sslobodr | d046be8 | 2019-01-16 10:02:22 -0500 | [diff] [blame] | 1 | /* |
| 2 | Copyright 2018 The Kubernetes Authors. |
| 3 | |
| 4 | Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | you may not use this file except in compliance with the License. |
| 6 | You may obtain a copy of the License at |
| 7 | |
| 8 | http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | |
| 10 | Unless required by applicable law or agreed to in writing, software |
| 11 | distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | See the License for the specific language governing permissions and |
| 14 | limitations under the License. |
| 15 | */ |
| 16 | |
| 17 | package exec |
| 18 | |
| 19 | import ( |
| 20 | "bytes" |
| 21 | "context" |
| 22 | "crypto/tls" |
| 23 | "errors" |
| 24 | "fmt" |
| 25 | "io" |
| 26 | "net" |
| 27 | "net/http" |
| 28 | "os" |
| 29 | "os/exec" |
| 30 | "reflect" |
| 31 | "sync" |
| 32 | "time" |
| 33 | |
| 34 | "golang.org/x/crypto/ssh/terminal" |
| 35 | "k8s.io/apimachinery/pkg/apis/meta/v1" |
| 36 | "k8s.io/apimachinery/pkg/runtime" |
| 37 | "k8s.io/apimachinery/pkg/runtime/schema" |
| 38 | "k8s.io/apimachinery/pkg/runtime/serializer" |
| 39 | utilruntime "k8s.io/apimachinery/pkg/util/runtime" |
| 40 | "k8s.io/client-go/pkg/apis/clientauthentication" |
| 41 | "k8s.io/client-go/pkg/apis/clientauthentication/v1alpha1" |
| 42 | "k8s.io/client-go/pkg/apis/clientauthentication/v1beta1" |
| 43 | "k8s.io/client-go/tools/clientcmd/api" |
| 44 | "k8s.io/client-go/transport" |
| 45 | "k8s.io/client-go/util/connrotation" |
| 46 | "k8s.io/klog" |
| 47 | ) |
| 48 | |
| 49 | const execInfoEnv = "KUBERNETES_EXEC_INFO" |
| 50 | |
| 51 | var scheme = runtime.NewScheme() |
| 52 | var codecs = serializer.NewCodecFactory(scheme) |
| 53 | |
| 54 | func init() { |
| 55 | v1.AddToGroupVersion(scheme, schema.GroupVersion{Version: "v1"}) |
| 56 | utilruntime.Must(v1alpha1.AddToScheme(scheme)) |
| 57 | utilruntime.Must(v1beta1.AddToScheme(scheme)) |
| 58 | utilruntime.Must(clientauthentication.AddToScheme(scheme)) |
| 59 | } |
| 60 | |
| 61 | var ( |
| 62 | // Since transports can be constantly re-initialized by programs like kubectl, |
| 63 | // keep a cache of initialized authenticators keyed by a hash of their config. |
| 64 | globalCache = newCache() |
| 65 | // The list of API versions we accept. |
| 66 | apiVersions = map[string]schema.GroupVersion{ |
| 67 | v1alpha1.SchemeGroupVersion.String(): v1alpha1.SchemeGroupVersion, |
| 68 | v1beta1.SchemeGroupVersion.String(): v1beta1.SchemeGroupVersion, |
| 69 | } |
| 70 | ) |
| 71 | |
| 72 | func newCache() *cache { |
| 73 | return &cache{m: make(map[string]*Authenticator)} |
| 74 | } |
| 75 | |
| 76 | func cacheKey(c *api.ExecConfig) string { |
| 77 | return fmt.Sprintf("%#v", c) |
| 78 | } |
| 79 | |
| 80 | type cache struct { |
| 81 | mu sync.Mutex |
| 82 | m map[string]*Authenticator |
| 83 | } |
| 84 | |
| 85 | func (c *cache) get(s string) (*Authenticator, bool) { |
| 86 | c.mu.Lock() |
| 87 | defer c.mu.Unlock() |
| 88 | a, ok := c.m[s] |
| 89 | return a, ok |
| 90 | } |
| 91 | |
| 92 | // put inserts an authenticator into the cache. If an authenticator is already |
