$ openssl asn1parse -i < [EXTENSIONS]
    0:d=0  hl=2 l=  14 cons: SEQUENCE          
    2:d=1  hl=2 l=  12 cons:  SEQUENCE          
    4:d=2  hl=2 l=   3 prim:   OBJECT            :X509v3 Basic Constraints
    9:d=2  hl=2 l=   1 prim:   BOOLEAN           :255
   12:d=2  hl=2 l=   2 prim:   OCTET STRING      [HEX DUMP]:3000
-----BEGIN EXTENSIONS-----
MA4wDAYDVR0TAQH/BAIwAA==
-----END EXTENSIONS-----

$ openssl asn1parse -i < [BASIC CONSTRAINTS]
    0:d=0  hl=2 l=   0 cons: SEQUENCE          
-----BEGIN BASIC CONSTRAINTS-----
MAA=
-----END BASIC CONSTRAINTS-----