From 586cc1d38ce3b88034e688b894cda0a6ddc1d278 Mon Sep 17 00:00:00 2001
From: Seth Vargo <seth@sethvargo.com>
Date: Mon, 15 Mar 2021 11:11:56 -0400
Subject: [PATCH] Merge pull request from GHSA-5v95-v8c8-3rh6

This fixes a security vulnerability where, with a carefully crafted request or malicious proxy, a user with UserWrite permissions could create another user with higher privileges than their own due to insufficient checks on the allowed set of permissions.
---
 pkg/rbac/rbac.go      | 10 ++++++++++
 pkg/rbac/rbac_test.go | 24 ++++++++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/pkg/rbac/rbac.go b/pkg/rbac/rbac.go
index 18c433bd1..94a0c9276 100644
--- a/pkg/rbac/rbac.go
+++ b/pkg/rbac/rbac.go
@@ -64,6 +64,16 @@ func Can(given Permission, target Permission) bool {
 func CompileAndAuthorize(actorPermission Permission, toUpdate []Permission) (Permission, error) {
 	var permission Permission
 	for _, update := range toUpdate {
+		// Verify the provided permission is a known permission. This prevents a
+		// security vulnerability whereby a carefully crafted request is able to
+		// provide a value that correctly passes an the bitwise AND check and then
+		// modifies the target permission using OR to escalate privilege.
+		if _, ok := PermissionMap[update]; !ok {
+			if update != LegacyRealmAdmin && update != LegacyRealmUser {
+				return 0, fmt.Errorf("provided permission %v is unknown", update)
+			}
+		}
+
 		// Verify that the user making changes has the permissions they are trying
 		// to grant. It is not valid for someone to grant permissions larger than
 		// they currently have.
diff --git a/pkg/rbac/rbac_test.go b/pkg/rbac/rbac_test.go
index d5e3dd2e6..d68bc01c0 100644
--- a/pkg/rbac/rbac_test.go
+++ b/pkg/rbac/rbac_test.go
@@ -57,6 +57,30 @@ func TestRequiredPermissions(t *testing.T) {
 			t.Errorf("expected error")
 		}
 	})
+
+	t.Run("legacy_admin", func(t *testing.T) {
+		t.Parallel()
+
+		if _, err := CompileAndAuthorize(LegacyRealmAdmin, []Permission{LegacyRealmAdmin}); err != nil {
+			t.Error(err)
+		}
+	})
+
+	t.Run("legacy_user", func(t *testing.T) {
+		t.Parallel()
+
+		if _, err := CompileAndAuthorize(LegacyRealmAdmin, []Permission{LegacyRealmUser}); err != nil {
+			t.Error(err)
+		}
+	})
+
+	t.Run("escalate", func(t *testing.T) {
+		t.Parallel()
+
+		if _, err := CompileAndAuthorize(UserRead|UserWrite, []Permission{16383}); err == nil {
+			t.Errorf("expected error")
+		}
+	})
 }
 
 func TestImpliedBy(t *testing.T) {