This changes the TLS and certificate handling in a few ways: - We always use TLS 1.2, both for sync connections (as previously) and the GUI/REST/discovery stuff. This is a tightening of the requirements on the GUI. AS far as I can tell from caniusethis.com every browser from 2013 and forward supports TLS 1.2, so I think we should be fine. - We always greate ECDSA certificates. Previously we'd create ECDSA-with-RSA certificates for sync connections and pure RSA certificates for the web stuff. The new default is more modern and the same everywhere. These certificates are OK in TLS 1.2. - We use the Go CPU detection stuff to choose the cipher suites to use, indirectly. The TLS package uses CPU capabilities probing to select either AES-GCM (fast if we have AES-NI) or ChaCha20 (faster if we don't). These CPU detection things aren't exported though, so the tlsutil package now does a quick TLS handshake with itself as part of init(). If the chosen cipher suite was AES-GCM we prioritize that, otherwise we prefer ChaCha20. Some might call this ugly. I think it's awesome.
This commit is contained in:
Jakob Borg
@@ -27,17 +27,74 @@ var (
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ErrIdentificationFailed = fmt.Errorf("failed to identify socket type")
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)
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// NewCertificate generates and returns a new TLS certificate. If tlsRSABits
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// is greater than zero we generate an RSA certificate with the specified
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// number of bits. Otherwise we create a 384 bit ECDSA certificate.
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func NewCertificate(certFile, keyFile, tlsDefaultCommonName string, tlsRSABits int) (tls.Certificate, error) {
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var priv interface{}
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var err error
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if tlsRSABits > 0 {
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priv, err = rsa.GenerateKey(rand.Reader, tlsRSABits)
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} else {
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priv, err = ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
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var (
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// The list of cipher suites we will use / suggest for TLS connections.
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// This is built based on the component slices below, depending on what
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// the hardware prefers.
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cipherSuites []uint16
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// Suites that are good and fast on hardware with AES-NI. These are
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// reordered from the Go default to put the 256 bit ciphers above the
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// 128 bit ones - because that looks cooler, even though there is
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// probably no relevant difference in strength yet.
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gcmSuites = []uint16{
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tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
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tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
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tls.TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,
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}
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// Suites that are good and fast on hardware *without* AES-NI.
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chaChaSuites = []uint16{
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tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
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tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
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}
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// The rest of the suites, minus DES stuff.
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otherSuites = []uint16{
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tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256,
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tls.TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA,
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256,
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tls.TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA,
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tls.TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA,
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tls.TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA,
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tls.TLS_RSA_WITH_AES_128_GCM_SHA256,
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tls.TLS_RSA_WITH_AES_256_GCM_SHA384,
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tls.TLS_RSA_WITH_AES_128_CBC_SHA256,
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tls.TLS_RSA_WITH_AES_128_CBC_SHA,
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tls.TLS_RSA_WITH_AES_256_CBC_SHA,
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}
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)
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func init() {
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// Creates the list of ciper suites that SecureDefault uses.
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cipherSuites = buildCipherSuites()
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}
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// SecureDefault returns a tls.Config with reasonable, secure defaults set.
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func SecureDefault() *tls.Config {
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// paranoia
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cs := make([]uint16, len(cipherSuites))
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copy(cs, cipherSuites)
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return &tls.Config{
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// TLS 1.2 is the minimum we accept
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MinVersion: tls.VersionTLS12,
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// We want the longer curves at the front, because that's more
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// secure (so the web tells me, don't ask me to explain the
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// details).
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CurvePreferences: []tls.CurveID{tls.CurveP521, tls.CurveP384, tls.CurveP256},
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// The cipher suite lists built above.
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CipherSuites: cs,
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// We've put some thought into this choice and would like it to
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// matter.
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PreferServerCipherSuites: true,
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}
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}
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// NewCertificate generates and returns a new TLS certificate.
