| 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. |