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fix(sec): use constant time check for internal token

(cherry picked from commit 53231bad61)
This commit is contained in:
Gusted 2024-10-25 08:18:26 +02:00 committed by forgejo-backport-action
parent d77096071d
commit 5f9a2ad1db
2 changed files with 3 additions and 1 deletions

1
release-notes/5719.md Normal file
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@ -0,0 +1 @@
Forgejo generates a token which is used to authenticate web endpoints that are only meant to be used internally, for instance when the SSH daemon is used to push a commit with Git. The verification of this token was not done in constant time and was susceptible to [timing attacks](https://en.wikipedia.org/wiki/Timing_attack). A pre-condition for such an attack is the precise measurements of the time for each operation. Since it requires observing the timing of network operations, the issue is mitigated when a Forgejo instance is accessed over the internet because the ISP introduce unpredictable random delays.

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@ -5,6 +5,7 @@
package private
import (
"crypto/subtle"
"net/http"
"strings"
@ -28,7 +29,7 @@ func CheckInternalToken(next http.Handler) http.Handler {
http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
return
}
if len(fields) != 2 || fields[0] != "Bearer" || fields[1] != setting.InternalToken {
if len(fields) != 2 || fields[0] != "Bearer" || subtle.ConstantTimeCompare([]byte(fields[1]), []byte(setting.InternalToken)) == 0 {
log.Debug("Forbidden attempt to access internal url: Authorization header: %s", tokens)
http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
} else {