[openssl-users] ASN.1: Parsing a 'private' class

[Massimiliano Pala]

Hi all,

I am trying to parse a sequence that has, after an integer, a 'private' 
(xclass) item. I was wondering what is the right templates / macros to 
be able to generate the ASN1 functions with the usual macro. An example 
of the structure I have to parse (B64 - DER), is the following:

MGICAQOAFGZKq8/wIYS7Iueq6NuaC3ESPqUKMAkGBSsOAwIaBQAwCwYHKoZIzjgEAQUABC8wLQIVAJTJ6W2QjBIbVQdAtLbPO3y1wazHAhRsXivNO/Eg4GMEgcmEx8OgsIxGzQ==

[ you can paste it into http://www.lapo.it/asn1js/ to get useful info. ]

The field that is giving me issues is the 2nd field in the sequence - 
offest 5, length 20 (i.e., after SEQUENCE (2 bytes) + INTEGER (3 bytes) 
and then the 20bytes field that I want to parse). The type is 0x80 - 
context specific. By using the ASN1_get_object() function, I get the 
correct size (20), the tag (0), and the xclass (128). Now, how do I go 
in order to generate the useful ASN1 function with teh usual macros ? 
Here's an example (besides the second field) for what I am trying to do:

ASN1_SEQUENCE(TYPE) = {

     ASN1_SIMPLE(TYPE, field1, ASN1_INTEGER),

     XXXXXXX(TYPE, field2, YYYYY),                      <<-- What shall be used here ? What Macro ?

     ASN1_SEQUENCE_OF(TYPE, field3, ASN1_OBJECT),

     ASN1_SEQUENCE_OF(TYPE, field3, ASN1_OBJECT),

     ASN1_SIMPLE(TYPE, field3, ASN1_OCTET_STRING)       <<-- This might be wrong as well - just noticed it is a very

} ASN1_SEQUENCE_END(TYPE)                                    weird encoding (octet-string that encapsulates a sequence of integers)


Is there a way to have the macros do the work (e.g., shall I use other 
macros - template? - to define the field somehow) ? Or shall I just 
write my own d2i_ and i2d_ functions ?

Please let me know,

Cheers,
Max