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.
15 A configuration file is divided into a number of sections. Each section
16 starts with a line B<[ section_name ]> and ends when a new section is
17 started or end of file is reached. A section name can consist of
18 alphanumeric characters and underscores.
20 The first section of a configuration file is special and is referred
21 to as the B<default> section this is usually unnamed and is from the
22 start of file until the first named section. When a name is being looked up
23 it is first looked up in a named section (if any) and then the
26 The environment is mapped onto a section called B<ENV>.
28 Comments can be included by preceding them with the B<#> character
30 Each section in a configuration file consists of a number of name and
31 value pairs of the form B<name=value>
33 The B<name> string can contain any alphanumeric characters as well as
34 a few punctuation symbols such as B<.> B<,> B<;> and B<_>.
36 The B<value> string consists of the string following the B<=> character
37 until end of line with any leading and trailing white space removed.
39 The value string undergoes variable expansion. This can be done by
40 including the form B<$var> or B<${var}>: this will substitute the value
41 of the named variable in the current section. It is also possible to
42 substitute a value from another section using the syntax B<$section::name>
43 or B<${section::name}>. By using the form B<$ENV::name> environment
44 variables can be substituted. It is also possible to assign values to
45 environment variables by using the name B<ENV::name>, this will work
46 if the program looks up environment variables using the B<CONF> library
47 instead of calling B<getenv()> directly.
49 It is possible to escape certain characters by using any kind of quote
50 or the B<\> character. By making the last character of a line a B<\>
51 a B<value> string can be spread across multiple lines. In addition
52 the sequences B<\n>, B<\r>, B<\b> and B<\t> are recognized.
56 If a configuration file attempts to expand a variable that doesn't exist
57 then an error is flagged and the file will not load. This can happen
58 if an attempt is made to expand an environment variable that doesn't
59 exist. For example the default OpenSSL master configuration file used
60 the value of B<HOME> which may not be defined on non Unix systems.
62 This can be worked around by including a B<default> section to provide
63 a default value: then if the environment lookup fails the default value
64 will be used instead. For this to work properly the default value must
65 be defined earlier in the configuration file than the expansion. See
66 the B<EXAMPLES> section for an example of how to do this.
68 If the same variable exists in the same section then all but the last
69 value will be silently ignored. In certain circumstances such as with
70 DNs the same field may occur multiple times. This is usually worked
71 around by ignoring any characters before an initial B<.> e.g.
78 Here is a sample configuration file using some of the features
81 # This is the default section.
84 RANDFILE= ${ENV::HOME}/.rnd
85 configdir=$ENV::HOME/config
89 # We are now in section one.
91 # Quotes permit leading and trailing whitespace
92 any = " any variable name "
94 other = A string that can \
96 by including \\ characters
98 message = Hello World\n
102 greeting = $section_one::message
104 This next example shows how to expand environment variables safely.
106 Suppose you want a variable called B<tmpfile> to refer to a
107 temporary filename. The directory it is placed in can determined by
108 the the B<TEMP> or B<TMP> environment variables but they may not be
109 set to any value at all. If you just include the environment variable
110 names and the variable doesn't exist then this will cause an error when
111 an attempt is made to load the configuration file. By making use of the
112 default section both values can be looked up with B<TEMP> taking
113 priority and B</tmp> used if neither is defined:
116 # The above value is used if TMP isn't in the environment
118 # The above value is used if TEMP isn't in the environment
119 tmpfile=${ENV::TEMP}/tmp.filename
123 Currently there is no way to include characters using the octal B<\nnn>
124 form. Strings are all null terminated so nulls cannot form part of
127 The escaping isn't quite right: if you want to use sequences like B<\n>
128 you can't use any quote escaping on the same line.
130 Files are loaded in a single pass. This means that an variable expansion
131 will only work if the variables referenced are defined earlier in the
136 L<x509(1)|x509(1)>, L<req(1)|req(1)>, L<ca(1)|ca(1)>