oidc.go

package auth

import (
	"encoding/json"
	"fmt"
	"net/http"
	"net/url"
	"time"

	"github.com/gravitational/teleport"
	"github.com/gravitational/teleport/lib/defaults"
	"github.com/gravitational/teleport/lib/services"
	"github.com/gravitational/teleport/lib/utils"
	"github.com/gravitational/trace"

	log "github.com/Sirupsen/logrus"
	"github.com/coreos/go-oidc/jose"
	"github.com/coreos/go-oidc/oauth2"
	"github.com/coreos/go-oidc/oidc"
)

func (s *AuthServer) getOIDCClient(conn services.OIDCConnector) (*oidc.Client, error) {
	s.lock.Lock()
	defer s.lock.Unlock()

	config := oidc.ClientConfig{
		RedirectURL: conn.GetRedirectURL(),
		Credentials: oidc.ClientCredentials{
			ID:     conn.GetClientID(),
			Secret: conn.GetClientSecret(),
		},
		// open id notifies provider that we are using OIDC scopes
		Scope: utils.Deduplicate(append([]string{"openid", "email"}, conn.GetScope()...)),
	}

	clientPack, ok := s.oidcClients[conn.GetName()]
	if ok && oidcConfigsEqual(clientPack.config, config) {
		return clientPack.client, nil
	}
	delete(s.oidcClients, conn.GetName())

	client, err := oidc.NewClient(config)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	client.SyncProviderConfig(conn.GetIssuerURL())

	s.oidcClients[conn.GetName()] = &oidcClient{client: client, config: config}

	return client, nil
}

func (s *AuthServer) UpsertOIDCConnector(connector services.OIDCConnector) error {
	return s.Identity.UpsertOIDCConnector(connector)
}

func (s *AuthServer) DeleteOIDCConnector(connectorName string) error {
	return s.Identity.DeleteOIDCConnector(connectorName)
}

func (s *AuthServer) CreateOIDCAuthRequest(req services.OIDCAuthRequest) (*services.OIDCAuthRequest, error) {
	connector, err := s.Identity.GetOIDCConnector(req.ConnectorID, true)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	oidcClient, err := s.getOIDCClient(connector)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	token, err := utils.CryptoRandomHex(TokenLenBytes)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	req.StateToken = token

	oauthClient, err := oidcClient.OAuthClient()
	if err != nil {
		return nil, trace.Wrap(err)
	}

	// online is OIDC online scope, "select_account" forces user to always select account
	req.RedirectURL = oauthClient.AuthCodeURL(req.StateToken, "online", "select_account")

	// if the connector has an Authentication Context Class Reference (ACR) value set,
	// update redirect url and add it as a query value.
	acrValue := connector.GetACR()
	if acrValue != "" {
		u, err := url.Parse(req.RedirectURL)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		q := u.Query()
		q.Set("acr_values", acrValue)
		u.RawQuery = q.Encode()
		req.RedirectURL = u.String()
	}

	log.Debugf("[OIDC] Redirect URL: %v", req.RedirectURL)

	err = s.Identity.CreateOIDCAuthRequest(req, defaults.OIDCAuthRequestTTL)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	return &req, nil
}

// ValidateOIDCAuthCallback is called by the proxy to check OIDC query parameters
// returned by OIDC Provider, if everything checks out, auth server
// will respond with OIDCAuthResponse, otherwise it will return error
func (a *AuthServer) ValidateOIDCAuthCallback(q url.Values) (*OIDCAuthResponse, error) {
	if error := q.Get("error"); error != "" {
		return nil, trace.OAuth2(oauth2.ErrorInvalidRequest, error, q)
	}

	code := q.Get("code")
	if code == "" {
		return nil, trace.OAuth2(
			oauth2.ErrorInvalidRequest, "code query param must be set", q)
	}

	stateToken := q.Get("state")
	if stateToken == "" {
		return nil, trace.OAuth2(
			oauth2.ErrorInvalidRequest, "missing state query param", q)
	}

	req, err := a.Identity.GetOIDCAuthRequest(stateToken)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	connector, err := a.Identity.GetOIDCConnector(req.ConnectorID, true)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	oidcClient, err := a.getOIDCClient(connector)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	// extract claims from both the id token and the userinfo endpoint and merge them
	claims, err := a.getClaims(oidcClient, connector.GetIssuerURL(), code)
	if err != nil {
		return nil, trace.OAuth2(
			oauth2.ErrorUnsupportedResponseType, "unable to construct claims", q)
	}
	log.Debugf("[OIDC] Claims: %v", claims)

