asn1parse(1ssl)asn1parse(1ssl)NAMEasn1parse - ASN.1 parsing tool
SYNOPSIS
openssl asn1parse [-inform PEM|DER] [-in filename] [-out filename]
[-noout] [-offset number] [-length number] [-i] [-oid filename] [-str‐
parse offset]
OPTIONS
The input format. DER is binary format and PEM (the default) is base64
encoded. The input file, default is standard input 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 -str‐
parse option. Does not output the parsed version of the input file.
Starting offset to begin parsing, default is start of file. Number of
bytes to parse, default is until end of file. Indents the output
according to the depth of the structures. A file containing additional
object identifiers (OIDs). The format of this file is described in the
Notes section below. Parses the content octets of the ASN.1 object
starting at offset. This option can be used multiple times to drill
down into a nested structure.
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.
NOTES
If an OID is not part of OpenSSL's internal table it will be repre‐
sented 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. For example: 1.2.3.4 shortName A long name
RESTRICTIONS
There should be options to change the format of input lines. The output
of some ASN.1ssl types is not handled well.
EXAMPLES
The output will typically contain lines like these:
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. The d=XX specifies the current depth. The
depth is increased within the scope of any SET or SEQUENCE. The hl=XX
gives the header length (tag and length octets) of the current type.
The 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 out‐
put.
In this example the bit string at offset 229 is the certificate public
key. The content octets of this will contain the public key informa‐
tion. This can be examined by 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
:E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840
F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91
D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855
CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3
EE9E1158A56E4A6F47E5897 135:d=1 hl=2 l= 3 prim: INTEGER
:010001
asn1parse(1ssl)