mirror of
https://github.com/tailscale/tailscale.git
synced 2024-12-02 06:25:37 +00:00
298 lines
9.0 KiB
Go
298 lines
9.0 KiB
Go
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// The tsidp command is an OpenID Connect Identity Provider server.
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package main
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import (
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"context"
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crand "crypto/rand"
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"crypto/rsa"
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"crypto/x509"
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"encoding/base64"
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"encoding/binary"
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"encoding/json"
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"encoding/pem"
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"flag"
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"fmt"
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"io"
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"log"
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"net/http"
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"net/netip"
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"os"
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"strings"
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"sync"
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"github.com/golang-jwt/jwt"
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"gopkg.in/square/go-jose.v2"
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"tailscale.com/client/tailscale"
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"tailscale.com/tailcfg"
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"tailscale.com/tsnet"
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"tailscale.com/tsweb"
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"tailscale.com/types/key"
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"tailscale.com/types/logger"
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"tailscale.com/types/views"
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"tailscale.com/util/must"
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)
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var (
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flagVerbose = flag.Bool("verbose", false, "be verbose")
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)
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func main() {
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flag.Parse()
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ctx := context.Background()
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ts := &tsnet.Server{
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Hostname: "idp",
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}
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if !*flagVerbose {
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ts.Logf = logger.Discard
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}
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st, err := ts.Up(ctx)
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if err != nil {
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log.Fatal(err)
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}
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lc, err := ts.LocalClient()
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if err != nil {
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log.Fatalf("getting local client: %v", err)
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}
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srv := &idpServer{
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lc: lc,
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serverURL: "https://" + strings.TrimSuffix(st.Self.DNSName, "."),
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}
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log.Printf("Running tsidp at %s ...", srv.serverURL)
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ln, err := ts.ListenTLS("tcp", ":443")
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if err != nil {
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log.Fatal(err)
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}
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log.Fatal(http.Serve(ln, srv))
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}
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type idpServer struct {
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lc *tailscale.LocalClient
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serverURL string // "https://foo.bar.ts.net"
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oidcSignerInitOnce sync.Once
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oidcSignerLazy jose.Signer
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oidcSignerError error
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}
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func (s *idpServer) ServeHTTP(w http.ResponseWriter, r *http.Request) {
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log.Printf("%v %v", r.Method, r.URL)
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if r.URL.Path == oidcJWKSPath {
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if err := s.serveJWKS(w, r); err != nil {
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log.Printf("Error serving JWKS: %v", err)
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}
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return
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}
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if r.URL.Path == oidcConfigPath {
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if err := s.serveOpenIDConfig(w, r); err != nil {
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log.Printf("Error serving OpenID config: %v", err)
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}
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return
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}
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if r.URL.Path == "/" {
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io.WriteString(w, "<html><body><h1>Tailscale OIDC IdP</h1>")
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return
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}
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if r.URL.Path == "/authorize" {
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redir := r.URL.Query().Get("redirect_uri")
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http.Redirect(w, r, redir, http.StatusFound)
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return
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}
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http.Error(w, "tsidp: not found", http.StatusNotFound)
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}
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const (
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oidcJWKSPath = "/.well-known/jwks.json"
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oidcConfigPath = "/.well-known/openid-configuration"
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)
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func (s *idpServer) oidcSigner() (jose.Signer, error) {
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s.oidcSignerInitOnce.Do(s.oidcSignerInit)
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return s.oidcSignerLazy, s.oidcSignerError
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}
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func (s *idpServer) oidcSignerInit() {
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id, k := s.oidcPrivateKey()
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s.oidcSignerLazy, s.oidcSignerError = jose.NewSigner(jose.SigningKey{
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Algorithm: jose.RS256,
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Key: k,
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}, &jose.SignerOptions{EmbedJWK: false, ExtraHeaders: map[jose.HeaderKey]interface{}{
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jose.HeaderType: "JWT",
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"kid": fmt.Sprint(id),
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}})
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}
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func (s *idpServer) oidcPrivateKey() (id uint64, k *rsa.PrivateKey) {
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id, k = mustGenRSAKey(2048)
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return
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}
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func (s *idpServer) serveJWKS(w http.ResponseWriter, r *http.Request) error {
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if r.URL.Path != oidcJWKSPath {
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return tsweb.Error(404, "", nil)
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}
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w.Header().Set("Content-Type", "application/json")
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id, k := s.oidcPrivateKey()
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// TODO(maisem): maybe only marshal this once and reuse?
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// TODO(maisem): implement key rotation.
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if err := json.NewEncoder(w).Encode(jose.JSONWebKeySet{
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Keys: []jose.JSONWebKey{
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{
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Key: k.Public(),
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Algorithm: string(jose.RS256),
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Use: "sig",
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KeyID: fmt.Sprint(id),
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},
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},
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}); err != nil {
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return tsweb.Error(500, err.Error(), err)
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}
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return nil
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}
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// openIDProviderMetadata is a partial representation of
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// https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata.
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type openIDProviderMetadata struct {
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Issuer string `json:"issuer"`
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AuthorizationEndpoint string `json:"authorization_endpoint,omitempty"`
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UserInfoEndpoint string `json:"userinfo_endpoint,omitempty"`
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JWKS_URI string `json:"jwks_uri"`
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ScopesSupported views.Slice[string] `json:"scopes_supported"`
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ResponseTypesSupported views.Slice[string] `json:"response_types_supported"`
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SubjectTypesSupported views.Slice[string] `json:"subject_types_supported"`
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ClaimsSupported views.Slice[string] `json:"claims_supported"`
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IDTokenSigningAlgValuesSupported views.Slice[string] `json:"id_token_signing_alg_values_supported"`
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// TODO(maisem): maybe add other fields?
