* [iptables PATCH] extensions: string: Clarify description of --to @ 2023-10-12 16:08 Phil Sutter 2023-10-12 18:17 ` Phil Sutter 2023-10-12 19:47 ` Pablo Neira Ayuso 0 siblings, 2 replies; 6+ messages in thread From: Phil Sutter @ 2023-10-12 16:08 UTC (permalink / raw) To: netfilter-devel String match indeed returns a match as long as the given pattern starts in the range of --from and --to, update the text accordingly. Also add a note regarding fragment boundaries. Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 Signed-off-by: Phil Sutter <phil@nwl.cc> --- extensions/libxt_string.man | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man index 2a470ece19c9d..efdda492ae78d 100644 --- a/extensions/libxt_string.man +++ b/extensions/libxt_string.man @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri Set the offset from which it starts looking for any matching. If not passed, default is 0. .TP \fB\-\-to\fP \fIoffset\fP -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 -(counting from 0) is the last one that is scanned. +Set the offset up to which should be scanned. If the pattern does not start +within this offset, it is not considered a match. If not passed, default is the packet size. +A second function of this parameter is instructing the kernel how much data +from the packet should be provided. With non-linear skbuffs (e.g. due to +fragmentation), a pattern extending past this offset may not be found. Also see +the related note below about Boyer-Moore algorithm in these cases. .TP [\fB!\fP] \fB\-\-string\fP \fIpattern\fP Matches the given pattern. -- 2.41.0 ^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [iptables PATCH] extensions: string: Clarify description of --to 2023-10-12 16:08 [iptables PATCH] extensions: string: Clarify description of --to Phil Sutter @ 2023-10-12 18:17 ` Phil Sutter 2023-10-12 19:47 ` Pablo Neira Ayuso 1 sibling, 0 replies; 6+ messages in thread From: Phil Sutter @ 2023-10-12 18:17 UTC (permalink / raw) To: netfilter-devel On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > String match indeed returns a match as long as the given pattern starts > in the range of --from and --to, update the text accordingly. > Also add a note regarding fragment boundaries. > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > Signed-off-by: Phil Sutter <phil@nwl.cc> Also applied. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [iptables PATCH] extensions: string: Clarify description of --to 2023-10-12 16:08 [iptables PATCH] extensions: string: Clarify description of --to Phil Sutter 2023-10-12 18:17 ` Phil Sutter @ 2023-10-12 19:47 ` Pablo Neira Ayuso 2023-10-12 20:14 ` Pablo Neira Ayuso 1 sibling, 1 reply; 6+ messages in thread From: Pablo Neira Ayuso @ 2023-10-12 19:47 UTC (permalink / raw) To: Phil Sutter; +Cc: netfilter-devel On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > String match indeed returns a match as long as the given pattern starts > in the range of --from and --to, update the text accordingly. > Also add a note regarding fragment boundaries. > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > Signed-off-by: Phil Sutter <phil@nwl.cc> > --- > extensions/libxt_string.man | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man > index 2a470ece19c9d..efdda492ae78d 100644 > --- a/extensions/libxt_string.man > +++ b/extensions/libxt_string.man > @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri > Set the offset from which it starts looking for any matching. If not passed, default is 0. > .TP > \fB\-\-to\fP \fIoffset\fP > -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 > -(counting from 0) is the last one that is scanned. > +Set the offset up to which should be scanned. If the pattern does not start > +within this offset, it is not considered a match. > If not passed, default is the packet size. > +A second function of this parameter is instructing the kernel how much data > +from the packet should be provided. With non-linear skbuffs (e.g. due to > +fragmentation), a pattern extending past this offset may not be found. Also see > +the related note below about Boyer-Moore algorithm in these cases. Then, matching on: - linear skbuff: if the pattern falls within from-to, all good. - non-linear skbuff: if pattern falls within from-to, but remaining patter This is clearly broken, the fix is just to document this? No attempt to fix it this from the kernel? ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [iptables PATCH] extensions: string: Clarify description of --to 2023-10-12 19:47 ` Pablo Neira Ayuso @ 2023-10-12 20:14 ` Pablo Neira Ayuso 2023-10-13 9:28 ` Phil Sutter 0 siblings, 1 reply; 6+ messages in thread From: Pablo Neira Ayuso @ 2023-10-12 20:14 UTC (permalink / raw) To: Phil Sutter; +Cc: netfilter-devel On Thu, Oct 12, 2023 at 09:47:38PM +0200, Pablo Neira Ayuso wrote: > On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > > String match indeed returns a match as long as the given pattern starts > > in the range of --from and --to, update the text accordingly. > > Also add a note regarding fragment boundaries. > > > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > > Signed-off-by: Phil Sutter <phil@nwl.cc> > > --- > > extensions/libxt_string.man | 8 ++++++-- > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man > > index 2a470ece19c9d..efdda492ae78d 100644 > > --- a/extensions/libxt_string.man > > +++ b/extensions/libxt_string.man > > @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri > > Set the offset from which it starts looking for any matching. If not passed, default is 0. > > .TP > > \fB\-\-to\fP \fIoffset\fP > > -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 > > -(counting from 0) is the last one that is scanned. > > +Set the offset up to which should be scanned. If the pattern does not start > > +within this offset, it is not considered a match. > > If not passed, default is the packet size. > > +A second function of this parameter is instructing the kernel how much data > > +from the packet should be provided. With non-linear skbuffs (e.g. due to > > +fragmentation), a pattern extending past this offset may not be found. Also see > > +the related note below about Boyer-Moore algorithm in these cases. > > Then, matching on: > > - linear skbuff: if the pattern falls within from-to, all good. > - non-linear skbuff: if pattern falls within from-to, but remaining > patter > > This is clearly broken, the fix is just to document this? > > No attempt to fix it this from the kernel? I would align linear skbuff behaviour to how non-linear skbuff works, that is, pattern matching stops at to. This requires a small patch for xt_string. ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [iptables PATCH] extensions: string: Clarify description of --to 2023-10-12 20:14 ` Pablo Neira Ayuso @ 2023-10-13 9:28 ` Phil Sutter 2023-10-13 10:08 ` Pablo Neira Ayuso 0 siblings, 1 reply; 6+ messages in thread From: Phil Sutter @ 2023-10-13 9:28 UTC (permalink / raw) To: Pablo Neira Ayuso; +Cc: netfilter-devel On Thu, Oct 12, 2023 at 10:14:31PM +0200, Pablo Neira Ayuso wrote: > On Thu, Oct 12, 2023 at 09:47:38PM +0200, Pablo Neira Ayuso wrote: > > On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > > > String match indeed returns a match as long as the given pattern starts > > > in the range of --from and --to, update the text accordingly. > > > Also add a note regarding fragment boundaries. > > > > > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > > > Signed-off-by: Phil Sutter <phil@nwl.cc> > > > --- > > > extensions/libxt_string.man | 8 ++++++-- > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man > > > index 2a470ece19c9d..efdda492ae78d 100644 > > > --- a/extensions/libxt_string.man > > > +++ b/extensions/libxt_string.man > > > @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri > > > Set the offset from which it starts looking for any matching. If not passed, default is 0. > > > .TP > > > \fB\-\-to\fP \fIoffset\fP > > > -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 > > > -(counting from 0) is the last one that is scanned. > > > +Set the offset up to which should be scanned. If the pattern does not start > > > +within this offset, it is not considered a match. > > > If not passed, default is the packet size. > > > +A second function of this parameter is instructing the kernel how much data > > > +from the packet should be provided. With non-linear skbuffs (e.g. due to > > > +fragmentation), a pattern extending past this offset may not be found. Also see > > > +the related note below about Boyer-Moore algorithm in