	// if we are sending acr values, make sure we also validate them
	acrValue := connector.GetACR()
	if acrValue != "" {
		err := a.validateACRValues(acrValue, connector.GetProvider(), claims)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		log.Debugf("[OIDC] ACR values %q successfully validated", acrValue)
	}

	ident, err := oidc.IdentityFromClaims(claims)
	if err != nil {
		return nil, trace.OAuth2(
			oauth2.ErrorUnsupportedResponseType, "unable to convert claims to identity", q)
	}
	log.Debugf("[IDENTITY] %q expires at: %v", ident.Email, ident.ExpiresAt)

	response := &OIDCAuthResponse{
		Identity: services.ExternalIdentity{ConnectorID: connector.GetName(), Username: ident.Email},
		Req:      *req,
	}

	log.Debugf("[OIDC] Applying %v claims to roles mappings", len(connector.GetClaimsToRoles()))
	if len(connector.GetClaimsToRoles()) != 0 {
		if err := a.createOIDCUser(connector, ident, claims); err != nil {
			return nil, trace.Wrap(err)
		}
	}

	if !req.CheckUser {
		return response, nil
	}

	user, err := a.Identity.GetUserByOIDCIdentity(services.ExternalIdentity{
		ConnectorID: req.ConnectorID, Username: ident.Email})
	if err != nil {
		return nil, trace.Wrap(err)
	}
	response.Username = user.GetName()

	var roles services.RoleSet
	roles, err = services.FetchRoles(user.GetRoles(), a.Access)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	sessionTTL := roles.AdjustSessionTTL(utils.ToTTL(a.clock, ident.ExpiresAt))
	bearerTokenTTL := utils.MinTTL(BearerTokenTTL, sessionTTL)

	if req.CreateWebSession {
		sess, err := a.NewWebSession(user.GetName())
		if err != nil {
			return nil, trace.Wrap(err)
		}
		// session will expire based on identity TTL and allowed session TTL
		sess.SetExpiryTime(a.clock.Now().UTC().Add(sessionTTL))
		// bearer token will expire based on the expected session renewal
		sess.SetBearerTokenExpiryTime(a.clock.Now().UTC().Add(bearerTokenTTL))
		if err := a.UpsertWebSession(user.GetName(), sess); err != nil {
			return nil, trace.Wrap(err)
		}
		response.Session = sess
	}

	if len(req.PublicKey) != 0 {
		certTTL := utils.MinTTL(utils.ToTTL(a.clock, ident.ExpiresAt), req.CertTTL)
		allowedLogins, err := roles.CheckLogins(certTTL)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		cert, err := a.GenerateUserCert(req.PublicKey, user, allowedLogins, certTTL, roles.CanForwardAgents(), req.Compatibility)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		response.Cert = cert

		authorities, err := a.GetCertAuthorities(services.HostCA, false)
		if err != nil {
			return nil, trace.Wrap(err)
		}
		for _, authority := range authorities {
			response.HostSigners = append(response.HostSigners, authority)
		}
	}

	return response, nil
}

// OIDCAuthResponse is returned when auth server validated callback parameters
// returned from OIDC provider
type OIDCAuthResponse struct {
	// Username is authenticated teleport username
	Username string `json:"username"`
	// Identity contains validated OIDC identity
	Identity services.ExternalIdentity `json:"identity"`
	// Web session will be generated by auth server if requested in OIDCAuthRequest
	Session services.WebSession `json:"session,omitempty"`
	// Cert will be generated by certificate authority
	Cert []byte `json:"cert,omitempty"`
	// Req is original oidc auth request
	Req services.OIDCAuthRequest `json:"req"`
	// HostSigners is a list of signing host public keys
	// trusted by proxy, used in console login
	HostSigners []services.CertAuthority `json:"host_signers"`
}

// buildRoles takes a connector and claims and returns a slice of roles. If the claims
// match a concrete roles in the connector, those roles are returned directly. If the
// claims match a template role in the connector, then that role is first created from
// the template, then returned.
func (a *AuthServer) buildRoles(connector services.OIDCConnector, ident *oidc.Identity, claims jose.Claims) ([]string, error) {
	roles := connector.MapClaims(claims)
	if len(roles) == 0 {
		role, err := connector.RoleFromTemplate(claims)
		if err != nil {
			log.Warningf("[OIDC] Unable to map claims to roles or role templates for %q: %v", connector.GetName(), err)
			return nil, trace.AccessDenied("unable to map claims to roles or role templates for %q: %v", connector.GetName(), err)
		}

		// figure out ttl for role. expires = now + ttl  =>  ttl = expires - now
		ttl := ident.ExpiresAt.Sub(a.clock.Now())

