prevent int64 overflow when reading the expiry date of the server config

handshake/server_config_client.go

@@ -4,10 +4,12 @@ import (
 	"bytes"
 	"encoding/binary"
 	"errors"
+	"math"
 	"time"
 
 	"github.com/lucas-clemente/quic-go/crypto"
 	"github.com/lucas-clemente/quic-go/qerr"
+	"github.com/lucas-clemente/quic-go/utils"
 )
 
 type serverConfigClient struct {
@@ -127,7 +129,10 @@ func (s *serverConfigClient) parseValues(tagMap map[Tag][]byte) error {
 	if len(expy) != 8 {
 		return qerr.Error(qerr.CryptoInvalidValueLength, "EXPY")
 	}
-	s.expiry = time.Unix(int64(binary.LittleEndian.Uint64(expy)), 0)
+	// make sure that the value doesn't overflow an int64
+	// furthermore, values close to MaxInt64 are not a valid input to time.Unix, thus set MaxInt64/2 as the maximum value here
+	expyTimestamp := utils.MinUint64(binary.LittleEndian.Uint64(expy), math.MaxInt64/2)
+	s.expiry = time.Unix(int64(expyTimestamp), 0)
 
 	// TODO: implement VER
 

handshake/server_config_client_test.go

@@ -235,6 +235,13 @@ var _ = Describe("Server Config", func() {
 				err := scfg.parseValues(tagMap)
 				Expect(err).To(MatchError("CryptoInvalidValueLength: EXPY"))
 			})
+
+			It("deals with absurdly large timestamps", func() {
+				tagMap[TagEXPY] = bytes.Repeat([]byte{0xff}, 8) // this would overflow the int64
+				err := scfg.parseValues(tagMap)
+				Expect(err).ToNot(HaveOccurred())
+				Expect(scfg.expiry.After(time.Now())).To(BeTrue())
+			})
 		})
 	})
 })

utils/minmax.go

@@ -34,6 +34,14 @@ func MaxUint64(a, b uint64) uint64 {
 	return a
 }
 
+// MinUint64 returns the maximum of two uint64
+func MinUint64(a, b uint64) uint64 {
+	if a < b {
+		return a
+	}
+	return b
+}
+
 // Min returns the minimum of two Ints
 func Min(a, b int) int {
 	if a < b {

utils/minmax_test.go

@@ -25,6 +25,11 @@ var _ = Describe("Min / Max", func() {
 			Expect(MaxUint64(7, 5)).To(Equal(uint64(7)))
 		})
 
+		It("returns the minimum uint64", func() {
+			Expect(MinUint64(5, 7)).To(Equal(uint64(5)))
+			Expect(MinUint64(7, 5)).To(Equal(uint64(5)))
+		})
+
 		It("returns the maximum int64", func() {
 			Expect(MaxInt64(5, 7)).To(Equal(int64(7)))
 			Expect(MaxInt64(7, 5)).To(Equal(int64(7)))