| 93 | // associated with the key, the first one is returned instead. |
| 94 | func (c *cache) put(s string, a *Authenticator) *Authenticator { |
| 95 | c.mu.Lock() |
| 96 | defer c.mu.Unlock() |
| 97 | existing, ok := c.m[s] |
| 98 | if ok { |
| 99 | return existing |
| 100 | } |
| 101 | c.m[s] = a |
| 102 | return a |
| 103 | } |
| 104 | |
| 105 | // GetAuthenticator returns an exec-based plugin for providing client credentials. |
| 106 | func GetAuthenticator(config *api.ExecConfig) (*Authenticator, error) { |
| 107 | return newAuthenticator(globalCache, config) |
| 108 | } |
| 109 | |
| 110 | func newAuthenticator(c *cache, config *api.ExecConfig) (*Authenticator, error) { |
| 111 | key := cacheKey(config) |
| 112 | if a, ok := c.get(key); ok { |
| 113 | return a, nil |
| 114 | } |
| 115 | |
| 116 | gv, ok := apiVersions[config.APIVersion] |
| 117 | if !ok { |
| 118 | return nil, fmt.Errorf("exec plugin: invalid apiVersion %q", config.APIVersion) |
| 119 | } |
| 120 | |
| 121 | a := &Authenticator{ |
| 122 | cmd: config.Command, |
| 123 | args: config.Args, |
| 124 | group: gv, |
| 125 | |
| 126 | stdin: os.Stdin, |
| 127 | stderr: os.Stderr, |
| 128 | interactive: terminal.IsTerminal(int(os.Stdout.Fd())), |
| 129 | now: time.Now, |
| 130 | environ: os.Environ, |
| 131 | } |
| 132 | |
| 133 | for _, env := range config.Env { |
| 134 | a.env = append(a.env, env.Name+"="+env.Value) |
| 135 | } |
| 136 | |
| 137 | return c.put(key, a), nil |
| 138 | } |
| 139 | |
| 140 | // Authenticator is a client credential provider that rotates credentials by executing a plugin. |
| 141 | // The plugin input and output are defined by the API group client.authentication.k8s.io. |
| 142 | type Authenticator struct { |
| 143 | // Set by the config |
| 144 | cmd string |
| 145 | args []string |
| 146 | group schema.GroupVersion |
| 147 | env []string |
| 148 | |
| 149 | // Stubbable for testing |
| 150 | stdin io.Reader |
| 151 | stderr io.Writer |
| 152 | interactive bool |
| 153 | now func() time.Time |
| 154 | environ func() []string |
| 155 | |
| 156 | // Cached results. |
| 157 | // |
| 158 | // The mutex also guards calling the plugin. Since the plugin could be |
| 159 | // interactive we want to make sure it's only called once. |
| 160 | mu sync.Mutex |
| 161 | cachedCreds *credentials |
| 162 | exp time.Time |
| 163 | |
| 164 | onRotate func() |
| 165 | } |
| 166 | |
| 167 | type credentials struct { |
| 168 | token string |
| 169 | cert *tls.Certificate |
| 170 | } |
| 171 | |
| 172 | // UpdateTransportConfig updates the transport.Config to use credentials |
| 173 | // returned by the plugin. |
| 174 | func (a *Authenticator) UpdateTransportConfig(c *transport.Config) error { |
| 175 | wt := c.WrapTransport |
| 176 | c.WrapTransport = func(rt http.RoundTripper) http.RoundTripper { |
| 177 | if wt != nil { |
| 178 | rt = wt(rt) |
| 179 | } |
| 180 | return &roundTripper{a, rt} |
| 181 | } |
| 182 | |
| 183 | if c.TLS.GetCert != nil { |
| 184 | return errors.New("can't add TLS certificate callback: transport.Config.TLS.GetCert already set") |
| 185 | } |
| 186 | c.TLS.GetCert = a.cert |
| 187 | |
| 188 | var dial func(ctx context.Context, network, addr string) (net.Conn, error) |