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func NewCertificate(certFile, keyFile, commonName string) (tls.Certificate, error) {
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priv, err := ecdsa.GenerateKey(elliptic.P384(), rand.Reader)
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if err != nil {
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return tls.Certificate{}, fmt.Errorf("generate key: %s", err)
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}
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@@ -48,11 +105,11 @@ func NewCertificate(certFile, keyFile, tlsDefaultCommonName string, tlsRSABits i
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template := x509.Certificate{
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SerialNumber: new(big.Int).SetInt64(rand.Int63()),
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Subject: pkix.Name{
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CommonName: tlsDefaultCommonName,
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CommonName: commonName,
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},
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NotBefore: notBefore,
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NotAfter: notAfter,
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NotBefore: notBefore,
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NotAfter: notAfter,
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SignatureAlgorithm: x509.ECDSAWithSHA256,
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KeyUsage: x509.KeyUsageKeyEncipherment | x509.KeyUsageDigitalSignature,
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ExtKeyUsage: []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth, x509.ExtKeyUsageClientAuth},
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BasicConstraintsValid: true,
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@@ -185,3 +242,79 @@ func pemBlockForKey(priv interface{}) (*pem.Block, error) {
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return nil, fmt.Errorf("unknown key type")
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}
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}
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// buildCipherSuites returns a list of cipher suites with either AES-GCM or
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// ChaCha20 at the top. This takes advantage of the CPU detection that the
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// TLS package does to create an optimal cipher suite list for the current
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// hardware.
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func buildCipherSuites() []uint16 {
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pref := preferredCipherSuite()
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for _, suite := range gcmSuites {
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if suite == pref {
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// Go preferred an AES-GCM suite. Use those first.
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return append(gcmSuites, append(chaChaSuites, otherSuites...)...)
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}
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}
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// Use ChaCha20 at the top, then AES-GCM etc.
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return append(chaChaSuites, append(gcmSuites, otherSuites...)...)
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}
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// preferredCipherSuite returns the cipher suite that is selected for a TLS
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// connection made with the Go defaults to ourselves. This is (currently,
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// probably) either a ChaCha20 suite or an AES-GCM suite, depending on what
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// the CPU detection has decided is fastest on this hardware.
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//
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// The function will return zero if something odd happens, and there's no
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// guarantee what cipher suite would be chosen anyway, so the return value
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// should be taken with a grain of salt.
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func preferredCipherSuite() uint16 {
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// This is one of our certs from NewCertificate above, to avoid having
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// to generate one at init time just for this function.
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crtBs := []byte(`-----BEGIN CERTIFICATE-----
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MIIBXDCCAQOgAwIBAgIIQUODl2/bE4owCgYIKoZIzj0EAwIwFDESMBAGA1UEAxMJ
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c3luY3RoaW5nMB4XDTE4MTAxNDA2MjU0M1oXDTQ5MTIzMTIzNTk1OVowFDESMBAG
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A1UEAxMJc3luY3RoaW5nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEMqP+1lL4
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0s/xtI3ygExzYc/GvLHr0qetpBrUVHaDwS/cR1yXDsYaJpJcUNtrf1XK49IlpWW1
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Ds8seQsSg7/9BaM/MD0wDgYDVR0PAQH/BAQDAgWgMB0GA1UdJQQWMBQGCCsGAQUF
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BwMBBggrBgEFBQcDAjAMBgNVHRMBAf8EAjAAMAoGCCqGSM49BAMCA0cAMEQCIFxY
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MDBA92FKqZYSZjmfdIbT1OI6S9CnAFvL/pJZJwNuAiAV7osre2NiCHtXABOvsGrH
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vKWqDvXcHr6Tlo+LmTAdyg==
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-----END CERTIFICATE-----
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`)
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keyBs := []byte(`-----BEGIN EC PRIVATE KEY-----
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MHcCAQEEIHtPxVHlj6Bhi9RgSR2/lAtIQ7APM9wmpaJAcds6TD2CoAoGCCqGSM49
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AwEHoUQDQgAEMqP+1lL40s/xtI3ygExzYc/GvLHr0qetpBrUVHaDwS/cR1yXDsYa
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JpJcUNtrf1XK49IlpWW1Ds8seQsSg7/9BQ==
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-----END EC PRIVATE KEY-----
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`)
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cert, err := tls.X509KeyPair(crtBs, keyBs)
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if err != nil {
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return 0
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}
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serverCfg := &tls.Config{
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MinVersion: tls.VersionTLS12,
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PreferServerCipherSuites: true,
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Certificates: []tls.Certificate{cert},
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}
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clientCfg := &tls.Config{
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MinVersion: tls.VersionTLS12,
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InsecureSkipVerify: true,
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}
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c0, c1 := net.Pipe()
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c := tls.Client(c0, clientCfg)
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go func() {
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c.Handshake()
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}()
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s := tls.Server(c1, serverCfg)
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if err := s.Handshake(); err != nil {
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return 0
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}
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return c.ConnectionState().CipherSuite
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}
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