --- a/net/netfilter/nft_exthdr.c
> > +++ b/net/netfilter/nft_exthdr.c
> > @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > const struct sctp_chunkhdr *sch;
> > struct sctp_chunkhdr _sch;
> >
> > + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
> > + goto err;
>
> nft_set_pktinfo_unspec() already initializes pkt->tprot to zero.
>
> I think it's safe to simplify this to:
>
> if (pkt->tprot != IPPROTO_SCTP)
Are you sure? Checking the spots that (should) initialize
tprot/tprot_set, in nft_do_chain_inet() it seems that if state->pf is
neither NFPROTO_IPV4 nor NFPROTO_IPV6, nft_do_chain() is called without
prior init. Maybe default case should call nft_set_pktinfo_unspec()?
BTW: The final return call in nft_do_chain_inet_ingress() is dead code,
right?
Thanks, Phil
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
2021-06-11 10:26 ` Phil Sutter
@ 2021-06-11 11:56 ` Pablo Neira Ayuso
2021-06-11 12:52 ` Phil Sutter
0 siblings, 1 reply; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-11 11:56 UTC (permalink / raw)
To: Phil Sutter, netfilter-devel, Florian Westphal
On Fri, Jun 11, 2021 at 12:26:24PM +0200, Phil Sutter wrote:
> On Thu, Jun 10, 2021 at 07:43:34PM +0200, Pablo Neira Ayuso wrote:
> > On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote:
> > > Since user space does not generate a payload dependency, plain sctp
> > > chunk matches cause searching in non-SCTP packets, too. Avoid this
> > > potential mis-interpretation of packet data by checking pkt->tprot.
> > >
> > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > ---
> > > net/netfilter/nft_exthdr.c | 5 ++++-
> > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > > index 7f705b5c09de8..1093bb83f8aeb 100644
> > > --- a/net/netfilter/nft_exthdr.c
> > > +++ b/net/netfilter/nft_exthdr.c
> > > @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > > const struct sctp_chunkhdr *sch;
> > > struct sctp_chunkhdr _sch;
> > >
> > > + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
> > > + goto err;
> >
> > nft_set_pktinfo_unspec() already initializes pkt->tprot to zero.
> >
> > I think it's safe to simplify this to:
> >
> > if (pkt->tprot != IPPROTO_SCTP)
>
> Are you sure? Checking the spots that (should) initialize
> tprot/tprot_set, in nft_do_chain_inet() it seems that if state->pf is
> neither NFPROTO_IPV4 nor NFPROTO_IPV6, nft_do_chain() is called without
> prior init. Maybe default case should call nft_set_pktinfo_unspec()?
state->pf in nft_do_chain_inet() can only be either NFPROTO_IPV4 or
NFPROTO_IPV6.
pkt->tprot_set is there to deal with a corner case: IPPROTO_IP (0).
If pkt->tprot_set == true and pkt->tprot == 0, it means: "match on
IPPROTO_IP". For other IPPROTO_*, checking pkt->tprot looks safe to me.
> BTW: The final return call in nft_do_chain_inet_ingress() is dead code,
> right?
You mean the default case of nft_do_chain_inet_ingress()? inet/ingress
is special, it allows you to filter IPv4 and IPv6 traffic only.
Anything else from ingress is accepted (you should filter it via
netdev family).
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
2021-06-11 11:56 ` Pablo Neira Ayuso
@ 2021-06-11 12:52 ` Phil Sutter
2021-06-11 14:54 ` Pablo Neira Ayuso
0 siblings, 1 reply; 6+ messages in thread
From: Phil Sutter @ 2021-06-11 12:52 UTC (permalink / raw)
To: Pablo Neira Ayuso; +Cc: netfilter-devel, Florian Westphal
On Fri, Jun 11, 2021 at 01:56:54PM +0200, Pablo Neira Ayuso wrote:
> On Fri, Jun 11, 2021 at 12:26:24PM +0200, Phil Sutter wrote:
> > On Thu, Jun 10, 2021 at 07:43:34PM +0200, Pablo Neira Ayuso wrote:
> > > On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote:
> > > > Since user space does not generate a payload dependency, plain sctp
> > > > chunk matches cause searching in non-SCTP packets, too. Avoid this
> > > > potential mis-interpretation of packet data by checking pkt->tprot.
> > > >
> > > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > > ---
> > > > net/netfilter/nft_exthdr.c | 5 ++++-
> > > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > > > index 7f705b5c09de8..1093bb83f8aeb 100644
> > > > --- a/net/netfilter/nft_exthdr.c
> > > > +++ b/net/netfilter/nft_exthdr.c
> > > > @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > > > const struct sctp_chunkhdr *sch;
> > > > struct sctp_chunkhdr _sch;
> > > >
> > > > + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
> > > > + goto err;
> > >
> > > nft_set_pktinfo_unspec() already initializes pkt->tprot to zero.
> > >
> > > I think it's safe to simplify this to:
> > >
> > > if (pkt->tprot != IPPROTO_SCTP)
> >
> > Are you sure? Checking the spots that (should) initialize
> > tprot/tprot_set, in nft_do_chain_inet() it seems that if state->pf is
> > neither NFPROTO_IPV4 nor NFPROTO_IPV6, nft_do_chain() is called without
> > prior init. Maybe default case should call nft_set_pktinfo_unspec()?
>
> state->pf in nft_do_chain_inet() can only be either NFPROTO_IPV4 or
> NFPROTO_IPV6.
Shouldn't there be a WARN_ON_ONCE or something in the default case then?
