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 --git a/crypto/x509/x509_vfy.c b/crypto/x509/x509_vfy.c
index 925fbb5412583423670fc68d67be85eec0ec4e1b..1dfe4f9f31a5827ae27e49c524d446c92f5c321a 100644 (file)
--- a/crypto/x509/x509_vfy.c
+++ b/crypto/x509/x509_vfy.c
@@ -1649,18 +1649,25 @@ static int check_policy(X509_STORE_CTX *ctx)
     }
     /* Invalid or inconsistent extensions */
     if (ret == X509_PCY_TREE_INVALID) {
-        int i;
+        int i, cbcalled = 0;
 
         /* Locate certificates with bad extensions and notify callback. */
-        for (i = 1; i < sk_X509_num(ctx->chain); i++) {
+        for (i = 0; i < sk_X509_num(ctx->chain); i++) {
             X509 *x = sk_X509_value(ctx->chain, i);
 
             if (!(x->ex_flags & EXFLAG_INVALID_POLICY))
                 continue;
+            cbcalled = 1;
             if (!verify_cb_cert(ctx, x, i,
                                 X509_V_ERR_INVALID_POLICY_EXTENSION))
                 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 == X509_PCY_TREE_FAILURE) {