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request_token.go
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request_token.go
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package tokencmd
import (
"crypto/tls"
"crypto/x509"
"encoding/json"
"fmt"
"io"
"io/ioutil"
"net"
"net/http"
"net/url"
"strings"
"github.com/RangelReale/osincli"
apierrs "k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/util/sets"
restclient "k8s.io/client-go/rest"
"k8s.io/klog"
"github.com/openshift/library-go/pkg/oauth/oauthdiscovery"
)
const (
// csrfTokenHeader is a marker header that indicates we are not a browser that got tricked into requesting basic auth
// Corresponds to the header expected by basic-auth challenging authenticators
// Copied from pkg/auth/authenticator/challenger/passwordchallenger/password_auth_handler.go
csrfTokenHeader = "X-CSRF-Token"
// Discovery endpoint for OAuth 2.0 Authorization Server Metadata
// See IETF Draft:
// https://tools.ietf.org/html/draft-ietf-oauth-discovery-04#section-2
// Copied from pkg/cmd/server/origin/nonapiserver.go
oauthMetadataEndpoint = "/.well-known/oauth-authorization-server"
// openShiftCLIClientID is the name of the CLI OAuth client, copied from pkg/oauth/apiserver/auth.go
openShiftCLIClientID = "openshift-challenging-client"
// pkce_s256 is sha256 hash per RFC7636, copied from github.com/RangelReale/osincli/pkce.go
pkce_s256 = "S256"
// token fakes the missing osin.TOKEN const
token osincli.AuthorizeRequestType = "token"
)
// ChallengeHandler handles responses to WWW-Authenticate challenges.
type ChallengeHandler interface {
// CanHandle returns true if the handler recognizes a challenge it thinks it can handle.
CanHandle(headers http.Header) bool
// HandleChallenge lets the handler attempt to handle a challenge.
// It is only invoked if CanHandle() returned true for the given headers.
// Returns response headers and true if the challenge is successfully handled.
// Returns false if the challenge was not handled, and an optional error in error cases.
HandleChallenge(requestURL string, headers http.Header) (http.Header, bool, error)
// CompleteChallenge is invoked with the headers from a successful server response
// received after having handled one or more challenges.
// Returns an error if the handler does not consider the challenge/response interaction complete.
CompleteChallenge(requestURL string, headers http.Header) error
// Release gives the handler a chance to release any resources held during a challenge/response sequence.
// It is always invoked, even in cases where no challenges were received or handled.
Release() error
}
type RequestTokenOptions struct {
ClientConfig *restclient.Config
Handler ChallengeHandler
OsinConfig *osincli.ClientConfig
Issuer string
TokenFlow bool
}
// RequestToken uses the cmd arguments to locate an openshift oauth server and attempts to authenticate via an
// OAuth code flow and challenge handling. It returns the access token if it gets one or an error if it does not.
func RequestToken(clientCfg *restclient.Config, reader io.Reader, defaultUsername string, defaultPassword string) (string, error) {
return NewRequestTokenOptions(clientCfg, reader, defaultUsername, defaultPassword, false).RequestToken()
}
func NewRequestTokenOptions(clientCfg *restclient.Config, reader io.Reader, defaultUsername string, defaultPassword string, tokenFlow bool) *RequestTokenOptions {
// priority ordered list of challenge handlers
// the SPNEGO ones must come before basic auth
var handlers []ChallengeHandler
if GSSAPIEnabled() {
klog.V(6).Info("GSSAPI Enabled")
handlers = append(handlers, NewNegotiateChallengeHandler(NewGSSAPINegotiator(defaultUsername)))
}
if SSPIEnabled() {
klog.V(6).Info("SSPI Enabled")
handlers = append(handlers, NewNegotiateChallengeHandler(NewSSPINegotiator(defaultUsername, defaultPassword, clientCfg.Host, reader)))
}
handlers = append(handlers, &BasicChallengeHandler{Host: clientCfg.Host, Reader: reader, Username: defaultUsername, Password: defaultPassword})
var handler ChallengeHandler
if len(handlers) == 1 {
handler = handlers[0]
} else {
handler = NewMultiHandler(handlers...)
