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crypto/tls: define api for delegated credentials so they are fetched …
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…using the same mechanisms used to fetch certificates #67 (#69)

Refactor new API

Address comments from review

Address comments from review 2

Address comments from review 3
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@claucece @Lekensteyn
claucece authored and Lekensteyn committed Jan 14, 2022
1 parent e169871 commit baea2bd
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Showing 6 changed files with 180 additions and 153 deletions.
2 changes: 0 additions & 2 deletions src/crypto/tls/auth.go
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Original file line number Diff line number Diff line change
Expand Up @@ -196,8 +196,6 @@ var rsaSignatureSchemes = []struct {
// and optionally filtered by its explicit SupportedSignatureAlgorithms.
//
// This function must be kept in sync with supportedSignatureAlgorithms.
// NOTE: for the PQ KEM exp or using Delegated Credentials, it must be kept in
// sync with supportedSignatureAlgorithmsDC.
func signatureSchemesForCertificate(version uint16, cert *Certificate) []SignatureScheme {
priv, ok := cert.PrivateKey.(crypto.Signer)
if !ok {
Expand Down
36 changes: 24 additions & 12 deletions src/crypto/tls/common.go
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Original file line number Diff line number Diff line change
Expand Up @@ -495,7 +495,8 @@ type ClientHelloInfo struct {

// SignatureSchemesDC lists the signature schemes that the client
// is willing to verify when using Delegated Credentials.
// This can be different from SignatureSchemes.
// This is and can be different from SignatureSchemes. SignatureSchemesDC
// is set only if the DelegatedCredentials Extension is being used.
// If Delegated Credentials are supported, this list should not be nil.
SignatureSchemesDC []SignatureScheme

Expand Down Expand Up @@ -557,6 +558,9 @@ type CertificateRequestInfo struct {

// SignatureSchemesDC lists the signature schemes that the server
// is willing to verify when using Delegated Credentials.
// This is and can be different from SignatureSchemes. SignatureSchemesDC
// is set only if the DelegatedCredentials Extension is being used.
// If Delegated Credentials are supported, this list should not be nil.
SignatureSchemesDC []SignatureScheme

// Version is the TLS version that was negotiated for this connection.
Expand Down Expand Up @@ -851,13 +855,6 @@ type Config struct {
// See https://tools.ietf.org/html/draft-ietf-tls-subcerts.
SupportDelegatedCredential bool

// GetDelegatedCredential returns a DelegatedCredential for use with the
// delegated credential extension based on the ClientHello. It only works
// with TLS 1.3. If this is nil, then the server will not offer
// a DelegatedCredential. If the call returns nil, the server is also
// not offering a DelegatedCredential.
GetDelegatedCredential func(*ClientHelloInfo, *CertificateRequestInfo) (*DelegatedCredential, crypto.PrivateKey, error)

// mutex protects sessionTicketKeys and autoSessionTicketKeys.
mutex sync.RWMutex
// sessionTicketKeys contains zero or more ticket keys. If set, it means the
Expand Down Expand Up @@ -949,7 +946,6 @@ func (c *Config) Clone() *Config {
Renegotiation: c.Renegotiation,
KeyLogWriter: c.KeyLogWriter,
SupportDelegatedCredential: c.SupportDelegatedCredential,
GetDelegatedCredential: c.GetDelegatedCredential,
ECHEnabled: c.ECHEnabled,
ClientECHConfigs: c.ClientECHConfigs,
ServerECHProvider: c.ServerECHProvider,
Expand Down Expand Up @@ -1493,6 +1489,16 @@ func (c *Config) writeKeyLog(label string, clientRandom, secret []byte) error {
// and is only for debugging, so a global mutex saves space.
var writerMutex sync.Mutex

// A DelegatedCredentialPair contains a Delegated Credential and its
// associated private key.
type DelegatedCredentialPair struct {
// DC is the delegated credential.
DC *DelegatedCredential
// PrivateKey is the private key used to derive the public key of
// contained in DC. PrivateKey must implement crypto.Signer.
PrivateKey crypto.PrivateKey
}

