1ASN1PARSE(1) OpenSSL ASN1PARSE(1)
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6 openssl-asn1parse, asn1parse - ASN.1 parsing tool
7
9 openssl asn1parse [-help] [-inform PEM|DER] [-in filename] [-out
10 filename] [-noout] [-offset number] [-length number] [-i] [-oid
11 filename] [-dump] [-dlimit num] [-strparse offset] [-genstr string]
12 [-genconf file] [-strictpem] [-item name]
13
15 The asn1parse command is a diagnostic utility that can parse ASN.1
16 structures. It can also be used to extract data from ASN.1 formatted
17 data.
18
20 -help
21 Print out a usage message.
22 -inform DER|PEM
24 The input format. DER is binary format and PEM (the default) is
25 base64 encoded.
26 -in filename
28 The input file, default is standard input.
29 -out filename
31 Output file to place the DER encoded data into. If this option is
32 not present then no data will be output. This is most useful when
33 combined with the -strparse option.
34 -noout
36 Don't output the parsed version of the input file.
37 -offset number
39 Starting offset to begin parsing, default is start of file.
40 -length number
42 Number of bytes to parse, default is until end of file.
43 -i Indents the output according to the "depth" of the structures.
45 -oid filename
47 A file containing additional OBJECT IDENTIFIERs (OIDs). The format
48 of this file is described in the NOTES section below.
49 -dump
51 Dump unknown data in hex format.
52 -dlimit num
54 Like -dump, but only the first num bytes are output.
55 -strparse offset
57 Parse the contents octets of the ASN.1 object starting at offset.
58 This option can be used multiple times to "drill down" into a
59 nested structure.
60 -genstr string, -genconf file
62 Generate encoded data based on string, file or both using
63 ASN1_generate_nconf(3) format. If file only is present then the
64 string is obtained from the default section using the name asn1.
65 The encoded data is passed through the ASN1 parser and printed out
66 as though it came from a file, the contents can thus be examined
67 and written to a file using the out option.
68 -strictpem
70 If this option is used then -inform will be ignored. Without this
71 option any data in a PEM format input file will be treated as being
72 base64 encoded and processed whether it has the normal PEM BEGIN
73 and END markers or not. This option will ignore any data prior to
74 the start of the BEGIN marker, or after an END marker in a PEM
75 file.
76 -item name
78 Attempt to decode and print the data as ASN1_ITEM name. This can be
79 used to print out the fields of any supported ASN.1 structure if
80 the type is known.
81 Output
83 The output will typically contain lines like this:
84 0:d=0 hl=4 l= 681 cons: SEQUENCE
86 .....
88 229:d=3 hl=3 l= 141 prim: BIT STRING
90 373:d=2 hl=3 l= 162 cons: cont [ 3 ]
91 376:d=3 hl=3 l= 159 cons: SEQUENCE
92 379:d=4 hl=2 l= 29 cons: SEQUENCE
93 381:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Subject Key Identifier
94 386:d=5 hl=2 l= 22 prim: OCTET STRING
95 410:d=4 hl=2 l= 112 cons: SEQUENCE
96 412:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Authority Key Identifier
97 417:d=5 hl=2 l= 105 prim: OCTET STRING
98 524:d=4 hl=2 l= 12 cons: SEQUENCE
99 .....
101 This example is part of a self-signed certificate. Each line starts
103 with the offset in decimal. d=XX specifies the current depth. The depth
104 is increased within the scope of any SET or SEQUENCE. hl=XX gives the
105 header length (tag and length octets) of the current type. l=XX gives
106 the length of the contents octets.
107 The -i option can be used to make the output more readable.
109 Some knowledge of the ASN.1 structure is needed to interpret the
111 output.
112 In this example the BIT STRING at offset 229 is the certificate public
114 key. The contents octets of this will contain the public key
115 information. This can be examined using the option -strparse 229 to
116 yield:
117 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
123 If an OID is not part of OpenSSL's internal table it will be
124 represented in numerical form (for example 1.2.3.4). The file passed to
125 the -oid option allows additional OIDs to be included. Each line
126 consists of three columns, the first column is the OID in numerical
127 format and should be followed by white space. The second column is the
128 "short name" which is a single word followed by white space. The final
129 column is the rest of the line and is the "long name". asn1parse
130 displays the long name. Example:
131 "1.2.3.4 shortName A long name"
133
135 Parse a file:
136 openssl asn1parse -in file.pem
138 Parse a DER file:
140 openssl asn1parse -inform DER -in file.der
142 Generate a simple UTF8String:
144 openssl asn1parse -genstr 'UTF8:Hello World'
146 Generate and write out a UTF8String, don't print parsed output:
148 openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
150 Generate using a config file:
152 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
154 Example config file:
156 asn1=SEQUENCE:seq_sect
158 [seq_sect]
160 field1=BOOL:TRUE
162 field2=EXP:0, UTF8:some random string
163
165 There should be options to change the format of output lines. The
166 output of some ASN.1 types is not well handled (if at all).
167
169 ASN1_generate_nconf(3)
170
172 Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
173 Licensed under the OpenSSL license (the "License"). You may not use
175 this file except in compliance with the License. You can obtain a copy
176 in the file LICENSE in the source distribution or at
177 <https://www.openssl.org/source/license.html>.
1781.1.1l 2021-09-15 ASN1PARSE(1)