}
return &RequestTokenOptions{
ClientConfig: clientCfg,
Handler: handler,
TokenFlow: tokenFlow,
}
}
// SetDefaultOsinConfig overwrites RequestTokenOptions.OsinConfig with the default CLI
// OAuth client and PKCE support if the server supports S256 / a code flow is being used
func (o *RequestTokenOptions) SetDefaultOsinConfig() error {
if o.OsinConfig != nil {
return fmt.Errorf("osin config is already set to: %#v", *o.OsinConfig)
}
// get the OAuth metadata directly from the api server
// we only want to use the ca data from our config
rt, err := restclient.TransportFor(o.ClientConfig)
if err != nil {
return err
}
requestURL := strings.TrimRight(o.ClientConfig.Host, "/") + oauthMetadataEndpoint
resp, err := request(rt, requestURL, nil)
if err != nil {
return err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("couldn't get %v: unexpected response status %v", requestURL, resp.StatusCode)
}
metadata := &oauthdiscovery.OauthAuthorizationServerMetadata{}
if err := json.NewDecoder(resp.Body).Decode(metadata); err != nil {
return err
}
// use the metadata to build the osin config
config := &osincli.ClientConfig{
ClientId: openShiftCLIClientID,
AuthorizeUrl: metadata.AuthorizationEndpoint,
TokenUrl: metadata.TokenEndpoint,
RedirectUrl: oauthdiscovery.OpenShiftOAuthTokenImplicitURL(metadata.Issuer),
}
if !o.TokenFlow && sets.NewString(metadata.CodeChallengeMethodsSupported...).Has(pkce_s256) {
if err := osincli.PopulatePKCE(config); err != nil {
return err
}
}
o.OsinConfig = config
o.Issuer = metadata.Issuer
return nil
}
// RequestToken locates an openshift oauth server and attempts to authenticate.
// It returns the access token if it gets one, or an error if it does not.
// It should only be invoked once on a given RequestTokenOptions instance.
// The Handler held by the options is released as part of this call.
// If RequestTokenOptions.OsinConfig is nil, it will be defaulted using SetDefaultOsinConfig.
// The caller is responsible for setting up the entire OsinConfig if the value is not nil.
func (o *RequestTokenOptions) RequestToken() (string, error) {
defer func() {
// Always release the handler
if err := o.Handler.Release(); err != nil {
// Release errors shouldn't fail the token request, just log
klog.V(4).Infof("error releasing handler: %v", err)
}
}()
if o.OsinConfig == nil {
if err := o.SetDefaultOsinConfig(); err != nil {
return "", err
}
}
// we are going to use this transport to talk
// with a server that may not be the api server
// thus we need to include the system roots
// in our ca data otherwise an external
// oauth server with a valid cert will fail with
// error: x509: certificate signed by unknown authority
rt, err := transportWithSystemRoots(o.Issuer, o.ClientConfig)
if err != nil {
return "", err
}
client, err := osincli.NewClient(o.OsinConfig)
if err != nil {
return "", err
}
client.Transport = rt
authorizeRequest := client.NewAuthorizeRequest(osincli.CODE) // assume code flow to start with
var oauthTokenFunc func(redirectURL string) (accessToken string, oauthError error)
if o.TokenFlow {
// access_token in fragment or error parameter
authorizeRequest.Type = token // manually override to token flow if necessary
oauthTokenFunc = oauthTokenFlow
} else {
// code or error parameter
oauthTokenFunc = func(redirectURL string) (accessToken string, oauthError error) {
return oauthCodeFlow(client, authorizeRequest, redirectURL)
}
}
// requestURL holds the current URL to make requests to. This can change if the server responds with a redirect
requestURL := authorizeRequest.GetAuthorizeUrl().String()
// requestHeaders holds additional headers to add to the request. This can be changed by o.Handlers
requestHeaders := http.Header{}
// requestedURLSet/requestedURLList hold the URLs we have requested, to prevent redirect loops. Gets reset when a challenge is handled.
