core: Use port ranges to avoid OOM with bad inputs (#2859)

* fix OOM issue caught by fuzzing

* use ParsedAddress as the struct name for the result of ParseNetworkAddress

* simplify code using the ParsedAddress type

* minor cleanups

1 files changed, 75 insertions, 26 deletions

diff --git a/listeners.go b/listeners.go
index 4464b78..37b4c29 100644
--- a/listeners.go
+++ b/listeners.go
@@ -257,52 +257,94 @@ type globalListener struct {
 	pc         net.PacketConn
 }
 
-var (
-	listeners   = make(map[string]*globalListener)
-	listenersMu sync.Mutex
-)
+// ParsedAddress contains the individual components
+// for a parsed network address of the form accepted
+// by ParseNetworkAddress(). Network should be a
+// network value accepted by Go's net package. Port
+// ranges are given by [StartPort, EndPort].
+type ParsedAddress struct {
+	Network   string
+	Host      string
+	StartPort uint
+	EndPort   uint
+}
+
+// JoinHostPort is like net.JoinHostPort, but where the port
+// is StartPort + offset.
+func (l ParsedAddress) JoinHostPort(offset uint) string {
+	return net.JoinHostPort(l.Host, strconv.Itoa(int(l.StartPort+offset)))
+}
 
-// ParseNetworkAddress parses addr, a string of the form "network/host:port"
-// (with any part optional) into its component parts. Because a port can
-// also be a port range, there may be multiple addresses returned.
-func ParseNetworkAddress(addr string) (network string, addrs []string, err error) {
+// PortRangeSize returns how many ports are in
+// pa's port range. Port ranges are inclusive,
+// so the size is the difference of start and
+// end ports plus one.
+func (pa ParsedAddress) PortRangeSize() uint {
+	return (pa.EndPort - pa.StartPort) + 1
+}
+
+// String reconstructs the address string to the form expected
+// by ParseNetworkAddress().
+func (pa ParsedAddress) String() string {
+	port := strconv.FormatUint(uint64(pa.StartPort), 10)
+	if pa.StartPort != pa.EndPort {
+		port += "-" + strconv.FormatUint(uint64(pa.EndPort), 10)
+	}
+	return JoinNetworkAddress(pa.Network, pa.Host, port)
+}
+
+// ParseNetworkAddress parses addr into its individual
+// components. The input string is expected to be of
+// the form "network/host:port-range" where any part is
+// optional. The default network, if unspecified, is tcp.
+// Port ranges are inclusive.
+//
+// Network addresses are distinct from URLs and do not
+// use URL syntax.
+func ParseNetworkAddress(addr string) (ParsedAddress, error) {
 	var host, port string
-	network, host, port, err = SplitNetworkAddress(addr)
+	network, host, port, err := SplitNetworkAddress(addr)
 	if network == "" {
 		network = "tcp"
 	}
 	if err != nil {
-		return
+		return ParsedAddress{}, err
 	}
 	if network == "unix" || network == "unixgram" || network == "unixpacket" {
-		addrs = []string{host}
-		return
+		return ParsedAddress{
+			Network: network,
+			Host:    host,
+		}, nil
 	}
 	ports := strings.SplitN(port, "-", 2)
 	if len(ports) == 1 {
 		ports = append(ports, ports[0])
 	}
-	var start, end int
-	start, err = strconv.Atoi(ports[0])
+	var start, end uint64
+	start, err = strconv.ParseUint(ports[0], 10, 16)
 	if err != nil {
-		return
+		return ParsedAddress{}, fmt.Errorf("invalid start port: %v", err)
 	}
-	end, err = strconv.Atoi(ports[1])
+	end, err = strconv.ParseUint(ports[1], 10, 16)
 	if err != nil {
-		return
+		return ParsedAddress{}, fmt.Errorf("invalid end port: %v", err)
 	}
 	if end < start {
-		err = fmt.Errorf("end port must be greater than start port")
-		return
+		return ParsedAddress{}, fmt.Errorf("end port must not be less than start port")
 	}
-	for p := start; p <= end; p++ {
-		addrs = append(addrs, net.JoinHostPort(host, fmt.Sprintf("%d", p)))
+	if (end - start) > maxPortSpan {
+		return ParsedAddress{}, fmt.Errorf("port range exceeds %d ports", maxPortSpan)
 	}
-	return
+	return ParsedAddress{
+		Network:   network,
+		Host:      host,
+		StartPort: uint(start),
+		EndPort:   uint(end),
+	}, nil
 }
 
 // SplitNetworkAddress splits a into its network, host, and port components.
-// Note that port may be a port range, or omitted for unix sockets.
+// Note that port may be a port range (:X-Y), or omitted for unix sockets.
 func SplitNetworkAddress(a string) (network, host, port string, err error) {
 	if idx := strings.Index(a, "/"); idx >= 0 {
 		network = strings.ToLower(strings.TrimSpace(a[:idx]))
@@ -317,9 +359,9 @@ func SplitNetworkAddress(a string) (network, host, port string, err error) {
 }
 
 // JoinNetworkAddress combines network, host, and port into a single
-// address string of the form "network/host:port". Port may be a
-// port range. For unix sockets, the network should be "unix" and
-// the path to the socket should be given in the host argument.
+// address string of the form accepted by ParseNetworkAddress(). For unix sockets, the network
+// should be "unix" and the path to the socket should be given as the
+// host parameter.
 func JoinNetworkAddress(network, host, port string) string {
 	var a string
 	if network != "" {
@@ -332,3 +374,10 @@ func JoinNetworkAddress(network, host, port string) string {
 	}
 	return a
 }
+
+var (
+	listeners   = make(map[string]*globalListener)
+	listenersMu sync.Mutex
+)
+
+const maxPortSpan = 65535