6 asn1parse - ASN.1 parsing tool
10 B<openssl> B<asn1parse>
27 The B<asn1parse> command is a diagnostic utility that can parse ASN.1
28 structures. It can also be used to extract data from ASN.1 formatted data.
34 =item B<-inform> B<DER|PEM>
36 the input format. B<DER> is binary format and B<PEM> (the default) is base64
41 the input file, default is standard input
43 =item B<-out filename>
45 output file to place the DER encoded data into. If this
46 option is not present then no data will be output. This is most useful when
47 combined with the B<-strparse> option.
51 don't output the parsed version of the input file.
53 =item B<-offset number>
55 starting offset to begin parsing, default is start of file.
57 =item B<-length number>
59 number of bytes to parse, default is until end of file.
63 indents the output according to the "depth" of the structures.
65 =item B<-oid filename>
67 a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
68 file is described in the NOTES section below.
72 dump unknown data in hex format.
76 like B<-dump>, but only the first B<num> bytes are output.
78 =item B<-strparse offset>
80 parse the contents octets of the ASN.1 object starting at B<offset>. This
81 option can be used multiple times to "drill down" into a nested structure.
83 =item B<-genstr string>, B<-genconf file>
85 generate encoded data based on B<string>, B<file> or both using
86 L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)> format. If B<file> only is
87 present then the string is obtained from the default section using the name
88 B<asn1>. The encoded data is passed through the ASN1 parser and printed out as
89 though it came from a file, the contents can thus be examined and written to a
90 file using the B<out> option.
96 The output will typically contain lines like this:
98 0:d=0 hl=4 l= 681 cons: SEQUENCE
102 229:d=3 hl=3 l= 141 prim: BIT STRING
103 373:d=2 hl=3 l= 162 cons: cont [ 3 ]
104 376:d=3 hl=3 l= 159 cons: SEQUENCE
105 379:d=4 hl=2 l= 29 cons: SEQUENCE
106 381:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Subject Key Identifier
107 386:d=5 hl=2 l= 22 prim: OCTET STRING
108 410:d=4 hl=2 l= 112 cons: SEQUENCE
109 412:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Authority Key Identifier
110 417:d=5 hl=2 l= 105 prim: OCTET STRING
111 524:d=4 hl=2 l= 12 cons: SEQUENCE
115 This example is part of a self signed certificate. Each line starts with the
116 offset in decimal. B<d=XX> specifies the current depth. The depth is increased
117 within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
118 (tag and length octets) of the current type. B<l=XX> gives the length of
121 The B<-i> option can be used to make the output more readable.
123 Some knowledge of the ASN.1 structure is needed to interpret the output.
125 In this example the BIT STRING at offset 229 is the certificate public key.
126 The contents octets of this will contain the public key information. This can
127 be examined using the option B<-strparse 229> to yield:
129 0:d=0 hl=3 l= 137 cons: SEQUENCE
130 3:d=1 hl=3 l= 129 prim: INTEGER :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
131 135:d=1 hl=2 l= 3 prim: INTEGER :010001
135 If an OID is not part of OpenSSL's internal table it will be represented in
136 numerical form (for example 1.2.3.4). The file passed to the B<-oid> option
137 allows additional OIDs to be included. Each line consists of three columns,
138 the first column is the OID in numerical format and should be followed by white
139 space. The second column is the "short name" which is a single word followed
140 by white space. The final column is the rest of the line and is the
141 "long name". B<asn1parse> displays the long name. Example:
143 C<1.2.3.4 shortName A long name>
149 openssl asn1parse -in file.pem
153 openssl asn1parse -inform DER -in file.der
155 Generate a simple UTF8String:
157 openssl asn1parse -genstr 'UTF8:Hello World'
159 Generate and write out a UTF8String, don't print parsed output:
161 openssl asn1parse -genstr 'UTF8:Hello World' -noout -out utf8.der
163 Generate using a config file:
165 openssl asn1parse -genconf asn1.cnf -noout -out asn1.der
169 asn1=SEQUENCE:seq_sect
174 field2=EXP:0, UTF8:some random string
179 There should be options to change the format of output lines. The output of some
180 ASN.1 types is not well handled (if at all).
184 L<ASN1_generate_nconf(3)|ASN1_generate_nconf(3)>