Hi all,
I actually figured it out, if anybody is curious about the solution for
parsing this CRYPTLIB signature envelope (in this case DSA) - write to
me directly, I will be happy to share the solution.
Cheers,
Max
On 8/29/15 6:56 PM, Massimiliano Pala wrote:
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
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