/usr/man/cat.1/asn1parse.1

ASN1PARSE(1)                 OpenSSL                 ASN1PARSE(1)

NAME

     openssl-asn1parse, 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

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ASN1PARSE(1)                 OpenSSL                 ASN1PARSE(1)

         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:

       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:

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ASN1PARSE(1)                 OpenSSL                 ASN1PARSE(1)

         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).

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ASN1PARSE(1)                 OpenSSL                 ASN1PARSE(1)

SEE ALSO

     ASN1_generate_nconf(3)

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See also openssl-asn1parse(1)