From 3629fb389e6ed5098dec8f59cbeab657c0c6bbde Mon Sep 17 00:00:00 2001
From: Terin Stock <terinjokes@gmail.com>
Date: Tue, 13 Nov 2018 00:36:08 -0800
Subject: [PATCH] fix: loosen LinkAttribute length checks (#8)

Loosen the LinkAttribute length checks, to parse links that store
information other than MAC addresses in the Address or Broadcast fields.

This change, for example, now allows IPIP, GRE over IP, 6to4, and IP
over Infiniband.

The fields continue to be net.HardwareAddr, which may result in slightly
unusual representations when printed as a string. This type can be cast
to other byte slice types by users, if necessary.

Fix: #7
---
 link.go      |  6 ++++--
 link_test.go | 44 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/link.go b/link.go
index 88b822f..a5c07ca 100644
--- a/link.go
+++ b/link.go
@@ -217,12 +217,14 @@ func (a *LinkAttributes) UnmarshalBinary(b []byte) error {
 		case iflaUnspec:
 			//unused attribute
 		case iflaAddress:
-			if len(attr.Data) != 6 {
+			l := len(attr.Data)
+			if l < 4 || l > 32 {
 				return errInvalidLinkMessageAttr
 			}
 			a.Address = attr.Data
 		case iflaBroadcast:
-			if len(attr.Data) != 6 {
+			l := len(attr.Data)
+			if l < 4 || l > 32 {
 				return errInvalidLinkMessageAttr
 			}
 			a.Broadcast = attr.Data
diff --git a/link_test.go b/link_test.go
index 2c6d8ad..e245533 100644
--- a/link_test.go
+++ b/link_test.go
@@ -69,6 +69,28 @@ func TestLinkMessageMarshalBinary(t *testing.T) {
 				0x05, 0x00, 0x06, 0x00, 0x00, 0x00, 0x00, 0x00,
 			},
 		},
+		{
+			name: "attributes ipip",
+			m: &LinkMessage{
+				Attributes: LinkAttributes{
+					Address:   []byte{10, 0, 0, 1},
+					Broadcast: []byte{255, 255, 255, 255},
+					Name:      "ipip",
+				},
+			},
+			b: []byte{
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x08, 0x00, 0x01, 0x00, 0x0a, 0x00, 0x00, 0x01,
+				0x08, 0x00, 0x02, 0x00, 0xff, 0xff, 0xff, 0xff,
+				0x09, 0x00, 0x03, 0x00, 0x69, 0x70, 0x69, 0x70,
+				0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x04, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x05, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x06, 0x00,
+				0x00, 0x00, 0x00, 0x00,
+			},
+		},
 	}
 
 	for _, tt := range tests {
@@ -188,6 +210,28 @@ func TestLinkMessageUnmarshalBinary(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "attributes ipip",
+			b: []byte{
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x06, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+				0x08, 0x00, 0x01, 0x00, 0x0a, 0x00, 0x00, 0x01,
+				0x08, 0x00, 0x02, 0x00, 0xff, 0xff, 0xff, 0xff,
+				0x09, 0x00, 0x03, 0x00, 0x69, 0x70, 0x69, 0x70,
+				0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x04, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x08, 0x00, 0x05, 0x00,
+				0x00, 0x00, 0x00, 0x00, 0x05, 0x00, 0x06, 0x00,
+				0x00, 0x00, 0x00, 0x00,
+			},
+			m: &LinkMessage{
+				Attributes: LinkAttributes{
+					Address:   []byte{10, 0, 0, 1},
+					Broadcast: []byte{255, 255, 255, 255},
+					Name:      "ipip",
+				},
+			},
+		},
 	}
 
 	for _, tt := range tests {