syncthing/lib/api/api_auth.go

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// Copyright (C) 2014 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
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package api
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import (
"crypto/tls"
"fmt"
"net"
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"net/http"
"strings"
"time"
ldap "github.com/go-ldap/ldap/v3"
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"github.com/syncthing/syncthing/lib/config"
"github.com/syncthing/syncthing/lib/db"
"github.com/syncthing/syncthing/lib/events"
"github.com/syncthing/syncthing/lib/rand"
"golang.org/x/exp/slices"
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)
const (
maxSessionLifetime = 7 * 24 * time.Hour
maxActiveSessions = 25
randomTokenLength = 64
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)
func emitLoginAttempt(success bool, username, address string, evLogger events.Logger) {
evLogger.Log(events.LoginAttempt, map[string]interface{}{
"success": success,
"username": username,
"remoteAddress": address,
})
if !success {
l.Infof("Wrong credentials supplied during API authorization from %s", address)
}
}
func antiBruteForceSleep() {
time.Sleep(time.Duration(rand.Intn(100)+100) * time.Millisecond)
}
func unauthorized(w http.ResponseWriter, shortID string) {
w.Header().Set("WWW-Authenticate", fmt.Sprintf(`Basic realm="Authorization Required (%s)"`, shortID))
http.Error(w, "Not Authorized", http.StatusUnauthorized)
}
func forbidden(w http.ResponseWriter) {
http.Error(w, "Forbidden", http.StatusForbidden)
}
func isNoAuthPath(path string) bool {
// Local variable instead of module var to prevent accidental mutation
noAuthPaths := []string{
"/",
"/index.html",
"/modal.html",
"/rest/svc/lang", // Required to load language settings on login page
}
// Local variable instead of module var to prevent accidental mutation
noAuthPrefixes := []string{
// Static assets
"/assets/",
"/syncthing/",
"/vendor/",
"/theme-assets/", // This leaks information from config, but probably not sensitive
// No-auth API endpoints
"/rest/noauth",
}
return slices.Contains(noAuthPaths, path) ||
slices.ContainsFunc(noAuthPrefixes, func(prefix string) bool {
return strings.HasPrefix(path, prefix)
})
}
type basicAuthAndSessionMiddleware struct {
cookieName string
shortID string
guiCfg config.GUIConfiguration
ldapCfg config.LDAPConfiguration
next http.Handler
evLogger events.Logger
tokens *tokenManager
}
func newBasicAuthAndSessionMiddleware(cookieName, shortID string, guiCfg config.GUIConfiguration, ldapCfg config.LDAPConfiguration, next http.Handler, evLogger events.Logger, miscDB *db.NamespacedKV) *basicAuthAndSessionMiddleware {
return &basicAuthAndSessionMiddleware{
cookieName: cookieName,
shortID: shortID,
guiCfg: guiCfg,
ldapCfg: ldapCfg,
next: next,
evLogger: evLogger,
tokens: newTokenManager("sessions", miscDB, maxSessionLifetime, maxActiveSessions),
}
}
func (m *basicAuthAndSessionMiddleware) ServeHTTP(w http.ResponseWriter, r *http.Request) {
if hasValidAPIKeyHeader(r, m.guiCfg) {
m.next.ServeHTTP(w, r)
return
}
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for _, cookie := range r.Cookies() {
// We iterate here since there may, historically, be multiple
// cookies with the same name but different path. Any "old" ones
// won't match an existing session and will be ignored, then
// later removed on logout or when timing out.
if cookie.Name == m.cookieName {
if m.tokens.Check(cookie.Value) {
m.next.ServeHTTP(w, r)
return
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}
}
}
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// Fall back to Basic auth if provided
if username, ok := attemptBasicAuth(r, m.guiCfg, m.ldapCfg, m.evLogger); ok {
m.createSession(username, false, w, r)
m.next.ServeHTTP(w, r)
return
}
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// Exception for static assets and REST calls that don't require authentication.
if isNoAuthPath(r.URL.Path) {
m.next.ServeHTTP(w, r)
return
}
lib/api: Check basic auth (and set session cookie) before noauth exceptions (#9159) This is motivated by the Android app: https://github.com/syncthing/syncthing-android/pull/1982#issuecomment-1752042554 The planned fix in response to basic auth behaviour changing in #8757 was to add the `Authorization` header when opening the WebView, but it turns out the function used only applies the header to the initial page load, not any subsequent script loads or AJAX calls. The `basicAuthAndSessionMiddleware` checks for no-auth exceptions before checking the `Authorization` header, so the header has no effect on the initial page load since the `/` path is a no-auth exception. Thus the Android app fails to log in when opening the WebView. This changes the order of checks in `basicAuthAndSessionMiddleware` so that the `Authorization` header is always checked if present, and a session cookie is set if it is valid. Only after that does the middleware fall back to checking for no-auth exceptions. `api_test.go` has been expanded with additional checks: - Check that a session cookie is set whenever correct basic auth is provided. - Check that a session cookie is not set when basic auth is incorrect. - Check that a session cookie is not set when authenticating with an API token (either via `X-Api-Key` or `Authorization: Bearer`). And an additional test case: - Check that requests to `/` always succeed, but receive a session cookie when correct basic auth is provided. I have manually verified that - The new assertions fail if the `createSession` call is removed in `basicAuthAndSessionMiddleware`. - The new test cases in e6e4df4d7034302b729ada6d91cff6e2b29678da fail before the change in 0e47d37e738d4c15736c496e01cd949afb372e71 is applied.
