auth.go

package main

import (
	"context"
	"crypto/hmac"
	"crypto/sha256"
	"encoding/json"
	"io"
	"net/http"
	"os"
	"sync"
	"time"

	"github.com/DHowett/ghostbin/account"
	"github.com/golang/glog"
	"github.com/golang/groupcache/lru"
	"github.com/gorilla/mux"
	"github.com/gorilla/sessions"
	"golang.org/x/crypto/scrypt"
)

const USER_CACHE_MAX_ENTRIES int = 1000

type contextKey int

const userContextKey contextKey = 0

type authReply struct {
	Status        string            `json:"status,omitempty"`
	Reason        string            `json:"reason,omitempty"`
	Type          string            `json:"type,omitempty"`
	ExtraData     map[string]string `json:"extra,omitempty"`
	InvalidFields []string          `json:"invalid_fields,omitempty"`
}

func authLoginPostHandler(w http.ResponseWriter, r *http.Request) {
	clientSession, err := clientLongtermSessionStore.Get(r, "authentication")
	if err != nil {
		glog.Errorln(err)
	}
	serverSession, err := sessionStore.Get(r, "session")
	if err != nil {
		glog.Errorln(err)
	}

	reply := &authReply{
		Status:    "invalid",
		ExtraData: make(map[string]string),
	}

	defer func() {
		w.WriteHeader(http.StatusOK)
		enc := json.NewEncoder(w)
		err := enc.Encode(reply)
		if err != nil {
			glog.Error(err)
		}
	}()

	var user *account.User

	loginType := r.FormValue("type")
	if loginType == "username" {
		// We don't have an assertion, hope we have a username/password
		reply.Type = "username"

		username, password, confirm := r.FormValue("username"), r.FormValue("password"), r.FormValue("confirm_password")

		promoteToken := r.FormValue("promote_token")
		promotion := false
		if promoteToken != "" {
			promotion = true
		}
		if promotion {
			v, ok := ephStore.Get("UPG|" + promoteToken)
			if !ok {
				reply.Reason = "invalid promotion token (30-min expiry?)"
				reply.InvalidFields = []string{"promote_token"}
				return
			}
			// Stomp the username from the form.
			username = v.(string)
		}

		if username == "" || password == "" {
			reply.Reason = "invalid username or password"
			reply.InvalidFields = []string{"username", "password"}
			return
		}

		newuser := userStore.Get(username)
		if newuser == nil {
			if promotion {
				// Don't allow new user creation; this should never happen.
				return
			}

			/*reply.Reason = "account creation has been disabled"
			reply.InvalidFields = []string{"username", "password", "confirm_password"}
			return*/

			if confirm == "" {
				reply.Status = "moreinfo"
				reply.InvalidFields = []string{"confirm_password"}
				return
			}
			if password != confirm {
				reply.Reason = "passwords don't match"
				reply.InvalidFields = []string{"password", "confirm_password"}
				return
			}
			newuser = userStore.Create(username)
			newuser.UpdateChallenge(password)
			user = newuser
		} else {
			if promotion {
				if confirm == "" {
					reply.Status = "moreinfo"
					reply.InvalidFields = []string{"confirm_password"}
					return
				}
				if password != confirm {
					reply.Reason = "passwords don't match"
					reply.InvalidFields = []string{"password", "confirm_password"}
					return
				}
				newuser.UpdateChallenge(password)
				delete(newuser.Values, "persona")
				reply.ExtraData["promoted"] = "true"
				user = newuser
				ephStore.Delete("UPG|" + promoteToken)
				healthServer.IncrementMetric("user.promotions.completed")
			} else {
				if newuser.Check(password) {
					user = newuser
				} else {
					reply.Reason = "invalid username or password"
					reply.InvalidFields = []string{"username", "password"}
				}
			}
		}
	} else if loginType == "token" {
		// Authentication Token
		reply.Type = "token"

		token := r.FormValue("token")
		if token == "" {
			reply.Reason = "authtoken login requested but no token provided"
			reply.InvalidFields = []string{"token"}
			return
		}

		u, ok := ephStore.Get("A|U|" + token)
		if !ok {
			w.WriteHeader(http.StatusTeapot) // I'm a teapot.
			reply.Reason = "that authenticated token isn't"
			reply.InvalidFields = []string{"token"}
			return
		}
		user = u.(*account.User)
	} else {
		reply.Reason = "invalid login type"
		reply.InvalidFields = []string{"type"}
		return
	}

	if user != nil {
		healthServer.IncrementMetric("user.login")

		// *HACK*
		// Inject the user into the request context for GetPastePermissions
		// to find.
		subr := r.WithContext(context.WithValue(r.Context(), userContextKey, user))

		// Attempt to aggregate user, session, and old perms.
		pastePerms := GetPastePermissions(subr)
		user.Values["permissions"] = pastePerms
		delete(serverSession.Values, "pastes")      // delete old perms
		delete(serverSession.Values, "permissions") // delete new session perms

		err := user.Save()
		if err != nil {
			reply.Reason = "failed to save user"
			reply.ExtraData["error"] = err.Error()
		} else {
			reply.Status = "valid"
			reply.ExtraData["username"] = user.Name
		}
		clientSession.Values["account2"] = user.Name
		err = sessions.Save(r, w)
		if err != nil {
			glog.Errorln(err)
		}

		if token := r.FormValue("requested_auth_token"); token != "" {
			ephStore.Put("A|U|"+token, user, 30*time.Minute)
		}
	}

