forbid empty multiaddrs

fixes #104

Author: Stebalien

codec.go

@@ -20,6 +20,10 @@ func stringToBytes(s string) ([]byte, error) {
 	// consume first empty elem
 	sp = sp[1:]
 
+	if len(sp) == 0 {
+		return nil, fmt.Errorf("failed to parse multiaddr %q: empty multiaddr", s)
+	}
+
 	for len(sp) > 0 {
 		name := sp[0]
 		p := ProtocolWithName(name)
@@ -58,6 +62,9 @@ func stringToBytes(s string) ([]byte, error) {
 }
 
 func validateBytes(b []byte) (err error) {
+	if len(b) == 0 {
+		return fmt.Errorf("empty multiaddr")
+	}
 	for len(b) > 0 {
 		code, n, err := ReadVarintCode(b)
 		if err != nil {
@@ -136,6 +143,9 @@ func readComponent(b []byte) (int, Component, error) {
 }
 
 func bytesToString(b []byte) (ret string, err error) {
+	if len(b) == 0 {
+		return "", fmt.Errorf("empty multiaddr")
+	}
 	var buf strings.Builder
 
 	for len(b) > 0 {

multiaddr.go

@@ -159,6 +159,10 @@ func (m *multiaddr) Decapsulate(o Multiaddr) Multiaddr {
 		return &multiaddr{bytes: cpy}
 	}
 
+	if i == 0 {
+		return nil
+	}
+
 	ma, err := NewMultiaddr(s1[:i])
 	if err != nil {
 		panic("Multiaddr.Decapsulate incorrect byte boundaries.")

multiaddr_test.go

@@ -377,8 +377,8 @@ func TestEncapsulate(t *testing.T) {
 
 	m4, _ := NewMultiaddr("/ip4/127.0.0.1")
 	d := c.Decapsulate(m4)
-	if s := d.String(); s != "" {
-		t.Error("decapsulate /ip4 failed.", "/", s)
+	if d != nil {
+		t.Error("decapsulate /ip4 failed: ", d)
 	}
 }
 
@@ -582,11 +582,11 @@ func TestBinaryMarshaler(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	addr2 := newMultiaddr(t, "")
+	var addr2 multiaddr
 	if err = addr2.UnmarshalBinary(b); err != nil {
 		t.Fatal(err)
 	}
-	if !addr.Equal(addr2) {
+	if !addr.Equal(&addr2) {
 		t.Error("expected equal addresses in circular marshaling test")
 	}
 }
@@ -598,11 +598,11 @@ func TestTextMarshaler(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	addr2 := newMultiaddr(t, "")
+	var addr2 multiaddr
 	if err = addr2.UnmarshalText(b); err != nil {
 		t.Fatal(err)
 	}
-	if !addr.Equal(addr2) {
+	if !addr.Equal(&addr2) {
 		t.Error("expected equal addresses in circular marshaling test")
 	}
 }
@@ -614,11 +614,11 @@ func TestJSONMarshaler(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	addr2 := newMultiaddr(t, "")
+	var addr2 multiaddr
 	if err = addr2.UnmarshalJSON(b); err != nil {
 		t.Fatal(err)
 	}
-	if !addr.Equal(addr2) {
+	if !addr.Equal(&addr2) {
 		t.Error("expected equal addresses in circular marshaling test")
 	}
 }

util_test.go

@@ -16,7 +16,6 @@ func TestSplitFirstLast(t *testing.T) {
 		[]string{ipStr, tcpStr, ipfsStr},
 		[]string{ipStr, tcpStr},
 		[]string{ipStr},
-		[]string{},
 	} {
 		addr := StringCast(strings.Join(x, ""))
 		head, tail := SplitFirst(addr)