implement HKDF expansion

2018-09-19 22:07:47 -04:00
parent 3eea16ce93
commit a1bea2c3af
3 changed files with 93 additions and 17 deletions
--- a/internal/crypto/hkdf.go
+++ b/internal/crypto/hkdf.go
@@ -3,6 +3,7 @@ package crypto
 import (
 	"crypto"
 	"crypto/hmac"
+	"encoding/binary"
 )

 // copied from https://github.com/cloudflare/tls-tris/blob/master/hkdf.go
@@ -17,3 +18,39 @@ func hkdfExtract(hash crypto.Hash, secret, salt []byte) []byte {
 	extractor.Write(secret)
 	return extractor.Sum(nil)
 }
+
+// copied from https://github.com/cloudflare/tls-tris/blob/master/hkdf.go
+func hkdfExpand(hash crypto.Hash, prk, info []byte, l int) []byte {
+	var (
+		expander = hmac.New(hash.New, prk)
+		res      = make([]byte, l)
+		counter  = byte(1)
+		prev     []byte
+	)
+
+	if l > 255*expander.Size() {
+		panic("hkdf: requested too much output")
+	}
+
+	p := res
+	for len(p) > 0 {
+		expander.Reset()
+		expander.Write(prev)
+		expander.Write(info)
+		expander.Write([]byte{counter})
+		prev = expander.Sum(prev[:0])
+		counter++
+		n := copy(p, prev)
+		p = p[n:]
+	}
+
+	return res
+}
+
+func qhkdfExpand(secret []byte, label string, length int) []byte {
+	qlabel := make([]byte, 2+1+5+len(label))
+	binary.BigEndian.PutUint16(qlabel[0:2], uint16(length))
+	qlabel[2] = uint8(5 + len(label))
+	copy(qlabel[3:], []byte("QUIC "+label))
+	return hkdfExpand(crypto.SHA256, secret, qlabel, length)
+}
--- a/internal/crypto/hkdf_test.go
+++ b/internal/crypto/hkdf_test.go
@@ -3,16 +3,66 @@ package crypto
 import (
 	"bytes"
 	"crypto"
+	"fmt"

 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )

