185 lines
5.1 KiB
Text
185 lines
5.1 KiB
Text
=pod
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=head1 NAME
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asn1parse - ASN.1 parsing tool
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=head1 SYNOPSIS
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B<openssl> B<asn1parse>
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[B<-inform PEM|DER>]
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[B<-in filename>]
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[B<-out filename>]
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[B<-noout>]
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[B<-offset number>]
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[B<-length number>]
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[B<-i>]
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[B<-oid filename>]
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[B<-dump>]
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[B<-dlimit num>]
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[B<-strparse offset>]
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[B<-genstr string>]
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[B<-genconf file>]
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=head1 DESCRIPTION
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The B<asn1parse> command is a diagnostic utility that can parse ASN.1
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structures. It can also be used to extract data from ASN.1 formatted data.
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=head1 OPTIONS
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=over 4
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=item B<-inform> B<DER|PEM>
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the input format. B<DER> is binary format and B<PEM> (the default) is base64
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encoded.
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=item B<-in filename>
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the input file, default is standard input
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=item B<-out filename>
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output file to place the DER encoded data into. If this
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option is not present then no data will be output. This is most useful when
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combined with the B<-strparse> option.
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=item B<-noout>
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don't output the parsed version of the input file.
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=item B<-offset number>
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starting offset to begin parsing, default is start of file.
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=item B<-length number>
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number of bytes to parse, default is until end of file.
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=item B<-i>
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indents the output according to the "depth" of the structures.
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=item B<-oid filename>
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a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
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file is described in the NOTES section below.
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=item B<-dump>
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dump unknown data in hex format.
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=item B<-dlimit num>
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like B<-dump>, but only the first B<num> bytes are output.
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=item B<-strparse offset>
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parse the contents octets of the ASN.1 object starting at B<offset>. This
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option can be used multiple times to "drill down" into a nested structure.
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=item B<-genstr string>, B<-genconf file>
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generate encoded data based on B<string>, B<file> or both using
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L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)> format. If B<file> only is
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present then the string is obtained from the default section using the name
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B<asn1>. The encoded data is passed through the ASN1 parser and printed out as
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though it came from a file, the contents can thus be examined and written to a
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file using the B<out> option.
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=back
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=head2 OUTPUT
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The output will typically contain lines like this:
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0:d=0 hl=4 l= 681 cons: SEQUENCE
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.....
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229:d=3 hl=3 l= 141 prim: BIT STRING
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373:d=2 hl=3 l= 162 cons: cont [ 3 ]
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376:d=3 hl=3 l= 159 cons: SEQUENCE
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379:d=4 hl=2 l= 29 cons: SEQUENCE
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381:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Subject Key Identifier
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386:d=5 hl=2 l= 22 prim: OCTET STRING
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410:d=4 hl=2 l= 112 cons: SEQUENCE
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412:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Authority Key Identifier
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417:d=5 hl=2 l= 105 prim: OCTET STRING
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524:d=4 hl=2 l= 12 cons: SEQUENCE
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.....
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This example is part of a self signed certificate. Each line starts with the
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offset in decimal. B<d=XX> specifies the current depth. The depth is increased
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within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
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(tag and length octets) of the current type. B<l=XX> gives the length of
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the contents octets.
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The B<-i> option can be used to make the output more readable.
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Some knowledge of the ASN.1 structure is needed to interpret the output.
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In this example the BIT STRING at offset 229 is the certificate public key.
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The contents octets of this will contain the public key information. This can
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be examined using the option B<-strparse 229> to yield:
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0:d=0 hl=3 l= 137 cons: SEQUENCE
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3:d=1 hl=3 l= 129 prim: INTEGER :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
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135:d=1 hl=2 l= 3 prim: INTEGER :010001
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=head1 NOTES
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If an OID is not part of OpenSSL's internal table it will be represented in
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numerical form (for example 1.2.3.4). The file passed to the B<-oid> option
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allows additional OIDs to be included. Each line consists of three columns,
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the first column is the OID in numerical format and should be followed by white
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space. The second column is the "short name" which is a single word followed
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by white space. The final column is the rest of the line and is the
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"long name". B<asn1parse> displays the long name. Example:
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C<1.2.3.4 shortName A long name>
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=head1 EXAMPLES
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Parse a file:
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openssl asn1parse -in file.pem
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Parse a DER file:
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openssl asn1parse -inform DER -in file.der
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Generate a simple UTF8String:
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openssl asn1parse -genstr 'UTF8:Hello World'
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Generate and write out a UTF8String, don't print parsed output:
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openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
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Generate using a config file:
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openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
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Example config file:
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asn1=SEQUENCE:seq_sect
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[seq_sect]
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field1=BOOL:TRUE
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field2=EXP:0, UTF8:some random string
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=head1 BUGS
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There should be options to change the format of output lines. The output of some
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ASN.1 types is not well handled (if at all).
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=head1 SEE ALSO
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L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)>
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=cut
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