Allow joining clusters when the server CA is trusted by the OS CA bundle (#2743)

* Add tests to clientaccess/token
* Fix issues in clientaccess/token identified by tests
* Update tests to close coverage gaps
* Remove redundant check turned up by code coverage reports
* Add warnings if CA hash will not be validated

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

pkg/clientaccess/token.go

@@ -13,10 +13,11 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+	"github.com/sirupsen/logrus"
 )
 
 var (
-	defaultClientTimeout = 20 * time.Second
+	defaultClientTimeout = 10 * time.Second
 
 	defaultClient = &http.Client{
 		Timeout: defaultClientTimeout,
@@ -32,8 +33,9 @@ var (
 )
 
 const (
-	tokenPrefix = "K10"
-	tokenFormat = "%s%s::%s:%s"
+	tokenPrefix  = "K10"
+	tokenFormat  = "%s%s::%s:%s"
+	caHashLength = sha256.Size * 2
 )
 
 type OverrideURLCallback func(config []byte) (*url.URL, error)
@@ -59,16 +61,10 @@ func ParseAndValidateToken(server string, token string) (*Info, error) {
 		return nil, err
 	}
 
-	if err := info.setServer(server); err != nil {
+	if err := info.setAndValidateServer(server); err != nil {
 		return nil, err
 	}
 
-	if info.caHash != "" {
-		if err := info.validateCAHash(); err != nil {
-			return nil, err
-		}
-	}
-
 	return info, nil
 }
 
@@ -82,26 +78,24 @@ func ParseAndValidateTokenForUser(server string, token string, username string)
 
 	info.Username = username
 
-	if err := info.setServer(server); err != nil {
+	if err := info.setAndValidateServer(server); err != nil {
 		return nil, err
 	}
 
-	if info.caHash != "" {
-		if err := info.validateCAHash(); err != nil {
-			return nil, err
-		}
-	}
-
 	return info, nil
 }
 
+// setAndValidateServer updates the remote server's cert info, and validates it against the provided hash
+func (info *Info) setAndValidateServer(server string) error {
+	if err := info.setServer(server); err != nil {
+		return err
+	}
+	return info.validateCAHash()
+}
+
 // validateCACerts returns a boolean indicating whether or not a CA bundle matches the provided hash,
 // and a string containing the hash of the CA bundle.
 func validateCACerts(cacerts []byte, hash string) (bool, string) {
-	if len(cacerts) == 0 && hash == "" {
-		return true, ""
-	}
-
 	newHash := hashCA(cacerts)
 	return hash == newHash, newHash
 }
@@ -126,6 +120,10 @@ func ParseUsernamePassword(token string) (string, string, bool) {
 func parseToken(token string) (*Info, error) {
 	var info = &Info{}
 
+	if len(token) == 0 {
+		return nil, errors.New("token must not be empty")
+	}
+
 	if !strings.HasPrefix(token, tokenPrefix) {
 		token = fmt.Sprintf(tokenFormat, tokenPrefix, "", "", token)
 	}
@@ -136,13 +134,17 @@ func parseToken(token string) (*Info, error) {
 	parts := strings.SplitN(token, "::", 2)
 	token = parts[0]
 	if len(parts) > 1 {
+		hashLen := len(parts[0])
+		if hashLen > 0 && hashLen != caHashLength {
+			return nil, errors.New("invalid token CA hash length")
+		}
 		info.caHash = parts[0]
 		token = parts[1]
 	}
 
 	parts = strings.SplitN(token, ":", 2)
-	if len(parts) != 2 {
-		return nil, fmt.Errorf("invalid token format")
+	if len(parts) != 2 || len(parts[1]) == 0 {
+		return nil, errors.New("invalid token format")
 	}
 
 	info.Username = parts[0]
@@ -212,10 +214,20 @@ func (info *Info) setServer(server string) error {
 
 // ValidateCAHash validates that info's caHash matches the CACerts hash.
 func (info *Info) validateCAHash() error {
-	if ok, serverHash := validateCACerts(info.CACerts, info.caHash); !ok {
-		return fmt.Errorf("token CA hash does not match the server CA hash: %s != %s", info.caHash, serverHash)
+	if len(info.caHash) > 0 && len(info.CACerts) == 0 {
+		// Warn if the user provided a CA hash but we're not going to validate because it's already trusted
+		logrus.Warn("Cluster CA certificate is trusted by the host CA bundle. " +
+			"Token CA hash will not be validated.")
+	} else if len(info.caHash) == 0 && len(info.CACerts) > 0 {
+		// Warn if the CA is self-signed but the user didn't provide a hash to validate it against
+		logrus.Warn("Cluster CA certificate is not trusted by the host CA bundle, but the token does not include a CA hash. " +
+			"Use the full token from the server's node-token file to enable Cluster CA validation.")
+	} else if len(info.CACerts) > 0 && len(info.caHash) > 0 {
+		// only verify CA hash if the server cert is not trusted by the OS CA bundle
+		if ok, serverHash := validateCACerts(info.CACerts, info.caHash); !ok {
+			return fmt.Errorf("token CA hash does not match the Cluster CA certificate hash: %s != %s", info.caHash, serverHash)
+		}
 	}
-
 	return nil
 }
 

