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cmd/containerboot,kube: consolidate the two kube clients

Browse Source 
We had two implemenetations of the kube client, merge them.

containerboot was also using a raw http.Transport, this also has
the side effect of making it use a http.Client

Signed-off-by: Maisem Ali <maisem@tailscale.com>
andrew/util-dnsconfig
Maisem Ali 2 years ago committed by Maisem Ali
parent 5eb8a2a86a
commit e1530cdfcc
4 changed files with 200 additions and 235 deletions
Show Stats Download Patch File Download Diff File

246
cmd/containerboot/kube.go
Unescape Escape View File

@ -6,138 +6,28 @@
package main package main
import ( import (
"bytes"
"context" "context"
"crypto/tls"
"crypto/x509"
"encoding/base64"
"encoding/json"
"fmt" "fmt"
"io"
"log" "log"
"net/http" "net/http"
"os" "os"
"path/filepath"
"strings"
"time"
"tailscale.com/kube"
"tailscale.com/tailcfg" "tailscale.com/tailcfg"
"tailscale.com/util/multierr"
) )
// checkSecretPermissions checks the secret access permissions of the current
// pod. It returns an error if the basic permissions tailscale needs are
// missing, and reports whether the patch permission is additionally present.
//
// Errors encountered during the access checking process are logged, but ignored
// so that the pod tries to fail alive if the permissions exist and there's just
// something wrong with SelfSubjectAccessReviews. There shouldn't be, pods
// should always be able to use SSARs to assess their own permissions, but since
// we didn't use to check permissions this way we'll be cautious in case some
// old version of k8s deviates from the current behavior.
func checkSecretPermissions(ctx context.Context, secretName string) (canPatch bool, err error) {
var errs []error
for _, verb := range []string{"get", "update"} {
ok, err := checkPermission(ctx, verb, secretName)
if err != nil {
log.Printf("error checking %s permission on secret %s: %v", verb, secretName, err)
} else if !ok {
errs = append(errs, fmt.Errorf("missing %s permission on secret %q", verb, secretName))
}
}
if len(errs) > 0 {
return false, multierr.New(errs...)
}
ok, err := checkPermission(ctx, "patch", secretName)
if err != nil {
log.Printf("error checking patch permission on secret %s: %v", secretName, err)
return false, nil
}
return ok, nil
}
// checkPermission reports whether the current pod has permission to use the
// given verb (e.g. get, update, patch) on secretName.
func checkPermission(ctx context.Context, verb, secretName string) (bool, error) {
sar := map[string]any{
"apiVersion": "authorization.k8s.io/v1",
"kind": "SelfSubjectAccessReview",
"spec": map[string]any{
"resourceAttributes": map[string]any{
"namespace": kubeNamespace,
"verb": verb,
"resource": "secrets",
"name": secretName,
},
},
}
bs, err := json.Marshal(sar)
if err != nil {
return false, err
}
req, err := http.NewRequest("POST", "/apis/authorization.k8s.io/v1/selfsubjectaccessreviews", bytes.NewReader(bs))
if err != nil {
return false, err
}
resp, err := doKubeRequest(ctx, req)
if err != nil {
return false, err
}
defer resp.Body.Close()
bs, err = io.ReadAll(resp.Body)
if err != nil {
return false, err
}
var res struct {
Status struct {
Allowed bool `json:"allowed"`
} `json:"status"`
}
if err := json.Unmarshal(bs, &res); err != nil {
return false, err
}
return res.Status.Allowed, nil
}
// findKeyInKubeSecret inspects the kube secret secretName for a data // findKeyInKubeSecret inspects the kube secret secretName for a data
// field called "authkey", and returns its value if present. // field called "authkey", and returns its value if present.
func findKeyInKubeSecret(ctx context.Context, secretName string) (string, error) { func findKeyInKubeSecret(ctx context.Context, secretName string) (string, error) {
req, err := http.NewRequest("GET", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s", kubeNamespace, secretName), nil) s, err := kc.GetSecret(ctx, secretName)
if err != nil {
return "", err
}
resp, err := doKubeRequest(ctx, req)
if err != nil {
if resp != nil && resp.StatusCode == http.StatusNotFound {
// Kube secret doesn't exist yet, can't have an authkey.
return "", nil
}
return "", err
}
defer resp.Body.Close()
bs, err := io.ReadAll(resp.Body)
if err != nil { if err != nil {
return "", err return "", err
} }
ak, ok := s.Data["authkey"]
// We use a map[string]any here rather than import corev1.Secret, if !ok {
// because we only do very limited things to the secret, and return "", nil
// importing corev1 adds 12MiB to the compiled binary.
var s map[string]any
if err := json.Unmarshal(bs, &s); err != nil {
return "", err
} }
if d, ok := s["data"].(map[string]any); ok { return string(ak), nil
if v, ok := d["authkey"].(string); ok {
bs, err := base64.StdEncoding.DecodeString(v)
if err != nil {
return "", err
}
return string(bs), nil
}
}
return "", nil
} }
// storeDeviceInfo writes deviceID into the "device_id" data field of the kube // storeDeviceInfo writes deviceID into the "device_id" data field of the kube
@ -145,65 +35,38 @@ func findKeyInKubeSecret(ctx context.Context, secretName string) (string, error)
func storeDeviceInfo(ctx context.Context, secretName string, deviceID tailcfg.StableNodeID, fqdn string) error { func storeDeviceInfo(ctx context.Context, secretName string, deviceID tailcfg.StableNodeID, fqdn string) error {
