openssl-asn1parse

ASN1PARSE(1SSL)                     OpenSSL                    ASN1PARSE(1SSL)

NAME
       openssl-asn1parse, asn1parse - ASN.1 parsing tool

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

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
       -help
           Print out a usage message.

       -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.

       -strictpem
           If this option is used then -inform will be ignored. Without this
           option any data in a PEM format input file will be treated as being
           base64 encoded and processed whether it has the normal PEM BEGIN
           and END markers or not. This option will ignore any data prior to
           the start of the BEGIN marker, or after an END marker in a PEM
           file.

       -item name
           Attempt to decode and print the data as ASN1_ITEM name. This can be
           used to print out the fields of any supported ASN.1 structure if
           the type is known.

   Output
       The output will typically contain lines like this:

         0:d=0  hl=4 l= 681 cons: SEQUENCE

       .....

         229:d=3  hl=3 l= 141 prim: BIT STRING
         373:d=2  hl=3 l= 162 cons: cont [ 3 ]
         376:d=3  hl=3 l= 159 cons: SEQUENCE
         379:d=4  hl=2 l=  29 cons: SEQUENCE
         381:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Identifier
         386:d=5  hl=2 l=  22 prim: OCTET STRING
         410:d=4  hl=2 l= 112 cons: SEQUENCE
         412:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Identifier
         417:d=5  hl=2 l= 105 prim: OCTET STRING
         524:d=4  hl=2 l=  12 cons: SEQUENCE

       .....

       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:

           0:d=0  hl=3 l= 137 cons: SEQUENCE
           3:d=1  hl=3 l= 129 prim: INTEGER           :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
         135:d=1  hl=2 l=   3 prim: INTEGER           :010001

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:

       "1.2.3.4       shortName       A long name"

EXAMPLES
       Parse a file:

        openssl asn1parse -in file.pem

       Parse a DER file:

        openssl asn1parse -inform DER -in file.der

       Generate a simple UTF8String:

        openssl asn1parse -genstr 'UTF8:Hello World'

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

        openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der

       Generate using a config file:

        openssl asn1parse -genconf asn1.cnf -noout -out asn1.der

       Example config file:

        asn1=SEQUENCE:seq_sect

        [seq_sect]

        field1=BOOL:TRUE
        field2=EXP:0, UTF8:some random string

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)

COPYRIGHT
       Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the OpenSSL license (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.

1.1.1f                            2023-10-10                   ASN1PARSE(1SSL)