Repository: vmware-tanzu/pinniped
Pull request #1116 (2022-04-13 16:31:52)

ldap/ad web ui proposal
Signed-off-by: Margo Crawford <margaretc@vmware.com>

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Patch:
diff --git a/internal/concierge/impersonator/impersonator.go b/internal/concierge/impersonator/impersonator.go
index 70155dba..828d94e9 100644
--- a/internal/concierge/impersonator/impersonator.go
+++ b/internal/concierge/impersonator/impersonator.go
@@ -472,7 +472,7 @@ func newImpersonationReverseProxyFunc(restConfig *rest.Config) (func(*genericapi
 		return nil, fmt.Errorf("could not get http/1.1 anonymous round tripper: %w", err)
 	}
 
-	http2RoundTripper, err := getTransportForProtocol(restConfig, "h2")
+	http2RoundTripper, err := getTransportForProtocol(restConfig, "h2") // TODO figure out why this leads to still supporting http1
 	if err != nil {
 		return nil, fmt.Errorf("could not get http/2.0 round tripper: %w", err)
 	}
@@ -812,15 +812,6 @@ func getTransportForProtocol(restConfig *rest.Config, protocol string) (http.Rou
 		return nil, fmt.Errorf("could not build transport: %w", err)
 	}
 
-	// For clients that support http2, transport.New calls http2.ConfigureTransports,
-	// which configures with both h2 and http/1.1,
-	// even when you explicitly only ask for h2.
-	// Override that change.
-	cfg, err := utilnet.TLSClientConfig(rt)
-	if err != nil {
-		return nil, fmt.Errorf("could not extract TLS config: %w", err)
-	}
-	cfg.NextProtos = []string{protocol}
 	if err := kubeclient.AssertSecureTransport(rt); err != nil {
 		return nil, err // make sure we only use a secure TLS config
 	}
diff --git a/proposals/1113_ldap-ad-web-ui/README.md b/proposals/1113_ldap-ad-web-ui/README.md
new file mode 100644
index 00000000..1a204c45
--- /dev/null
+++ b/proposals/1113_ldap-ad-web-ui/README.md
@@ -0,0 +1,211 @@
+---
+title: "Web UI for LDAP/AD login"
+authors: [ "@margocrawf" ]
+status: "accepted"
+approval_date: "May 11, 2022"
+---
+
+*Disclaimer*: Proposals are point-in-time designs and decisions.
+Once approved and implemented, they become historical documents.
+If you are reading an old proposal, please be aware that the
+features described herein might have continued to evolve since.
+
+# Web UI for LDAP/AD login
+
+## Problem Statement
+Today the supervisor only supports a single, hard coded public OAuth client called
+"pinniped-cli" which supports the pinniped CLI’s interactions with the Pinniped Supervisor.
+When clients log in to their IDPs using LDAP or Active Directory, they are prompted to enter their
+credentials the Pinniped CLI without a browser opening.
+The pinniped cli sends the client credentials to the Supervisor, which sends them to the identity provider.
+The "pinniped-cli" client is privileged and as such is trusted to handle a user's credentials
+when authenticating with systems that do not provide an authentication UI (i.e. LDAP).
+
+However, Pinniped is planning to introduce support for dynamic OAuth clients.
+These clients should _not_ be trusted to handle a user's IDP credentials.
+Therefore, we need a mechanism for untrusted clients to acquire Pinniped's downstream tokens while
+leaving the IDP credential handling to the Pinniped supervisor.
+
+## Proposal
+Pinniped must provide a simple login screen in order to support UIs that wish
+to authenticate with the Pinniped Supervisor to gain access to a cluster without
+requiring each app to handle IDP credentials.
+
+### Goals and Non-goals
+
+#### Goals
+* Prevent OAuth clients, other than the Pinniped CLI, from providing credentials via the authorization request
+* Provide a minimal feature set (ie user id, password & submit button only)
+* Provide generalized error messaging for failed logins that do not expose sensitive information (i.e. we should say "invalid username or password"
+  but do not expose whether it's the username or password that's incorrect)
+* Provide information easily allowing a user to identify the screen as belonging to Pinniped and which upstream IdP is being represented (e.g. IdP name)
+* Address basic security concerns for web forms (HTTPS, passwords use a password field, CSRF protection, redirect protection)
+* Prevent LDAP injection attacks
+* Rely on the upstream IdP to address advanced security concerns (brute force protection, username enumeration, etc)
+* Screens are accessible and friendly to screen readers
+* Screens are friendly to password managers
+
+#### Non-goals
+* A rich client (ie the use of javascript)
+* Advanced UI features (e.g. remember me, reveal password).
+* Branding & customization beyond the information listed in the goals used to identify the login screen belongs to Pinniped.
+* Supporting SSO integrations
+* Internationalization or localization. The CLI doesn't currently support this either.
+
+### Specification / How it Solves the Use Cases
+
+#### API Changes
+
+The supervisor must accept requests from other clients, as detailed
+in the (todo) proposal for dynamic client registration.
+When a client other than pinniped-cli makes an authorization endpoint request with `response_type=code` and their