pkg/clientaccess/token_test.go

@@ -0,0 +1,401 @@
+package clientaccess
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/pem"
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/rancher/dynamiclistener/cert"
+	"github.com/rancher/dynamiclistener/factory"
+	"github.com/rancher/k3s/pkg/bootstrap"
+	"github.com/rancher/k3s/pkg/daemons/config"
+	"github.com/stretchr/testify/assert"
+)
+
+var (
+	defaultUsername = "server"
+	defaultPassword = "token"
+)
+
+// TestTrustedCA confirms that tokens are validated when the server uses a cert (self-signed or otherwise)
+// that is trusted by the OS CA bundle. This test must be run first, since it mucks with the system root certs.
+func TestTrustedCA(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, false)
+	defer server.Close()
+
+	testInfo := &Info{
+		CACerts:  getServerCA(server),
+		BaseURL:  server.URL,
+		Username: defaultUsername,
+		Password: defaultPassword,
+		caHash:   hashCA(getServerCA(server)),
+	}
+
+	testCases := []struct {
+		token    string
+		expected string
+	}{
+		{defaultPassword, ""},
+		{testInfo.String(), testInfo.Username},
+	}
+
+	// Point OS CA bundle at this test's CA cert to simulate a trusted CA cert.
+	// Note that this only works if the OS CA bundle has not yet been loaded in this process,
+	// as it is cached for the duration of the process lifetime.
+	// Ref: https://github.com/golang/go/issues/41888
+	path := t.TempDir() + "/ca.crt"
+	writeServerCA(server, path)
+	os.Setenv("SSL_CERT_FILE", path)
+
+	for _, testCase := range testCases {
+		info, err := ParseAndValidateToken(server.URL, testCase.token)
+		if assert.NoError(err, testCase) {
+			assert.Nil(info.CACerts, testCase)
+			assert.Equal(testCase.expected, info.Username, testCase.token)
+		}
+
+		info, err = ParseAndValidateTokenForUser(server.URL, testCase.token, "agent")
+		if assert.NoError(err, testCase) {
+			assert.Nil(info.CACerts, testCase)
+			assert.Equal("agent", info.Username, testCase)
+		}
+	}
+
+	// Confirm that the cert is actually trusted by the OS CA bundle by making a request
+	// with empty cert pool
+	testInfo.CACerts = nil
+	res, err := Get("/v1-k3s/server-bootstrap", testInfo)
+	assert.NoError(err)
+	assert.NotEmpty(res)
+}
+
+// TestUntrustedCA confirms that tokens are validated when the server uses a self-signed cert
+// that is NOT trusted by the OS CA bundle.
+func TestUntrustedCA(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, false)
+	defer server.Close()
+
+	testInfo := &Info{
+		CACerts:  getServerCA(server),
+		BaseURL:  server.URL,
+		Username: defaultUsername,
+		Password: defaultPassword,
+		caHash:   hashCA(getServerCA(server)),
+	}
+
+	testCases := []struct {
+		token    string
+		expected string
+	}{
+		{defaultPassword, ""},
+		{testInfo.String(), testInfo.Username},
+	}
+
+	for _, testCase := range testCases {
+		info, err := ParseAndValidateToken(server.URL, testCase.token)
+		if assert.NoError(err, testCase) {
+			assert.Equal(testInfo.CACerts, info.CACerts, testCase)
+			assert.Equal(testCase.expected, info.Username, testCase)
+		}
+
+		info, err = ParseAndValidateTokenForUser(server.URL, testCase.token, "agent")
+		if assert.NoError(err, testCase) {
+			assert.Equal(testInfo.CACerts, info.CACerts, testCase)
+			assert.Equal("agent", info.Username, testCase)
+		}
+	}
+}
+
+// TestInvalidServers tests that invalid server URLs are properly rejected
+func TestInvalidServers(t *testing.T) {
+	assert := assert.New(t)
+	testCases := []struct {
+		server   string
+		token    string
+		expected string
+	}{
+		{" https://localhost:6443", "token", "Invalid server url, failed to parse:  https://localhost:6443: parse \" https://localhost:6443\": first path segment in URL cannot contain colon"},
+		{"http://localhost:6443", "token", "only https:// URLs are supported, invalid scheme: http://localhost:6443"},
+	}
+
+	for _, testCase := range testCases {
+		_, err := ParseAndValidateToken(testCase.server, testCase.token)
+		assert.EqualError(err, testCase.expected, testCase)
+
+		_, err = ParseAndValidateTokenForUser(testCase.server, testCase.token, defaultUsername)
+		assert.EqualError(err, testCase.expected, testCase)
+	}
+}
+
+// TestInvalidTokens tests that tokens which are empty, invalid, or incorrect are properly rejected
