Fix a crash in X509v3_asid_subset()

If the asnum or rdi fields are NULL and the ASIdentifiers are otherwise
subsets then this will result in a crash. Of note is that rdi will usually
be NULL.

Reported by Theo Buehler (@botovq)

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Yang <kaishen.yy@antfin.com>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/18514)

(cherry picked from commit 01fc9b6bce82f0534d6673659a0e59a71f57ee82)

1 files changed, 22 insertions, 9 deletions

diff --git a/crypto/x509v3/v3_asid.c b/crypto/x509v3/v3_asid.c
index ac68572672..9bdc682978 100644
--- a/crypto/x509v3/v3_asid.c
+++ b/crypto/x509v3/v3_asid.c
@@ -700,15 +700,28 @@ static int asid_contains(ASIdOrRanges *parent, ASIdOrRanges *child)
  */
 int X509v3_asid_subset(ASIdentifiers *a, ASIdentifiers *b)
 {
-    return (a == NULL ||
-            a == b ||
-            (b != NULL &&
-             !X509v3_asid_inherits(a) &&
-             !X509v3_asid_inherits(b) &&
-             asid_contains(b->asnum->u.asIdsOrRanges,
-                           a->asnum->u.asIdsOrRanges) &&
-             asid_contains(b->rdi->u.asIdsOrRanges,
-                           a->rdi->u.asIdsOrRanges)));
+    int subset;
+
+    if (a == NULL || a == b)
+        return 1;
+
+    if (b == NULL)
+        return 0;
+
+    if (X509v3_asid_inherits(a) || X509v3_asid_inherits(b))
+        return 0;
+
+    subset = a->asnum == NULL
+             || (b->asnum != NULL
+                 && asid_contains(b->asnum->u.asIdsOrRanges,
+                                  a->asnum->u.asIdsOrRanges));
+    if (!subset)
+        return 0;
+
+    return a->rdi == NULL
+           || (b->rdi != NULL
+               && asid_contains(b->rdi->u.asIdsOrRanges,
+                                a->rdi->u.asIdsOrRanges));
 }
 
 /*