mirror of
https://github.com/juanfont/headscale.git
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7cc58af932
Adds knobs to configure three aspects of the OpenID Connect flow: * Custom scopes to override the default "openid profile email". * Custom parameters to be added to the Authorize Endpoint request. * Domain allowlisting for authenticated principals. * User allowlisting for authenticated principals.
377 lines
9.2 KiB
Go
377 lines
9.2 KiB
Go
package headscale
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import (
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"bytes"
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"context"
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"crypto/rand"
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"encoding/hex"
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"errors"
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"fmt"
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"html/template"
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"net/http"
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"strings"
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"time"
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"github.com/coreos/go-oidc/v3/oidc"
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"github.com/gin-gonic/gin"
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"github.com/rs/zerolog/log"
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"golang.org/x/oauth2"
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"tailscale.com/types/key"
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)
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const (
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randomByteSize = 16
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)
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type IDTokenClaims struct {
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Name string `json:"name,omitempty"`
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Groups []string `json:"groups,omitempty"`
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Email string `json:"email"`
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Username string `json:"preferred_username,omitempty"`
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}
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func (h *Headscale) initOIDC() error {
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var err error
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// grab oidc config if it hasn't been already
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if h.oauth2Config == nil {
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h.oidcProvider, err = oidc.NewProvider(context.Background(), h.cfg.OIDC.Issuer)
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if err != nil {
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log.Error().
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Err(err).
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Caller().
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Msgf("Could not retrieve OIDC Config: %s", err.Error())
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return err
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}
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h.oauth2Config = &oauth2.Config{
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ClientID: h.cfg.OIDC.ClientID,
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ClientSecret: h.cfg.OIDC.ClientSecret,
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Endpoint: h.oidcProvider.Endpoint(),
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RedirectURL: fmt.Sprintf(
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"%s/oidc/callback",
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strings.TrimSuffix(h.cfg.ServerURL, "/"),
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),
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Scopes: h.cfg.OIDC.Scope,
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}
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}
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return nil
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}
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// RegisterOIDC redirects to the OIDC provider for authentication
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// Puts machine key in cache so the callback can retrieve it using the oidc state param
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// Listens in /oidc/register/:mKey.
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func (h *Headscale) RegisterOIDC(ctx *gin.Context) {
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machineKeyStr := ctx.Param("mkey")
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if machineKeyStr == "" {
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ctx.String(http.StatusBadRequest, "Wrong params")
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return
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}
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log.Trace().
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Caller().
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Str("machine_key", machineKeyStr).
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Msg("Received oidc register call")
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randomBlob := make([]byte, randomByteSize)
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if _, err := rand.Read(randomBlob); err != nil {
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log.Error().
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Caller().
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Msg("could not read 16 bytes from rand")
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ctx.String(http.StatusInternalServerError, "could not read 16 bytes from rand")
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return
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}
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stateStr := hex.EncodeToString(randomBlob)[:32]
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// place the machine key into the state cache, so it can be retrieved later
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h.registrationCache.Set(stateStr, machineKeyStr, registerCacheExpiration)
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// Add any extra parameter provided in the configuration to the Authorize Endpoint request
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extras := make([]oauth2.AuthCodeOption, 0, len(h.cfg.OIDC.ExtraParams))
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for k, v := range h.cfg.OIDC.ExtraParams {
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extras = append(extras, oauth2.SetAuthURLParam(k, v))
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}
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authURL := h.oauth2Config.AuthCodeURL(stateStr, extras...)
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log.Debug().Msgf("Redirecting to %s for authentication", authURL)
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ctx.Redirect(http.StatusFound, authURL)
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}
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type oidcCallbackTemplateConfig struct {
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User string
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Verb string
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}
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var oidcCallbackTemplate = template.Must(
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template.New("oidccallback").Parse(`<html>
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<body>
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<h1>headscale</h1>
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<p>
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{{.Verb}} as {{.User}}, you can now close this window.
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</p>
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</body>
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</html>`),
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)
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// OIDCCallback handles the callback from the OIDC endpoint
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// Retrieves the mkey from the state cache and adds the machine to the users email namespace
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// TODO: A confirmation page for new machines should be added to avoid phishing vulnerabilities
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// TODO: Add groups information from OIDC tokens into machine HostInfo
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// Listens in /oidc/callback.
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func (h *Headscale) OIDCCallback(ctx *gin.Context) {
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code := ctx.Query("code")
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state := ctx.Query("state")
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if code == "" || state == "" {
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ctx.String(http.StatusBadRequest, "Wrong params")
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return
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}
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oauth2Token, err := h.oauth2Config.Exchange(context.Background(), code)
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if err != nil {
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log.Error().
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Err(err).
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Caller().
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Msg("Could not exchange code for token")
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ctx.String(http.StatusBadRequest, "Could not exchange code for token")
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return
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}
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log.Trace().
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Caller().
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Str("code", code).
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Str("state", state).
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Msg("Got oidc callback")
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rawIDToken, rawIDTokenOK := oauth2Token.Extra("id_token").(string)
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if !rawIDTokenOK {
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ctx.String(http.StatusBadRequest, "Could not extract ID Token")
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return
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}
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verifier := h.oidcProvider.Verifier(&oidc.Config{ClientID: h.cfg.OIDC.ClientID})
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idToken, err := verifier.Verify(context.Background(), rawIDToken)
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if err != nil {
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log.Error().
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Err(err).
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Caller().
