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plugin/file: handle empty non-terminal wildcard sources (#8386)

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RFC 4592 permits a wildcard source of synthesis to exist as an empty non-terminal. Track wildcard names proven by descendant records and return NODATA when such a source is selected.

Fixes #4256

Signed-off-by: houyuwushang <liuluoqianqiu@outlook.com>
This commit is contained in:
houyuwushang
2026-08-04 09:37:38 +08:00
committed by GitHub
parent 9ddc4fdb8f
commit d74404f8ac
2 changed files with 115 additions and 12 deletions
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36
plugin/file/lookup.go
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@@ -54,10 +54,10 @@ func (z *Zone) Lookup(ctx context.Context, state request.Request, qname string)
}
var (
found, shot bool
parts string
i int
elem, wildElem *tree.Elem
found, shot bool
parts, wildName string
i int
elem, wildElem *tree.Elem
)
loop, _ := ctx.Value(dnsserver.LoopKey{}).(int)
@@ -99,6 +99,11 @@ func (z *Zone) Lookup(ctx context.Context, state request.Request, qname string)
wildcard := replaceWithAsteriskLabel(parts)
if wild, found := tr.Search(wildcard); found {
wildElem = wild
wildName = wild.Name()
} else if hasDescendant(tr, wildcard) {
// A wildcard domain may exist as an empty non-terminal.
wildElem = nil
wildName = wildcard
}
// Keep on searching, because maybe we hit an empty-non-terminal (which aren't
@@ -188,8 +193,12 @@ func (z *Zone) Lookup(ctx context.Context, state request.Request, qname string)
// Haven't found the original name.
// Found wildcard.
if wildElem != nil && !closerENTExists(tr, qname, wildElem.Name()) {
// Found a wildcard source of synthesis. It may be an empty non-terminal.
if wildName != "" && !closerENTExists(tr, qname, wildName) {
if wildElem == nil {
return nil, ap.soa(do), nil, NoData
}
// set metadata value for the wildcard record that synthesized the result
metadata.SetValueFunc(ctx, "zone/wildcard", func() string {
return wildElem.Name()
@@ -236,10 +245,8 @@ func (z *Zone) Lookup(ctx context.Context, state request.Request, qname string)
// Hacky way to get around empty-non-terminals. If a longer name does exist, but this qname, does not, it
// must be an empty-non-terminal. If so, we do the proper NXDOMAIN handling, but set the rcode to be success.
if x, found := tr.Next(qname); found {
if dns.IsSubDomain(qname, x.Name()) {
rcode = Success
}
if hasDescendant(tr, qname) {
rcode = Success
}
ret := ap.soa(do)
@@ -292,8 +299,7 @@ func closerENTExists(tr *tree.Tree, qname, wildcardName string) bool {
if name == parent || !dns.IsSubDomain(parent, name) {
return false
}
// An ENT exists at `name` iff tr.Next(name) returns a descendant of name.
if x, found := tr.Next(name); found && dns.IsSubDomain(name, x.Name()) {
if hasDescendant(tr, name) {
return true
}
offset, end = dns.NextLabel(name, 0)
@@ -301,6 +307,12 @@ func closerENTExists(tr *tree.Tree, qname, wildcardName string) bool {
return false
}
// hasDescendant reports whether the tree contains a name strictly below name.
func hasDescendant(tr *tree.Tree, name string) bool {
x, found := tr.Next(name)
return found && tree.Less(x, name) != 0 && dns.IsSubDomain(name, x.Name())
}
// typeFromElem returns the type tp from e and adds signatures (if they exist) and do is true.
func typeFromElem(elem *tree.Elem, tp uint16, do bool) []dns.RR {
rrs := elem.Type(tp)