+func TestInvalidTokens(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, false)
+	defer server.Close()
+
+	testCases := []struct {
+		server   string
+		token    string
+		expected string
+	}{
+		{server.URL, "", "token must not be empty"},
+		{server.URL, "K10::", "invalid token format"},
+		{server.URL, "K10::x", "invalid token format"},
+		{server.URL, "K10::x:", "invalid token format"},
+		{server.URL, "K10XX::x:y", "invalid token CA hash length"},
+		{server.URL,
+			"K10XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX::x:y",
+			"token CA hash does not match the Cluster CA certificate hash: XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX != " + hashCA(getServerCA(server))},
+	}
+
+	for _, testCase := range testCases {
+		info, err := ParseAndValidateToken(testCase.server, testCase.token)
+		assert.EqualError(err, testCase.expected, testCase)
+		assert.Nil(info, testCase)
+
+		info, err = ParseAndValidateTokenForUser(testCase.server, testCase.token, defaultUsername)
+		assert.EqualError(err, testCase.expected, testCase)
+		assert.Nil(info, testCase)
+	}
+}
+
+// TestInvalidCredentials tests that tokens which don't have valid credentials are rejected
+func TestInvalidCredentials(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, false)
+	defer server.Close()
+
+	testInfo := &Info{
+		CACerts:  getServerCA(server),
+		BaseURL:  server.URL,
+		Username: "nobody",
+		Password: "invalid",
+		caHash:   hashCA(getServerCA(server)),
+	}
+
+	testCases := []string{
+		testInfo.Password,
+		testInfo.String(),
+	}
+
+	for _, testCase := range testCases {
+		info, err := ParseAndValidateToken(server.URL, testCase)
+		assert.NoError(err, testCase)
+		if assert.NotNil(info) {
+			res, err := Get("/v1-k3s/server-bootstrap", info)
+			assert.Error(err, testCase)
+			assert.Empty(res, testCase)
+		}
+
+		info, err = ParseAndValidateTokenForUser(server.URL, testCase, defaultUsername)
+		assert.NoError(err, testCase)
+		if assert.NotNil(info) {
+			res, err := Get("/v1-k3s/server-bootstrap", info)
+			assert.Error(err, testCase)
+			assert.Empty(res, testCase)
+		}
+	}
+}
+
+// TestWrongCert tests that errors are returned when the server's cert isn't issued by its CA
+func TestWrongCert(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, true)
+	defer server.Close()
+
+	info, err := ParseAndValidateToken(server.URL, defaultPassword)
+	assert.Error(err)
+	assert.Nil(info)
+
+	info, err = ParseAndValidateTokenForUser(server.URL, defaultPassword, defaultUsername)
+	assert.Error(err)
+	assert.Nil(info)
+}
+
+// TestConnectionFailures tests that connections are timed out properly
+func TestConnectionFailures(t *testing.T) {
+	testDuration := (defaultClientTimeout * 2) + time.Second
+	assert := assert.New(t)
+	testCases := []struct {
+		server string
+		token  string
+	}{
+		{"https://192.0.2.1:6443", "token"}, // RFC 5735 TEST-NET-1 for use in documentation and example code
+		{"https://localhost:1", "token"},
+	}
+
+	for _, testCase := range testCases {
+		startTime := time.Now()
+		info, err := ParseAndValidateToken(testCase.server, testCase.token)
+		assert.Error(err, testCase)
+		assert.Nil(info, testCase)
+		assert.WithinDuration(time.Now(), startTime, testDuration, testCase)
+
+		startTime = time.Now()
+		info, err = ParseAndValidateTokenForUser(testCase.server, testCase.token, defaultUsername)
+		assert.Error(err, testCase)
+		assert.Nil(info, testCase)
+		assert.WithinDuration(startTime, time.Now(), testDuration, testCase)
+	}
+}
+
+// TestUserPass tests that usernames and passwords are parsed or not parsed from token strings
+func TestUserPass(t *testing.T) {
+	assert := assert.New(t)
+	testCases := []struct {
+		token    string
+		username string
+		password string
+		expect   bool
+	}{
+		{"K10XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX::username:password", "username", "password", true},
+		{"password", "", "password", true},
+		{"K10X::x", "", "", false},
+	}
+
+	for _, testCase := range testCases {
+		username, password, ok := ParseUsernamePassword(testCase.token)
+		assert.Equal(testCase.expect, ok, testCase)
+		if ok {
+			assert.Equal(testCase.username, username, testCase)
+			assert.Equal(testCase.password, password, testCase)