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Msg("failed to verify id token")
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ctx.String(http.StatusBadRequest, "Failed to verify id token")
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return
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}
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// TODO: we can use userinfo at some point to grab additional information about the user (groups membership, etc)
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// userInfo, err := oidcProvider.UserInfo(context.Background(), oauth2.StaticTokenSource(oauth2Token))
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// if err != nil {
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// c.String(http.StatusBadRequest, fmt.Sprintf("Failed to retrieve userinfo"))
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// return
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// }
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// Extract custom claims
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var claims IDTokenClaims
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if err = idToken.Claims(&claims); err != nil {
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log.Error().
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Err(err).
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Caller().
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Msg("Failed to decode id token claims")
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ctx.String(
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http.StatusBadRequest,
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"Failed to decode id token claims",
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)
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return
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}
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// If AllowedDomains is provided, check that the authenticated principal ends with @<alloweddomain>.
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if len(h.cfg.OIDC.AllowedDomains) > 0 {
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if at := strings.LastIndex(claims.Email, "@"); at < 0 ||
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!IsStringInSlice(h.cfg.OIDC.AllowedDomains, claims.Email[at+1:]) {
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log.Error().Msg("authenticated principal does not match any allowed domain")
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ctx.String(
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http.StatusBadRequest,
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"unauthorized principal (domain mismatch)",
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)
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return
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}
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}
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// If AllowedUsers is provided, check that the authenticated princial is part of that list.
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if len(h.cfg.OIDC.AllowedUsers) > 0 &&
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!IsStringInSlice(h.cfg.OIDC.AllowedUsers, claims.Email) {
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log.Error().Msg("authenticated principal does not match any allowed user")
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ctx.String(http.StatusBadRequest, "unauthorized principal (user mismatch)")
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return
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}
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// retrieve machinekey from state cache
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machineKeyIf, machineKeyFound := h.registrationCache.Get(state)
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if !machineKeyFound {
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log.Error().
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Msg("requested machine state key expired before authorisation completed")
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ctx.String(http.StatusBadRequest, "state has expired")
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return
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}
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machineKeyFromCache, machineKeyOK := machineKeyIf.(string)
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var machineKey key.MachinePublic
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err = machineKey.UnmarshalText(
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[]byte(MachinePublicKeyEnsurePrefix(machineKeyFromCache)),
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)
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if err != nil {
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log.Error().
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Msg("could not parse machine public key")
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ctx.String(http.StatusBadRequest, "could not parse public key")
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return
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}
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if !machineKeyOK {
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log.Error().Msg("could not get machine key from cache")
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ctx.String(
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http.StatusInternalServerError,
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"could not get machine key from cache",
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)
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return
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}
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// retrieve machine information if it exist
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// The error is not important, because if it does not
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// exist, then this is a new machine and we will move
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// on to registration.
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machine, _ := h.GetMachineByMachineKey(machineKey)
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if machine != nil {
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log.Trace().
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Caller().
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Str("machine", machine.Name).
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Msg("machine already registered, reauthenticating")
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h.RefreshMachine(machine, time.Time{})
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var content bytes.Buffer
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if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
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User: claims.Email,
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Verb: "Reauthenticated",
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}); err != nil {
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log.Error().
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Str("func", "OIDCCallback").
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Str("type", "reauthenticate").
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Err(err).
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Msg("Could not render OIDC callback template")
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ctx.Data(
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http.StatusInternalServerError,
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"text/html; charset=utf-8",
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[]byte("Could not render OIDC callback template"),
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)
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}
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ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes())
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return
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}
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namespaceName, err := NormalizeToFQDNRules(
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claims.Email,
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h.cfg.OIDC.StripEmaildomain,
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)
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if err != nil {
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log.Error().Err(err).Caller().Msgf("couldn't normalize email")
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ctx.String(
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http.StatusInternalServerError,
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"couldn't normalize email",
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)
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return
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}
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// register the machine if it's new
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log.Debug().Msg("Registering new machine after successful callback")
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namespace, err := h.GetNamespace(namespaceName)
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if errors.Is(err, errNamespaceNotFound) {
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namespace, err = h.CreateNamespace(namespaceName)
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if err != nil {
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log.Error().
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Err(err).
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Caller().
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Msgf("could not create new namespace '%s'", namespaceName)
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ctx.String(
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http.StatusInternalServerError,
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"could not create new namespace",
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)
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return
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}
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} else if err != nil {
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log.Error().
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Caller().
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Err(err).
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Str("namespace", namespaceName).
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Msg("could not find or create namespace")
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ctx.String(
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http.StatusInternalServerError,
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"could not find or create namespace",
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)
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return
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}
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machineKeyStr := MachinePublicKeyStripPrefix(machineKey)
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_, err = h.RegisterMachineFromAuthCallback(
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machineKeyStr,
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namespace.Name,
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RegisterMethodOIDC,
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)
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if err != nil {
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log.Error().
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Caller().
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Err(err).
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Msg("could not register machine")
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ctx.String(
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http.StatusInternalServerError,
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"could not register machine",
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)
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return
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}
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var content bytes.Buffer
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if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
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User: claims.Email,
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Verb: "Authenticated",
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}); err != nil {
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log.Error().
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Str("func", "OIDCCallback").
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Str("type", "authenticate").
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Err(err).
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Msg("Could not render OIDC callback template")
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ctx.Data(
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http.StatusInternalServerError,
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"text/html; charset=utf-8",
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[]byte("Could not render OIDC callback template"),
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)
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}
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ctx.Data(http.StatusOK, "text/html; charset=utf-8", content.Bytes())
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}
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