Origin: backport, https://git.openssl.org/gitweb/?p=openssl.git;a=commit;h=b013765abfa80036dc779dd0e50602c57bb3bf95

From b013765abfa80036dc779dd0e50602c57bb3bf95 Mon Sep 17 00:00:00 2001
From: Matt Caswell <matt@openssl.org>
Date: Tue, 7 Mar 2023 16:52:55 +0000
Subject: [PATCH] Ensure that EXFLAG_INVALID_POLICY is checked even in leaf
 certs

Even though we check the leaf cert to confirm it is valid, we
later ignored the invalid flag and did not notice that the leaf
cert was bad.

Fixes: CVE-2023-0465

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20588)
diff -wpruN --no-dereference '--exclude=*.orig' a~/crypto/x509/x509_vfy.c a/crypto/x509/x509_vfy.c
--- a~/crypto/x509/x509_vfy.c	1970-01-01 00:00:00
+++ a/crypto/x509/x509_vfy.c	1970-01-01 00:00:00
@@ -1765,16 +1765,23 @@ static int check_policy(X509_STORE_CTX *
          * Locate certificates with bad extensions and notify callback.
          */
         X509 *x;
-        int i;
-        for (i = 1; i < sk_X509_num(ctx->chain); i++) {
+        int i, cbcalled = 0;
+        for (i = 0; i < sk_X509_num(ctx->chain); i++) {
             x = sk_X509_value(ctx->chain, i);
             if (!(x->ex_flags & EXFLAG_INVALID_POLICY))
                 continue;
+            cbcalled = 1;
             ctx->current_cert = x;
             ctx->error = X509_V_ERR_INVALID_POLICY_EXTENSION;
             if (!ctx->verify_cb(0, ctx))
                 return 0;
         }
+        if (!cbcalled) {
+            /* Should not be able to get here */
+            X509err(X509_F_CHECK_POLICY, ERR_R_INTERNAL_ERROR);
+            return 0;
+        }
+        /* The callback ignored the error so we return success */
         return 1;
     }
     if (ret == -2) {