1=pod
2
3=head1 NAME
4
5asn1parse - ASN.1 parsing tool
6
7=head1 SYNOPSIS
8
9B<openssl> B<asn1parse>
10[B<-inform PEM|DER>]
11[B<-in filename>]
12[B<-out filename>]
13[B<-noout>]
14[B<-offset number>]
15[B<-length number>]
16[B<-i>]
17[B<-oid filename>]
18[B<-strparse offset>]
19[B<-genstr string>]
20[B<-genconf file>]
21
22=head1 DESCRIPTION
23
24The B<asn1parse> command is a diagnostic utility that can parse ASN.1
25structures. It can also be used to extract data from ASN.1 formatted data.
26
27=head1 OPTIONS
28
29=over 4
30
31=item B<-inform> B<DER|PEM>
32
33the input format. B<DER> is binary format and B<PEM> (the default) is base64
34encoded.
35
36=item B<-in filename>
37
38the input file, default is standard input
39
40=item B<-out filename>
41
42output file to place the DER encoded data into. If this
43option is not present then no data will be output. This is most useful when
44combined with the B<-strparse> option.
45
46=item B<-noout>
47
48don't output the parsed version of the input file.
49
50=item B<-offset number>
51
52starting offset to begin parsing, default is start of file.
53
54=item B<-length number>
55
56number of bytes to parse, default is until end of file.
57
58=item B<-i>
59
60indents the output according to the "depth" of the structures.
61
62=item B<-oid filename>
63
64a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
65file is described in the NOTES section below.
66
67=item B<-strparse offset>
68
69parse the contents octets of the ASN.1 object starting at B<offset>. This
70option can be used multiple times to "drill down" into a nested structure.
71
72=item B<-genstr string>, B<-genconf file>
73
74generate encoded data based on B<string>, B<file> or both using
75L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)> format. If B<file> only is
76present then the string is obtained from the default section using the name
77B<asn1>. The encoded data is passed through the ASN1 parser and printed out as
78though it came from a file, the contents can thus be examined and written to a
79file using the B<out> option.
80
81=back
82
83=head2 OUTPUT
84
85The output will typically contain lines like this:
86
87  0:d=0  hl=4 l= 681 cons: SEQUENCE
88
89.....
90
91  229:d=3  hl=3 l= 141 prim: BIT STRING
92  373:d=2  hl=3 l= 162 cons: cont [ 3 ]
93  376:d=3  hl=3 l= 159 cons: SEQUENCE
94  379:d=4  hl=2 l=  29 cons: SEQUENCE
95  381:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Identifier
96  386:d=5  hl=2 l=  22 prim: OCTET STRING
97  410:d=4  hl=2 l= 112 cons: SEQUENCE
98  412:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Identifier
99  417:d=5  hl=2 l= 105 prim: OCTET STRING
100  524:d=4  hl=2 l=  12 cons: SEQUENCE
101
102.....
103
104This example is part of a self signed certificate. Each line starts with the
105offset in decimal. B<d=XX> specifies the current depth. The depth is increased
106within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
107(tag and length octets) of the current type. B<l=XX> gives the length of
108the contents octets.
109
110The B<-i> option can be used to make the output more readable.
111
112Some knowledge of the ASN.1 structure is needed to interpret the output.
113
114In this example the BIT STRING at offset 229 is the certificate public key.
115The contents octets of this will contain the public key information. This can
116be examined using the option B<-strparse 229> to yield:
117
118    0:d=0  hl=3 l= 137 cons: SEQUENCE
119    3:d=1  hl=3 l= 129 prim: INTEGER           :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
120  135:d=1  hl=2 l=   3 prim: INTEGER           :010001
121
122=head1 NOTES
123
124If an OID is not part of OpenSSL's internal table it will be represented in
125numerical form (for example 1.2.3.4). The file passed to the B<-oid> option
126allows additional OIDs to be included. Each line consists of three columns,
127the first column is the OID in numerical format and should be followed by white
128space. The second column is the "short name" which is a single word followed
129by white space. The final column is the rest of the line and is the
130"long name". B<asn1parse> displays the long name. Example:
131
132C<1.2.3.4	shortName	A long name>
133
134=head1 EXAMPLES
135
136Parse a file:
137
138 openssl asn1parse -in file.pem
139
140Parse a DER file:
141
142 openssl asn1parse -inform DER -in file.der
143
144Generate a simple UTF8String:
145
146 openssl asn1parse -genstr 'UTF8:Hello World'
147
148Generate and write out a UTF8String, don't print parsed output:
149
150 openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
151
152Generate using a config file:
153
154 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
155
156Example config file:
157
158 asn1=SEQUENCE:seq_sect
159
160 [seq_sect]
161
162 field1=BOOL:TRUE
163 field2=EXP:0, UTF8:some random string
164
165
166=head1 BUGS
167
168There should be options to change the format of output lines. The output of some
169ASN.1 types is not well handled (if at all).
170
171=head1 SEE ALSO
172
173L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)>
174
175=cut
176