+IDP is an LDAP or Active Directory IDP, the user will be redirected to the new login page.
+The login page should display the IDP name and indicate that it belongs to Pinniped.
+When a client other than the Pinniped CLI makes an authorization endpoint request with
+custom Username/Password headers, they should be rejected.
+
+The discovery metadata for LDAP/AD IDPS should indicate that they support a flow of `browser_authcode`.
+
+The state param should be augmented to include the IDP type as well as the IDP name. The type
+should be included in `UpstreamStateParamData` so that later when we get it back in the callback
+request we can tell which IDP it is referring to. This will require an update to
+`UpstreamStataParamData.FormatVersion`, which would mean that logins in progress at the time of
+upgrade would fail.
+
+The pinniped cli should default to using the cli-based password flow, but when the `--upstream-identity-provider-flow`,
+flag specifies `browser_authcode`, it will open a browser to log in
+instead of prompting for username and password. Some users (for example, IDE plugins for kubernetes)
+may wish to authenticate using the pinniped cli but without access to a terminal.
+
+Here is how the login flow might work:
+1. The supervisor receives an authorization request.
+   1. If the client_id param is not "pinniped-cli", and it includes username and password via the custom headers, reject the request.
+   2. If the request does not include the custom username/password headers, assume we want to use the webpage login.
+   3. Today, the CLI specifies the IDP name and type as request parameters, but the server currently ignores these
+      since the Supervisor does not allow multiple idps today. This could be enhanced in the future to use the requested
+      IDP when the params are present, and to show another UI page to allow the end user to choose which IDP when the params
+      are not present. This leaves room for future multiple IDP support in this flow,
+      however, the details are outside the scope of this proposal.
+   4. Encode the request parameters into a state param like is done today for the `OIDCIdentityProvider`.
+      In addition to the values encoded today (auth params, upstream IDP name, nonce, csrf token and pkce),
+      encode the upstream IDP type.
+   5. Set a CSRF cookie on the response like what we do for OIDC today.
+   6. Return a redirect to the LDAP web url. This should take the form `<issuer-url>/login`
+2. The client receives the redirect and follows it to `<issuer-url>/login`
+3. The supervisor receives the GET request to `<issuer-url>/login` and renders a simple login form with the Pinniped
+logo and the IDP name.
+   1. The submission should be POST `<issuer-url>/login`.
+   2. The state param’s value is written into a hidden form input, properly escaped.
+   3. Username and password form inputs are shown.
+4. The supervisor receives the POST request.
+   1. Decode your state form param to reconstitute the original authorization request params
+   (the client’s nonce and PKCE, requested scopes, etc) and also compare the incoming CSRF cookie to the value
+   from the state param. This code would be identical to what we do in the upstream OIDC callback endpoint today.
+   If the decoded state param’s timestamp is too old, it might be prudent to reject the request.
+   2. Using the idp name/type from the state param, look up the IDP, bind to it, verify the username/password and
+   get the users downstream username and groups.
+   3. If the login succeeds, mint an authcode and store the session as a secret the same way as we do on the
+   callback endpoint today, and return the new authcode. If `response_mode=form_post` was requested, return a 200
+   with Pinniped's form post html page, to be displayed on the login page. If it is `query`, return a redirect
+   with the authcode as a query param. Default behavior when `response_mode` is unspecified should be handled
+   by other parts of the code, but it should default to `query` on the supervisor.
+   4. If the login fails, respond with a redirect to `<issuer-url>/login` with an error type as the query param,
+   so the login page can render an error message. Allow the user to retry login the same way we do with the CLI today
+   (we leave brute force protection to the IDP). Display two types of errors-- "login error" (incorrect username or password)
+   or "internal error" for something that can't be easily fixed by the user (for example, requests to the LDAP server timing
+   out, LDAP queries malformed). The error that is displayed to the user should be generic but should suggest to the user
+   whether they should try again, or contact their administrator. (thanks @vrabbi for the suggestion!)
+
+#### Upgrades
+
+This change is backwards compatible. Users would see no changes unless they decided to register
+a new client or change the pinniped cli flags.
+
+However if they do choose to register a new client they may need to update the following:
+- FederationDomains today may be using private certificate authorities. These are trusted