+		}
+	}
+}
+
+// TestParseAndGet tests URL handling along some hard-to-reach code paths
+func TestParseAndGet(t *testing.T) {
+	assert := assert.New(t)
+	server := newTLSServer(t, defaultUsername, defaultPassword, false)
+	defer server.Close()
+
+	testCases := []struct {
+		extraBasePre  string
+		extraBasePost string
+		path          string
+		parseFail     bool
+		getFail       bool
+	}{
+		{"/", "", "/cacerts", false, false},
+		{"/%2", "", "/cacerts", true, false},
+		{"", "", "/%2", false, true},
+		{"", "/%2", "/cacerts", false, true},
+	}
+
+	for _, testCase := range testCases {
+		info, err := ParseAndValidateTokenForUser(server.URL+testCase.extraBasePre, defaultPassword, defaultUsername)
+		// Check for expected error when parsing server + token
+		if testCase.parseFail {
+			assert.Error(err, testCase)
+		} else if assert.NoError(err, testCase) {
+			info.BaseURL = server.URL + testCase.extraBasePost
+			_, err := Get(testCase.path, info)
+			// Check for expected error when making Get request
+			if testCase.getFail {
+				assert.Error(err, testCase)
+			} else {
+				assert.NoError(err, testCase)
+			}
+		}
+	}
+}
+
+// newTLSServer returns a HTTPS server that mocks the basic functionality required to validate K3s join tokens.
+// Each call to this function will generate new CA and server certificates unique to the returned server.
+func newTLSServer(t *testing.T, username, password string, sendWrongCA bool) *httptest.Server {
+	var server *httptest.Server
+	server = httptest.NewUnstartedServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path == "/v1-k3s/server-bootstrap" {
+			if authUsername, authPassword, ok := r.BasicAuth(); ok != true || authPassword != password || authUsername != username {
+				http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
+				return
+			}
+			bootstrapData := &config.ControlRuntimeBootstrap{}
+			w.Header().Set("Content-Type", "application/json")
+			if err := bootstrap.Write(w, bootstrapData); err != nil {
+				t.Errorf("failed to write bootstrap: %v", err)
+			}
+			return
+		}
+
+		if r.URL.Path == "/cacerts" {
+			w.Header().Set("Content-Type", "text/plain")
+			if _, err := w.Write(getServerCA(server)); err != nil {
+				t.Errorf("Failed to write cacerts: %v", err)
+			}
+			return
+		}
+
+		http.Error(w, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+	}))
+
+	// Create new CA cert and key
+	caCert, caKey, err := factory.GenCA()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Generate new server cert; reuse the key from the CA
+	cfg := cert.Config{
+		CommonName:   "localhost",
+		Organization: []string{"testing"},
+		Usages:       []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+		AltNames: cert.AltNames{
+			DNSNames: []string{"localhost"},
+			IPs:      []net.IP{net.IPv4(127, 0, 0, 1)},
+		},
+	}
+	serverCert, err := cert.NewSignedCert(cfg, caKey, caCert, caKey)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Bind server and CA certs into chain for TLS listener configuration
+	server.TLS = &tls.Config{}
+	server.TLS.Certificates = []tls.Certificate{
+		{Certificate: [][]byte{serverCert.Raw}, Leaf: serverCert, PrivateKey: caKey},
+		{Certificate: [][]byte{caCert.Raw}, Leaf: caCert},
+	}
+
+	if sendWrongCA {
+		// Create new CA cert and key and use that as the CA cert instead of the one that actually signed the server cert
+		badCert, _, err := factory.GenCA()
+		if err != nil {
+			t.Fatal(err)
+		}
+		server.TLS.Certificates[1].Certificate[0] = badCert.Raw
+		server.TLS.Certificates[1].Leaf = badCert
+	}
+
+	server.StartTLS()
+	return server
+}
+
+// getServerCA returns a byte slice containing the PEM encoding of the server's CA certificate
+func getServerCA(server *httptest.Server) []byte {
+	certLen := len(server.TLS.Certificates)
+	return pem.EncodeToMemory(&pem.Block{Type: "CERTIFICATE", Bytes: server.TLS.Certificates[certLen-1].Certificate[0]})
+}
+
+// writeServerCA writes the PEM-encoded server certificate to a given path
+func writeServerCA(server *httptest.Server, path string) error {
+	certOut, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer certOut.Close()
+
+	if _, err := certOut.Write(getServerCA(server)); err != nil {
+		return err
+	}
+
+	return nil
+}