From 681b4d8edca1bcfea5bce685d77ea7b82ed3e7b3 Mon Sep 17 00:00:00 2001
From: Neal Patel <nealpatel@google.com>
Date: Thu, 30 Jan 2025 14:10:09 -0500
Subject: [PATCH] jws: split token into fixed number of parts

Thanks to 'jub0bs' for reporting this issue.

Fixes #71490
Fixes CVE-2025-22868

Change-Id: I2552731f46d4907f29aafe7863c558387b6bd6e2
Reviewed-on: https://go-review.googlesource.com/c/oauth2/+/652155
Auto-Submit: Gopher Robot <gobot@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
Reviewed-by: Roland Shoemaker <roland@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 jws/jws.go | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/jws/jws.go b/jws/jws.go
index 95015648b..6f03a49d3 100644
--- a/jws/jws.go
+++ b/jws/jws.go
@@ -165,11 +165,11 @@ func Encode(header *Header, c *ClaimSet, key *rsa.PrivateKey) (string, error) {
 // Verify tests whether the provided JWT token's signature was produced by the private key
 // associated with the supplied public key.
 func Verify(token string, key *rsa.PublicKey) error {
-	parts := strings.Split(token, ".")
-	if len(parts) != 3 {
+	if strings.Count(token, ".") != 2 {
 		return errors.New("jws: invalid token received, token must have 3 parts")
 	}
 
+	parts := strings.SplitN(token, ".", 3)
 	signedContent := parts[0] + "." + parts[1]
 	signatureString, err := base64.RawURLEncoding.DecodeString(parts[2])
 	if err != nil {