requestedURLSet := sets.NewString()
requestedURLList := []string{}
handledChallenge := false
for {
// Make the request
resp, err := request(rt, requestURL, requestHeaders)
if err != nil {
return "", err
}
defer resp.Body.Close()
if resp.StatusCode == http.StatusUnauthorized {
if resp.Header.Get("WWW-Authenticate") != "" {
if !o.Handler.CanHandle(resp.Header) {
return "", apierrs.NewUnauthorized("unhandled challenge")
}
// Handle the challenge
newRequestHeaders, shouldRetry, err := o.Handler.HandleChallenge(requestURL, resp.Header)
if err != nil {
return "", err
}
if !shouldRetry {
return "", apierrs.NewUnauthorized("challenger chose not to retry the request")
}
// Remember if we've ever handled a challenge
handledChallenge = true
// Reset request set/list. Since we're setting different headers, it is legitimate to request the same urls
requestedURLSet = sets.NewString()
requestedURLList = []string{}
// Use the response to the challenge as the new headers
requestHeaders = newRequestHeaders
continue
}
// Unauthorized with no challenge
unauthorizedError := apierrs.NewUnauthorized("")
// Attempt to read body content and include as an error detail
if details, err := ioutil.ReadAll(resp.Body); err == nil && len(details) > 0 {
unauthorizedError.ErrStatus.Details = &metav1.StatusDetails{
Causes: []metav1.StatusCause{
{Message: string(details)},
},
}
}
return "", unauthorizedError
}
// if we've ever handled a challenge, see if the handler also considers the interaction complete.
// this is required for negotiate flows with mutual authentication.
if handledChallenge {
if err := o.Handler.CompleteChallenge(requestURL, resp.Header); err != nil {
return "", err
}
}
if resp.StatusCode == http.StatusFound {
redirectURL := resp.Header.Get("Location")
// OAuth response case
accessToken, err := oauthTokenFunc(redirectURL)
if err != nil {
return "", err
}
if len(accessToken) > 0 {
return accessToken, nil
}
// Non-OAuth response, just follow the URL
// add to our list of redirects
requestedURLList = append(requestedURLList, redirectURL)
// detect loops
if !requestedURLSet.Has(redirectURL) {
requestedURLSet.Insert(redirectURL)
requestURL = redirectURL
continue
}
return "", apierrs.NewInternalError(fmt.Errorf("redirect loop: %s", strings.Join(requestedURLList, " -> ")))
}
// Unknown response
return "", apierrs.NewInternalError(fmt.Errorf("unexpected response: %d", resp.StatusCode))
}
}
// oauthTokenFlow attempts to extract an OAuth token from location's fragment's access_token value.
// It only returns an error if something "impossible" happens (location is not a valid URL) or a definite
// OAuth error is contained in the location URL. No error is returned if location does not contain a token.
// It is assumed that location was not part of the OAuth flow; it was a redirect that the client needs to follow
// as part of the challenge flow (an authenticating proxy for example) and not a redirect step in the OAuth flow.
func oauthTokenFlow(location string) (string, error) {
u, err := url.Parse(location)
if err != nil {
return "", err
}
if oauthErr := oauthErrFromValues(u.Query()); oauthErr != nil {
return "", oauthErr
}
// Grab the raw fragment ourselves, since the stdlib URL parsing decodes parts of it
fragment := ""
if parts := strings.SplitN(location, "#", 2); len(parts) == 2 {
fragment = parts[1]
}
fragmentValues, err := url.ParseQuery(fragment)
if err != nil {
return "", err
}
return fragmentValues.Get("access_token"), nil
}
// oauthCodeFlow performs the OAuth code flow if location has a code parameter.
