126 lines
2.4 KiB
Go
126 lines
2.4 KiB
Go
package main
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import (
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"bufio"
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"net/http"
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"os"
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"path/filepath"
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"sync"
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"time"
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"github.com/calmh/syncthing/osutil"
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)
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var csrfTokens []string
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var csrfMut sync.Mutex
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// Check for CSRF token on /rest/ URLs. If a correct one is not given, reject
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// the request with 403. For / and /index.html, set a new CSRF cookie if none
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// is currently set.
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func csrfMiddleware(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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// Allow requests carrying a valid API key
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if validAPIKey(r.Header.Get("X-API-Key")) {
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next.ServeHTTP(w, r)
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return
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}
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// Allow requests for the front page, and set a CSRF cookie if there isn't already a valid one.
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if r.URL.Path == "/" || r.URL.Path == "/index.html" {
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cookie, err := r.Cookie("CSRF-Token")
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if err != nil || !validCsrfToken(cookie.Value) {
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cookie = &http.Cookie{
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Name: "CSRF-Token",
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Value: newCsrfToken(),
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}
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http.SetCookie(w, cookie)
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}
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next.ServeHTTP(w, r)
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return
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}
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// Verify the CSRF token
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token := r.Header.Get("X-CSRF-Token")
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if !validCsrfToken(token) {
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http.Error(w, "CSRF Error", 403)
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return
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}
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next.ServeHTTP(w, r)
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})
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}
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func validCsrfToken(token string) bool {
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csrfMut.Lock()
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defer csrfMut.Unlock()
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for _, t := range csrfTokens {
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if t == token {
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return true
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}
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}
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return false
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}
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func newCsrfToken() string {
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bs := make([]byte, 30)
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_, err := rand.Reader.Read(bs)
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if err != nil {
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l.Fatalln(err)
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}
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token := base64.StdEncoding.EncodeToString(bs)
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csrfMut.Lock()
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csrfTokens = append(csrfTokens, token)
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if len(csrfTokens) > 10 {
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csrfTokens = csrfTokens[len(csrfTokens)-10:]
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}
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defer csrfMut.Unlock()
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saveCsrfTokens()
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return token
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}
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func saveCsrfTokens() {
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name := filepath.Join(confDir, "csrftokens.txt")
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tmp := fmt.Sprintf("%s.tmp.%d", name, time.Now().UnixNano())
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f, err := os.OpenFile(tmp, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0644)
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if err != nil {
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return
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}
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defer os.Remove(tmp)
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for _, t := range csrfTokens {
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_, err := fmt.Fprintln(f, t)
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if err != nil {
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return
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}
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}
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err = f.Close()
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if err != nil {
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return
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}
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osutil.Rename(tmp, name)
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}
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func loadCsrfTokens() {
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name := filepath.Join(confDir, "csrftokens.txt")
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f, err := os.Open(name)
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if err != nil {
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return
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}
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defer f.Close()
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s := bufio.NewScanner(f)
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for s.Scan() {
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csrfTokens = append(csrfTokens, s.Text())
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}
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}
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