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