// It only returns an error if something "impossible" happens (location is not a valid URL)
// or a definite OAuth error is encountered during the code flow. Other errors are assumed to be caused
// by location not being part of the OAuth flow; it was a redirect that the client needs to follow as part
// of the challenge flow (an authenticating proxy for example) and not a redirect step in the OAuth flow.
func oauthCodeFlow(client *osincli.Client, authorizeRequest *osincli.AuthorizeRequest, location string) (string, error) {
// Make a request out of the URL since that is what AuthorizeRequest.HandleRequest expects to extract data from
req, err := http.NewRequest(http.MethodGet, location, nil)
if err != nil {
return "", err
}
req.ParseForm()
if oauthErr := oauthErrFromValues(req.Form); oauthErr != nil {
return "", oauthErr
}
if len(req.Form.Get("code")) == 0 {
return "", nil // no code parameter so this is not part of the OAuth flow
}
// any errors after this are fatal because we are committed to an OAuth flow now
authorizeData, err := authorizeRequest.HandleRequest(req)
if err != nil {
return "", osinToOAuthError(err)
}
accessRequest := client.NewAccessRequest(osincli.AUTHORIZATION_CODE, authorizeData)
accessData, err := accessRequest.GetToken()
if err != nil {
return "", osinToOAuthError(err)
}
return accessData.AccessToken, nil
}
// osinToOAuthError creates a better error message for osincli.Error
func osinToOAuthError(err error) error {
if osinErr, ok := err.(*osincli.Error); ok {
return createOAuthError(osinErr.Id, osinErr.Description)
}
return err
}
func oauthErrFromValues(values url.Values) error {
if errorCode := values.Get("error"); len(errorCode) > 0 {
errorDescription := values.Get("error_description")
return createOAuthError(errorCode, errorDescription)
}
return nil
}
func createOAuthError(errorCode, errorDescription string) error {
return fmt.Errorf("%s %s", errorCode, errorDescription)
}
func request(rt http.RoundTripper, requestURL string, requestHeaders http.Header) (*http.Response, error) {
// Build the request
req, err := http.NewRequest(http.MethodGet, requestURL, nil)
if err != nil {
return nil, err
}
for k, v := range requestHeaders {
req.Header[k] = v
}
req.Header.Set(csrfTokenHeader, "1")
// Make the request
return rt.RoundTrip(req)
}
func transportWithSystemRoots(issuer string, clientConfig *restclient.Config) (http.RoundTripper, error) {
// copy the config so we can freely mutate it
configWithSystemRoots := restclient.CopyConfig(clientConfig)
// explicitly unset CA cert information
// this will make the transport use the system roots or OS specific verification
// this is required to have reasonable behavior on windows (cannot get system roots)
// in general there is no good with to say "I want system roots plus this CA bundle"
// so we just try system roots first before using the kubeconfig CA bundle
configWithSystemRoots.CAFile = ""
configWithSystemRoots.CAData = nil
systemRootsRT, err := restclient.TransportFor(configWithSystemRoots)
if err != nil {
return nil, err
}
// build a request to probe the OAuth server CA
req, err := http.NewRequest(http.MethodHead, issuer, nil)
if err != nil {
return nil, err
}
// see if get a certificate error when using the system roots
// we perform the check using this transport (instead of the kubeconfig based one)
// because it is most likely to work with a route (which is what the OAuth server uses in 4.0+)
// note that both transports are "safe" to use (in the sense that they have valid TLS configurations)
// thus the fallback case is not an "unsafe" operation
_, err = systemRootsRT.RoundTrip(req)
switch err.(type) {
case nil:
// no error meaning the system roots work with the OAuth server
klog.V(4).Info("using system roots as no error was encountered")
return systemRootsRT, nil
case x509.UnknownAuthorityError, x509.HostnameError, x509.CertificateInvalidError, x509.SystemRootsError,
tls.RecordHeaderError, *net.OpError:
// fallback to the CA in the kubeconfig since the system roots did not work
// we are very broad on the errors here to avoid failing when we should fallback
klog.V(4).Infof("falling back to kubeconfig CA due to possible x509 error: %v", err)
return restclient.TransportFor(clientConfig)
default:
switch err {
case io.EOF, io.ErrUnexpectedEOF, io.ErrNoProgress:
// also fallback on various io errors
klog.V(4).Infof("falling back to kubeconfig CA due to possible IO error: %v", err)
return restclient.TransportFor(clientConfig)
}
// unknown error, fail (ideally should never occur)
klog.V(4).Infof("unexpected error during system roots probe: %v", err)
return nil, err
}
}