projects / J-u-boot.git / blame
| Commit | Line | Data |
|---|---|---|
| e2c04faf AT |
1 | ASN1 |
| 2 | ==== | |
| 3 | ||
| 4 | Abstract Syntax Notation One (or ASN1) is a standard by ITU-T and ISO/IEC | |
| 5 | and used as a description language for defining data structure in | |
| 6 | an independent manner. | |
| 7 | Any data described in ASN1 notation can be serialized (or encoded) and | |
| 8 | de-serialized (or decoded) with well-defined encoding rules. | |
| 9 | ||
| 10 | A combination of ASN1 compiler and ASN1 decoder library function will | |
| 11 | provide a function interface for parsing encoded binary into specific | |
| 12 | data structure: | |
| 13 | 1) define data structure in a text file (*.asn1) | |
| 14 | 2) define "action" routines for specific "tags" defined in (1) | |
| 15 | 3) generate bytecode as a C file (*.asn1.[ch]) from *.asn1 file | |
| 16 | with ASN1 compiler (tools/asn1_compiler) | |
| 17 | 4) call a ASN1 decoder (asn1_ber_decoder()) with bytecode and data | |
| 18 | ||
| 19 | Usage of ASN1 compiler | |
| 20 | ---------------------- | |
| 21 | asn1_compiler [-v] [-d] <grammar-file> <c-file> <hdr-file> | |
| 22 | ||
| 23 | <grammar-file>: ASN1 input file | |
| 24 | <c-file>: generated C file | |
| 25 | <hdr-file>: generated include file | |
| 26 | ||
| 27 | Usage of ASN1 decoder | |
| 28 | --------------------- | |
| 29 | int asn1_ber_decoder(const struct asn1_decoder *decoder, void *context, | |
| 30 | const unsigned char *data, size_t datalen); | |
| 31 | ||
| 32 | @decoder: bytecode binary | |
| 33 | @context: context for decoder | |
| 34 | @data: data to be parsed | |
| 35 | @datalen: size of data | |
| 36 | ||
| 37 | ||
| 38 | As of writing this, ASN1 compiler and decoder are used to implement | |
| 39 | X509 certificate parser, pcks7 message parser and RSA public key parser | |
| 40 | for UEFI secure boot. |