Limit OIDs to 128 components

The longest OID known by oid-info.com is 34 components[1], so 128
should be plenty and will limit the potential for attacks.

[1] http://oid-info.com/get/1.3.6.1.4.1.1248.1.1.2.1.3.21.69.112.115.111.110.32.83.116.121.108.117.115.32.80.114.111.32.52.57.48.48

Signed-off-by: David Horstmann <david.horstmann@arm.com>

include/mbedtls/oid.h

@@ -63,6 +63,11 @@
 #define MBEDTLS_OID_X509_EXT_FRESHEST_CRL                (1 << 14)
 #define MBEDTLS_OID_X509_EXT_NS_CERT_TYPE                (1 << 16)
 
+/*
+ * Maximum number of OID components allowed
+ */
+#define MBEDTLS_OID_MAX_COMPONENTS              128
+
 /*
  * Top level OID tuples
  */