// A Certificate is a chain of one or more certificates, leaf first.
type Certificate struct {
Certificate [][]byte
Expand All @@ -1510,9 +1516,15 @@ type Certificate struct {
// SignedCertificateTimestamps contains an optional list of Signed
// Certificate Timestamps which will be served to clients that request it.
SignedCertificateTimestamps [][]byte
// DelegatedCredential is a serialized Delegated Credential, signed by
// the leaf certificate.
// If not supported, this will be nil.
// DelegatedCredentials are a list of Delegated Credentials with their
// corresponding private keys, signed by the leaf certificate.
// If there are no delegated credentials, this field is nil.
DelegatedCredentials []DelegatedCredentialPair
// DelegatedCredential is the delegated credential to be used in the
// handshake.
// If there are no delegated credentials, this field is nil.
// NOTE: Do not fill this field, as it will be filled depending on
// the provided list of delegated credentials.
DelegatedCredential []byte
// Leaf is the parsed form of the leaf certificate, which may be initialized
// using x509.ParseCertificate to reduce per-handshake processing. If nil,
Expand Down
155 changes: 63 additions & 92 deletions src/crypto/tls/delegated_credentials_test.go
View file
Original file line number Diff line number Diff line change
Expand Up @@ -17,13 +17,6 @@ import (
"time"
)

// dcAndPrivateKey stores a Delegated Credential and its corresponding private
// key.
type dcAndPrivateKey struct {
*DelegatedCredential
privateKey crypto.PrivateKey
}

// These test keys were generated with the following program, available in the
// crypto/tls directory:
//
Expand Down Expand Up @@ -137,12 +130,12 @@ ZyJKvc2KqjGeZh0Or5pq6ZJb0zR7WPdz5aJIzaZ5YcxLMSv0KwaAEPH2
`

var (
dcTestConfig *Config
dcTestCerts map[string]*Certificate
serverDC []*dcAndPrivateKey
clientDC []*dcAndPrivateKey
dcNow time.Time
dcTestDCScheme = []SignatureScheme{ECDSAWithP256AndSHA256, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512, Ed25519}
dcTestConfig *Config
dcTestCerts map[string]*Certificate
serverDC []DelegatedCredentialPair
clientDC []DelegatedCredentialPair
dcNow time.Time
dcTestDCSignatureScheme = []SignatureScheme{ECDSAWithP256AndSHA256, Ed25519, ECDSAWithP384AndSHA384, ECDSAWithP521AndSHA512}
)

func init() {
Expand Down Expand Up @@ -232,7 +225,7 @@ func initDCTest() {
}
dcTestCerts["no dc"] = noDcCert

// The root certificates for the client.
// The root certificates for the peer.
dcTestConfig.RootCAs = x509.NewCertPool()

for _, c := range dcTestCerts {
Expand All @@ -243,20 +236,19 @@ func initDCTest() {
dcTestConfig.RootCAs.AddCert(dcRoot)
}

for i := 0; i < len(dcTestDCScheme); i++ {
dc, sk, err := NewDelegatedCredential(dcCertP256, dcTestDCScheme[i], dcNow.Sub(dcCertP256.Leaf.NotBefore)+dcMaxTTL, false)
for i := 0; i < len(dcTestDCSignatureScheme); i++ {
dc, priv, err := NewDelegatedCredential(dcCertP256, dcTestDCSignatureScheme[i], dcNow.Sub(dcCertP256.Leaf.NotBefore)+dcMaxTTL, false)
if err != nil {
panic(err)
}
serverDC = append(serverDC, &dcAndPrivateKey{dc, sk})
serverDC = append(serverDC, DelegatedCredentialPair{dc, priv})

dc, sk, err = NewDelegatedCredential(dcCertP256, dcTestDCScheme[i], dcNow.Sub(dcCertP256.Leaf.NotBefore)+dcMaxTTL, true)
dc, priv, err = NewDelegatedCredential(dcCertP256, dcTestDCSignatureScheme[i], dcNow.Sub(dcCertP256.Leaf.NotBefore)+dcMaxTTL, true)
if err != nil {
panic(err)
}
clientDC = append(clientDC, &dcAndPrivateKey{dc, sk})
clientDC = append(clientDC, DelegatedCredentialPair{dc, priv})
}

}

func publicKeysEqual(publicKey, publicKey2 crypto.PublicKey, algo SignatureScheme) error {
Expand Down Expand Up @@ -387,7 +379,7 @@ func TestDelegatedCredentialMarshal(t *testing.T) {
cert := dcTestCerts["dcEd25519"]
time := dcNow.Sub(cert.Leaf.NotBefore) + dcMaxTTL

for _, sig := range dcTestDCScheme {
for _, sig := range dcTestDCSignatureScheme {
delegatedCred, _, err := NewDelegatedCredential(cert, sig, time, false)
if err != nil {
t.Fatal(err)
Expand Down Expand Up @@ -418,24 +410,44 @@ func TestDelegatedCredentialMarshal(t *testing.T) {
}
}