		// upsert templated role
		err = a.Access.UpsertRole(role, ttl)
		if err != nil {
			log.Warningf("[OIDC] Unable to upsert templated role for connector: %q: %v", connector.GetName(), err)
			return nil, trace.AccessDenied("unable to upsert templated role: %q: %v", connector.GetName(), err)
		}

		roles = []string{role.GetName()}
	}

	return roles, nil
}

func (a *AuthServer) createOIDCUser(connector services.OIDCConnector, ident *oidc.Identity, claims jose.Claims) error {
	roles, err := a.buildRoles(connector, ident, claims)
	if err != nil {
		return trace.Wrap(err)
	}

	log.Debugf("[IDENTITY] %v/%v is a dynamic identity, generating user with roles: %v", connector.GetName(), ident.Email, roles)
	user, err := services.GetUserMarshaler().GenerateUser(&services.UserV2{
		Kind:    services.KindUser,
		Version: services.V2,
		Metadata: services.Metadata{
			Name:      ident.Email,
			Namespace: defaults.Namespace,
		},
		Spec: services.UserSpecV2{
			Roles:          roles,
			Expires:        ident.ExpiresAt,
			OIDCIdentities: []services.ExternalIdentity{{ConnectorID: connector.GetName(), Username: ident.Email}},
			CreatedBy: services.CreatedBy{
				User: services.UserRef{Name: "system"},
				Time: time.Now().UTC(),
				Connector: &services.ConnectorRef{
					Type:     teleport.ConnectorOIDC,
					ID:       connector.GetName(),
					Identity: ident.Email,
				},
			},
		},
	})
	if err != nil {
		return trace.Wrap(err)
	}

	// check if a user exists already
	existingUser, err := a.GetUser(ident.Email)
	if err != nil {
		if !trace.IsNotFound(err) {
			return trace.Wrap(err)
		}
	}

	// check if exisiting user is a non-oidc user, if so, return an error
	if existingUser != nil {
		connectorRef := existingUser.GetCreatedBy().Connector
		if connectorRef == nil || connectorRef.Type != teleport.ConnectorOIDC || connectorRef.ID != connector.GetName() {
			return trace.AlreadyExists("user %q already exists and is not OIDC user", existingUser.GetName())
		}
	}

	// no non-oidc user exists, create or update the exisiting oidc user
	err = a.UpsertUser(user)
	if err != nil {
		return trace.Wrap(err)
	}

	return nil
}

// claimsFromIDToken extracts claims from the ID token.
func claimsFromIDToken(oidcClient *oidc.Client, idToken string) (jose.Claims, error) {
	jwt, err := jose.ParseJWT(idToken)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	err = oidcClient.VerifyJWT(jwt)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	log.Debugf("[OIDC] Extracting claims from ID token")

	claims, err := jwt.Claims()
	if err != nil {
		return nil, trace.Wrap(err)
	}

	return claims, nil
}

// claimsFromUserInfo finds the UserInfo endpoint from the provider config and then extracts claims from it.
//
// Note: We don't request signed JWT responses for UserInfo, instead we force the provider config and
// the issuer to be HTTPS and leave integrity and confidentiality to TLS. Authenticity is taken care of
// during the token exchange.
func claimsFromUserInfo(oidcClient *oidc.Client, issuerURL string, accessToken string) (jose.Claims, error) {
	err := isHTTPS(issuerURL)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	oac, err := oidcClient.OAuthClient()
	if err != nil {
		return nil, trace.Wrap(err)
	}
	hc := oac.HttpClient()

	// go get the provider config so we can find out where the UserInfo endpoint
	// is. if the provider doesn't offer a UserInfo endpoint return not found.
	pc, err := oidc.FetchProviderConfig(oac.HttpClient(), issuerURL)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	if pc.UserInfoEndpoint == nil {
		return nil, trace.NotFound("UserInfo endpoint not found")
	}

	endpoint := pc.UserInfoEndpoint.String()
	err = isHTTPS(endpoint)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	log.Debugf("[OIDC] Fetching claims from UserInfo endpoint: %q", endpoint)

	req, err := http.NewRequest("GET", endpoint, nil)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", accessToken))

	resp, err := hc.Do(req)
	if err != nil {
		return nil, trace.Wrap(err)
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode > 299 {
		return nil, trace.AccessDenied("bad status code: %v", resp.StatusCode)
	}

	var claims jose.Claims
	err = json.NewDecoder(resp.Body).Decode(&claims)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	return claims, nil
}

