[crypto] Differentiate "untrusted root" and "incomplete chain" error cases

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/crypto/x509.c

 	__einfo_error ( EINFO_EACCES_PATH_LEN )
 #define EINFO_EACCES_PATH_LEN \
 	__einfo_uniqify ( EINFO_EACCES, 0x05, "Maximum path length exceeded" )
+#define EACCES_UNTRUSTED \
+	__einfo_error ( EINFO_EACCES_UNTRUSTED )
+#define EINFO_EACCES_UNTRUSTED \
+	__einfo_uniqify ( EINFO_EACCES, 0x06, "Untrusted root certificate" )
 
 /** "commonName" object identifier */
 static uint8_t oid_common_name[] = { ASN1_OID_COMMON_NAME };
 		if ( ( rc = x509_validate_time ( current, time ) ) != 0 )
 			return rc;
 
-		/* Succeed if we have reached a root certificate */
+		/* Succeed if we have reached a trusted root certificate */
 		if ( x509_validate_root ( current, root ) == 0 )
 			return 0;
 
+		/* Fail if we have reached an untrusted root certificate */
+		if ( asn1_compare ( &current->issuer.raw,
+				    &current->subject.raw ) == 0 ) {
+			DBGC ( context, "X509 chain %p reached untrusted root "
+			       "certificate\n", context );
+			return -EACCES_UNTRUSTED;
+		}
+
 		/* Get next certificate in chain */
 		if ( ( rc = parse_next ( next, current, context ) ) != 0 ) {
 			DBGC ( context, "X509 chain %p could not get next "

src/net/tls.c

 #include <ipxe/tls.h>
 
 /* Disambiguate the various error causes */
-#define EACCES_UNTRUSTED \
-	__einfo_error ( EINFO_EACCES_UNTRUSTED )
-#define EINFO_EACCES_UNTRUSTED \
-	__einfo_uniqify ( EINFO_EACCES, 0x01, "Untrusted certificate chain" )
+#define EACCES_INCOMPLETE \
+	__einfo_error ( EINFO_EACCES_INCOMPLETE )
+#define EINFO_EACCES_INCOMPLETE \
+	__einfo_uniqify ( EINFO_EACCES, 0x01, "Incomplete certificate chain" )
 #define EACCES_WRONG_NAME \
 	__einfo_error ( EINFO_EACCES_WRONG_NAME )
 #define EINFO_EACCES_WRONG_NAME \
 	/* Return error at end of chain */
 	if ( context->current >= context->end ) {
 		DBGC ( tls, "TLS %p reached end of certificate chain\n", tls );
-		return -EACCES_UNTRUSTED;
+		return -EACCES_INCOMPLETE;
 	}
 
 	/* Extract current certificate and update context */