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resolver/dns: error if target ends with a colon instead of assuming the default port #2150

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merged 3 commits into from
Jun 22, 2018
Merged

resolver/dns: error if target ends with a colon instead of assuming the default port #2150

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881c423
resolver/dns: error if target ends with a colon instead of assuming t…
dfawley Jun 13, 2018
5ca60d8
clarify error and add comment
dfawley Jun 22, 2018
e096cd7
remove accidentally included file
dfawley Jun 22, 2018
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17 changes: 11 additions & 6 deletions resolver/dns/dns_resolver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,13 @@ const (
)

var (
errMissingAddr = errors.New("missing address")
errMissingAddr = errors.New("dns resolver: missing address")

// Addresses ending with a colon that is supposed to be the separator
// between host and port is not allowed. E.g. "::" is a valid address as
// it is an IPv6 address (host only) and "[::]:" is invalid as it ends with
// a colon as the host and port separator
errEndsWithColon = errors.New("dns resolver: missing port after port-separator colon")
)

// NewBuilder creates a dnsBuilder which is used to factory DNS resolvers.
Expand Down Expand Up @@ -297,7 +303,6 @@ func formatIP(addr string) (addrIP string, ok bool) {
// target: "ipv4-host:80" returns host: "ipv4-host", port: "80"
// target: "[ipv6-host]" returns host: "ipv6-host", port: "443"
// target: ":80" returns host: "localhost", port: "80"
// target: ":" returns host: "localhost", port: "443"
func parseTarget(target string) (host, port string, err error) {
if target == "" {
return "", "", errMissingAddr
Expand All @@ -307,15 +312,15 @@ func parseTarget(target string) (host, port string, err error) {
return target, defaultPort, nil
}
if host, port, err = net.SplitHostPort(target); err == nil {
if port == "" {
// If the port field is empty (target ends with colon), e.g. "[::1]:", this is an error.
return "", "", errEndsWithColon
}
// target has port, i.e ipv4-host:port, [ipv6-host]:port, host-name:port
if host == "" {
// Keep consistent with net.Dial(): If the host is empty, as in ":80", the local system is assumed.
host = "localhost"
}
if port == "" {
// If the port field is empty(target ends with colon), e.g. "[::1]:", defaultPort is used.
port = defaultPort
}
return host, port, nil
}
if host, port, err = net.SplitHostPort(target + ":" + defaultPort); err == nil {
Expand Down
6 changes: 4 additions & 2 deletions resolver/dns/dns_resolver_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -815,7 +815,7 @@ func testIPResolver(t *testing.T) {
{"127.0.0.1:12345", []resolver.Address{{Addr: "127.0.0.1:12345"}}},
{"::1", []resolver.Address{{Addr: "[::1]" + colonDefaultPort}}},
{"[::1]:12345", []resolver.Address{{Addr: "[::1]:12345"}}},
{"[::1]:", []resolver.Address{{Addr: "[::1]:443"}}},
{"[::1]", []resolver.Address{{Addr: "[::1]:443"}}},
{"2001:db8:85a3::8a2e:370:7334", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]" + colonDefaultPort}}},
{"[2001:db8:85a3::8a2e:370:7334]", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]" + colonDefaultPort}}},
{"[2001:db8:85a3::8a2e:370:7334]:12345", []resolver.Address{{Addr: "[2001:db8:85a3::8a2e:370:7334]:12345"}}},
Expand Down Expand Up @@ -867,6 +867,7 @@ func TestResolveFunc(t *testing.T) {
{"www.google.com", nil},
{"foo.bar:12345", nil},
{"127.0.0.1", nil},
{"::", nil},
{"127.0.0.1:12345", nil},
{"[::1]:80", nil},
{"[2001:db8:a0b:12f0::1]:21", nil},
Expand All @@ -875,7 +876,8 @@ func TestResolveFunc(t *testing.T) {
{"[fe80::1%lo0]:80", nil},
{"golang.org:http", nil},
{"[2001:db8::1]:http", nil},
{":", nil},
{"[2001:db8::1]:", errEndsWithColon},
{":", errEndsWithColon},
{"", errMissingAddr},
{"[2001:db8:a0b:12f0::1", errForInvalidTarget},
}
Expand Down