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reject small CHLOs to prevent amplification attacks

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fixes #1
This commit is contained in:
Lucas Clemente
2016-05-19 16:20:22 +02:00
parent c748a8dfc0
commit f86875f746
3 changed files with 17 additions and 2 deletions
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4
handshake/crypto_setup.go
View File

@@ -167,6 +167,10 @@ func (h *CryptoSetup) isInchoateCHLO(cryptoData map[Tag][]byte) bool {
}
func (h *CryptoSetup) handleInchoateCHLO(sni string, data []byte, cryptoData map[Tag][]byte) ([]byte, error) {
if len(data) < protocol.ClientHelloMinimumSize {
return nil, qerr.Error(qerr.CryptoInvalidValueLength, "CHLO too small")
}
var chloOrNil []byte
if h.version > protocol.VersionNumber(30) {
chloOrNil = data

12
handshake/crypto_setup_test.go
View File

@@ -130,7 +130,7 @@ var _ = Describe("Crypto setup", func() {
Context("when responding to client messages", func() {
It("generates REJ messages", func() {
response, err := cs.handleInchoateCHLO("", []byte("chlo"), nil)
response, err := cs.handleInchoateCHLO("", bytes.Repeat([]byte{'a'}, protocol.ClientHelloMinimumSize), nil)
Expect(err).ToNot(HaveOccurred())
Expect(response).To(HavePrefix("REJ"))
Expect(response).To(ContainSubstring("certcompressed"))
@@ -163,7 +163,10 @@ var _ = Describe("Crypto setup", func() {
})
It("handles long handshake", func() {
WriteHandshakeMessage(&stream.dataToRead, TagCHLO, map[Tag][]byte{TagSNI: []byte("quic.clemente.io")})
WriteHandshakeMessage(&stream.dataToRead, TagCHLO, map[Tag][]byte{
TagSNI: []byte("quic.clemente.io"),
TagPAD: bytes.Repeat([]byte{'a'}, protocol.ClientHelloMinimumSize),
})
WriteHandshakeMessage(&stream.dataToRead, TagCHLO, map[Tag][]byte{TagSCID: scfg.ID, TagSNO: cs.nonce, TagSNI: []byte("quic.clemente.io")})
err := cs.HandleCryptoStream()
Expect(err).NotTo(HaveOccurred())
@@ -192,6 +195,11 @@ var _ = Describe("Crypto setup", func() {
It("recognizes proper CHLOs", func() {
Expect(cs.isInchoateCHLO(map[Tag][]byte{TagSCID: scfg.ID, TagSNO: cs.nonce})).To(BeFalse())
})
It("errors on too short inchoate CHLOs", func() {
_, err := cs.handleInchoateCHLO("", bytes.Repeat([]byte{'a'}, protocol.ClientHelloMinimumSize-1), nil)
Expect(err).To(MatchError("CryptoInvalidValueLength: CHLO too small"))
})
})
It("errors without SNI", func() {

3
protocol/protocol.go
View File

@@ -54,3 +54,6 @@ const DefaultRetransmissionTime = 500 * time.Millisecond
// MinRetransmissionTime is the minimum RTO time
const MinRetransmissionTime = 200 * time.Millisecond
// ClientHelloMinimumSize is the minimum size the server expectes an inchoate CHLO to have.
const ClientHelloMinimumSize = 1024