| 189 | if c.Dial != nil { |
| 190 | dial = c.Dial |
| 191 | } else { |
| 192 | dial = (&net.Dialer{Timeout: 30 * time.Second, KeepAlive: 30 * time.Second}).DialContext |
| 193 | } |
| 194 | d := connrotation.NewDialer(dial) |
| 195 | a.onRotate = d.CloseAll |
| 196 | c.Dial = d.DialContext |
| 197 | |
| 198 | return nil |
| 199 | } |
| 200 | |
| 201 | type roundTripper struct { |
| 202 | a *Authenticator |
| 203 | base http.RoundTripper |
| 204 | } |
| 205 | |
| 206 | func (r *roundTripper) RoundTrip(req *http.Request) (*http.Response, error) { |
| 207 | // If a user has already set credentials, use that. This makes commands like |
| 208 | // "kubectl get --token (token) pods" work. |
| 209 | if req.Header.Get("Authorization") != "" { |
| 210 | return r.base.RoundTrip(req) |
| 211 | } |
| 212 | |
| 213 | creds, err := r.a.getCreds() |
| 214 | if err != nil { |
| 215 | return nil, fmt.Errorf("getting credentials: %v", err) |
| 216 | } |
| 217 | if creds.token != "" { |
| 218 | req.Header.Set("Authorization", "Bearer "+creds.token) |
| 219 | } |
| 220 | |
| 221 | res, err := r.base.RoundTrip(req) |
| 222 | if err != nil { |
| 223 | return nil, err |
| 224 | } |
| 225 | if res.StatusCode == http.StatusUnauthorized { |
| 226 | resp := &clientauthentication.Response{ |
| 227 | Header: res.Header, |
| 228 | Code: int32(res.StatusCode), |
| 229 | } |
| 230 | if err := r.a.maybeRefreshCreds(creds, resp); err != nil { |
| 231 | klog.Errorf("refreshing credentials: %v", err) |
| 232 | } |
| 233 | } |
| 234 | return res, nil |
| 235 | } |
| 236 | |
| 237 | func (a *Authenticator) credsExpired() bool { |
| 238 | if a.exp.IsZero() { |
| 239 | return false |
| 240 | } |
| 241 | return a.now().After(a.exp) |
| 242 | } |
| 243 | |
| 244 | func (a *Authenticator) cert() (*tls.Certificate, error) { |
| 245 | creds, err := a.getCreds() |
| 246 | if err != nil { |
| 247 | return nil, err |
| 248 | } |
| 249 | return creds.cert, nil |
| 250 | } |
| 251 | |
| 252 | func (a *Authenticator) getCreds() (*credentials, error) { |
| 253 | a.mu.Lock() |
| 254 | defer a.mu.Unlock() |
| 255 | if a.cachedCreds != nil && !a.credsExpired() { |
| 256 | return a.cachedCreds, nil |
| 257 | } |
| 258 | |
| 259 | if err := a.refreshCredsLocked(nil); err != nil { |
| 260 | return nil, err |
| 261 | } |
| 262 | return a.cachedCreds, nil |
| 263 | } |
| 264 | |
| 265 | // maybeRefreshCreds executes the plugin to force a rotation of the |
| 266 | // credentials, unless they were rotated already. |
| 267 | func (a *Authenticator) maybeRefreshCreds(creds *credentials, r *clientauthentication.Response) error { |
| 268 | a.mu.Lock() |
| 269 | defer a.mu.Unlock() |
| 270 | |
| 271 | // Since we're not making a new pointer to a.cachedCreds in getCreds, no |
| 272 | // need to do deep comparison. |
| 273 | if creds != a.cachedCreds { |
| 274 | // Credentials already rotated. |
| 275 | return nil |
| 276 | } |
| 277 | |
| 278 | return a.refreshCredsLocked(r) |
| 279 | } |
| 280 | |
| 281 | // refreshCredsLocked executes the plugin and reads the credentials from |
| 282 | // stdout. It must be called while holding the Authenticator's mutex. |
| 283 | func (a *Authenticator) refreshCredsLocked(r *clientauthentication.Response) error { |