	// reply serialized in defer above. just for fun.
}

func authLogoutPostHandler(w http.ResponseWriter, r *http.Request) {
	ses, _ := clientLongtermSessionStore.Get(r, "authentication")
	delete(ses.Values, "account2")
	err := sessions.Save(r, w)
	if err != nil {
		glog.Errorln(err)
	}
}

func authTokenHandler(w http.ResponseWriter, r *http.Request) {
	authToken, _ := generateRandomBase32String(20, 32)
	ephStore.Put("A|"+authToken, true, 30*time.Minute)
	url, _ := router.Get("auth_token_login").URL("token", authToken)
	w.Header().Set("Location", url.String())
	w.WriteHeader(http.StatusSeeOther)
}

func authTokenPageHandler(w http.ResponseWriter, r *http.Request) {
	token := mux.Vars(r)["token"]
	_, ok := ephStore.Get("A|" + token)
	if !ok {
		return
	}

	user := GetUser(r)
	if user != nil {
		ephStore.Put("A|U|"+token, user, 30*time.Minute)
	}
	RenderPage(w, r, "authtoken", map[string]string{"token": token})
}

type AuthChallengeProvider struct{}

func (a *AuthChallengeProvider) DeriveKey(password string, salt []byte) []byte {
	if password == "" {
		return nil
	}

	key, err := scrypt.Key([]byte(password), salt, 16384, 8, 1, 32)
	if err != nil {
		panic(err)
	}

	return key
}

func (a *AuthChallengeProvider) RandomSalt() []byte {
	b, err := generateRandomBytes(32)
	if err != nil {
		panic(err)
	}
	return b
}

func (a *AuthChallengeProvider) Challenge(message []byte, key []byte) []byte {
	shaHmac := hmac.New(sha256.New, key)
	shaHmac.Write(message)
	challenge := shaHmac.Sum(nil)
	return challenge
}

func GetUser(r *http.Request) *account.User {
	if ui := r.Context().Value(userContextKey); ui != nil {
		if u, ok := ui.(*account.User); ok {
			return u
		}
	}
	return nil
}

type userLookupWrapper struct {
	http.Handler
}

func (u userLookupWrapper) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	ses, _ := clientLongtermSessionStore.Get(r, "authentication")
	account, ok := ses.Values["account2"].(string)
	if ok {
		user := userStore.Get(account)
		r = r.WithContext(context.WithValue(r.Context(), userContextKey, user))
	}
	u.Handler.ServeHTTP(w, r)
}

type ManglingUserStore struct {
	account.AccountStore
}

func (m *ManglingUserStore) mangle(name string) string {
	if len(name) > 2 && name[:2] == "1$" {
		return name
	}
	sum := sha256.Sum256([]byte(name))
	return "1$" + base32Encoder.EncodeToString(sum[:])
}

func (m *ManglingUserStore) Get(name string) *account.User {
	return m.AccountStore.Get(m.mangle(name))
}

func (m *ManglingUserStore) Create(name string) *account.User {
	return m.AccountStore.Create(m.mangle(name))
}

type CachingUserStore struct {
	account.AccountStore
	mu    sync.RWMutex
	cache *lru.Cache
}

func (c *CachingUserStore) fromCache(name string) *account.User {
	c.mu.RLock()
	var user *account.User
	if c.cache != nil {
		if u, ok := c.cache.Get(name); ok {
			user = u.(*account.User)
		}
	}
	c.mu.RUnlock()
	return user
}

func (c *CachingUserStore) putCache(name string, user *account.User) {
	c.mu.Lock()
	if c.cache == nil {
		c.cache = &lru.Cache{
			MaxEntries: USER_CACHE_MAX_ENTRIES,
		}
	}
	c.cache.Add(name, user)
	c.mu.Unlock()
}

func (c *CachingUserStore) Get(name string) *account.User {
	user := c.fromCache(name)
	if user == nil {
		user = c.AccountStore.Get(name)
		if user != nil {
			c.putCache(user.Name, user)
		}
	}
	return user
}

func (c *CachingUserStore) Create(name string) *account.User {
	user := c.fromCache(name)
	if user == nil {
		user = c.AccountStore.Create(name)
		if user != nil {
			c.putCache(user.Name, user)
		}
	}
	return user
}

type PromoteFirstUserToAdminStore struct {
	Path string
	account.AccountStore
	firstUserCheckDone bool
}

func (c *PromoteFirstUserToAdminStore) Create(name string) *account.User {
	firstUser := false
	if !c.firstUserCheckDone {
		accountDir, err := os.Open(c.Path)
		if err != nil {
			firstUser = true
		} else {
			defer accountDir.Close()
			_, err = accountDir.Readdirnames(1)
			if err == io.EOF {
				firstUser = true
			}
		}
		c.firstUserCheckDone = true
	}

	user := c.AccountStore.Create(name)
	if firstUser {
		user.Values["user.permissions"] = PastePermission{"admin": true}
	}
	return user
}

func adminPromoteHandler(w http.ResponseWriter, r *http.Request) {
	username := r.FormValue("username")
	user := userStore.Get(username)
	if user != nil {
		perms, ok := user.Values["user.permissions"].(PastePermission)
		if !ok {
			perms = PastePermission{}
		}
		perms["admin"] = true
		user.Values["user.permissions"] = perms
		user.Save()
		SetFlash(w, "success", "Promoted "+username+".")
	} else {
		SetFlash(w, "error", "Couldn't find "+username+" to promote.")
	}
	w.Header().Set("Location", "/admin")
	w.WriteHeader(http.StatusSeeOther)
}

func init() {
	RegisterTemplateFunction("user", func(r *RenderContext) *account.User {
		return GetUser(r.Request)
	})
}