+  for our use case but a browser will flag them as unsafe. Admins will have to transition to letsencrypt
+  or another public Certificate Authority to prevent making end users click past messages about the certificate
+  being untrusted.
+- The name of the idp custom resource is currently not published to users logging in with Pinniped.
+  We plan on exposing this to indicate to users which idp they are logging in to.
+  Admins may need to update this to something more user-friendly.
+  Note: While branding is an important part of the user experience, and we may consider adding
+  the option to customize the page or add new fields (such as an IDP "display name" field), we
+  are choosing to defer this work until later. We want to get the MVP work done and into users'
+  hands and hope to hear more from the community once the MVP is completed.
+  For the MVP, we should not add new config but should remind admins that the IDP field field
+  is now displayed.
+
+To enable users to upgrade smoothly, the behavior of the Pinniped CLI when it encounters multiple possible flow options will change.
+Previously, the team had decided that the CLI should fail when there were multiple options (e.g. when it's could
+use either the `browser_authcode` flow or the `cli_password` flow). However, that behavior would break existing
+kubeconfigs once the `browser_authcode` flow was introduced to the IDP discovery doc.
+Instead we are opting to prioritize based on the order listed in the IDP discovery doc.
+Users will still have the option to override this priority with the `--upstream-identity-provider-flow` flag,
+but that flag will not be required.
+
+#### Tests
+
+Chromedriver browser based integration tests will be needed to ensure that a user can log in from a web-based app
+by entering their ldap credentials into the web page, as well as unit tests.
+
+With the pinniped cli:
+- succeeds with correct username and password
+- fails with incorrect username, shows useful but nonspecific error message
+- fails with incorrect password, shows useful but nonspecific error message
+Once dynamic clients are implemented:
+- fails when attempting to pass username/password as headers on requests to the authorize endpoint
+- tests of the rest of the dynamic client functionality that should be detailed as part of that proposal
+
+#### New Dependencies
+This should be kept to a very simple HTML page with minimal, clean CSS styling.
+Javascript should be avoided.
+The styling should match the [form post html page](https://github.com/vmware-tanzu/pinniped/tree/main/internal/oidc/provider/formposthtml)
+as much as possible, we should reuse some of the existing css and add to it to keep the style consistent.
+
+#### Observability Considerations
+* The existing logging in `upstreamldap.go` should be sufficient for logging the attempted logins.
+  Further logging should be proposed as a separate proposal.
+
+#### Security Considerations
+* Preventing LDAP injection attacks: this should be done server-side using our existing
+  string escaping.
+* CSRF protection via a CSRF cookie: this should be similar to the way it is done for the
+  OIDCIdentityProvider today
+* The new UI page must be HTTPS.
+
+#### Documentation Considerations
+This new feature will require documentation to explain how to configure it and to publicise that it is available.
+This should include:
+* A blog post describing the feature
+* Website documentation in the form of a how-to guide
+
+### Other Approaches Considered
+Today, users can configure Dex if they want a web-based LDAP login.
+This introduces complexity because they have to install, configure and
+maintain both Pinniped and Dex in order to use this feature. It also means
+that users do not benefit from the opinionated `ActiveDirectoryIdentityProvider`
+config because Dex does not have an equivalent.
+
+## Answered Questions
+* Q: What is the format for the URL? (`issuer/some/path`? Something else?)
+  A: `<issuer>/login`
+* Q: Can we make it so we can reuse the existing cert, or will we need a new wildcard cert?
+  A: Since the page is hosted on the issuer, we can reuse the existing `FederationDomain` cert.
+* Q: Currently we have little validation on branding requirements. Is specifying the IDP name enough for users to understand
+  how to log in? How many users will be blocked on using this feature until they can have a company name and logo on the login page?
+  A: For our initial release, we will only specify the IDP name. We are open to adding further customization in response to feedback
+  from users once the feature is released.
+
+## Open Questions
+None.
+
+## Implementation Plan
+While this work is intended to supplement the dynamic client work, parts of it
+can be implemented independently.
+The pinniped cli can support a web based ui flow via a command line flag, or environment variable.
+Then once dynamic clients exist, we can add functionality to accept requests
+from those clients as well.
+
+## Implementation PRs
+- https://github.com/vmware-tanzu/pinniped/pull/1163


