gotosocial/internal/api/client/auth/callback.go
Dominik Süß 199b685f43
[feature] overhaul the oidc system (#961)
* [feature] overhaul the oidc system

this allows for more flexible username handling and prevents account
takeover using old email addresses

* [feature] add migration path for old OIDC users

* [feature] nicer error reporting for users

* [docs] document the new OIDC flow

* [fix] return early on oidc error

* [docs]: add comments on the finalization logic
2022-12-06 14:15:56 +01:00

312 lines
11 KiB
Go

/*
GoToSocial
Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
package auth
import (
"context"
"errors"
"fmt"
"net"
"net/http"
"strings"
"github.com/gin-contrib/sessions"
"github.com/gin-gonic/gin"
"github.com/google/uuid"
"github.com/superseriousbusiness/gotosocial/internal/api"
"github.com/superseriousbusiness/gotosocial/internal/config"
"github.com/superseriousbusiness/gotosocial/internal/db"
"github.com/superseriousbusiness/gotosocial/internal/gtserror"
"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
"github.com/superseriousbusiness/gotosocial/internal/oauth"
"github.com/superseriousbusiness/gotosocial/internal/oidc"
"github.com/superseriousbusiness/gotosocial/internal/validate"
)
// extraInfo wraps a form-submitted username and transmitted name
type extraInfo struct {
Username string `form:"username"`
Name string `form:"name"` // note that this is only used for re-rendering the page in case of an error
}
// CallbackGETHandler parses a token from an external auth provider.
func (m *Module) CallbackGETHandler(c *gin.Context) {
s := sessions.Default(c)
// check the query vs session state parameter to mitigate csrf
// https://auth0.com/docs/secure/attack-protection/state-parameters
returnedInternalState := c.Query(callbackStateParam)
if returnedInternalState == "" {
m.clearSession(s)
err := fmt.Errorf("%s parameter not found on callback query", callbackStateParam)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
return
}
savedInternalStateI := s.Get(sessionInternalState)
savedInternalState, ok := savedInternalStateI.(string)
if !ok {
m.clearSession(s)
err := fmt.Errorf("key %s was not found in session", sessionInternalState)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
return
}
if returnedInternalState != savedInternalState {
m.clearSession(s)
err := errors.New("mismatch between callback state and saved state")
api.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGet)
return
}
// retrieve stored claims using code
code := c.Query(callbackCodeParam)
if code == "" {
m.clearSession(s)
err := fmt.Errorf("%s parameter not found on callback query", callbackCodeParam)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
return
}
claims, errWithCode := m.idp.HandleCallback(c.Request.Context(), code)
if errWithCode != nil {
m.clearSession(s)
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
// We can use the client_id on the session to retrieve
// info about the app associated with the client_id
clientID, ok := s.Get(sessionClientID).(string)
if !ok || clientID == "" {
m.clearSession(s)
err := fmt.Errorf("key %s was not found in session", sessionClientID)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, oauth.HelpfulAdvice), m.processor.InstanceGet)
return
}
app := &gtsmodel.Application{}
if err := m.db.GetWhere(c.Request.Context(), []db.Where{{Key: sessionClientID, Value: clientID}}, app); err != nil {
m.clearSession(s)
safe := fmt.Sprintf("application for %s %s could not be retrieved", sessionClientID, clientID)
var errWithCode gtserror.WithCode
if err == db.ErrNoEntries {
errWithCode = gtserror.NewErrorBadRequest(err, safe, oauth.HelpfulAdvice)
} else {
errWithCode = gtserror.NewErrorInternalError(err, safe, oauth.HelpfulAdvice)
}
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
user, errWithCode := m.fetchUserForClaims(c.Request.Context(), claims, net.IP(c.ClientIP()), app.ID)
if errWithCode != nil {
m.clearSession(s)
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
if user == nil {
// no user exists yet - let's ask them for their preferred username
instance, errWithCode := m.processor.InstanceGet(c.Request.Context(), config.GetHost())
if errWithCode != nil {
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
// store the claims in the session - that way we know the user is authenticated when processing the form later
s.Set(sessionClaims, claims)
s.Set(sessionAppID, app.ID)
if err := s.Save(); err != nil {
m.clearSession(s)
api.ErrorHandler(c, gtserror.NewErrorInternalError(err), m.processor.InstanceGet)
return
}
c.HTML(http.StatusOK, "finalize.tmpl", gin.H{
"instance": instance,
"name": claims.Name,
"preferredUsername": claims.PreferredUsername,
})
return
}
s.Set(sessionUserID, user.ID)
if err := s.Save(); err != nil {
m.clearSession(s)
api.ErrorHandler(c, gtserror.NewErrorInternalError(err), m.processor.InstanceGet)
return
}
c.Redirect(http.StatusFound, OauthAuthorizePath)
}
// FinalizePOSTHandler registers the user after additional data has been provided
func (m *Module) FinalizePOSTHandler(c *gin.Context) {
s := sessions.Default(c)
form := &extraInfo{}
if err := c.ShouldBind(form); err != nil {
m.clearSession(s)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, oauth.HelpfulAdvice), m.processor.InstanceGet)
return
}
// since we have multiple possible validation error, `validationError` is a shorthand for rendering them
validationError := func(err error) {