// First check if the secret exists at all. Even if running on // First check if the secret exists at all. Even if running on
// kubernetes, we do not necessarily store state in a k8s secret. // kubernetes, we do not necessarily store state in a k8s secret.
req, err := http.NewRequest("GET", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s", kubeNamespace, secretName), nil) if _, err := kc.GetSecret(ctx, secretName); err != nil {
if err != nil { if s, ok := err.(*kube.Status); ok {
return err if s.Code >= 400 && s.Code <= 499 {
} // Assume the secret doesn't exist, or we don't have
resp, err := doKubeRequest(ctx, req) // permission to access it.
if err != nil { return nil
if resp != nil && resp.StatusCode >= 400 && resp.StatusCode <= 499 { }
// Assume the secret doesn't exist, or we don't have
// permission to access it.
return nil
} }
return err return err
} }
m := map[string]map[string]string{ m := &kube.Secret{
"stringData": { Data: map[string][]byte{
"device_id": string(deviceID), "device_id": []byte(deviceID),
"device_fqdn": fqdn, "device_fqdn": []byte(fqdn),
}, },
} }
var b bytes.Buffer return kc.StrategicMergePatchSecret(ctx, secretName, m, "tailscale-container")
if err := json.NewEncoder(&b).Encode(m); err != nil {
return err
}
req, err = http.NewRequest("PATCH", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s?fieldManager=tailscale-container", kubeNamespace, secretName), &b)
if err != nil {
return err
}
req.Header.Set("Content-Type", "application/strategic-merge-patch+json")
if _, err := doKubeRequest(ctx, req); err != nil {
return err
}
return nil
} }
// deleteAuthKey deletes the 'authkey' field of the given kube // deleteAuthKey deletes the 'authkey' field of the given kube
// secret. No-op if there is no authkey in the secret. // secret. No-op if there is no authkey in the secret.
func deleteAuthKey(ctx context.Context, secretName string) error { func deleteAuthKey(ctx context.Context, secretName string) error {
// m is a JSON Patch data structure, see https://jsonpatch.com/ or RFC 6902. // m is a JSON Patch data structure, see https://jsonpatch.com/ or RFC 6902.
m := []struct { m := []kube.JSONPatch{
Op string `json:"op"`
Path string `json:"path"`
}{
{ {
Op: "remove", Op: "remove",
Path: "/data/authkey", Path: "/data/authkey",
}, },
} }
var b bytes.Buffer if err := kc.JSONPatchSecret(ctx, secretName, m); err != nil {
if err := json.NewEncoder(&b).Encode(m); err != nil { if s, ok := err.(*kube.Status); ok && s.Code == http.StatusUnprocessableEntity {
return err
}
req, err := http.NewRequest("PATCH", fmt.Sprintf("/api/v1/namespaces/%s/secrets/%s?fieldManager=tailscale-container", kubeNamespace, secretName), &b)
if err != nil {
return err
}
req.Header.Set("Content-Type", "application/json-patch+json")
if resp, err := doKubeRequest(ctx, req); err != nil {
if resp != nil && resp.StatusCode == http.StatusUnprocessableEntity {
// This is kubernetes-ese for "the field you asked to // This is kubernetes-ese for "the field you asked to
// delete already doesn't exist", aka no-op. // delete already doesn't exist", aka no-op.
return nil return nil
@ -213,65 +76,22 @@ func deleteAuthKey(ctx context.Context, secretName string) error {
return nil return nil
} }
var ( var kc *kube.Client
kubeHost string
kubeNamespace string
kubeToken string
kubeHTTP *http.Transport
)
func initKube(root string) { func initKube(root string) {
// If running in Kubernetes, set things up so that doKubeRequest if root != "/" {
// can talk successfully to the kube apiserver. // If we are running in a test, we need to set the root path to the fake
if os.Getenv("KUBERNETES_SERVICE_HOST") == "" { // service account directory.
return kube.SetRootPathForTesting(root)
} }
var err error
kubeHost = os.Getenv("KUBERNETES_SERVICE_HOST") + ":" + os.Getenv("KUBERNETES_SERVICE_PORT_HTTPS") kc, err = kube.New()
bs, err := os.ReadFile(filepath.Join(root, "var/run/secrets/kubernetes.io/serviceaccount/namespace"))
if err != nil {
log.Fatalf("Error reading kube namespace: %v", err)
}
kubeNamespace = strings.TrimSpace(string(bs))
bs, err = os.ReadFile(filepath.Join(root, "var/run/secrets/kubernetes.io/serviceaccount/token"))
if err != nil {
log.Fatalf("Error reading kube token: %v", err)
}
kubeToken = strings.TrimSpace(string(bs))
bs, err = os.ReadFile(filepath.Join(root, "var/run/secrets/kubernetes.io/serviceaccount/ca.crt"))
if err != nil {
log.Fatalf("Error reading kube CA cert: %v", err)
}
cp := x509.NewCertPool()
cp.AppendCertsFromPEM(bs)
kubeHTTP = &http.Transport{
TLSClientConfig: &tls.Config{
RootCAs: cp,
},
IdleConnTimeout: time.Second,
}
}
// doKubeRequest sends r to the kube apiserver.
func doKubeRequest(ctx context.Context, r *http.Request) (*http.Response, error) {
if kubeHTTP == nil {
panic("not in kubernetes")
}
r.URL.Scheme = "https"
r.URL.Host = kubeHost
r.Header.Set("Authorization", "Bearer "+kubeToken)
r.Header.Set("Accept", "application/json")
resp, err := kubeHTTP.RoundTrip(r)
if err != nil { if err != nil {
return nil, err log.Fatalf("Error creating kube client: %v", err)
} }
if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusCreated { if root != "/" {
return resp, fmt.Errorf("got non-200/201 status code %d", resp.StatusCode) // If we are running in a test, we need to set the URL to the
// httptest server.
kc.SetURL(fmt.Sprintf("https://%s:%s", os.Getenv("KUBERNETES_SERVICE_HOST"), os.Getenv("KUBERNETES_SERVICE_PORT_HTTPS")))
} }
return resp, nil
} }

2
cmd/containerboot/main.go
Unescape Escape View File

@ -123,7 +123,7 @@ func main() {
defer cancel() defer cancel()
if cfg.InKubernetes && cfg.KubeSecret != "" { if cfg.InKubernetes && cfg.KubeSecret != "" {
canPatch, err := checkSecretPermissions(ctx, cfg.KubeSecret) canPatch, err := kc.CheckSecretPermissions(ctx, cfg.KubeSecret)
if err != nil { if err != nil {
log.Fatalf("Some Kubernetes permissions are missing, please check your RBAC configuration: %v", err) log.Fatalf("Some Kubernetes permissions are missing, please check your RBAC configuration: %v", err)
} }

8
cmd/containerboot/main_test.go
Unescape Escape View File

@ -607,7 +607,7 @@ func TestContainerBoot(t *testing.T) {
}() }()
var wantCmds []string var wantCmds []string
for _, p := range test.Phases { for i, p := range test.Phases {
lapi.Notify(p.Notify) lapi.Notify(p.Notify)
wantCmds = append(wantCmds, p.WantCmds...) wantCmds = append(wantCmds, p.WantCmds...)
waitArgs(t, 2*time.Second, d, argFile, strings.Join(wantCmds, "\n")) waitArgs(t, 2*time.Second, d, argFile, strings.Join(wantCmds, "\n"))
@ -626,7 +626,7 @@ func TestContainerBoot(t *testing.T) {
return nil return nil
}) })
if err != nil { if err != nil {
t.Fatal(err) t.Fatalf("phase %d: %v", i, err)
} }
err = tstest.WaitFor(2*time.Second, func() error { err = tstest.WaitFor(2*time.Second, func() error {
for path, want := range p.WantFiles { for path, want := range p.WantFiles {
@ -983,13 +983,13 @@ func (k *kubeServer) serveSecret(w http.ResponseWriter, r *http.Request) {
} }
case "application/strategic-merge-patch+json": case "application/strategic-merge-patch+json":
req := struct { req := struct {
Data map[string]string `json:"stringData"` Data map[string][]byte `json:"data"`
}{} }{}
if err := json.Unmarshal(bs, &req); err != nil { if err := json.Unmarshal(bs, &req); err != nil {
panic(fmt.Sprintf("json decode failed: %v. Body:\n\n%s", err, string(bs))) panic(fmt.Sprintf("json decode failed: %v. Body:\n\n%s", err, string(bs)))
} }
for key, val := range req.Data { for key, val := range req.Data {
k.secret[key] = val k.secret[key] = string(val)
} }
default: default:
panic(fmt.Sprintf("unknown content type %q", r.Header.Get("Content-Type"))) panic(fmt.Sprintf("unknown content type %q", r.Header.Get("Content-Type")))

