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net/{packet,tstun},wgengine/filter: fix unknown IP protocol handling

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01b90df2fa added SCTP support before
(with explicit parsing for ports) and
69de3bf7bf tried to add support for
arbitrary IP protocols (as long as the ACL permited a port of "*",
since we might not know how to find ports from an arbitrary IP
protocol, if it even has such a concept). But apparently that latter
commit wasn't tested end-to-end enough. It had a lot of tests, but the
tests made assumptions about layering that either weren't true, or
regressed since 1.20. Notably, it didn't remove the (*Filter).pre
bidirectional filter that dropped all "unknown" protocol packets both
leaving and entering, even if there were explicit protocol matches
allowing them in.

Also, don't map all unknown protocols to 0. Keep their IP protocol
number parsed so it's matchable by later layers. Only reject illegal
things.

Fixes #6423
Updates #2162
Updates #2163

Change-Id: I9659b3ece86f4db51d644f9b34df78821758842c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick
2022-12-22 12:51:06 -08:00
committed by Brad Fitzpatrick
parent 3386a59cf1
commit c1a2e2c380
4 changed files with 73 additions and 15 deletions
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11
wgengine/filter/filter.go
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@@ -452,7 +452,7 @@ func (f *Filter) runIn4(q *packet.Parsed) (r Response, why string) {
return Accept, "tsmp ok"
default:
if f.matches4.matchProtoAndIPsOnlyIfAllPorts(q) {
return Accept, "otherproto ok"
return Accept, "other-portless ok"
}
return Drop, unknownProtoString(q.IPProto)
}
@@ -512,7 +512,7 @@ func (f *Filter) runIn6(q *packet.Parsed) (r Response, why string) {
return Accept, "tsmp ok"
default:
if f.matches6.matchProtoAndIPsOnlyIfAllPorts(q) {
return Accept, "otherproto ok"
return Accept, "other-portless ok"
}
return Drop, unknownProtoString(q.IPProto)
}
@@ -577,12 +577,7 @@ func (f *Filter) pre(q *packet.Parsed, rf RunFlags, dir direction) Response {
return Drop
}
switch q.IPProto {
case ipproto.Unknown:
// Unknown packets are dangerous; always drop them.
f.logRateLimit(rf, q, dir, Drop, "unknown")
return Drop
case ipproto.Fragment:
if q.IPProto == ipproto.Fragment {
// Fragments after the first always need to be passed through.
// Very small fragments are considered Junk by Parsed.
f.logRateLimit(rf, q, dir, Accept, "fragment")