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+=pod
+
+=head1 NAME
+
+asn1parse - ASN.1 parsing tool
+
+=head1 SYNOPSIS
+
+B<openssl> B<asn1parse>
+[B<-inform PEM|DER>]
+[B<-in filename>]
+[B<-out filename>]
+[B<-noout>]
+[B<-offset number>]
+[B<-length number>]
+[B<-i>]
+[B<-oid filename>]
+[B<-strparse offset>]
+
+=head1 DESCRIPTION
+
+The B<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.
+
+=head1 OPTIONS
+
+=over 4
+
+=item B<-inform> B<DER|PEM>
+
+the input format. B<DER> is binary format and B<PEM> (the default) is base64
+encoded.
+
+=item B<-in filename>
+
+the input file, default is standard input
+
+=item B<-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 B<-strparse> option.
+
+=item B<-noout>
+
+don't output the parsed version of the input file.
+
+=item B<-offset number>
+
+starting offset to begin parsing, default is start of file.
+
+=item B<-length number>
+
+number of bytes to parse, default is until end of file.
+
+=item B<-i>
+
+indents the output according to the "depth" of the structures.
+
+=item B<-oid filename>
+
+a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
+file is described in the NOTES section below.
+
+=item B<-strparse offset>
+
+parse the contents octets of the ASN.1 object starting at B<offset>. This
+option can be used multiple times to "drill down" into a nested structure.
+
+
+=back
+
+=head2 OUTPUT
+
+The output will typically contain lines like this:
+
+  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. B<d=XX> specifies the current depth. The depth is increased
+within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
+(tag and length octets) of the current type. B<l=XX> gives the length of
+the contents octets.
+
+The B<-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 B<-strparse 229> to yield:
+
+    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
+
+=head1 NOTES
+
+If 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 B<-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". B<asn1parse> displays the long name. Example:
+
+C<1.2.3.4	shortName	A long name>
+
+=head1 BUGS
+
+There should be options to change the format of input lines. The output of some
+ASN.1 types is not well handled (if at all).
+
+=cut