var dcTests = []struct {
var dcServerTests = []struct {
clientDCSupport bool
clientMaxVers uint16
serverMaxVers uint16
expectSuccess bool
expectDC bool
name string
}{
{true, VersionTLS13, VersionTLS13, true, true, "tls13: DC client support"},
{false, VersionTLS13, VersionTLS13, true, false, "DC not client support"},
{true, VersionTLS12, VersionTLS13, true, false, "client using TLS 1.2. No DC is supported in that version."},
{true, VersionTLS13, VersionTLS12, true, false, "server using TLS 1.2. No DC is supported in that version."},
{true, VersionTLS11, VersionTLS13, true, false, "client using TLS 1.1. No DC is supported in that version."},
{true, VersionTLS13, VersionTLS10, false, false, "server using TLS 1.0. No DC is supported in that version."},
}

var dcClientTests = []struct {
serverDCSupport bool
clientMaxVers uint16
serverMaxVers uint16
expectSuccess bool
expectDC bool
name string
}{
{true, true, VersionTLS13, VersionTLS13, true, true, "tls13: DC server and client support"},
{true, false, VersionTLS13, VersionTLS13, true, false, "DC not server support"},
{false, true, VersionTLS13, VersionTLS13, true, false, "DC not client support"},
{true, true, VersionTLS12, VersionTLS13, true, false, "client using TLS 1.2. No DC is supported in that version."},
{true, true, VersionTLS13, VersionTLS12, true, false, "server using TLS 1.2. No DC is supported in that version."},
{true, true, VersionTLS11, VersionTLS13, true, false, "client using TLS 1.1. No DC is supported in that version."},
{true, true, VersionTLS13, VersionTLS10, false, false, "server using TLS 1.0. No DC is supported in that version."},
{true, VersionTLS13, VersionTLS13, true, true, "tls13: DC server support"},
{false, VersionTLS13, VersionTLS13, true, false, "DC not server support"},
{true, VersionTLS12, VersionTLS13, true, false, "client using TLS 1.2. No DC is supported in that version."},
{true, VersionTLS13, VersionTLS12, true, false, "server using TLS 1.2. No DC is supported in that version."},
{true, VersionTLS11, VersionTLS13, true, false, "client using TLS 1.1. No DC is supported in that version."},
{true, VersionTLS13, VersionTLS10, false, false, "server using TLS 1.0. No DC is supported in that version."},
}

// dcCount defines the delegated credential to be used as returned by the
// getCertificate or getClientCertificate callback. This allows to use
// delegated credentials with different algorithms at each run of the
// tests.
var dcCount int

// Checks that the client suppports a version >= 1.3 and accepts Delegated
// Credentials. If so, it returns the delegation certificate; otherwise it
// returns a non-delegated certificate.
Expand All @@ -446,7 +458,9 @@ func testServerGetCertificate(ch *ClientHelloInfo) (*Certificate, error) {
}

if versOk && ch.SupportsDelegatedCredential {
return dcTestCerts["dcP256"], nil
serverCert := dcTestCerts["dcP256"]
serverCert.DelegatedCredentials = serverDC[dcCount:]
return serverCert, nil
}
return dcTestCerts["no dc"], nil

Expand All @@ -462,45 +476,17 @@ func testClientGetCertificate(cr *CertificateRequestInfo) (*Certificate, error)
}

if versOk && cr.SupportsDelegatedCredential {
return dcTestCerts["dcP256"], nil
clientCert := dcTestCerts["dcP256"]
clientCert.DelegatedCredentials = clientDC[dcCount:]
return clientCert, nil
}
return dcTestCerts["no dc"], nil

}

// sets the dc to use for testing
var dcCounter = 0

// Checks that the client supports the signature algorithm supported by the test
// server, and that the server has a Delegated Credential.
func testGetDelegatedCredential(ch *ClientHelloInfo, cr *CertificateRequestInfo) (*DelegatedCredential, crypto.PrivateKey, error) {
if ch != nil {
schemeOk := false
for _, scheme := range ch.SignatureSchemesDC {
schemeOk = schemeOk || (scheme == dcTestDCScheme[dcCounter])
}

if schemeOk && ch.SupportsDelegatedCredential {
return serverDC[dcCounter].DelegatedCredential, serverDC[dcCounter].privateKey, nil
}
} else if cr != nil {
schemeOk := false
for _, scheme := range cr.SignatureSchemesDC {
schemeOk = schemeOk || (scheme == dcTestDCScheme[dcCounter])
}

if schemeOk && cr.SupportsDelegatedCredential {
return clientDC[dcCounter].DelegatedCredential, clientDC[dcCounter].privateKey, nil
}
}

return nil, nil, nil
}

// Tests the handshake and one round of application data. Returns true if the
// connection correctly used a Delegated Credential.
func testConnWithDC(t *testing.T, clientMsg, serverMsg string, clientConfig, serverConfig *Config, peer string) (bool, error) {
initDCTest()
ln := newLocalListener(t)
defer ln.Close()

