6 config - OpenSSL CONF library configuration files
10 The OpenSSL CONF library can be used to read configuration files.
11 It is used for the OpenSSL master configuration file B<openssl.cnf>
12 and in a few other places like B<SPKAC> files and certificate extension
13 files for the B<x509> utility. OpenSSL applications can also use the
14 CONF library for their own purposes.
16 A configuration file is divided into a number of sections. Each section
17 starts with a line B<[ section_name ]> and ends when a new section is
18 started or end of file is reached. A section name can consist of
19 alphanumeric characters and underscores.
21 The first section of a configuration file is special and is referred
22 to as the B<default> section this is usually unnamed and is from the
23 start of file until the first named section. When a name is being looked up
24 it is first looked up in a named section (if any) and then the
27 The environment is mapped onto a section called B<ENV>.
29 Comments can be included by preceding them with the B<#> character
31 Each section in a configuration file consists of a number of name and
32 value pairs of the form B<name=value>
34 The B<name> string can contain any alphanumeric characters as well as
35 a few punctuation symbols such as B<.> B<,> B<;> and B<_>.
37 The B<value> string consists of the string following the B<=> character
38 until end of line with any leading and trailing white space removed.
40 The value string undergoes variable expansion. This can be done by
41 including the form B<$var> or B<${var}>: this will substitute the value
42 of the named variable in the current section. It is also possible to
43 substitute a value from another section using the syntax B<$section::name>
44 or B<${section::name}>. By using the form B<$ENV::name> environment
45 variables can be substituted. It is also possible to assign values to
46 environment variables by using the name B<ENV::name>, this will work
47 if the program looks up environment variables using the B<CONF> library
48 instead of calling B<getenv()> directly.
50 It is possible to escape certain characters by using any kind of quote
51 or the B<\> character. By making the last character of a line a B<\>
52 a B<value> string can be spread across multiple lines. In addition
53 the sequences B<\n>, B<\r>, B<\b> and B<\t> are recognized.
55 =head1 OPENSSL LIBRARY CONFIGURATION
57 In OpenSSL 0.9.7 and later applications can automatically configure certain
58 aspects of OpenSSL using the master OpenSSL configuration file, or optionally
59 an alternative configuration file. The B<openssl> utility includes this
60 functionality: any sub command uses the master OpenSSL configuration file
61 unless an option is used in the sub command to use an alternative configuration
64 To enable library configuration the default section needs to contain an
65 appropriate line which points to the main configuration section. The default
66 name is B<openssl_conf> which is used by the B<openssl> utility. Other
67 applications may use an alternative name such as B<myapplicaton_conf>.
69 The configuration section should consist of a set of name value pairs which
70 contain specific module configuration information. The B<name> represents
71 the name of the I<configuration module> the meaning of the B<value> is
72 module specific: it may, for example, represent a further configuration
73 section containing configuration module specific information. E.g.
75 openssl_conf = openssl_init
79 oid_section = new_oids
80 engines = engine_section
88 ... engine stuff here ...
90 Currently there are two supported configuration modules supported. One for
91 ASN1 objects another for ENGINE configuration.
93 =head2 ASN1 OBJECT CONFIGURATION MODULE
95 This module has the name B<oid_section>. The value of this variable points
96 to a section containing name value pairs of OIDs: the name is the OID short
97 and long name, the value is the numerical form of the OID. Although some of
98 the B<openssl> utility sub commands already have their own ASN1 OBJECT section
99 functionality not all do. By using the ASN1 OBJECT configuration module
100 B<all> the B<openssl> utility sub commands can see the new objects as well
101 as any compliant applications. For example:
105 some_new_oid = 1.2.3.4
106 some_other_oid = 1.2.3.5
108 =head2 ENGINE CONFIGURATION MODULE
114 If a configuration file attempts to expand a variable that doesn't exist
115 then an error is flagged and the file will not load. This can happen
116 if an attempt is made to expand an environment variable that doesn't
117 exist. For example in a previous version of OpenSSL the default OpenSSL
118 master configuration file used the value of B<HOME> which may not be
119 defined on non Unix systems and would cause an error.
121 This can be worked around by including a B<default> section to provide
122 a default value: then if the environment lookup fails the default value
123 will be used instead. For this to work properly the default value must
124 be defined earlier in the configuration file than the expansion. See
125 the B<EXAMPLES> section for an example of how to do this.
127 If the same variable exists in the same section then all but the last
128 value will be silently ignored. In certain circumstances such as with
129 DNs the same field may occur multiple times. This is usually worked
130 around by ignoring any characters before an initial B<.> e.g.
137 Here is a sample configuration file using some of the features
140 # This is the default section.
143 RANDFILE= ${ENV::HOME}/.rnd
144 configdir=$ENV::HOME/config
148 # We are now in section one.
150 # Quotes permit leading and trailing whitespace
151 any = " any variable name "
153 other = A string that can \
154 cover several lines \
155 by including \\ characters
157 message = Hello World\n
161 greeting = $section_one::message
163 This next example shows how to expand environment variables safely.
165 Suppose you want a variable called B<tmpfile> to refer to a
166 temporary filename. The directory it is placed in can determined by
167 the the B<TEMP> or B<TMP> environment variables but they may not be
168 set to any value at all. If you just include the environment variable
169 names and the variable doesn't exist then this will cause an error when
170 an attempt is made to load the configuration file. By making use of the
171 default section both values can be looked up with B<TEMP> taking
172 priority and B</tmp> used if neither is defined:
175 # The above value is used if TMP isn't in the environment
177 # The above value is used if TEMP isn't in the environment
178 tmpfile=${ENV::TEMP}/tmp.filename
182 Currently there is no way to include characters using the octal B<\nnn>
183 form. Strings are all null terminated so nulls cannot form part of
186 The escaping isn't quite right: if you want to use sequences like B<\n>
187 you can't use any quote escaping on the same line.
189 Files are loaded in a single pass. This means that an variable expansion
190 will only work if the variables referenced are defined earlier in the
195 L<x509(1)|x509(1)>, L<req(1)|req(1)>, L<ca(1)|ca(1)>