On Mon, Nov 22, 2010, john dodge wrote: > Hello > > I'm having a basic issue encoding a custom object. > > I would like the binary output of a new object I've created to appear in DER > encoded output as the following TLV > > 0x5F20 0x08 [8 bytes of value] > > I think this is implicit,application specific and primitive, so I have the > following new definitions > > #define > ASN1_EX_TYPE(ASN1_TFLG_APPLICATION_IMPLICIT, tag, stname, field, > type)ASN1_IMPLICIT_APPLICATION(stname, field, type, tag) > \#defineASN1_TFLG_APPLICATION_IMPLICIT ASN1_TFLG_IMPTAG|ASN1_TFLG_APPLICATION > > and I choose to declare my object as an ASN1_BIT_STRING like this > ASN1_IMPLICIT_APPLICATION(CUSTOMCERT > > I have checked that the length of the populated bit string internally is 8. > The > encoder/decoder and ASN1Parse run through OK. However the binary result I > actually get in DER format is this > > 0x5F20 0x09 0x03 [8 bytes of value] > > So I have an extra '0x03' which is presumably a V_ASN1_BIT_STRING tag, which > I > don't want. This pushes the length from 8 to 9 > > So how can I lose this extra encoded byte without confusing my encoder or > decoder ? I don't need to use an ASN1_BIT_STRING - anything that lets me > populate with 8 arbitrary bytes is fine. There may be a better way to achieve > the 0x5F20 tag than my guesses above. > > thanks in advance > > John_CINF, subject_customcert_id, ASN1_BIT_STRING, 0x20), >
When you encode a BIT STRING the first octet is automatically generated and parsed because it represents the number of unused bits. The length fields in the ASN1_BIT_STRING structure are modifed to reflect this. If the first octet doesn't reprsent the number of unused bits then you should use a more appropriate type such as an OCTET STRING instead. Steve. -- Dr Stephen N. Henson. OpenSSL project core developer. Commercial tech support now available see: http://www.openssl.org ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