 var _ = Describe("HKDF", func() {
-	// test case A.1 from https://tools.ietf.org/html/rfc5869
-	It("extracts", func() {
-		salt := []byte{0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa, 0xb, 0xc}
-		secret := bytes.Repeat([]byte{0x0b}, 22)
-		Expect(hkdfExtract(crypto.SHA256, secret, salt)).To(Equal([]byte{0x7, 0x77, 0x9, 0x36, 0x2c, 0x2e, 0x32, 0xdf, 0xd, 0xdc, 0x3f, 0xd, 0xc4, 0x7b, 0xba, 0x63, 0x90, 0xb6, 0xc7, 0x3b, 0xb5, 0xf, 0x9c, 0x31, 0x22, 0xec, 0x84, 0x4a, 0xd7, 0xc2, 0xb3, 0xe5}))
-	})
+	type testcase struct {
+		name                                    string
+		hash                                    crypto.Hash
+		salt, secret, info, extracted, expanded []byte
+	}
+	// test cases taken from https://tools.ietf.org/html/rfc5869#appendix-A
+	testcases := []testcase{
+		{
+			name:      "RFC5869 A.1",
+			hash:      crypto.SHA256,
+			salt:      []byte{0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa, 0xb, 0xc},
+			secret:    bytes.Repeat([]byte{0x0b}, 22),
+			info:      []byte{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9},
+			extracted: []byte{0x7, 0x77, 0x9, 0x36, 0x2c, 0x2e, 0x32, 0xdf, 0xd, 0xdc, 0x3f, 0xd, 0xc4, 0x7b, 0xba, 0x63, 0x90, 0xb6, 0xc7, 0x3b, 0xb5, 0xf, 0x9c, 0x31, 0x22, 0xec, 0x84, 0x4a, 0xd7, 0xc2, 0xb3, 0xe5},
+			expanded:  []byte{0x3c, 0xb2, 0x5f, 0x25, 0xfa, 0xac, 0xd5, 0x7a, 0x90, 0x43, 0x4f, 0x64, 0xd0, 0x36, 0x2f, 0x2a, 0x2d, 0x2d, 0xa, 0x90, 0xcf, 0x1a, 0x5a, 0x4c, 0x5d, 0xb0, 0x2d, 0x56, 0xec, 0xc4, 0xc5, 0xbf, 0x34, 0x0, 0x72, 0x8, 0xd5, 0xb8, 0x87, 0x18, 0x58, 0x65},
+		},
+		{
+			name:      "RFC5869 A.2",
+			hash:      crypto.SHA256,
+			salt:      []byte{0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf},
+			secret:    []byte{0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f},
+			info:      []byte{0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff},
+			extracted: []byte{0x6, 0xa6, 0xb8, 0x8c, 0x58, 0x53, 0x36, 0x1a, 0x6, 0x10, 0x4c, 0x9c, 0xeb, 0x35, 0xb4, 0x5c, 0xef, 0x76, 0x0, 0x14, 0x90, 0x46, 0x71, 0x1, 0x4a, 0x19, 0x3f, 0x40, 0xc1, 0x5f, 0xc2, 0x44},
+			expanded:  []byte{0xb1, 0x1e, 0x39, 0x8d, 0xc8, 0x3, 0x27, 0xa1, 0xc8, 0xe7, 0xf7, 0x8c, 0x59, 0x6a, 0x49, 0x34, 0x4f, 0x1, 0x2e, 0xda, 0x2d, 0x4e, 0xfa, 0xd8, 0xa0, 0x50, 0xcc, 0x4c, 0x19, 0xaf, 0xa9, 0x7c, 0x59, 0x4, 0x5a, 0x99, 0xca, 0xc7, 0x82, 0x72, 0x71, 0xcb, 0x41, 0xc6, 0x5e, 0x59, 0xe, 0x9, 0xda, 0x32, 0x75, 0x60, 0xc, 0x2f, 0x9, 0xb8, 0x36, 0x77, 0x93, 0xa9, 0xac, 0xa3, 0xdb, 0x71, 0xcc, 0x30, 0xc5, 0x81, 0x79, 0xec, 0x3e, 0x87, 0xc1, 0x4c, 0x1, 0xd5, 0xc1, 0xf3, 0x43, 0x4f, 0x1d, 0x87},
+		},
+		{
+			name:      "RFC5869 A.3",
+			hash:      crypto.SHA256,
+			secret:    bytes.Repeat([]byte{0x0b}, 22),
+			extracted: []byte{0x19, 0xef, 0x24, 0xa3, 0x2c, 0x71, 0x7b, 0x16, 0x7f, 0x33, 0xa9, 0x1d, 0x6f, 0x64, 0x8b, 0xdf, 0x96, 0x59, 0x67, 0x76, 0xaf, 0xdb, 0x63, 0x77, 0xac, 0x43, 0x4c, 0x1c, 0x29, 0x3c, 0xcb, 0x4},
+			expanded:  []byte{0x8d, 0xa4, 0xe7, 0x75, 0xa5, 0x63, 0xc1, 0x8f, 0x71, 0x5f, 0x80, 0x2a, 0x6, 0x3c, 0x5a, 0x31, 0xb8, 0xa1, 0x1f, 0x5c, 0x5e, 0xe1, 0x87, 0x9e, 0xc3, 0x45, 0x4e, 0x5f, 0x3c, 0x73, 0x8d, 0x2d, 0x9d, 0x20, 0x13, 0x95, 0xfa, 0xa4, 0xb6, 0x1a, 0x96, 0xc8},
+		},
+		{
+			name:      "RFC5869 A.4",
+			hash:      crypto.SHA1,
+			salt:      []byte{0x0, 0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8, 0x9, 0xa, 0xb, 0xc},
+			secret:    bytes.Repeat([]byte{0x0b}, 11),
+			info:      []byte{0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9},
+			extracted: []byte{0x9b, 0x6c, 0x18, 0xc4, 0x32, 0xa7, 0xbf, 0x8f, 0xe, 0x71, 0xc8, 0xeb, 0x88, 0xf4, 0xb3, 0xb, 0xaa, 0x2b, 0xa2, 0x43},
+			expanded:  []byte{0x8, 0x5a, 0x1, 0xea, 0x1b, 0x10, 0xf3, 0x69, 0x33, 0x6, 0x8b, 0x56, 0xef, 0xa5, 0xad, 0x81, 0xa4, 0xf1, 0x4b, 0x82, 0x2f, 0x5b, 0x9, 0x15, 0x68, 0xa9, 0xcd, 0xd4, 0xf1, 0x55, 0xfd, 0xa2, 0xc2, 0x2e, 0x42, 0x24, 0x78, 0xd3, 0x5, 0xf3, 0xf8, 0x96},
+		},
+	}
+
+	for i := range testcases {
+		t := testcases[i]
+
+		It(fmt.Sprintf("case %s: extracts", t.name), func() {
+			Expect(hkdfExtract(t.hash, t.secret, t.salt)).To(Equal(t.extracted))
+		})
+
+		It(fmt.Sprintf("case %s: expands", t.name), func() {
+			prk := hkdfExtract(t.hash, t.secret, t.salt)
+			Expect(hkdfExpand(t.hash, prk, t.info, len(t.expanded))).To(Equal(t.expanded))
+		})
+	}
 })
--- a/internal/crypto/key_derivation.go
+++ b/internal/crypto/key_derivation.go
@@ -1,9 +1,6 @@
 package crypto

 import (
-	"crypto"
-	"encoding/binary"
-
 	"github.com/bifurcation/mint"
 	"github.com/lucas-clemente/quic-go/internal/protocol"
 )
@@ -19,14 +16,6 @@ type TLSExporter interface {
 	ComputeExporter(label string, context []byte, keyLength int) ([]byte, error)
 }

-func qhkdfExpand(secret []byte, label string, length int) []byte {
-	qlabel := make([]byte, 2+1+5+len(label))
-	binary.BigEndian.PutUint16(qlabel[0:2], uint16(length))
-	qlabel[2] = uint8(5 + len(label))
-	copy(qlabel[3:], []byte("QUIC "+label))
-	return mint.HkdfExpand(crypto.SHA256, secret, qlabel, length)
-}
-
 // DeriveAESKeys derives the AES keys and creates a matching AES-GCM AEAD instance
 func DeriveAESKeys(tls TLSExporter, pers protocol.Perspective) (AEAD, error) {
 	var myLabel, otherLabel string