// mergeClaims merges b into a.
func mergeClaims(a jose.Claims, b jose.Claims) (jose.Claims, error) {
	for k, v := range b {
		_, ok := a[k]
		if !ok {
			a[k] = v
		}
	}

	return a, nil
}

// getClaims gets claims from ID token and UserInfo and returns UserInfo claims merged into ID token claims.
func (a *AuthServer) getClaims(oidcClient *oidc.Client, issuerURL string, code string) (jose.Claims, error) {
	var err error

	oac, err := oidcClient.OAuthClient()
	if err != nil {
		return nil, trace.Wrap(err)
	}

	t, err := oac.RequestToken(oauth2.GrantTypeAuthCode, code)
	if err != nil {
		return nil, trace.Wrap(err)
	}

	idTokenClaims, err := claimsFromIDToken(oidcClient, t.IDToken)
	if err != nil {
		log.Debugf("[OIDC] Unable to fetch ID token claims: %v", err)
		return nil, trace.Wrap(err)
	}
	log.Debugf("[OIDC] ID Token claims: %v", idTokenClaims)

	userInfoClaims, err := claimsFromUserInfo(oidcClient, issuerURL, t.AccessToken)
	if err != nil {
		if trace.IsNotFound(err) {
			log.Debugf("[OIDC] Provider doesn't offer UserInfo endpoint. Returning token claims: %v", idTokenClaims)
			return idTokenClaims, nil
		}
		log.Debugf("[OIDC] Unable to fetch UserInfo claims: %v", err)
		return nil, trace.Wrap(err)
	}
	log.Debugf("[OIDC] UserInfo claims: %v", userInfoClaims)

	// make sure that the subject in the userinfo claim matches the subject in
	// the id token otherwise there is the possibility of a token substitution attack.
	// see section 16.11 of the oidc spec for more details.
	var idsub string
	var uisub string
	var exists bool
	if idsub, exists, err = idTokenClaims.StringClaim("sub"); err != nil || !exists {
		log.Debugf("[OIDC] unable to extract sub from ID token")
		return nil, trace.Wrap(err)
	}
	if uisub, exists, err = userInfoClaims.StringClaim("sub"); err != nil || !exists {
		log.Debugf("[OIDC] unable to extract sub from UserInfo")
		return nil, trace.Wrap(err)
	}
	if idsub != uisub {
		log.Debugf("[OIDC] Claim subjects don't match %q != %q", idsub, uisub)
		return nil, trace.BadParameter("invalid subject in UserInfo")
	}

	claims, err := mergeClaims(idTokenClaims, userInfoClaims)
	if err != nil {
		log.Debugf("[OIDC] Unable to merge claims: %v", err)
		return nil, trace.Wrap(err)
	}

	return claims, nil
}

// validateACRValues validates that we get an appropriate response for acr values. By default
// we expect the same value we send, but this function also handles Identity Provider specific
// forms of validation.
func (a *AuthServer) validateACRValues(acrValue string, identityProvider string, claims jose.Claims) error {
	switch identityProvider {
	case teleport.NetIQ:
		log.Debugf("[OIDC] Validating ACR values with %q rules", identityProvider)

		tokenAcr, ok := claims["acr"]
		if !ok {
			return trace.BadParameter("acr not found in claims")
		}
		tokenAcrMap, ok := tokenAcr.(map[string]interface{})
		if !ok {
			return trace.BadParameter("acr unexpected type: %T", tokenAcr)
		}
		tokenAcrValues, ok := tokenAcrMap["values"]
		if !ok {
			return trace.BadParameter("acr.values not found in claims")
		}
		tokenAcrValuesSlice, ok := tokenAcrValues.([]interface{})
		if !ok {
			return trace.BadParameter("acr.values unexpected type: %T", tokenAcr)
		}

		acrValueMatched := false
		for _, v := range tokenAcrValuesSlice {
			vv, ok := v.(string)
			if !ok {
				continue
			}
			if acrValue == vv {
				acrValueMatched = true
				break
			}
		}
		if !acrValueMatched {
			log.Debugf("[OIDC] No ACR match found for %q in %q", acrValue, tokenAcrValues)
			return trace.BadParameter("acr claim does not match")
		}
	default:
		log.Debugf("[OIDC] Validating ACR values with default rules")

		claimValue, exists, err := claims.StringClaim("acr")
		if !exists {
			return trace.BadParameter("acr claim does not exist")
		}
		if err != nil {
			return trace.Wrap(err)
		}
		if claimValue != acrValue {
			log.Debugf("[OIDC] No ACR match found %q != %q", acrValue, claimValue)
			return trace.BadParameter("acr claim does not match")
		}
	}

	return nil
}