5 asn1parse - ASN.1 parsing tool
9 B<openssl> B<asn1parse>
25 The B<asn1parse> command is a diagnostic utility that can parse ASN.1
26 structures. It can also be used to extract data from ASN.1 formatted data.
32 =item B<-inform> B<DER|PEM>
34 the input format. B<DER> is binary format and B<PEM> (the default) is base64
39 the input file, default is standard input
41 =item B<-out filename>
43 output file to place the DER encoded data into. If this
44 option is not present then no data will be output. This is most useful when
45 combined with the B<-strparse> option.
49 don't output the parsed version of the input file.
51 =item B<-offset number>
53 starting offset to begin parsing, default is start of file.
55 =item B<-length number>
57 number of bytes to parse, default is until end of file.
61 indents the output according to the "depth" of the structures.
63 =item B<-oid filename>
65 a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
66 file is described in the NOTES section below.
68 =item B<-strparse offset>
70 parse the contents octets of the ASN.1 object starting at B<offset>. This
71 option can be used multiple times to "drill down" into a nested structure.
73 =item B<-genstr string>, B<-genconf file>
75 generate encoded data based on B<string>, B<file> or both using
76 L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)> format. If B<file> only is
77 present then the string is obtained from the default section using the name
78 B<asn1>. The encoded data is passed through the ASN1 parser and printed out as
79 though it came from a file, the contents can thus be examined and written to a
80 file using the B<out> option.
84 If this option is used then B<-inform> will be ignored. Without this option any
85 data in a PEM format input file will be treated as being base64 encoded and
86 processed whether it has the normal PEM BEGIN and END markers or not. This
87 option will ignore any data prior to the start of the BEGIN marker, or after an
88 END marker in a PEM file.
94 The output will typically contain lines like this:
96 0:d=0 hl=4 l= 681 cons: SEQUENCE
100 229:d=3 hl=3 l= 141 prim: BIT STRING
101 373:d=2 hl=3 l= 162 cons: cont [ 3 ]
102 376:d=3 hl=3 l= 159 cons: SEQUENCE
103 379:d=4 hl=2 l= 29 cons: SEQUENCE
104 381:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Subject Key Identifier
105 386:d=5 hl=2 l= 22 prim: OCTET STRING
106 410:d=4 hl=2 l= 112 cons: SEQUENCE
107 412:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Authority Key Identifier
108 417:d=5 hl=2 l= 105 prim: OCTET STRING
109 524:d=4 hl=2 l= 12 cons: SEQUENCE
113 This example is part of a self signed certificate. Each line starts with the
114 offset in decimal. B<d=XX> specifies the current depth. The depth is increased
115 within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
116 (tag and length octets) of the current type. B<l=XX> gives the length of
119 The B<-i> option can be used to make the output more readable.
121 Some knowledge of the ASN.1 structure is needed to interpret the output.
123 In this example the BIT STRING at offset 229 is the certificate public key.
124 The contents octets of this will contain the public key information. This can
125 be examined using the option B<-strparse 229> to yield:
127 0:d=0 hl=3 l= 137 cons: SEQUENCE
128 3:d=1 hl=3 l= 129 prim: INTEGER :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
129 135:d=1 hl=2 l= 3 prim: INTEGER :010001
133 If an OID is not part of OpenSSL's internal table it will be represented in
134 numerical form (for example 1.2.3.4). The file passed to the B<-oid> option
135 allows additional OIDs to be included. Each line consists of three columns,
136 the first column is the OID in numerical format and should be followed by white
137 space. The second column is the "short name" which is a single word followed
138 by white space. The final column is the rest of the line and is the
139 "long name". B<asn1parse> displays the long name. Example:
141 C<1.2.3.4 shortName A long name>
147 openssl asn1parse -in file.pem
151 openssl asn1parse -inform DER -in file.der
153 Generate a simple UTF8String:
155 openssl asn1parse -genstr 'UTF8:Hello World'
157 Generate and write out a UTF8String, don't print parsed output:
159 openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
161 Generate using a config file:
163 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
167 asn1=SEQUENCE:seq_sect
172 field2=EXP:0, UTF8:some random string
177 There should be options to change the format of output lines. The output of some
178 ASN.1 types is not well handled (if at all).
182 L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)>