Looking at nf_hook(), it seems entirely possible to me that state->pf
might be NFPROTO_ARP, for instance. That's probably just me not getting
it, but things we rely upon shouldn't be hidden that well, right?
> pkt->tprot_set is there to deal with a corner case: IPPROTO_IP (0).
> If pkt->tprot_set == true and pkt->tprot == 0, it means: "match on
> IPPROTO_IP". For other IPPROTO_*, checking pkt->tprot looks safe to me.
Ah, thanks for clarifying! So whenever I check a specific value that's
non-zero, tprot_set doesn't matter. Should I send a patch for the same
change in nft_tcp_header_pointer(), too? (That's where I copied the code
from. ;)
> > BTW: The final return call in nft_do_chain_inet_ingress() is dead code,
> > right?
>
> You mean the default case of nft_do_chain_inet_ingress()? inet/ingress
> is special, it allows you to filter IPv4 and IPv6 traffic only.
> Anything else from ingress is accepted (you should filter it via
> netdev family).
Oh, sorry. Looks like I had tomatoes on the eyes[1]: I missed that the
non-default cases just 'break' and therefore hit the function's last
line.
Thanks, Phil
[1] Famous German idiom.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only
2021-06-11 12:52 ` Phil Sutter
@ 2021-06-11 14:54 ` Pablo Neira Ayuso
0 siblings, 0 replies; 6+ messages in thread
From: Pablo Neira Ayuso @ 2021-06-11 14:54 UTC (permalink / raw)
To: Phil Sutter, netfilter-devel, Florian Westphal
On Fri, Jun 11, 2021 at 02:52:48PM +0200, Phil Sutter wrote:
> On Fri, Jun 11, 2021 at 01:56:54PM +0200, Pablo Neira Ayuso wrote:
> > On Fri, Jun 11, 2021 at 12:26:24PM +0200, Phil Sutter wrote:
> > > On Thu, Jun 10, 2021 at 07:43:34PM +0200, Pablo Neira Ayuso wrote:
> > > > On Thu, Jun 10, 2021 at 04:23:16PM +0200, Phil Sutter wrote:
> > > > > Since user space does not generate a payload dependency, plain sctp
> > > > > chunk matches cause searching in non-SCTP packets, too. Avoid this
> > > > > potential mis-interpretation of packet data by checking pkt->tprot.
> > > > >
> > > > > Fixes: 133dc203d77df ("netfilter: nft_exthdr: Support SCTP chunks")
> > > > > Signed-off-by: Phil Sutter <phil@nwl.cc>
> > > > > ---
> > > > > net/netfilter/nft_exthdr.c | 5 ++++-
> > > > > 1 file changed, 4 insertions(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/net/netfilter/nft_exthdr.c b/net/netfilter/nft_exthdr.c
> > > > > index 7f705b5c09de8..1093bb83f8aeb 100644
> > > > > --- a/net/netfilter/nft_exthdr.c
> > > > > +++ b/net/netfilter/nft_exthdr.c
> > > > > @@ -312,6 +312,9 @@ static void nft_exthdr_sctp_eval(const struct nft_expr *expr,
> > > > > const struct sctp_chunkhdr *sch;
> > > > > struct sctp_chunkhdr _sch;
> > > > >
> > > > > + if (!pkt->tprot_set || pkt->tprot != IPPROTO_SCTP)
> > > > > + goto err;
> > > >
> > > > nft_set_pktinfo_unspec() already initializes pkt->tprot to zero.
> > > >
> > > > I think it's safe to simplify this to:
> > > >
> > > > if (pkt->tprot != IPPROTO_SCTP)
> > >
> > > Are you sure? Checking the spots that (should) initialize
> > > tprot/tprot_set, in nft_do_chain_inet() it seems that if state->pf is
> > > neither NFPROTO_IPV4 nor NFPROTO_IPV6, nft_do_chain() is called without
> > > prior init. Maybe default case should call nft_set_pktinfo_unspec()?
> >
> > state->pf in nft_do_chain_inet() can only be either NFPROTO_IPV4 or
> > NFPROTO_IPV6.
>
> Shouldn't there be a WARN_ON_ONCE or something in the default case then?
> Looking at nf_hook(), it seems entirely possible to me that state->pf
> might be NFPROTO_ARP, for instance. That's probably just me not getting
> it, but things we rely upon shouldn't be hidden that well, right?
nft_do_chain_inet() is called from the NFPROTO_INET hook, which
results in either NFPROTO_IPV4 or NFPROTO_IPV6.
This is hot path, I would not add more code there. The default case is
just there to avoid a warning from gcc.
Probably a comment like /* Should not ever happen */ for the default
case in nft_do_chain_inet() is fine with you? :)
> > pkt->tprot_set is there to deal with a corner case: IPPROTO_IP (0).
> > If pkt->tprot_set == true and pkt->tprot == 0, it means: "match on
> > IPPROTO_IP". For other IPPROTO_*, checking pkt->tprot looks safe to me.
>
> Ah, thanks for clarifying! So whenever I check a specific value that's
> non-zero, tprot_set doesn't matter. Should I send a patch for the same
> change in nft_tcp_header_pointer(), too? (That's where I copied the code
> from. ;)
I think so, that's fine indeed.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-06-11 14:54 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-10 14:23 [nf-next PATCH] netfilter: nft_exthdr: Search chunks in SCTP packets only Phil Sutter
2021-06-10 17:43 ` Pablo Neira Ayuso
2021-06-11 10:26 ` Phil Sutter
2021-06-11 11:56 ` Pablo Neira Ayuso
2021-06-11 12:52 ` Phil Sutter
2021-06-11 14:54 ` Pablo Neira Ayuso
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