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.\" ========================================================================
.\"
.IX Title "ASN1PARSE 1"
.TH ASN1PARSE 1 "2019-12-20" "1.0.2u" "OpenSSL"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
openssl\-asn1parse,
asn1parse \- ASN.1 parsing tool
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fBopenssl\fR \fBasn1parse\fR
[\fB\-inform PEM|DER\fR]
[\fB\-in filename\fR]
[\fB\-out filename\fR]
[\fB\-noout\fR]
[\fB\-offset number\fR]
[\fB\-length number\fR]
[\fB\-i\fR]
[\fB\-oid filename\fR]
[\fB\-dump\fR]
[\fB\-dlimit num\fR]
[\fB\-strparse offset\fR]
[\fB\-genstr string\fR]
[\fB\-genconf file\fR]
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \fBasn1parse\fR 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.
.SH "OPTIONS"
.IX Header "OPTIONS"
.IP "\fB\-inform\fR \fBDER|PEM\fR" 4
.IX Item "-inform DER|PEM"
the input format. \fB\s-1DER\s0\fR is binary format and \fB\s-1PEM\s0\fR (the default) is base64
encoded.
.IP "\fB\-in filename\fR" 4
.IX Item "-in filename"
the input file, default is standard input
.IP "\fB\-out filename\fR" 4
.IX 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 \fB\-strparse\fR option.
.IP "\fB\-noout\fR" 4
.IX Item "-noout"
don't output the parsed version of the input file.
.IP "\fB\-offset number\fR" 4
.IX Item "-offset number"
starting offset to begin parsing, default is start of file.
.IP "\fB\-length number\fR" 4
.IX Item "-length number"
number of bytes to parse, default is until end of file.
.IP "\fB\-i\fR" 4
.IX Item "-i"
indents the output according to the \*(L"depth\*(R" of the structures.
.IP "\fB\-oid filename\fR" 4
.IX 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.
.IP "\fB\-dump\fR" 4
.IX Item "-dump"
dump unknown data in hex format.
.IP "\fB\-dlimit num\fR" 4
.IX Item "-dlimit num"
like \fB\-dump\fR, but only the first \fBnum\fR bytes are output.
.IP "\fB\-strparse offset\fR" 4
.IX Item "-strparse offset"
parse the contents octets of the \s-1ASN.1\s0 object starting at \fBoffset\fR. This
option can be used multiple times to \*(L"drill down\*(R" into a nested structure.
.IP "\fB\-genstr string\fR, \fB\-genconf file\fR" 4
.IX Item "-genstr string, -genconf file"
generate encoded data based on \fBstring\fR, \fBfile\fR or both using
\&\fBASN1_generate_nconf\fR\|(3) format. If \fBfile\fR only is
present then the string is obtained from the default section using the name
\&\fBasn1\fR. 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 \fBout\fR option.
.SS "\s-1OUTPUT\s0"
.IX Subsection "OUTPUT"
The output will typically contain lines like this:
.PP
.Vb 1
\&  0:d=0  hl=4 l= 681 cons: SEQUENCE
.Ve
.PP
\&.....
.PP
.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
.PP
\&.....
.PP
This example is part of a self signed certificate. Each line starts with the
offset in decimal. \fBd=XX\fR specifies the current depth. The depth is increased
within the scope of any \s-1SET\s0 or \s-1SEQUENCE.\s0 \fBhl=XX\fR gives the header length
(tag and length octets) of the current type. \fBl=XX\fR gives the length of
the contents octets.
.PP
The \fB\-i\fR option can be used to make the output more readable.
.PP
Some knowledge of the \s-1ASN.1\s0 structure is needed to interpret the output.
.PP
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 \fB\-strparse 229\fR to yield:
.PP
.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
.SH "NOTES"
.IX 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 \fB\-oid\fR 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 white space. The final column is the rest of the line and is the
\&\*(L"long name\*(R". \fBasn1parse\fR displays the long name. Example:
.PP
\&\f(CW\*(C`1.2.3.4	shortName	A long name\*(C'\fR
.SH "EXAMPLES"
.IX Header "EXAMPLES"
Parse a file:
.PP
.Vb 1
\& openssl asn1parse \-in file.pem
.Ve
.PP
Parse a \s-1DER\s0 file:
.PP
.Vb 1
\& openssl asn1parse \-inform DER \-in file.der
.Ve
.PP
Generate a simple UTF8String:
.PP
.Vb 1
\& openssl asn1parse \-genstr \*(AqUTF8:Hello World\*(Aq
.Ve
.PP
Generate and write out a UTF8String, don't print parsed output:
.PP
.Vb 1
\& openssl asn1parse \-genstr \*(AqUTF8:Hello World\*(Aq \-noout \-out utf8.der
.Ve
.PP
Generate using a config file:
.PP
.Vb 1
\& openssl asn1parse \-genconf asn1.cnf \-noout \-out asn1.der
.Ve
.PP
Example config file:
.PP
.Vb 1
\& asn1=SEQUENCE:seq_sect
\&
\& [seq_sect]
\&
\& field1=BOOL:TRUE
\& field2=EXP:0, UTF8:some random string
.Ve
.SH "BUGS"
.IX 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).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fBASN1_generate_nconf\fR\|(3)