1 files changed, 86 insertions, 13 deletions

diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index 0caa51c1e..135a60b12 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -15,6 +15,7 @@
 package header
 
 import (
+	"crypto/sha256"
 	"encoding/binary"
 	"strings"
 
@@ -90,6 +91,23 @@ const (
 	// IPv6Any is the non-routable IPv6 "any" meta address. It is also
 	// known as the unspecified address.
 	IPv6Any tcpip.Address = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
+
+	// IIDSize is the size of an interface identifier (IID), in bytes, as
+	// defined by RFC 4291 section 2.5.1.
+	IIDSize = 8
+
+	// IIDOffsetInIPv6Address is the offset, in bytes, from the start
+	// of an IPv6 address to the beginning of the interface identifier
+	// (IID) for auto-generated addresses. That is, all bytes before
+	// the IIDOffsetInIPv6Address-th byte are the prefix bytes, and all
+	// bytes including and after the IIDOffsetInIPv6Address-th byte are
+	// for the IID.
+	IIDOffsetInIPv6Address = 8
+
+	// OpaqueIIDSecretKeyMinBytes is the recommended minimum number of bytes
+	// for the secret key used to generate an opaque interface identifier as
+	// outlined by RFC 7217.
+	OpaqueIIDSecretKeyMinBytes = 16
 )
 
 // IPv6EmptySubnet is the empty IPv6 subnet. It may also be known as the
@@ -266,27 +284,43 @@ func SolicitedNodeAddr(addr tcpip.Address) tcpip.Address {
 	return solicitedNodeMulticastPrefix + addr[len(addr)-3:]
 }
 
+// EthernetAdddressToModifiedEUI64IntoBuf populates buf with a modified EUI-64
+// from a 48-bit Ethernet/MAC address, as per RFC 4291 section 2.5.1.
+//
+// buf MUST be at least 8 bytes.
+func EthernetAdddressToModifiedEUI64IntoBuf(linkAddr tcpip.LinkAddress, buf []byte) {
+	buf[0] = linkAddr[0] ^ 2
+	buf[1] = linkAddr[1]
+	buf[2] = linkAddr[2]
+	buf[3] = 0xFF
+	buf[4] = 0xFE
+	buf[5] = linkAddr[3]
+	buf[6] = linkAddr[4]
+	buf[7] = linkAddr[5]
+}
+
+// EthernetAddressToModifiedEUI64 computes a modified EUI-64 from a 48-bit
+// Ethernet/MAC address, as per RFC 4291 section 2.5.1.
+func EthernetAddressToModifiedEUI64(linkAddr tcpip.LinkAddress) [IIDSize]byte {
+	var buf [IIDSize]byte
+	EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, buf[:])
+	return buf
+}
+
 // LinkLocalAddr computes the default IPv6 link-local address from a link-layer
 // (MAC) address.
 func LinkLocalAddr(linkAddr tcpip.LinkAddress) tcpip.Address {
-	// Convert a 48-bit MAC to an EUI-64 and then prepend the link-local
-	// header, FE80::.
+	// Convert a 48-bit MAC to a modified EUI-64 and then prepend the
+	// link-local header, FE80::.
 	//
 	// The conversion is very nearly:
 	//	aa:bb:cc:dd:ee:ff => FE80::Aabb:ccFF:FEdd:eeff
 	// Note the capital A. The conversion aa->Aa involves a bit flip.
-	lladdrb := [16]byte{
-		0:  0xFE,
-		1:  0x80,
-		8:  linkAddr[0] ^ 2,
-		9:  linkAddr[1],
-		10: linkAddr[2],
-		11: 0xFF,
-		12: 0xFE,
-		13: linkAddr[3],
-		14: linkAddr[4],
-		15: linkAddr[5],
+	lladdrb := [IPv6AddressSize]byte{
+		0: 0xFE,
+		1: 0x80,
 	}
+	EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, lladdrb[IIDOffsetInIPv6Address:])
 	return tcpip.Address(lladdrb[:])
 }
 
@@ -298,3 +332,42 @@ func IsV6LinkLocalAddress(addr tcpip.Address) bool {
 	}
 	return addr[0] == 0xfe && (addr[1]&0xc0) == 0x80
 }
+
+// AppendOpaqueInterfaceIdentifier appends a 64 bit opaque interface identifier
+// (IID) to buf as outlined by RFC 7217 and returns the extended buffer.
+//
+// The opaque IID is generated from the cryptographic hash of the concatenation
+// of the prefix, NIC's name, DAD counter (DAD retry counter) and the secret
+// key. The secret key SHOULD be at least OpaqueIIDSecretKeyMinBytes bytes and
+// MUST be generated to a pseudo-random number. See RFC 4086 for randomness
+// requirements for security.
+//
+// If buf has enough capacity for the IID (IIDSize bytes), a new underlying
+// array for the buffer will not be allocated.
+func AppendOpaqueInterfaceIdentifier(buf []byte, prefix tcpip.Subnet, nicName string, dadCounter uint8, secretKey []byte) []byte {
+	// As per RFC 7217 section 5, the opaque identifier can be generated as a
+	// cryptographic hash of the concatenation of each of the function parameters.
+	// Note, we omit the optional Network_ID field.
+	h := sha256.New()
+	// h.Write never returns an error.
+	h.Write([]byte(prefix.ID()[:IIDOffsetInIPv6Address]))
+	h.Write([]byte(nicName))
+	h.Write([]byte{dadCounter})
+	h.Write(secretKey)
+
+	var sumBuf [sha256.Size]byte
+	sum := h.Sum(sumBuf[:0])
+
+	return append(buf, sum[:IIDSize]...)
+}
+
+// LinkLocalAddrWithOpaqueIID computes the default IPv6 link-local address with
+// an opaque IID.
+func LinkLocalAddrWithOpaqueIID(nicName string, dadCounter uint8, secretKey []byte) tcpip.Address {
+	lladdrb := [IPv6AddressSize]byte{
+		0: 0xFE,
+		1: 0x80,
+	}
+
+	return tcpip.Address(AppendOpaqueInterfaceIdentifier(lladdrb[:IIDOffsetInIPv6Address], IPv6LinkLocalPrefix.Subnet(), nicName, dadCounter, secretKey))
+}