Expand Down Expand Up @@ -569,38 +555,30 @@ func TestDCHandshakeServerAuth(t *testing.T) {

clientConfig := dcTestConfig.Clone()
serverConfig := dcTestConfig.Clone()
serverConfig.GetCertificate = testServerGetCertificate
clientConfig.InsecureSkipVerify = true

for i, test := range dcTests {
for i, test := range dcServerTests {
clientConfig.SupportDelegatedCredential = test.clientDCSupport

for dcCounter < len(dcTestDCScheme)-1 {
if test.serverDCSupport {
serverConfig.GetDelegatedCredential = testGetDelegatedCredential
dcCounter++
} else {
serverConfig.GetDelegatedCredential = nil
}

initDCTest()
for dcCount = 0; dcCount < len(dcTestDCSignatureScheme); dcCount++ {
serverConfig.GetCertificate = testServerGetCertificate
clientConfig.MaxVersion = test.clientMaxVers
serverConfig.MaxVersion = test.serverMaxVers

usedDC, err := testConnWithDC(t, clientMsg, serverMsg, clientConfig, serverConfig, "client")

if err != nil && test.expectSuccess {
t.Errorf("test #%d (%s) fails: %s", i+1, test.name, err.Error())
t.Errorf("test #%d (%s) with signature algorithm #%d fails: %s", i, test.name, dcCount, err.Error())
} else if err == nil && !test.expectSuccess {
t.Errorf("test #%d (%s) succeeds; expected failure", i+1, test.name)
t.Errorf("test #%d (%s) with signature algorithm #%d succeeds; expected failure", i, test.name, dcCount)
}

if usedDC != test.expectDC {
t.Errorf("test #%d (%s) usedDC = %v; expected %v", i+1, test.name, usedDC, test.expectDC)
t.Errorf("test #%d (%s) with signature algorithm #%d usedDC = %v; expected %v", i, test.name, dcCount, usedDC, test.expectDC)
}
}
}

dcCounter = 0
}

// Test the client authentication with the Delegated Credential extension.
Expand All @@ -614,34 +592,27 @@ func TestDCHandshakeClientAuth(t *testing.T) {
clientConfig := dcTestConfig.Clone()
clientConfig.GetClientCertificate = testClientGetCertificate

for i, test := range dcTests {
for j, test := range dcClientTests {
serverConfig.SupportDelegatedCredential = test.serverDCSupport

for dcCounter < len(dcTestDCScheme)-1 {
if test.clientDCSupport {
clientConfig.GetDelegatedCredential = testGetDelegatedCredential
dcCounter++
} else {
clientConfig.GetDelegatedCredential = nil
}

initDCTest()
for dcCount = 0; dcCount < len(dcTestDCSignatureScheme); dcCount++ {
serverConfig.MaxVersion = test.serverMaxVers
clientConfig.MaxVersion = test.clientMaxVers

usedDC, err := testConnWithDC(t, clientMsg, serverMsg, clientConfig, serverConfig, "server")

if err != nil && test.expectSuccess {
t.Errorf("test #%d (%s) fails: %s", i+1, test.name, err.Error())
t.Errorf("test #%d (%s) with signature algorithm #%d fails: %s", j, test.name, dcCount, err.Error())
} else if err == nil && !test.expectSuccess {
t.Errorf("test #%d (%s) succeeds; expected failure", i+1, test.name)
t.Errorf("test #%d (%s) with signature algorithm #%d succeeds; expected failure", j, test.name, dcCount)
}

if usedDC != test.expectDC {
t.Errorf("test #%d (%s) usedDC = %v; expected %v", i+1, test.name, usedDC, test.expectDC)
t.Errorf("test #%d (%s) with signature algorithm #%d usedDC = %v; expected %v", j, test.name, dcCount, usedDC, test.expectDC)
}
}
}
dcCounter = 0
}

// Test server and client authentication with the Delegated Credential extension.
Expand All @@ -657,19 +628,19 @@ func TestDCHandshakeClientAndServerAuth(t *testing.T) {

serverConfig.SupportDelegatedCredential = true
clientConfig.SupportDelegatedCredential = true
clientConfig.GetDelegatedCredential = testGetDelegatedCredential
serverConfig.GetDelegatedCredential = testGetDelegatedCredential

serverConfig.MaxVersion = VersionTLS13
clientConfig.MaxVersion = VersionTLS13

initDCTest()

usedDC, err := testConnWithDC(t, clientMsg, serverMsg, clientConfig, serverConfig, "both")

if err != nil {
t.Errorf("test server and client auth fails: %s", err.Error())
}

if usedDC != true {
t.Errorf("test server and client auth does not succed")
t.Errorf("test server and client auth does not succeed")
}
}
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