ContainerImage.Pinniped/internal/oidc/oidc.go

// Copyright 2020-2022 the Pinniped contributors. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

// Package oidc contains common OIDC functionality needed by Pinniped.
package oidc

import (
	"crypto/subtle"
	"errors"
	"fmt"
	"net/http"
	"time"

	coreosoidc "github.com/coreos/go-oidc/v3/oidc"
	"github.com/felixge/httpsnoop"
	"github.com/ory/fosite"
	"github.com/ory/fosite/compose"
	errorsx "github.com/pkg/errors"

	"go.pinniped.dev/generated/latest/apis/supervisor/idpdiscovery/v1alpha1"
	"go.pinniped.dev/internal/httputil/httperr"
	"go.pinniped.dev/internal/oidc/csrftoken"
	"go.pinniped.dev/internal/oidc/jwks"
	"go.pinniped.dev/internal/oidc/provider"
	"go.pinniped.dev/internal/oidc/provider/formposthtml"
	"go.pinniped.dev/internal/plog"
	"go.pinniped.dev/internal/psession"
	"go.pinniped.dev/pkg/oidcclient/nonce"
	"go.pinniped.dev/pkg/oidcclient/pkce"
)

const (
	WellKnownEndpointPath     = "/.well-known/openid-configuration"
	AuthorizationEndpointPath = "/oauth2/authorize"
	TokenEndpointPath         = "/oauth2/token" //nolint:gosec // ignore lint warning that this is a credential
	CallbackEndpointPath      = "/callback"
	JWKSEndpointPath          = "/jwks.json"
	PinnipedIDPsPathV1Alpha1  = "/v1alpha1/pinniped_identity_providers"
	PinnipedLoginPath         = "/login"
)

const (
	// Just in case we need to make a breaking change to the format of the upstream state param,
	// we are including a format version number. This gives the opportunity for a future version of Pinniped
	// to have the consumer of this format decide to reject versions that it doesn't understand.
	//
	// Version 1 was the original version.
	// Version 2 added the UpstreamType field to the UpstreamStateParamData struct.
	UpstreamStateParamFormatVersion = "2"

	// The `name` passed to the encoder for encoding the upstream state param value. This name is short
	// because it will be encoded into the upstream state param value and we're trying to keep that small.
	UpstreamStateParamEncodingName = "s"

	// CSRFCookieName is the name of the browser cookie which shall hold our CSRF value.
	// The `__Host` prefix has a special meaning. See:
	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Cookies#Cookie_prefixes.
	CSRFCookieName = "__Host-pinniped-csrf"

	// CSRFCookieEncodingName is the `name` passed to the encoder for encoding and decoding the CSRF
	// cookie contents.
	CSRFCookieEncodingName = "csrf"

	// The name of the issuer claim specified in the OIDC spec.
	IDTokenIssuerClaim = "iss"

	// The name of the subject claim specified in the OIDC spec.
	IDTokenSubjectClaim = "sub"

	// DownstreamUsernameClaim is a custom claim in the downstream ID token
	// whose value is mapped from a claim in the upstream token.
	// By default the value is the same as the downstream subject claim's.
	DownstreamUsernameClaim = "username"

	// DownstreamGroupsClaim is what we will use to encode the groups in the downstream OIDC ID token
	// information.
	DownstreamGroupsClaim = "groups"

	// DownstreamGroupsScope is a custom scope that determines whether the
	// groups claim will be returned in ID tokens.
	DownstreamGroupsScope = "groups"

	// RequestAudienceScope is a custom scope that determines whether a RFC8693 token
	// exchange is allowed to request a different audience.
	RequestAudienceScope = "pinniped:request-audience"

	// CSRFCookieLifespan is the length of time that the CSRF cookie is valid. After this time, the
	// Supervisor's authorization endpoint should give the browser a new CSRF cookie. We set it to
	// a week so that it is unlikely to expire during a login.
	CSRFCookieLifespan = time.Hour * 24 * 7
)

// Encoder is the encoding side of the securecookie.Codec interface.
type Encoder interface {
	Encode(name string, value interface{}) (string, error)
}

// Decoder is the decoding side of the securecookie.Codec interface.
type Decoder interface {
	Decode(name, value string, into interface{}) error
}

// Codec is both the encoding and decoding sides of the securecookie.Codec interface. It is
// interface'd here so that we properly wrap the securecookie dependency.
type Codec interface {
	Encoder
	Decoder
}