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// Currently we fill out the REQUIRED fields, scopes_supported and claims_supported.
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}
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type tailscaleClaims struct {
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jwt.Claims `json:",inline"`
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Key key.NodePublic `json:"key"` // the node public key
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Addresses views.Slice[netip.Prefix] `json:"addresses"` // the Tailscale IPs of the node
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NodeID tailcfg.NodeID `json:"nid"` // the stable node ID
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NodeName string `json:"node"` // name of the node
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Tailnet string `json:"tailnet"` // tailnet (like tail-scale.ts.net)
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// Tags is the list of tags the node is tagged with prefixed with the Tailnet name.
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Tags []string `json:"tags,omitempty"` // the tags on the node (like alice.github:tag:foo or example.com:tag:foo)
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// User is the emailish of the user prefixed with the Tailnet name.
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User string `json:"user,omitempty"` // user emailish (like alice.github:alice@github or example.com:bob@example.com)
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UserID tailcfg.UserID `json:"uid,omitempty"` // user legacy id
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}
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var (
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openIDSupportedClaims = views.SliceOf([]string{
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// Standard claims, these correspond to fields in jwt.Claims.
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"sub", "aud", "exp", "iat", "iss", "jti", "nbf",
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// Tailscale claims, these correspond to fields in tailscaleClaims.
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"key", "addresses", "nid", "node", "tailnet", "tags", "user", "uid",
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})
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// As defined in the OpenID spec this should be "openid".
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openIDSupportedScopes = views.SliceOf([]string{"openid", "email", "profile"})
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// We only support getting the id_token.
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openIDSupportedReponseTypes = views.SliceOf([]string{"id_token", "code"})
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// The type of the "sub" field in the JWT, which means it is globally unique identifier.
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// The other option is "pairwise", which means the identifier is different per receiving 3p.
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openIDSupportedSubjectTypes = views.SliceOf([]string{"public"})
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// The algo used for signing. The OpenID spec says "The algorithm RS256 MUST be included."
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// https://openid.net/specs/openid-connect-discovery-1_0.html#ProviderMetadata
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openIDSupportedSigningAlgos = views.SliceOf([]string{string(jose.RS256)})
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)
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func (s *idpServer) serveOpenIDConfig(w http.ResponseWriter, r *http.Request) error {
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if r.URL.Path != oidcConfigPath {
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return tsweb.Error(404, "", nil)
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}
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w.Header().Set("Content-Type", "application/json")
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if err := json.NewEncoder(io.MultiWriter(w, os.Stderr)).Encode(openIDProviderMetadata{
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Issuer: s.serverURL + "/",
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JWKS_URI: s.serverURL + oidcJWKSPath,
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UserInfoEndpoint: s.serverURL + "/userinfo",
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AuthorizationEndpoint: s.serverURL + "/authorize", // TODO: add /<nodeid> suffix
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ScopesSupported: openIDSupportedScopes,
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ResponseTypesSupported: openIDSupportedReponseTypes,
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SubjectTypesSupported: openIDSupportedSubjectTypes,
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ClaimsSupported: openIDSupportedClaims,
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IDTokenSigningAlgValuesSupported: openIDSupportedSigningAlgos,
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}); err != nil {
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log.Printf("Error encoding JSON: %v", err)
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http.Error(w, err.Error(), http.StatusInternalServerError)
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}
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return nil
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}
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const (
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minimumRSAKeySize = 2048
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)
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// mustGenRSAKey generates a new RSA key with the provided number of bits. It
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// panics on failure. bits must be at least minimumRSAKeySizeBytes * 8.
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func mustGenRSAKey(bits int) (kid uint64, k *rsa.PrivateKey) {
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if bits < minimumRSAKeySize {
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panic("request to generate a too-small RSA key")
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}
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kid = must.Get(readUint64(crand.Reader))
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k = must.Get(rsa.GenerateKey(crand.Reader, bits))
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return
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}
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// readUint64 reads from r until 8 bytes represent a non-zero uint64.
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func readUint64(r io.Reader) (uint64, error) {
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for {
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var b [8]byte
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if _, err := io.ReadFull(r, b[:]); err != nil {
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return 0, err
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}
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if v := binary.BigEndian.Uint64(b[:]); v != 0 {
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return v, nil
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}
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}
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}
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// rsaPrivateKeyJSONWrapper is the the JSON serialization
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// format used by RSAPrivateKey.
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type rsaPrivateKeyJSONWrapper struct {
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Key string
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ID uint64
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}
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func marshalKeyJSON(k *rsa.PrivateKey, kid uint64) ([]byte, error) {
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b := pem.Block{
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Type: "RSA PRIVATE KEY",
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Bytes: x509.MarshalPKCS1PrivateKey(k),
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}
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bts := pem.EncodeToMemory(&b)
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return json.Marshal(rsaPrivateKeyJSONWrapper{
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Key: base64.URLEncoding.EncodeToString(bts),
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ID: kid,
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})
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}
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func unmarshalKeyJSON(b []byte) (*rsa.PrivateKey, uint64, error) {
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var wrapper rsaPrivateKeyJSONWrapper
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if err := json.Unmarshal(b, &wrapper); err != nil {
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return nil, 0, err
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}
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if len(wrapper.Key) == 0 {
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return nil, 0, nil
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}
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b64dec, err := base64.URLEncoding.DecodeString(wrapper.Key)
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if err != nil {
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return nil, 0, err
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}
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blk, _ := pem.Decode(b64dec)
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k, err := x509.ParsePKCS1PrivateKey(blk.Bytes)
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return k, wrapper.ID, err
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}
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