* [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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