DESCRIPTIONThe 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.
-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.
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.
h1=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:
NOTESIf 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
RestrictionsThere should be options to change the format of input lines.
The output of some ASN.1 types is not well handled (if at all).