these cases. > > > > Then, matching on: > > > > - linear skbuff: if the pattern falls within from-to, all good. > > - non-linear skbuff: if pattern falls within from-to, but remaining > > patter > > > > This is clearly broken, the fix is just to document this? > > > > No attempt to fix it this from the kernel? > > I would align linear skbuff behaviour to how non-linear skbuff works, > that is, pattern matching stops at to. This requires a small patch for > xt_string. Sounds reasonable. My efforts at documenting the current behaviour probably show how unintuitive this currently is. Thanks for the suggestion! Cheers, Phil ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [iptables PATCH] extensions: string: Clarify description of --to 2023-10-13 9:28 ` Phil Sutter @ 2023-10-13 10:08 ` Pablo Neira Ayuso 0 siblings, 0 replies; 6+ messages in thread From: Pablo Neira Ayuso @ 2023-10-13 10:08 UTC (permalink / raw) To: Phil Sutter, netfilter-devel On Fri, Oct 13, 2023 at 11:28:53AM +0200, Phil Sutter wrote: > On Thu, Oct 12, 2023 at 10:14:31PM +0200, Pablo Neira Ayuso wrote: > > On Thu, Oct 12, 2023 at 09:47:38PM +0200, Pablo Neira Ayuso wrote: > > > On Thu, Oct 12, 2023 at 06:08:42PM +0200, Phil Sutter wrote: > > > > String match indeed returns a match as long as the given pattern starts > > > > in the range of --from and --to, update the text accordingly. > > > > Also add a note regarding fragment boundaries. > > > > > > > > Closes: https://bugzilla.netfilter.org/show_bug.cgi?id=1707 > > > > Signed-off-by: Phil Sutter <phil@nwl.cc> > > > > --- > > > > extensions/libxt_string.man | 8 ++++++-- > > > > 1 file changed, 6 insertions(+), 2 deletions(-) > > > > > > > > diff --git a/extensions/libxt_string.man b/extensions/libxt_string.man > > > > index 2a470ece19c9d..efdda492ae78d 100644 > > > > --- a/extensions/libxt_string.man > > > > +++ b/extensions/libxt_string.man > > > > @@ -7,9 +7,13 @@ Select the pattern matching strategy. (bm = Boyer-Moore, kmp = Knuth-Pratt-Morri > > > > Set the offset from which it starts looking for any matching. If not passed, default is 0. > > > > .TP > > > > \fB\-\-to\fP \fIoffset\fP > > > > -Set the offset up to which should be scanned. That is, byte \fIoffset\fP-1 > > > > -(counting from 0) is the last one that is scanned. > > > > +Set the offset up to which should be scanned. If the pattern does not start > > > > +within this offset, it is not considered a match. > > > > If not passed, default is the packet size. > > > > +A second function of this parameter is instructing the kernel how much data > > > > +from the packet should be provided. With non-linear skbuffs (e.g. due to > > > > +fragmentation), a pattern extending past this offset may not be found. Also see > > > > +the related note below about Boyer-Moore algorithm in these cases. > > > > > > Then, matching on: > > > > > > - linear skbuff: if the pattern falls within from-to, all good. > > > - non-linear skbuff: if pattern falls within from-to, but remaining > > > patter > > > > > > This is clearly broken, the fix is just to document this? > > > > > > No attempt to fix it this from the kernel? > > > > I would align linear skbuff behaviour to how non-linear skbuff works, > > that is, pattern matching stops at to. This requires a small patch for > > xt_string. > > Sounds reasonable. My efforts at documenting the current behaviour > probably show how unintuitive this currently is. I'd suggest you fix it from skb_find_text() to discard a match if it goes over the "--to" boundary. I think the "slidding" matching after the to boundary (that only works with linear skbuff) is something the user does not want, when they specify a [ from, to ] range, they really mean to narrow it down to such range. And if the user ever wants this, a flag could be exposed to provide such behaviour. Thanks. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2023-10-13 10:08 UTC | newest] Thread overview: 6+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2023-10-12 16:08 [iptables PATCH] extensions: string: Clarify description of --to Phil Sutter 2023-10-12 18:17 ` Phil Sutter 2023-10-12 19:47 ` Pablo Neira Ayuso 2023-10-12 20:14 ` Pablo Neira Ayuso 2023-10-13 9:28 ` Phil Sutter 2023-10-13 10:08 ` Pablo Neira Ayuso
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