// UpstreamStateParamData is the format of the state parameter that we use when we communicate to an
// upstream OIDC provider.
//
// Keep the JSON to a minimal size because the upstream provider could impose size limitations on
// the state param.
type UpstreamStateParamData struct {
	AuthParams    string              `json:"p"`
	UpstreamName  string              `json:"u"`
	UpstreamType  string              `json:"t"`
	Nonce         nonce.Nonce         `json:"n"`
	CSRFToken     csrftoken.CSRFToken `json:"c"`
	PKCECode      pkce.Code           `json:"k"`
	FormatVersion string              `json:"v"`
}

type TimeoutsConfiguration struct {
	// The length of time that our state param that we encrypt and pass to the upstream OIDC IDP should be considered
	// valid. If a state param generated by the authorize endpoint is sent to the callback endpoint after this much
	// time has passed, then the callback endpoint should reject it. This allows us to set a limit on how long
	// the end user has to finish their login with the upstream IDP, including the time that it takes to fumble
	// with password manager and two-factor authenticator apps, and also accounting for taking a coffee break while
	// the browser is sitting at the upstream IDP's login page.
	UpstreamStateParamLifespan time.Duration

	// How long an authcode issued by the callback endpoint is valid. This determines how much time the end user
	// has to come back to exchange the authcode for tokens at the token endpoint.
	AuthorizeCodeLifespan time.Duration

	// The lifetime of an downstream access token issued by the token endpoint. Access tokens should generally
	// be fairly short-lived.
	AccessTokenLifespan time.Duration

	// The lifetime of an downstream ID token issued by the token endpoint. This should generally be the same
	// as the AccessTokenLifespan, or longer if it would be useful for the user's proof of identity to be valid
	// for longer than their proof of authorization.
	IDTokenLifespan time.Duration

	// The lifetime of an downstream refresh token issued by the token endpoint. This should generally be
	// significantly longer than the access token lifetime, so it can be used to refresh the access token
	// multiple times. Once the refresh token expires, the user's session is over and they will need
	// to start a new authorization request, which will require them to log in again with the upstream IDP
	// in their web browser.
	RefreshTokenLifespan time.Duration

	// AuthorizationCodeSessionStorageLifetime is the length of time after which an authcode is allowed to be garbage
	// collected from storage. Authcodes are kept in storage after they are redeemed to allow the system to mark the
	// authcode as already used, so it can reject any future uses of the same authcode with special case handling which
	// include revoking the access and refresh tokens associated with the session. Therefore, this should be
	// significantly longer than the AuthorizeCodeLifespan, and there is probably no reason to make it longer than
	// the sum of the AuthorizeCodeLifespan and the RefreshTokenLifespan.
	AuthorizationCodeSessionStorageLifetime time.Duration

	// PKCESessionStorageLifetime is the length of time after which PKCE data is allowed to be garbage collected from
	// storage. PKCE sessions are closely related to authorization code sessions. After the authcode is successfully
	// redeemed, the PKCE session is explicitly deleted. After the authcode expires, the PKCE session is no longer needed,
	// but it is not explicitly deleted. Therefore, this can be just slightly longer than the AuthorizeCodeLifespan. We'll
	// avoid making it exactly the same as AuthorizeCodeLifespan to avoid any chance of the garbage collector deleting it
	// while it is being used.
	PKCESessionStorageLifetime time.Duration

	// OIDCSessionStorageLifetime is the length of time after which the OIDC session data related to an authcode
	// is allowed to be garbage collected from storage. Due to a bug in an underlying library, these are not explicitly
	// deleted. Similar to the PKCE session, they are not needed anymore after the corresponding authcode has expired.
	// Therefore, this can be just slightly longer than the AuthorizeCodeLifespan. We'll avoid making it exactly the same
	// as AuthorizeCodeLifespan to avoid any chance of the garbage collector deleting it while it is being used.
	OIDCSessionStorageLifetime time.Duration

	// AccessTokenSessionStorageLifetime is the length of time after which an access token's session data is allowed
	// to be garbage collected from storage.  These must exist in storage for as long as the refresh token is valid
	// or else the refresh flow will not work properly. So this must be longer than RefreshTokenLifespan.
	AccessTokenSessionStorageLifetime time.Duration

	// RefreshTokenSessionStorageLifetime is the length of time after which a refresh token's session data is allowed
	// to be garbage collected from storage. These must exist in storage for as long as the refresh token is valid.
	// Therefore, this can be just slightly longer than the RefreshTokenLifespan. We'll avoid making it exactly the same
	// as RefreshTokenLifespan to avoid any chance of the garbage collector deleting it while it is being used.
	// If an expired token is still stored when the user tries to refresh it, then they will get a more specific
	// error message telling them that the token is expired, rather than a more generic error that is returned
	// when the token does not exist. If this is desirable, then the RefreshTokenSessionStorageLifetime can be made
	// to be significantly larger than RefreshTokenLifespan, at the cost of slower cleanup.
	RefreshTokenSessionStorageLifetime time.Duration
}

