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Title "OPENSSL-ASN1PARSE 1" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
openssl-asn1parse - ASN.1 parsing command Header "SYNOPSIS" \fBopenssl asn1parse [-help] [-inform \s-1DER\s0|\s-1PEM\s0] [-in filename] [-out filename] [-noout] [-offset number] [-length number] [-i] [-oid filename] [-dump] [-dlimit num] [-strparse offset] [-genstr string] [-genconf file] [-strictpem] [-item name] Header "DESCRIPTION" This command is a diagnostic utility that can parse \s-1ASN.1\s0 structures. It can also be used to extract data from \s-1ASN.1\s0 formatted data. Header "OPTIONS" Item "-help" Print out a usage message. Item "-inform DER|PEM" The input format; the default is \s-1PEM\s0. See openssl-format-options\|(1) for details. Item "-in filename" The input file, default is standard input. Item "-out filename" Output file to place the \s-1DER\s0 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. Item "-noout" Don't output the parsed version of the input file. Item "-offset number" Starting offset to begin parsing, default is start of file. Item "-length number" Number of bytes to parse, default is until end of file. Item "-i" Indents the output according to the \*(L"depth\*(R" of the structures. Item "-oid filename" A file containing additional \s-1OBJECT\s0 IDENTIFIERs (OIDs). The format of this file is described in the \s-1NOTES\s0 section below. Item "-dump" Dump unknown data in hex format. Item "-dlimit num" Like -dump, but only the first num bytes are output. Item "-strparse offset" Parse the contents octets of the \s-1ASN.1\s0 object starting at offset. This option can be used multiple times to \*(L"drill down\*(R" into a nested structure. Item "-genstr string, -genconf file" Generate encoded data based on string, file or both using \fBASN1_generate_nconf\|(3) format. If file only is present then the string is obtained from the default section using the name \fBasn1. The encoded data is passed through the \s-1ASN1\s0 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. Item "-strictpem" If this option is used then -inform will be ignored. Without this option any data in a \s-1PEM\s0 format input file will be treated as being base64 encoded and processed whether it has the normal \s-1PEM BEGIN\s0 and \s-1END\s0 markers or not. This option will ignore any data prior to the start of the \s-1BEGIN\s0 marker, or after an \s-1END\s0 marker in a \s-1PEM\s0 file. Item "-item name" Attempt to decode and print the data as an \s-1ASN1_ITEM\s0 name. This can be used to print out the fields of any supported \s-1ASN.1\s0 structure if the type is known. Subsection "Output" The output will typically contain lines like this:

.Vb 1 0:d=0 hl=4 l= 681 cons: SEQUENCE .Ve

.....

.Vb 10 229: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 .Ve

.....

This example is part of a self-signed certificate. Each line starts with the offset in decimal. \*(C`d=XX\*(C' specifies the current depth. The depth is increased within the scope of any \s-1SET\s0 or \s-1SEQUENCE.\s0 \*(C`hl=XX\*(C' gives the header length (tag and length octets) of the current type. \*(C`l=XX\*(C' gives the length of the contents octets.

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

Some knowledge of the \s-1ASN.1\s0 structure is needed to interpret the output.

In this example the \s-1BIT STRING\s0 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 \*(C`-strparse 229\*(C' to yield:

.Vb 3 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 .Ve

Header "NOTES" If an \s-1OID\s0 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 \s-1OID\s0 in numerical format and should be followed by white space. The second column is the \*(L"short name\*(R" which is a single word followed by whitespace. The final column is the rest of the line and is the \*(L"long name\*(R". Example:

\f(CW\*(C`1.2.3.4 shortName A long name\*(C'

For any \s-1OID\s0 with an associated short and long name, this command will display the long name.

Header "EXAMPLES" Parse a file:

.Vb 1 openssl asn1parse -in file.pem .Ve

Parse a \s-1DER\s0 file:

.Vb 1 openssl asn1parse -inform DER -in file.der .Ve

Generate a simple UTF8String:

.Vb 1 openssl asn1parse -genstr \*(AqUTF8:Hello World\*(Aq .Ve

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

.Vb 1 openssl asn1parse -genstr \*(AqUTF8:Hello World\*(Aq -noout -out utf8.der .Ve

Generate using a config file:

.Vb 1 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der .Ve

Example config file:

.Vb 1 asn1=SEQUENCE:seq_sect \& [seq_sect] \& field1=BOOL:TRUE field2=EXP:0, UTF8:some random string .Ve

Header "BUGS" There should be options to change the format of output lines. The output of some \s-1ASN.1\s0 types is not well handled (if at all). Header "SEE ALSO" \fBopenssl\|(1), \fBASN1_generate_nconf\|(3) Header "COPYRIGHT" Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.