th5/alert.go
Adam Langley 4e47a4aef7 crypto/tls: support TLS_FALLBACK_SCSV as a server.
A new attack on CBC padding in SSLv3 was released yesterday[1]. Go only
supports SSLv3 as a server, not as a client. An easy fix is to change
the default minimum version to TLS 1.0 but that seems a little much
this late in the 1.4 process as it may break some things.

Thus this patch adds server support for TLS_FALLBACK_SCSV[2] -- a
mechanism for solving the fallback problem overall. Chrome has
implemented this since February and Google has urged others to do so in
light of yesterday's news.

With this change, clients can indicate that they are doing a fallback
connection and Go servers will be able to correctly reject them.

[1] http://googleonlinesecurity.blogspot.com/2014/10/this-poodle-bites-exploiting-ssl-30.html
[2] https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-00

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/157090043
2014-10-15 17:54:04 -07:00

80 lines
2.6 KiB
Go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tls
import "strconv"
type alert uint8
const (
// alert level
alertLevelWarning = 1
alertLevelError = 2
)
const (
alertCloseNotify alert = 0
alertUnexpectedMessage alert = 10
alertBadRecordMAC alert = 20
alertDecryptionFailed alert = 21
alertRecordOverflow alert = 22
alertDecompressionFailure alert = 30
alertHandshakeFailure alert = 40
alertBadCertificate alert = 42
alertUnsupportedCertificate alert = 43
alertCertificateRevoked alert = 44
alertCertificateExpired alert = 45
alertCertificateUnknown alert = 46
alertIllegalParameter alert = 47
alertUnknownCA alert = 48
alertAccessDenied alert = 49
alertDecodeError alert = 50
alertDecryptError alert = 51
alertProtocolVersion alert = 70
alertInsufficientSecurity alert = 71
alertInternalError alert = 80
alertInappropriateFallback alert = 86
alertUserCanceled alert = 90
alertNoRenegotiation alert = 100
)
var alertText = map[alert]string{
alertCloseNotify: "close notify",
alertUnexpectedMessage: "unexpected message",
alertBadRecordMAC: "bad record MAC",
alertDecryptionFailed: "decryption failed",
alertRecordOverflow: "record overflow",
alertDecompressionFailure: "decompression failure",
alertHandshakeFailure: "handshake failure",
alertBadCertificate: "bad certificate",
alertUnsupportedCertificate: "unsupported certificate",
alertCertificateRevoked: "revoked certificate",
alertCertificateExpired: "expired certificate",
alertCertificateUnknown: "unknown certificate",
alertIllegalParameter: "illegal parameter",
alertUnknownCA: "unknown certificate authority",
alertAccessDenied: "access denied",
alertDecodeError: "error decoding message",
alertDecryptError: "error decrypting message",
alertProtocolVersion: "protocol version not supported",
alertInsufficientSecurity: "insufficient security level",
alertInternalError: "internal error",
alertInappropriateFallback: "inappropriate fallback",
alertUserCanceled: "user canceled",
alertNoRenegotiation: "no renegotiation",
}
func (e alert) String() string {
s, ok := alertText[e]
if ok {
return s
}
return "alert(" + strconv.Itoa(int(e)) + ")"
}
func (e alert) Error() string {
return e.String()
}