On Mon, Oct 09, 2023 at 11:55:36PM +0200, Theo Buehler wrote:
> On Mon, Oct 09, 2023 at 11:50:14PM +0200, Tobias Heider wrote:
> > On Mon, Oct 09, 2023 at 11:24:19PM +0200, Theo Buehler wrote:
> > > On Mon, Oct 09, 2023 at 10:49:53PM +0200, Tobias Heider wrote:
> > > > ipsecctl wrongly assumes that strings like the pf tag or
> > > > the identities are always null terminated.
> > > > The diff below fixes the cases that always kill my
> > > > ipsecctl -m when running a fuzzer.
> > > >
> > > > ok?
> > > >
> > > > Index: pfkdump.c
> > > > ===================================================================
> > > > RCS file: /mount/openbsd/cvs/src/sbin/ipsecctl/pfkdump.c,v
> > > > retrieving revision 1.57
> > > > diff -u -p -r1.57 pfkdump.c
> > > > --- pfkdump.c 7 Aug 2023 04:10:08 -0000 1.57
> > > > +++ pfkdump.c 9 Oct 2023 20:41:54 -0000
> > > > @@ -406,9 +406,11 @@ print_tag(struct sadb_ext *ext, struct s
> > > > {
> > > > struct sadb_x_tag *stag = (struct sadb_x_tag *)ext;
> > > > char *p;
> > > > + int plen;
> > > >
> > > > p = (char *)(stag + 1);
> > > > - printf("%s", p);
> > > > + plen = (stag->sadb_x_tag_len * 8) - sizeof(*stag);
> > >
> > > If I understand correctly this attempts to undo the computation in
> > > export_tag(). So this computes PADUP(stag->sadb_x_tag_taglen) where
> > > PADUP() rounds up to the next multiple of 8. Should this not use
> > > stag->sadb_x_tag_taglen - 1 instead, which is the strlen of the tag?
> >
> > Thanks, I don't think this version can read out-of-bounds,
> > see explanation below, but sadb_x_tag_taglen is certainly even better.
Actually looking at net/pfkeyv2_parsemessage.c there is a good reason to
use sadb_x_tag_len here too. The generic header length field gets validated
in pfkeyv2_parsemessage() before being forwarded to userland,
sadb_x_tag_taglen doesn't.
But we might want to harden that too.
> >
> > >
> > > > + printf("%.*s", plen, p);
> > > > }
> > > >
> > > > static void
> > > > @@ -590,10 +592,12 @@ static void
> > > > print_ident(struct sadb_ext *ext, struct sadb_msg *msg, int opts)
> > > > {
> > > > struct sadb_ident *ident = (struct sadb_ident *)ext;
> > > > + int ilen;
> > > >
> > > > - printf("type %s id %llu: %s",
> > > > + ilen = (ident->sadb_ident_len * 8) - sizeof(*ident);
> > >
> > > Similar problem here, but there doesn't seem to be an easy way to get
> > > the actual length of the identity. Doesn't this still overread?
> >
> > Not as far as I understand it. The whole payload is sadb_ident + string +
> > eventual
> > zero padding. We read the string until we hit the first null byte or the
> > end of the
> > whole payload which should be safe.
>
> Ok, if this is guaranteed to have zero padding if the length isn't a
> multiple of 8 the remainder then I have no concern apart from the extra
> parentheses.
fair enough
