This document gives a brief description about ASN1 compiler as well as ASN1 decoder.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org --- doc/README.asn1 | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) create mode 100644 doc/README.asn1
diff --git a/doc/README.asn1 b/doc/README.asn1 new file mode 100644 index 000000000000..1359b93aef0b --- /dev/null +++ b/doc/README.asn1 @@ -0,0 +1,40 @@ +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.