Check for trailing garbage in X509_addr_get_afi()

Per RFC 3779 2.2.3.3, the addressFamily field contains the 2-byte AFI
and an optional 1-byte SAFI. Nothing else. The optional SAFI is nowhere
exposed in the API. It is used expliclty only for pretty printing. There
are implicit uses in a few places, notably for sorting/comparing where
trailing garbage would be erroneously taken into account.

Erroring in this situation will let us avoid this in upcoming revisions.

ok inoguchi jsing

diff --git a/lib/libcrypto/x509/x509_addr.c b/lib/libcrypto/x509/x509_addr.c
index 64dd830..fda73b3 100644 (file)
--- a/lib/libcrypto/x509/x509_addr.c
+++ b/lib/libcrypto/x509/x509_addr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: x509_addr.c,v 1.29 2021/12/28 15:49:11 tb Exp $ */
+/*     $OpenBSD: x509_addr.c,v 1.30 2021/12/28 15:59:13 tb Exp $ */
 /*
  * Contributed to the OpenSSL Project by the American Registry for
  * Internet Numbers ("ARIN").
@@ -354,6 +354,10 @@ X509v3_addr_get_afi(const IPAddressFamily *f)
        if (!CBS_get_u16(&cbs, &afi))
                return 0;
 
+       /* One byte for the optional SAFI, everything else is garbage. */
+       if (CBS_len(&cbs) > 1)
+               return 0;
+
        return afi;
 }