5 asn1parse - ASN.1 parsing tool
9 B<openssl> B<asn1parse>
22 The B<asn1parse> command is a diagnostic utility that can parse ASN.1
23 structures. It can also be used to extract data from ASN.1 formatted data.
29 =item B<-inform> B<DER|PEM>
31 the input format. B<DER> is binary format and B<PEM> (the default) is base64
36 the input file, default is standard input
38 =item B<-out filename>
40 output file to place the DER encoded data into. If this
41 option is not present then no data will be output. This is most useful when
42 combined with the B<-strparse> option.
46 don't output the parsed version of the input file.
48 =item B<-offset number>
50 starting offset to begin parsing, default is start of file.
52 =item B<-length number>
54 number of bytes to parse, default is until end of file.
58 indents the output according to the "depth" of the structures.
60 =item B<-oid filename>
62 a file containing additional OBJECT IDENTIFIERs (OIDs). The format of this
63 file is described in the NOTES section below.
65 =item B<-strparse offset>
67 parse the contents octets of the ASN.1 object starting at B<offset>. This
68 option can be used multiple times to "drill down" into a nested structure.
75 The output will typically contain lines like this:
77 0:d=0 hl=4 l= 681 cons: SEQUENCE
81 229:d=3 hl=3 l= 141 prim: BIT STRING
82 373:d=2 hl=3 l= 162 cons: cont [ 3 ]
83 376:d=3 hl=3 l= 159 cons: SEQUENCE
84 379:d=4 hl=2 l= 29 cons: SEQUENCE
85 381:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Subject Key Identifier
86 386:d=5 hl=2 l= 22 prim: OCTET STRING
87 410:d=4 hl=2 l= 112 cons: SEQUENCE
88 412:d=5 hl=2 l= 3 prim: OBJECT :X509v3 Authority Key Identifier
89 417:d=5 hl=2 l= 105 prim: OCTET STRING
90 524:d=4 hl=2 l= 12 cons: SEQUENCE
94 This example is part of a self signed certificate. Each line starts with the
95 offset in decimal. B<d=XX> specifies the current depth. The depth is increased
96 within the scope of any SET or SEQUENCE. B<hl=XX> gives the header length
97 (tag and length octets) of the current type. B<l=XX> gives the length of
100 The B<-i> option can be used to make the output more readable.
102 Some knowledge of the ASN.1 structure is needed to interpret the output.
104 In this example the BIT STRING at offset 229 is the certificate public key.
105 The contents octets of this will contain the public key information. This can
106 be examined using the option B<-strparse 229> to yield:
108 0:d=0 hl=3 l= 137 cons: SEQUENCE
109 3:d=1 hl=3 l= 129 prim: INTEGER :E5D21E1F5C8D208EA7A2166C7FAF9F6BDF2059669C60876DDB70840F1A5AAFA59699FE471F379F1DD6A487E7D5409AB6A88D4A9746E24B91D8CF55DB3521015460C8EDE44EE8A4189F7A7BE77D6CD3A9AF2696F486855CF58BF0EDF2B4068058C7A947F52548DDF7E15E96B385F86422BEA9064A3EE9E1158A56E4A6F47E5897
110 135:d=1 hl=2 l= 3 prim: INTEGER :010001
114 If an OID is not part of OpenSSL's internal table it will be represented in
115 numerical form (for example 1.2.3.4). The file passed to the B<-oid> option
116 allows additional OIDs to be included. Each line consists of three columns,
117 the first column is the OID in numerical format and should be followed by white
118 space. The second column is the "short name" which is a single word followed
119 by white space. The final column is the rest of the line and is the
120 "long name". B<asn1parse> displays the long name. Example:
122 C<1.2.3.4 shortName A long name>
126 There should be options to change the format of input lines. The output of some
127 ASN.1 types is not well handled (if at all).