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// Some browsers don't send the Authorization request header unless prompted by a 401 response.
// This enables https://user:pass@localhost style URLs to keep working.
if m.guiCfg.SendBasicAuthPrompt {
unauthorized(w, m.shortID)
return
}
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forbidden(w)
}
func (m *basicAuthAndSessionMiddleware) passwordAuthHandler(w http.ResponseWriter, r *http.Request) {
var req struct {
Username string
Password string
StayLoggedIn bool
}
if err := unmarshalTo(r.Body, &req); err != nil {
l.Debugln("Failed to parse username and password:", err)
http.Error(w, "Failed to parse username and password.", http.StatusBadRequest)
return
}
if auth(req.Username, req.Password, m.guiCfg, m.ldapCfg) {
m.createSession(req.Username, req.StayLoggedIn, w, r)
w.WriteHeader(http.StatusNoContent)
return
}
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emitLoginAttempt(false, req.Username, r.RemoteAddr, m.evLogger)
antiBruteForceSleep()
forbidden(w)
}
func attemptBasicAuth(r *http.Request, guiCfg config.GUIConfiguration, ldapCfg config.LDAPConfiguration, evLogger events.Logger) (string, bool) {
username, password, ok := r.BasicAuth()
if !ok {
return "", false
}
l.Debugln("Sessionless HTTP request with authentication; this is expensive.")
if auth(username, password, guiCfg, ldapCfg) {
return username, true
}
usernameFromIso := string(iso88591ToUTF8([]byte(username)))
passwordFromIso := string(iso88591ToUTF8([]byte(password)))
if auth(usernameFromIso, passwordFromIso, guiCfg, ldapCfg) {
return usernameFromIso, true
}
emitLoginAttempt(false, username, r.RemoteAddr, evLogger)
lib/api: Check basic auth (and set session cookie) before noauth exceptions (#9159) This is motivated by the Android app: https://github.com/syncthing/syncthing-android/pull/1982#issuecomment-1752042554 The planned fix in response to basic auth behaviour changing in #8757 was to add the `Authorization` header when opening the WebView, but it turns out the function used only applies the header to the initial page load, not any subsequent script loads or AJAX calls. The `basicAuthAndSessionMiddleware` checks for no-auth exceptions before checking the `Authorization` header, so the header has no effect on the initial page load since the `/` path is a no-auth exception. Thus the Android app fails to log in when opening the WebView. This changes the order of checks in `basicAuthAndSessionMiddleware` so that the `Authorization` header is always checked if present, and a session cookie is set if it is valid. Only after that does the middleware fall back to checking for no-auth exceptions. `api_test.go` has been expanded with additional checks: - Check that a session cookie is set whenever correct basic auth is provided. - Check that a session cookie is not set when basic auth is incorrect. - Check that a session cookie is not set when authenticating with an API token (either via `X-Api-Key` or `Authorization: Bearer`). And an additional test case: - Check that requests to `/` always succeed, but receive a session cookie when correct basic auth is provided. I have manually verified that - The new assertions fail if the `createSession` call is removed in `basicAuthAndSessionMiddleware`. - The new test cases in e6e4df4d7034302b729ada6d91cff6e2b29678da fail before the change in 0e47d37e738d4c15736c496e01cd949afb372e71 is applied.
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antiBruteForceSleep()
return "", false
}
func (m *basicAuthAndSessionMiddleware) createSession(username string, persistent bool, w http.ResponseWriter, r *http.Request) {
sessionid := m.tokens.New()
// Best effort detection of whether the connection is HTTPS --
// either directly to us, or as used by the client towards a reverse
// proxy who sends us headers.
connectionIsHTTPS := r.TLS != nil ||
strings.ToLower(r.Header.Get("x-forwarded-proto")) == "https" ||
strings.Contains(strings.ToLower(r.Header.Get("forwarded")), "proto=https")
// If the connection is HTTPS, or *should* be HTTPS, set the Secure
// bit in cookies.
useSecureCookie := connectionIsHTTPS || m.guiCfg.UseTLS()
maxAge := 0
if persistent {
maxAge = int(maxSessionLifetime.Seconds())
}
http.SetCookie(w, &http.Cookie{
Name: m.cookieName,
Value: sessionid,
// In HTTP spec Max-Age <= 0 means delete immediately,
// but in http.Cookie MaxAge = 0 means unspecified (session) and MaxAge < 0 means delete immediately
MaxAge: maxAge,
Secure: useSecureCookie,
Path: "/",
})
emitLoginAttempt(true, username, r.RemoteAddr, m.evLogger)
}
func (m *basicAuthAndSessionMiddleware) handleLogout(w http.ResponseWriter, r *http.Request) {
for _, cookie := range r.Cookies() {
// We iterate here since there may, historically, be multiple
// cookies with the same name but different path. We drop them
// all.