| 284 | cred := &clientauthentication.ExecCredential{ |
| 285 | Spec: clientauthentication.ExecCredentialSpec{ |
| 286 | Response: r, |
| 287 | Interactive: a.interactive, |
| 288 | }, |
| 289 | } |
| 290 | |
| 291 | env := append(a.environ(), a.env...) |
| 292 | if a.group == v1alpha1.SchemeGroupVersion { |
| 293 | // Input spec disabled for beta due to lack of use. Possibly re-enable this later if |
| 294 | // someone wants it back. |
| 295 | // |
| 296 | // See: https://github.com/kubernetes/kubernetes/issues/61796 |
| 297 | data, err := runtime.Encode(codecs.LegacyCodec(a.group), cred) |
| 298 | if err != nil { |
| 299 | return fmt.Errorf("encode ExecCredentials: %v", err) |
| 300 | } |
| 301 | env = append(env, fmt.Sprintf("%s=%s", execInfoEnv, data)) |
| 302 | } |
| 303 | |
| 304 | stdout := &bytes.Buffer{} |
| 305 | cmd := exec.Command(a.cmd, a.args...) |
| 306 | cmd.Env = env |
| 307 | cmd.Stderr = a.stderr |
| 308 | cmd.Stdout = stdout |
| 309 | if a.interactive { |
| 310 | cmd.Stdin = a.stdin |
| 311 | } |
| 312 | |
| 313 | if err := cmd.Run(); err != nil { |
| 314 | return fmt.Errorf("exec: %v", err) |
| 315 | } |
| 316 | |
| 317 | _, gvk, err := codecs.UniversalDecoder(a.group).Decode(stdout.Bytes(), nil, cred) |
| 318 | if err != nil { |
| 319 | return fmt.Errorf("decoding stdout: %v", err) |
| 320 | } |
| 321 | if gvk.Group != a.group.Group || gvk.Version != a.group.Version { |
| 322 | return fmt.Errorf("exec plugin is configured to use API version %s, plugin returned version %s", |
| 323 | a.group, schema.GroupVersion{Group: gvk.Group, Version: gvk.Version}) |
| 324 | } |
| 325 | |
| 326 | if cred.Status == nil { |
| 327 | return fmt.Errorf("exec plugin didn't return a status field") |
| 328 | } |
| 329 | if cred.Status.Token == "" && cred.Status.ClientCertificateData == "" && cred.Status.ClientKeyData == "" { |
| 330 | return fmt.Errorf("exec plugin didn't return a token or cert/key pair") |
| 331 | } |
| 332 | if (cred.Status.ClientCertificateData == "") != (cred.Status.ClientKeyData == "") { |
| 333 | return fmt.Errorf("exec plugin returned only certificate or key, not both") |
| 334 | } |
| 335 | |
| 336 | if cred.Status.ExpirationTimestamp != nil { |
| 337 | a.exp = cred.Status.ExpirationTimestamp.Time |
| 338 | } else { |
| 339 | a.exp = time.Time{} |
| 340 | } |
| 341 | |
| 342 | newCreds := &credentials{ |
| 343 | token: cred.Status.Token, |
| 344 | } |
| 345 | if cred.Status.ClientKeyData != "" && cred.Status.ClientCertificateData != "" { |
| 346 | cert, err := tls.X509KeyPair([]byte(cred.Status.ClientCertificateData), []byte(cred.Status.ClientKeyData)) |
| 347 | if err != nil { |
| 348 | return fmt.Errorf("failed parsing client key/certificate: %v", err) |
| 349 | } |
| 350 | newCreds.cert = &cert |
| 351 | } |
| 352 | |
| 353 | oldCreds := a.cachedCreds |
| 354 | a.cachedCreds = newCreds |
| 355 | // Only close all connections when TLS cert rotates. Token rotation doesn't |
| 356 | // need the extra noise. |
| 357 | if a.onRotate != nil && oldCreds != nil && !reflect.DeepEqual(oldCreds.cert, a.cachedCreds.cert) { |
| 358 | a.onRotate() |
| 359 | } |
| 360 | return nil |
| 361 | } |