Codex

ASN1PARSE

Section: OpenSSL (1SSL)

Updated: 2015-01-08

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NAME

asn1parse - ASN.1 parsing tool

SYNOPSIS

openssl asn1parse [-inform PEM|DER] [-in filename] [-out filename] [-noout] [-offset number] [-length number] [-i] [-oid filename] [-dump] [-dlimit num] [-strparse offset] [-genstr string] [-genconf file]

DESCRIPTION

The asn1parse command is a diagnostic utility that can parse ASN.1 structures. It can also be used to extract data from ASN.1 formatted data.

OPTIONS

-inform DER|PEM
the input format. DER is binary format and PEM (the default) is base64 encoded.:
-in filename
the input file, default is standard input:
-out filename
output file to place the DER encoded data into. If this option is not present then no data will be output. This is most useful when combined with the -strparse option.:
-noout
don't output the parsed version of the input file.:
-offset number
starting offset to begin parsing, default is start of file.:
-length number
number of bytes to parse, default is until end of file.:
-i
indents the output according to the ``depth'' of the structures.:
-oid filename
a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this file is described in the NOTES section below.:
-dump
dump unknown data in hex format.:
-dlimit num
like -dump, but only the first num bytes are output.:
-strparse offset
parse the contents octets of the ASN.1 object starting at offset. This option can be used multiple times to ``drill down'' into a nested structure.:
-genstr string, -genconf file
generate encoded data based on string, file or both using ASN1_generate_nconf?(3) format. If file only is present then the string is obtained from the default section using the name asn1. The encoded data is passed through the ASN1 parser and printed out as though it came from a file, the contents can thus be examined and written to a file using the out option.:

OUTPUT

The output will typically contain lines like this:

.....

.....

This example is part of a self signed certificate. Each line starts with the offset in decimal. d=XX specifies the current depth. The depth is increased within the scope of any SET or SEQUENCE. hl=XX gives the header length (tag and length octets) of the current type. l=XX gives the length of the contents octets.

The -i option can be used to make the output more readable.

Some knowledge of the ASN.1 structure is needed to interpret the output.

In this example the BIT STRING at offset 229 is the certificate public key. The contents octets of this will contain the public key information. This can be examined using the option -strparse 229 to yield:

NOTES

If an OID is not part of OpenSSL's internal table it will be represented in numerical form (for example 1.2.3.4). The file passed to the -oid option allows additional OIDs to be included. Each line consists of three columns, the first column is the OID in numerical format and should be followed by white space. The second column is the ``short name which is a single word followed by white space. The final column is the rest of the line and is the ``long name. asn1parse displays the long name. Example:

       shortName A long name"

EXAMPLES

Parse a file:

Parse a DER file:

Generate a simple UTF8String:

Generate and write out a UTF8String, don't print parsed output:

Generate using a config file:

Example config file:

BUGS

There should be options to change the format of output lines. The output of some ASN.1 types is not well handled (if at all).

SEE ALSO

ASN1_generate_nconf?(3)


Index

NAME

SYNOPSIS

DESCRIPTION

OPTIONS

OUTPUT

NOTES

EXAMPLES

BUGS

SEE ALSO


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