instance, errWithCode := m.processor.InstanceGet(c.Request.Context(), config.GetHost())
if errWithCode != nil {
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
c.HTML(http.StatusOK, "finalize.tmpl", gin.H{
"instance": instance,
"name": form.Name,
"preferredUsername": form.Username,
"error": err,
})
}
// check if the username conforms to the spec
if err := validate.Username(form.Username); err != nil {
validationError(err)
return
}
// see if the username is still available
usernameAvailable, err := m.db.IsUsernameAvailable(c.Request.Context(), form.Username)
if err != nil {
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, oauth.HelpfulAdvice), m.processor.InstanceGet)
return
}
if !usernameAvailable {
validationError(fmt.Errorf("Username %s is already taken", form.Username))
return
}
// retrieve the information previously set by the oidc logic
appID, ok := s.Get(sessionAppID).(string)
if !ok {
err := fmt.Errorf("key %s was not found in session", sessionAppID)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, oauth.HelpfulAdvice), m.processor.InstanceGet)
return
}
// retrieve the claims returned by the IDP. Having this present means that we previously already verified these claims
claims, ok := s.Get(sessionClaims).(*oidc.Claims)
if !ok {
err := fmt.Errorf("key %s was not found in session", sessionClaims)
api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, oauth.HelpfulAdvice), m.processor.InstanceGet)
return
}
// we're now ready to actually create the user
user, errWithCode := m.createUserFromOIDC(c.Request.Context(), claims, form, net.IP(c.ClientIP()), appID)
if errWithCode != nil {
m.clearSession(s)
api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
return
}
s.Delete(sessionClaims)
s.Delete(sessionAppID)
s.Set(sessionUserID, user.ID)
if err := s.Save(); err != nil {
m.clearSession(s)
api.ErrorHandler(c, gtserror.NewErrorInternalError(err), m.processor.InstanceGet)
return
}
c.Redirect(http.StatusFound, OauthAuthorizePath)
}
func (m *Module) fetchUserForClaims(ctx context.Context, claims *oidc.Claims, ip net.IP, appID string) (*gtsmodel.User, gtserror.WithCode) {
if claims.Sub == "" {
err := errors.New("no sub claim found - is your provider OIDC compliant?")
return nil, gtserror.NewErrorBadRequest(err, err.Error())
}
user, err := m.db.GetUserByExternalID(ctx, claims.Sub)
if err == nil {
return user, nil
}
if err != db.ErrNoEntries {
err := fmt.Errorf("error checking database for externalID %s: %s", claims.Sub, err)
return nil, gtserror.NewErrorInternalError(err)
}
if !config.GetOIDCLinkExisting() {
return nil, nil
}
// fallback to email if we want to link existing users
user, err = m.db.GetUserByEmailAddress(ctx, claims.Email)
if err == db.ErrNoEntries {
return nil, nil
} else if err != nil {
err := fmt.Errorf("error checking database for email %s: %s", claims.Email, err)
return nil, gtserror.NewErrorInternalError(err)
}
// at this point we have found a matching user but still need to link the newly received external ID
user.ExternalID = claims.Sub
err = m.db.UpdateUser(ctx, user, "external_id")
if err != nil {
err := fmt.Errorf("error linking existing user %s: %s", claims.Email, err)
return nil, gtserror.NewErrorInternalError(err)
}
return user, nil
}
func (m *Module) createUserFromOIDC(ctx context.Context, claims *oidc.Claims, extraInfo *extraInfo, ip net.IP, appID string) (*gtsmodel.User, gtserror.WithCode) {
// check if the email address is available for use; if it's not there's nothing we can so
emailAvailable, err := m.db.IsEmailAvailable(ctx, claims.Email)
if err != nil {
return nil, gtserror.NewErrorBadRequest(err)
}
if !emailAvailable {
help := "The email address given to us by your authentication provider already exists in our records and the server administrator has not enabled account migration"
return nil, gtserror.NewErrorConflict(fmt.Errorf("email address %s is not available", claims.Email), help)
}
// check if the user is in any recognised admin groups
var admin bool
for _, g := range claims.Groups {
if strings.EqualFold(g, "admin") || strings.EqualFold(g, "admins") {
admin = true
}
}
// We still need to set *a* password even if it's not a password the user will end up using, so set something random.
// We'll just set two uuids on top of each other, which should be long + random enough to baffle any attempts to crack.
//
// If the user ever wants to log in using gts password rather than oidc flow, they'll have to request a password reset, which is fine
password := uuid.NewString() + uuid.NewString()
// Since this user is created via oidc, which has been set up by the admin, we can assume that the account is already
// implicitly approved, and that the email address has already been verified: otherwise, we end up in situations where
// the admin first approves the user in OIDC, and then has to approve them again in GoToSocial, which doesn't make sense.
//
// In other words, if a user logs in via OIDC, they should be able to use their account straight away.
//
// See: https://github.com/superseriousbusiness/gotosocial/issues/357
requireApproval := false
emailVerified := true
// create the user! this will also create an account and store it in the database so we don't need to do that here
user, err := m.db.NewSignup(ctx, extraInfo.Username, "", requireApproval, claims.Email, password, ip, "", appID, emailVerified, claims.Sub, admin)
if err != nil {
return nil, gtserror.NewErrorInternalError(err)
}
return user, nil
}