179
kube/client.go
Unescape Escape View File

@ -14,11 +14,15 @@ import (
"encoding/json" "encoding/json"
"fmt" "fmt"
"io" "io"
"log"
"net/http" "net/http"
"net/url"
"os" "os"
"path/filepath" "path/filepath"
"sync" "sync"
"time" "time"
"tailscale.com/util/multierr"
) )
const ( const (
@ -26,7 +30,19 @@ const (
defaultURL = "https://kubernetes.default.svc" defaultURL = "https://kubernetes.default.svc"
) )
// rootPathForTests is set by tests to override the root path to the
// service account directory.
var rootPathForTests string
// SetRootPathForTesting sets the path to the service account directory.
func SetRootPathForTesting(p string) {
rootPathForTests = p
}
func readFile(n string) ([]byte, error) { func readFile(n string) ([]byte, error) {
if rootPathForTests != "" {
return os.ReadFile(filepath.Join(rootPathForTests, saPath, n))
}
return os.ReadFile(filepath.Join(saPath, n)) return os.ReadFile(filepath.Join(saPath, n))
} }
@ -68,6 +84,12 @@ func New() (*Client, error) {
}, nil }, nil
} }
// SetURL sets the URL to use for the Kubernetes API.
// This is used only for testing.
func (c *Client) SetURL(url string) {
c.url = url
}
func (c *Client) expireToken() { func (c *Client) expireToken() {
c.mu.Lock() c.mu.Lock()
defer c.mu.Unlock() defer c.mu.Unlock()
@ -111,28 +133,27 @@ func getError(resp *http.Response) error {
return st return st
} }
func (c *Client) doRequest(ctx context.Context, method, url string, in, out any) error { func setHeader(key, value string) func(*http.Request) {
tk, err := c.getOrRenewToken() return func(req *http.Request) {
if err != nil { req.Header.Set(key, value)
return err
}
var body io.Reader
if in != nil {
var b bytes.Buffer
if err := json.NewEncoder(&b).Encode(in); err != nil {
return err
}
body = &b
} }
req, err := http.NewRequestWithContext(ctx, method, url, body) }
// doRequest performs an HTTP request to the Kubernetes API.
// If in is not nil, it is expected to be a JSON-encodable object and will be
// sent as the request body.
// If out is not nil, it is expected to be a pointer to an object that can be
// decoded from JSON.
// If the request fails with a 401, the token is expired and a new one is
// requested.
func (c *Client) doRequest(ctx context.Context, method, url string, in, out any, opts ...func(*http.Request)) error {
req, err := c.newRequest(ctx, method, url, in)
if err != nil { if err != nil {
return err return err
} }
if body != nil { for _, opt := range opts {
req.Header.Add("Content-Type", "application/json") opt(req)
} }
req.Header.Add("Accept", "application/json")
req.Header.Add("Authorization", "Bearer "+tk)
resp, err := c.client.Do(req) resp, err := c.client.Do(req)
if err != nil { if err != nil {
return err return err
@ -150,6 +171,36 @@ func (c *Client) doRequest(ctx context.Context, method, url string, in, out any)
return nil return nil
} }
func (c *Client) newRequest(ctx context.Context, method, url string, in any) (*http.Request, error) {
tk, err := c.getOrRenewToken()
if err != nil {
return nil, err
}
var body io.Reader
if in != nil {
switch in := in.(type) {
case []byte:
body = bytes.NewReader(in)
default:
var b bytes.Buffer
if err := json.NewEncoder(&b).Encode(in); err != nil {
return nil, err
}
body = &b
}
}
req, err := http.NewRequestWithContext(ctx, method, url, body)
if err != nil {
return nil, err
}
if body != nil {
req.Header.Add("Content-Type", "application/json")
}
req.Header.Add("Accept", "application/json")
req.Header.Add("Authorization", "Bearer "+tk)
return req, nil
}
// GetSecret fetches the secret from the Kubernetes API. // GetSecret fetches the secret from the Kubernetes API.
func (c *Client) GetSecret(ctx context.Context, name string) (*Secret, error) { func (c *Client) GetSecret(ctx context.Context, name string) (*Secret, error) {
s := &Secret{Data: make(map[string][]byte)} s := &Secret{Data: make(map[string][]byte)}