// Get the defaults for the Supervisor server.
func DefaultOIDCTimeoutsConfiguration() TimeoutsConfiguration {
	accessTokenLifespan := 2 * time.Minute
	authorizationCodeLifespan := 10 * time.Minute
	refreshTokenLifespan := 9 * time.Hour

	return TimeoutsConfiguration{
		UpstreamStateParamLifespan:              90 * time.Minute,
		AuthorizeCodeLifespan:                   authorizationCodeLifespan,
		AccessTokenLifespan:                     accessTokenLifespan,
		IDTokenLifespan:                         accessTokenLifespan,
		RefreshTokenLifespan:                    refreshTokenLifespan,
		AuthorizationCodeSessionStorageLifetime: authorizationCodeLifespan + refreshTokenLifespan,
		PKCESessionStorageLifetime:              authorizationCodeLifespan + (1 * time.Minute),
		OIDCSessionStorageLifetime:              authorizationCodeLifespan + (1 * time.Minute),
		AccessTokenSessionStorageLifetime:       refreshTokenLifespan + accessTokenLifespan,
		RefreshTokenSessionStorageLifetime:      refreshTokenLifespan + accessTokenLifespan,
	}
}

func FositeOauth2Helper(
	oauthStore interface{},
	issuer string,
	hmacSecretOfLengthAtLeast32Func func() []byte,
	jwksProvider jwks.DynamicJWKSProvider,
	timeoutsConfiguration TimeoutsConfiguration,
) fosite.OAuth2Provider {
	oauthConfig := &compose.Config{
		IDTokenIssuer: issuer,

		AuthorizeCodeLifespan: timeoutsConfiguration.AuthorizeCodeLifespan,
		IDTokenLifespan:       timeoutsConfiguration.IDTokenLifespan,
		AccessTokenLifespan:   timeoutsConfiguration.AccessTokenLifespan,
		RefreshTokenLifespan:  timeoutsConfiguration.RefreshTokenLifespan,

		ScopeStrategy: fosite.ExactScopeStrategy,
		EnforcePKCE:   true,

		// "offline_access" as per https://openid.net/specs/openid-connect-core-1_0.html#OfflineAccess
		RefreshTokenScopes: []string{coreosoidc.ScopeOfflineAccess},

		// The default is to support all prompt values from the spec.
		// See https://openid.net/specs/openid-connect-core-1_0.html#AuthRequest
		AllowedPromptValues: nil,

		// Use the fosite default to make it more likely that off the shelf OIDC clients can work with the supervisor.
		MinParameterEntropy: fosite.MinParameterEntropy,
	}

	provider := compose.Compose(
		oauthConfig,
		oauthStore,
		&compose.CommonStrategy{
			// Note that Fosite requires the HMAC secret to be at least 32 bytes.
			CoreStrategy:               newDynamicOauth2HMACStrategy(oauthConfig, hmacSecretOfLengthAtLeast32Func),
			OpenIDConnectTokenStrategy: newDynamicOpenIDConnectECDSAStrategy(oauthConfig, jwksProvider),
		},
		nil, // hasher, defaults to using BCrypt when nil. Used for hashing client secrets.
		compose.OAuth2AuthorizeExplicitFactory,
		compose.OAuth2RefreshTokenGrantFactory,
		compose.OpenIDConnectExplicitFactory,
		compose.OpenIDConnectRefreshFactory,
		compose.OAuth2PKCEFactory,
		TokenExchangeFactory, // handle the "urn:ietf:params:oauth:grant-type:token-exchange" grant type
	)
	provider.(*fosite.Fosite).FormPostHTMLTemplate = formposthtml.Template()
	return provider
}

// FositeErrorForLog generates a list of information about the provided Fosite error that can be
// passed to a plog function (e.g., plog.Info()).
//
// Sample usage:
//   err := someFositeLibraryFunction()
//   if err != nil {
//     	plog.Info("some error", FositeErrorForLog(err)...)
//      ...
//    }
func FositeErrorForLog(err error) []interface{} {
	rfc6749Error := fosite.ErrorToRFC6749Error(err)
	keysAndValues := make([]interface{}, 0)
	keysAndValues = append(keysAndValues, "name")
	keysAndValues = append(keysAndValues, rfc6749Error.Error()) // Error() returns the ErrorField
	keysAndValues = append(keysAndValues, "status")
	keysAndValues = append(keysAndValues, rfc6749Error.Status()) // Status() encodes the CodeField as a string
	keysAndValues = append(keysAndValues, "description")
	keysAndValues = append(keysAndValues, rfc6749Error.GetDescription()) // GetDescription() returns the DescriptionField and the HintField
	keysAndValues = append(keysAndValues, "debug")
	keysAndValues = append(keysAndValues, rfc6749Error.Debug()) // Debug() returns the DebugField
	if cause := rfc6749Error.Cause(); cause != nil {            // Cause() returns the underlying error, or nil
		keysAndValues = append(keysAndValues, "cause")
		keysAndValues = append(keysAndValues, cause.Error())
	}
	return keysAndValues
}

