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tsdns: be more strict with type validation.

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Previously, a type AAAA query would be answered with an A record
if only an IPv4 address was available. This is irrelevant for us
while we only use IPv4, but it will be a bug one day,
so it's worth being precise about semantics.

Signed-off-by: Dmytro Shynkevych <dmytro@tailscale.com>
This commit is contained in:
Dmytro Shynkevych
2020-08-27 00:40:30 -04:00
parent bc34788e65
commit 34a7e7c12b
2 changed files with 47 additions and 5 deletions
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wgengine/tsdns/tsdns.go
+16 -5
View File
@@ -182,7 +182,8 @@ func (r *Resolver) NextResponse() (Packet, error) {
}
}
// Resolve maps a given domain name to the IP address of the host that owns it.
// Resolve maps a given domain name to the IP address of the host that owns it,
// if the IP address conforms to the DNS resource type given by tp (one of A, AAAA, ALL).
// The domain name must be in canonical form (with a trailing period).
func (r *Resolver) Resolve(domain string, tp dns.Type) (netaddr.IP, dns.RCode, error) {
r.mu.Lock()
@@ -209,8 +210,18 @@ func (r *Resolver) Resolve(domain string, tp dns.Type) (netaddr.IP, dns.RCode, e
return netaddr.IP{}, dns.RCodeNameError, nil
}
switch tp {
case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
// Refactoring note: this must happen after we check suffixes,
// otherwise we will respond with NOTIMP to requests that should be forwarded.
switch {
case tp == dns.TypeA || tp == dns.TypeALL:
if !addr.Is4() {
return netaddr.IP{}, dns.RCodeSuccess, nil
}
return addr, dns.RCodeSuccess, nil
case tp == dns.TypeAAAA || tp == dns.TypeALL:
if !addr.Is6() {
return netaddr.IP{}, dns.RCodeSuccess, nil
}
return addr, dns.RCodeSuccess, nil
default:
return netaddr.IP{}, dns.RCodeNotImplemented, errNotImplemented
@@ -284,7 +295,7 @@ type response struct {
Question dns.Question
// Name is the response to a PTR query.
Name string
// IP is the response to an A, AAAA, or ANY query.
// IP is the response to an A, AAAA, or ALL query.
IP netaddr.IP
}
@@ -395,7 +406,7 @@ func marshalResponse(resp *response) ([]byte, error) {
case dns.TypeA, dns.TypeAAAA, dns.TypeALL:
if resp.IP.Is4() {
err = marshalARecord(resp.Question.Name, resp.IP, &builder)
} else {
} else if resp.IP.Is6() {
err = marshalAAAARecord(resp.Question.Name, resp.IP, &builder)
}
case dns.TypePTR: