41 lines
1.4 KiB
Plaintext
41 lines
1.4 KiB
Plaintext
|
ASN1
|
||
|
|
====
|
||
|
|
|
||
|
|
Abstract Syntax Notation One (or ASN1) is a standard by ITU-T and ISO/IEC
|
||
|
|
and used as a description language for defining data structure in
|
||
|
|
an independent manner.
|
||
|
|
Any data described in ASN1 notation can be serialized (or encoded) and
|
||
|
|
de-serialized (or decoded) with well-defined encoding rules.
|
||
|
|
|
||
|
|
A combination of ASN1 compiler and ASN1 decoder library function will
|
||
|
|
provide a function interface for parsing encoded binary into specific
|
||
|
|
data structure:
|
||
|
|
1) define data structure in a text file (*.asn1)
|
||
|
|
2) define "action" routines for specific "tags" defined in (1)
|
||
|
|
3) generate bytecode as a C file (*.asn1.[ch]) from *.asn1 file
|
||
|
|
with ASN1 compiler (tools/asn1_compiler)
|
||
|
|
4) call a ASN1 decoder (asn1_ber_decoder()) with bytecode and data
|
||
|
|
|
||
|
|
Usage of ASN1 compiler
|
||
|
|
----------------------
|
||
|
|
asn1_compiler [-v] [-d] <grammar-file> <c-file> <hdr-file>
|
||
|
|
|
||
|
|
<grammar-file>: ASN1 input file
|
||
|
|
<c-file>: generated C file
|
||
|
|
<hdr-file>: generated include file
|
||
|
|
|
||
|
|
Usage of ASN1 decoder
|
||
|
|
---------------------
|
||
|
|
int asn1_ber_decoder(const struct asn1_decoder *decoder, void *context,
|
||
|
|
const unsigned char *data, size_t datalen);
|
||
|
|
|
||
|
|
@decoder: bytecode binary
|
||
|
|
@context: context for decoder
|
||
|
|
@data: data to be parsed
|
||
|
|
@datalen: size of data
|
||
|
|
|
||
|
|
|
||
|
|
As of writing this, ASN1 compiler and decoder are used to implement
|
||
|
|
X509 certificate parser, pcks7 message parser and RSA public key parser
|
||
|
|
for UEFI secure boot.
|