type UpstreamOIDCIdentityProvidersLister interface {
	GetOIDCIdentityProviders() []provider.UpstreamOIDCIdentityProviderI
}

type UpstreamLDAPIdentityProvidersLister interface {
	GetLDAPIdentityProviders() []provider.UpstreamLDAPIdentityProviderI
}

type UpstreamActiveDirectoryIdentityProviderLister interface {
	GetActiveDirectoryIdentityProviders() []provider.UpstreamLDAPIdentityProviderI
}

type UpstreamIdentityProvidersLister interface {
	UpstreamOIDCIdentityProvidersLister
	UpstreamLDAPIdentityProvidersLister
	UpstreamActiveDirectoryIdentityProviderLister
}

func GrantScopeIfRequested(authorizeRequester fosite.AuthorizeRequester, scopeName string) {
	if ScopeWasRequested(authorizeRequester, scopeName) {
		authorizeRequester.GrantScope(scopeName)
	}
}

func ScopeWasRequested(authorizeRequester fosite.AuthorizeRequester, scopeName string) bool {
	for _, scope := range authorizeRequester.GetRequestedScopes() {
		if scope == scopeName {
			return true
		}
	}
	return false
}

func ReadStateParamAndValidateCSRFCookie(r *http.Request, cookieDecoder Decoder, stateDecoder Decoder) (string, *UpstreamStateParamData, error) {
	csrfValue, err := readCSRFCookie(r, cookieDecoder)
	if err != nil {
		return "", nil, err
	}

	encodedState, decodedState, err := readStateParam(r, stateDecoder)
	if err != nil {
		return "", nil, err
	}

	err = validateCSRFValue(decodedState, csrfValue)
	if err != nil {
		return "", nil, err
	}

	return encodedState, decodedState, nil
}

func readCSRFCookie(r *http.Request, cookieDecoder Decoder) (csrftoken.CSRFToken, error) {
	receivedCSRFCookie, err := r.Cookie(CSRFCookieName)
	if err != nil {
		// Error means that the cookie was not found
		return "", httperr.Wrap(http.StatusForbidden, "CSRF cookie is missing", err)
	}

	var csrfFromCookie csrftoken.CSRFToken
	err = cookieDecoder.Decode(CSRFCookieEncodingName, receivedCSRFCookie.Value, &csrfFromCookie)
	if err != nil {
		return "", httperr.Wrap(http.StatusForbidden, "error reading CSRF cookie", err)
	}

	return csrfFromCookie, nil
}

func readStateParam(r *http.Request, stateDecoder Decoder) (string, *UpstreamStateParamData, error) {
	encodedState := r.FormValue("state")

	if encodedState == "" {
		return "", nil, httperr.New(http.StatusBadRequest, "state param not found")
	}

	var state UpstreamStateParamData
	if err := stateDecoder.Decode(
		UpstreamStateParamEncodingName,
		r.FormValue("state"),
		&state,
	); err != nil {
		return "", nil, httperr.New(http.StatusBadRequest, "error reading state")
	}

	if state.FormatVersion != UpstreamStateParamFormatVersion {
		return "", nil, httperr.New(http.StatusUnprocessableEntity, "state format version is invalid")
	}

	return encodedState, &state, nil
}

func validateCSRFValue(state *UpstreamStateParamData, csrfCookieValue csrftoken.CSRFToken) error {
	if subtle.ConstantTimeCompare([]byte(state.CSRFToken), []byte(csrfCookieValue)) != 1 {
		return httperr.New(http.StatusForbidden, "CSRF value does not match")
	}
	return nil
}