Test patch:
diff --git a/internal/concierge/impersonator/impersonator_test.go b/internal/concierge/impersonator/impersonator_test.go
index cf68a510..6eedd950 100644
--- a/internal/concierge/impersonator/impersonator_test.go
+++ b/internal/concierge/impersonator/impersonator_test.go
@@ -5,8 +5,6 @@ package impersonator
 
 import (
 	"context"
-	"crypto/tls"
-	"crypto/x509"
 	"fmt"
 	"math/rand"
 	"net"
@@ -703,28 +701,7 @@ func TestImpersonator(t *testing.T) {
 			testKubeAPIServerWasCalled := false
 			var testKubeAPIServerSawHeaders http.Header
 			testKubeAPIServer := tlsserver.TLSTestServer(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				tlsConfigFunc := func(rootCAs *x509.CertPool) *tls.Config {
-					// Requests to get configmaps, flowcontrol requests, and healthz requests
-					// are not done by our http round trippers that specify only one protocol
-					// (either http1.1 or http2, not both).
-					// For all other requests from the impersonator, if it is not an upgrade
-					// request it should only be using http2.
-					// If it is an upgrade request it should only be using http1.1, but that
-					// is covered by the AssertTLS function.
-					secure := ptls.Secure(rootCAs)
-					switch r.URL.Path {
-					case "/api/v1/namespaces/kube-system/configmaps",
-						"/apis/flowcontrol.apiserver.k8s.io/v1beta2/prioritylevelconfigurations",
-						"/apis/flowcontrol.apiserver.k8s.io/v1beta2/flowschemas",
-						"/healthz":
-					default:
-						if !httpstream.IsUpgradeRequest(r) {
-							secure.NextProtos = []string{secure.NextProtos[0]}
-						}
-					}
-					return secure
-				}
-				tlsserver.AssertTLS(t, r, tlsConfigFunc)
+				tlsserver.AssertTLS(t, r, ptls.Secure)
 
 				switch r.URL.Path {
 				case "/api/v1/namespaces/kube-system/configmaps":
@@ -1803,28 +1780,7 @@ func TestImpersonatorHTTPHandler(t *testing.T) {
 			testKubeAPIServerWasCalled := false
 			testKubeAPIServerSawHeaders := http.Header{}
 			testKubeAPIServer := tlsserver.TLSTestServer(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				tlsConfigFunc := func(rootCAs *x509.CertPool) *tls.Config {
-					// Requests to get configmaps, flowcontrol requests, and healthz requests
-					// are not done by our http round trippers that specify only one protocol
-					// (either http1.1 or http2, not both).
-					// For all other requests from the impersonator, if it is not an upgrade
-					// request it should only be using http2.
-					// If it is an upgrade request it should only be using http1.1, but that
-					// is covered by the AssertTLS function.
-					secure := ptls.Secure(rootCAs)
-					switch r.URL.Path {
-					case "/api/v1/namespaces/kube-system/configmaps",
-						"/apis/flowcontrol.apiserver.k8s.io/v1beta2/prioritylevelconfigurations",
-						"/apis/flowcontrol.apiserver.k8s.io/v1beta2/flowschemas",
-						"/healthz":
-					default:
-						if !httpstream.IsUpgradeRequest(r) {
-							secure.NextProtos = []string{secure.NextProtos[0]}
-						}
-					}
-					return secure
-				}
-				tlsserver.AssertTLS(t, r, tlsConfigFunc)
+				tlsserver.AssertTLS(t, r, ptls.Secure)
 
 				testKubeAPIServerWasCalled = true
 				testKubeAPIServerSawHeaders = r.Header