asn1parse.pod revision 279265 
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<-dump>]
19[B<-dlimit num>]
20[B<-strparse offset>]
21[B<-genstr string>]
22[B<-genconf file>]
23
24=head1 DESCRIPTION
25
26The B<asn1parse> command is a diagnostic utility that can parse ASN.1
27structures. It can also be used to extract data from ASN.1 formatted data.
28
29=head1 OPTIONS
30
31=over 4
32
33=item B<-inform> B<DER|PEM>
34
35the input format. B<DER> is binary format and B<PEM> (the default) is base64
36encoded.
37
38=item B<-in filename>
39
40the input file, default is standard input
41
42=item B<-out filename>
43
44output file to place the DER encoded data into. If this
45option is not present then no data will be output. This is most useful when
46combined with the B<-strparse> option.
47
48=item B<-noout>
49
50don't output the parsed version of the input file.
51
52=item B<-offset number>
53
54starting offset to begin parsing, default is start of file.
55
56=item B<-length number>
57
58number of bytes to parse, default is until end of file.
59
60=item B<-i>
61
62indents the output according to the "depth" of the structures.
63
64=item B<-oid filename>
65
66a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
67file is described in the NOTES section below.
68
69=item B<-dump>
70
71dump unknown data in hex format.
72
73=item B<-dlimit num>
74
75like B<-dump>, but only the first B<num> bytes are output.
76
77=item B<-strparse offset>
78
79parse the contents octets of the ASN.1 object starting at B<offset>. This
80option can be used multiple times to "drill down" into a nested structure.
81
82=item B<-genstr string>, B<-genconf file>
83
84generate encoded data based on B<string>, B<file> or both using
85ASN1_generate_nconf() format. If B<file> only is present then the string
86is obtained from the default section using the name B<asn1>. The encoded
87data is passed through the ASN1 parser and printed out as though it came
88from a file, the contents can thus be examined and written to a file
89using the B<out> option. 
90
91=back
92
93=head2 OUTPUT
94
95The output will typically contain lines like this:
96
97  0:d=0  hl=4 l= 681 cons: SEQUENCE          
98
99.....
100
101  229:d=3  hl=3 l= 141 prim: BIT STRING        
102  373:d=2  hl=3 l= 162 cons: cont [ 3 ]        
103  376:d=3  hl=3 l= 159 cons: SEQUENCE          
104  379:d=4  hl=2 l=  29 cons: SEQUENCE          
105  381:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Subject Key Identifier
106  386:d=5  hl=2 l=  22 prim: OCTET STRING      
107  410:d=4  hl=2 l= 112 cons: SEQUENCE          
108  412:d=5  hl=2 l=   3 prim: OBJECT            :X509v3 Authority Key Identifier
109  417:d=5  hl=2 l= 105 prim: OCTET STRING      
110  524:d=4  hl=2 l=  12 cons: SEQUENCE          
111
112.....
113
114This example is part of a self signed certificate. Each line starts with the
115offset in decimal. B<d=XX> specifies the current depth. The depth is increased
116within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
117(tag and length octets) of the current type. B<l=XX> gives the length of
118the contents octets.
119
120The B<-i> option can be used to make the output more readable.
121
122Some knowledge of the ASN.1 structure is needed to interpret the output. 
123
124In this example the BIT STRING at offset 229 is the certificate public key.
125The contents octets of this will contain the public key information. This can
126be examined using the option B<-strparse 229> to yield:
127
128    0:d=0  hl=3 l= 137 cons: SEQUENCE          
129    3:d=1  hl=3 l= 129 prim: INTEGER           :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
130  135:d=1  hl=2 l=   3 prim: INTEGER           :010001
131
132=head1 NOTES
133
134If an OID is not part of OpenSSL's internal table it will be represented in
135numerical form (for example 1.2.3.4). The file passed to the B<-oid> option 
136allows additional OIDs to be included. Each line consists of three columns,
137the first column is the OID in numerical format and should be followed by white
138space. The second column is the "short name" which is a single word followed
139by white space. The final column is the rest of the line and is the
140"long name". B<asn1parse> displays the long name. Example:
141
142C<1.2.3.4	shortName	A long name>
143
144=head1 EXAMPLES
145
146Parse a file:
147
148 openssl asn1parse -in file.pem
149
150Parse a DER file:
151
152 openssl asn1parse -inform DER -in file.der
153
154Generate a simple UTF8String:
155
156 openssl asn1parse -genstr 'UTF8:Hello World'
157
158Generate and write out a UTF8String, don't print parsed output:
159
160 openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
161
162Generate using a config file:
163
164 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
165
166Example config file:
167
168 asn1=SEQUENCE:seq_sect
169
170 [seq_sect]
171
172 field1=BOOL:TRUE
173 field2=EXP:0, UTF8:some random string
174
175
176=head1 BUGS
177
178There should be options to change the format of output lines. The output of some
179ASN.1 types is not well handled (if at all).
180
181=cut
182