@ -169,3 +220,97 @@ func (c *Client) CreateSecret(ctx context.Context, s *Secret) error {
func (c *Client) UpdateSecret(ctx context.Context, s *Secret) error { func (c *Client) UpdateSecret(ctx context.Context, s *Secret) error {
return c.doRequest(ctx, "PUT", c.secretURL(s.Name), s, nil) return c.doRequest(ctx, "PUT", c.secretURL(s.Name), s, nil)
} }
// JSONPatch is a JSON patch operation.
// It currently (2023-03-02) only supports the "remove" operation.
//
// https://tools.ietf.org/html/rfc6902
type JSONPatch struct {
Op string `json:"op"`
Path string `json:"path"`
}
// JSONPatchSecret updates a secret in the Kubernetes API using a JSON patch.
// It currently (2023-03-02) only supports the "remove" operation.
func (c *Client) JSONPatchSecret(ctx context.Context, name string, patch []JSONPatch) error {
for _, p := range patch {
if p.Op != "remove" {
panic(fmt.Errorf("unsupported JSON patch operation: %q", p.Op))
}
}
return c.doRequest(ctx, "PATCH", c.secretURL(name), patch, nil, setHeader("Content-Type", "application/json-patch+json"))
}
// StrategicMergePatchSecret updates a secret in the Kubernetes API using a
// strategic merge patch.
// If a fieldManager is provided, it will be used to track the patch.
func (c *Client) StrategicMergePatchSecret(ctx context.Context, name string, s *Secret, fieldManager string) error {
surl := c.secretURL(name)
if fieldManager != "" {
uv := url.Values{
"fieldManager": {fieldManager},
}
surl += "?" + uv.Encode()
}
s.Namespace = c.ns
s.Name = name
return c.doRequest(ctx, "PATCH", surl, s, nil, setHeader("Content-Type", "application/strategic-merge-patch+json"))
}
// CheckSecretPermissions checks the secret access permissions of the current
// pod. It returns an error if the basic permissions tailscale needs are
// missing, and reports whether the patch permission is additionally present.
//
// Errors encountered during the access checking process are logged, but ignored
// so that the pod tries to fail alive if the permissions exist and there's just
// something wrong with SelfSubjectAccessReviews. There shouldn't be, pods
// should always be able to use SSARs to assess their own permissions, but since
// we didn't use to check permissions this way we'll be cautious in case some
// old version of k8s deviates from the current behavior.
func (c *Client) CheckSecretPermissions(ctx context.Context, secretName string) (canPatch bool, err error) {
var errs []error
for _, verb := range []string{"get", "update"} {
ok, err := c.checkPermission(ctx, verb, secretName)
if err != nil {
log.Printf("error checking %s permission on secret %s: %v", verb, secretName, err)
} else if !ok {
errs = append(errs, fmt.Errorf("missing %s permission on secret %q", verb, secretName))
}
}
if len(errs) > 0 {
return false, multierr.New(errs...)
}
ok, err := c.checkPermission(ctx, "patch", secretName)
if err != nil {
log.Printf("error checking patch permission on secret %s: %v", secretName, err)
return false, nil
}
return ok, nil
}
// checkPermission reports whether the current pod has permission to use the
// given verb (e.g. get, update, patch) on secretName.
func (c *Client) checkPermission(ctx context.Context, verb, secretName string) (bool, error) {
sar := map[string]any{
"apiVersion": "authorization.k8s.io/v1",
"kind": "SelfSubjectAccessReview",
"spec": map[string]any{
"resourceAttributes": map[string]any{
"namespace": c.ns,
"verb": verb,
"resource": "secrets",
"name": secretName,
},
},
}
var res struct {
Status struct {
Allowed bool `json:"allowed"`
} `json:"status"`
}
url := c.url + "/apis/authorization.k8s.io/v1/selfsubjectaccessreviews"
if err := c.doRequest(ctx, "POST", url, sar, &res); err != nil {
return false, err
}
return res.Status.Allowed, nil
}

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