if cookie.Name == m.cookieName {
m.tokens.Delete(cookie.Value)
// Delete the cookie
http.SetCookie(w, &http.Cookie{
Name: m.cookieName,
Value: "",
MaxAge: -1,
Secure: cookie.Secure,
Path: cookie.Path,
})
}
}
w.WriteHeader(http.StatusNoContent)
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}
func auth(username string, password string, guiCfg config.GUIConfiguration, ldapCfg config.LDAPConfiguration) bool {
if guiCfg.AuthMode == config.AuthModeLDAP {
return authLDAP(username, password, ldapCfg)
} else {
return authStatic(username, password, guiCfg)
}
}
func authStatic(username string, password string, guiCfg config.GUIConfiguration) bool {
return guiCfg.CompareHashedPassword(password) == nil && username == guiCfg.User
}
func authLDAP(username string, password string, cfg config.LDAPConfiguration) bool {
address := cfg.Address
hostname, _, err := net.SplitHostPort(address)
if err != nil {
hostname = address
}
var connection *ldap.Conn
if cfg.Transport == config.LDAPTransportTLS {
connection, err = ldap.DialTLS("tcp", address, &tls.Config{
ServerName: hostname,
InsecureSkipVerify: cfg.InsecureSkipVerify,
})
} else {
connection, err = ldap.Dial("tcp", address)
}
if err != nil {
l.Warnln("LDAP Dial:", err)
return false
}
if cfg.Transport == config.LDAPTransportStartTLS {
err = connection.StartTLS(&tls.Config{InsecureSkipVerify: cfg.InsecureSkipVerify})
if err != nil {
l.Warnln("LDAP Start TLS:", err)
return false
}
}
defer connection.Close()
bindDN := formatOptionalPercentS(cfg.BindDN, escapeForLDAPDN(username))
err = connection.Bind(bindDN, password)
if err != nil {
l.Warnln("LDAP Bind:", err)
return false
}
if cfg.SearchFilter == "" && cfg.SearchBaseDN == "" {
// We're done here.
return true
}
if cfg.SearchFilter == "" || cfg.SearchBaseDN == "" {
l.Warnln("LDAP configuration: both searchFilter and searchBaseDN must be set, or neither.")
return false
}
// If a search filter and search base is set we do an LDAP search for
// the user. If this matches precisely one user then we are good to go.
// The search filter uses the same %s interpolation as the bind DN.
searchString := formatOptionalPercentS(cfg.SearchFilter, escapeForLDAPFilter(username))
const sizeLimit = 2 // we search for up to two users -- we only want to match one, so getting any number >1 is a failure.
const timeLimit = 60 // Search for up to a minute...
searchReq := ldap.NewSearchRequest(cfg.SearchBaseDN, ldap.ScopeWholeSubtree, ldap.DerefFindingBaseObj, sizeLimit, timeLimit, false, searchString, nil, nil)
res, err := connection.Search(searchReq)
if err != nil {
l.Warnln("LDAP Search:", err)
return false
}
if len(res.Entries) != 1 {
l.Infof("Wrong number of LDAP search results, %d != 1", len(res.Entries))
return false
}
return true
}
// escapeForLDAPFilter escapes a value that will be used in a filter clause
func escapeForLDAPFilter(value string) string {
// https://social.technet.microsoft.com/wiki/contents/articles/5392.active-directory-ldap-syntax-filters.aspx#Special_Characters
// Backslash must always be first in the list so we don't double escape them.
return escapeRunes(value, []rune{'\\', '*', '(', ')', 0})
}
// escapeForLDAPDN escapes a value that will be used in a bind DN
func escapeForLDAPDN(value string) string {
// https://social.technet.microsoft.com/wiki/contents/articles/5312.active-directory-characters-to-escape.aspx
// Backslash must always be first in the list so we don't double escape them.
return escapeRunes(value, []rune{'\\', ',', '#', '+', '<', '>', ';', '"', '=', ' ', 0})
}
func escapeRunes(value string, runes []rune) string {
for _, e := range runes {
value = strings.ReplaceAll(value, string(e), fmt.Sprintf("\\%X", e))
}
return value
}
func formatOptionalPercentS(template string, username string) string {
var replacements []any
nReps := strings.Count(template, "%s") - strings.Count(template, "%%s")
if nReps < 0 {
nReps = 0
}
for i := 0; i < nReps; i++ {
replacements = append(replacements, username)
}
return fmt.Sprintf(template, replacements...)
}
// Convert an ISO-8859-1 encoded byte string to UTF-8. Works by the
// principle that ISO-8859-1 bytes are equivalent to unicode code points,
// that a rune slice is a list of code points, and that stringifying a slice
// of runes generates UTF-8 in Go.
func iso88591ToUTF8(s []byte) []byte {
runes := make([]rune, len(s))
for i := range s {
runes[i] = rune(s[i])
}
return []byte(string(runes))
}