From 47190f3c831f16fedcb0072811ebe5aad920c1c9 Mon Sep 17 00:00:00 2001
From: Mariano Cano <mariano.cano@gmail.com>
Date: Tue, 14 May 2024 12:15:09 -0700
Subject: [PATCH] Require ClientAuth when verifying an X5cInsecure certificate

The X5cInsecure certificate is used by step-ca to renew certificates
without using mTLS, usually expired certificates. Certificate.Verify
defaults to require ServerAuth if no KeyUsages is set as an option. But
due to how these tokens are used, it makes more sense to require only
ClientAuth.

Related to smallstep/certificates#1843
---
 jose/parse.go | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/jose/parse.go b/jose/parse.go
index 9807af03..760c4f16 100644
--- a/jose/parse.go
+++ b/jose/parse.go
@@ -267,6 +267,9 @@ func ParseX5cInsecure(tok string, roots []*x509.Certificate) (*JSONWebToken, [][
 		Intermediates: interPool,
 		// A hack so we skip validity period validation.
 		CurrentTime: leaf.NotAfter.Add(-1 * time.Minute),
+		KeyUsages: []x509.ExtKeyUsage{
+			x509.ExtKeyUsageClientAuth,
+		},
 	})
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "error verifying x5cInsecure certificate chain")