// FindUpstreamIDPByNameAndType finds the requested IDP by name and type, or returns an error.
// Note that AD and LDAP IDPs both return the same interface type, but different ProviderTypes values.
func FindUpstreamIDPByNameAndType(
	idpLister UpstreamIdentityProvidersLister,
	upstreamName string,
	upstreamType string,
) (
	provider.UpstreamOIDCIdentityProviderI,
	provider.UpstreamLDAPIdentityProviderI,
	psession.ProviderType,
	error,
) {
	switch upstreamType {
	case string(v1alpha1.IDPTypeOIDC):
		for _, p := range idpLister.GetOIDCIdentityProviders() {
			if p.GetName() == upstreamName {
				return p, nil, psession.ProviderTypeOIDC, nil
			}
		}
	case string(v1alpha1.IDPTypeLDAP):
		for _, p := range idpLister.GetLDAPIdentityProviders() {
			if p.GetName() == upstreamName {
				return nil, p, psession.ProviderTypeLDAP, nil
			}
		}
	case string(v1alpha1.IDPTypeActiveDirectory):
		for _, p := range idpLister.GetActiveDirectoryIdentityProviders() {
			if p.GetName() == upstreamName {
				return nil, p, psession.ProviderTypeActiveDirectory, nil
			}
		}
	}
	return nil, nil, "", errors.New("provider not found")
}

// WriteAuthorizeError writes an authorization error as it should be returned by the authorization endpoint and other
// similar endpoints that are the end of the downstream authcode flow. Errors responses are written in the usual fosite style.
func WriteAuthorizeError(w http.ResponseWriter, oauthHelper fosite.OAuth2Provider, authorizeRequester fosite.AuthorizeRequester, err error, isBrowserless bool) {
	if plog.Enabled(plog.LevelTrace) {
		// When trace level logging is enabled, include the stack trace in the log message.
		keysAndValues := FositeErrorForLog(err)
		errWithStack := errorsx.WithStack(err)
		keysAndValues = append(keysAndValues, "errWithStack")
		// klog always prints error values using %s, which does not include stack traces,
		// so convert the error to a string which includes the stack trace here.
		keysAndValues = append(keysAndValues, fmt.Sprintf("%+v", errWithStack))
		plog.Trace("authorize response error", keysAndValues...)
	} else {
		plog.Info("authorize response error", FositeErrorForLog(err)...)
	}
	if isBrowserless {
		w = rewriteStatusSeeOtherToStatusFoundForBrowserless(w)
	}
	// Return an error according to OIDC spec 3.1.2.6 (second paragraph).
	oauthHelper.WriteAuthorizeError(w, authorizeRequester, err)
}

// PerformAuthcodeRedirect successfully completes a downstream login by creating a session and
// writing the authcode redirect response as it should be returned by the authorization endpoint and other
// similar endpoints that are the end of the downstream authcode flow.
func PerformAuthcodeRedirect(
	r *http.Request,
	w http.ResponseWriter,
	oauthHelper fosite.OAuth2Provider,
	authorizeRequester fosite.AuthorizeRequester,
	openIDSession *psession.PinnipedSession,
	isBrowserless bool,
) {
	authorizeResponder, err := oauthHelper.NewAuthorizeResponse(r.Context(), authorizeRequester, openIDSession)
	if err != nil {
		plog.WarningErr("error while generating and saving authcode", err)
		WriteAuthorizeError(w, oauthHelper, authorizeRequester, err, isBrowserless)
		return
	}
	if isBrowserless {
		w = rewriteStatusSeeOtherToStatusFoundForBrowserless(w)
	}
	oauthHelper.WriteAuthorizeResponse(w, authorizeRequester, authorizeResponder)
}

func rewriteStatusSeeOtherToStatusFoundForBrowserless(w http.ResponseWriter) http.ResponseWriter {
	// rewrite http.StatusSeeOther to http.StatusFound for backwards compatibility with old pinniped CLIs.
	// we can drop this in a few releases once we feel enough time has passed for users to update.
	//
	// WriteAuthorizeResponse/WriteAuthorizeError calls used to result in http.StatusFound until
	// https://github.com/ory/fosite/pull/636 changed it to http.StatusSeeOther to address
	// https://tools.ietf.org/id/draft-ietf-oauth-security-topics-18.html#section-4.11
	// Safari has the bad behavior in the case of http.StatusFound and not just http.StatusTemporaryRedirect.
	//
	// in the browserless flows, the OAuth client is the pinniped CLI and it already has access to the user's
	// password.  Thus there is no security issue with using http.StatusFound vs. http.StatusSeeOther.
	return httpsnoop.Wrap(w, httpsnoop.Hooks{
		WriteHeader: func(delegate httpsnoop.WriteHeaderFunc) httpsnoop.WriteHeaderFunc {
			return func(code int) {
				if code == http.StatusSeeOther {
					code = http.StatusFound
				}
				delegate(code)
			}
		},
	})
}