5 config - OpenSSL CONF library configuration files
9 The OpenSSL CONF library can be used to read configuration files.
10 It is used for the OpenSSL master configuration file B<openssl.cnf>
11 and in a few other places like B<SPKAC> files and certificate extension
12 files for the B<x509> utility. OpenSSL applications can also use the
13 CONF library for their own purposes.
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 section is usually unnamed and spans 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 Other files can be included using the B<.include> directive followed
31 by a path. If the path points to a directory all files with
32 names ending with B<.cnf> or B<.conf> are included from the directory.
33 Recursive inclusion of directories from files in such directory is not
34 supported. That means the files in the included directory can also contain
35 B<.include> directives but only inclusion of regular files is supported
36 there. The inclusion of directories is not supported on systems without
39 It is strongly recommended to use absolute paths with the B<.include>
40 directive. Relative paths are evaluated based on the application current
41 working directory so unless the configuration file containing the
42 B<.include> directive is application specific the inclusion will not
45 There can be optional B<=> character and whitespace characters between
46 B<.include> directive and the path which can be useful in cases the
47 configuration file needs to be loaded by old OpenSSL versions which do
48 not support the B<.include> syntax. They would bail out with error
49 if the B<=> character is not present but with it they just ignore
52 Each section in a configuration file consists of a number of name and
53 value pairs of the form B<name=value>
55 The B<name> string can contain any alphanumeric characters as well as
56 a few punctuation symbols such as B<.> B<,> B<;> and B<_>.
58 The B<value> string consists of the string following the B<=> character
59 until end of line with any leading and trailing white space removed.
61 The value string undergoes variable expansion. This can be done by
62 including the form B<$var> or B<${var}>: this will substitute the value
63 of the named variable in the current section. It is also possible to
64 substitute a value from another section using the syntax B<$section::name>
65 or B<${section::name}>. By using the form B<$ENV::name> environment
66 variables can be substituted. It is also possible to assign values to
67 environment variables by using the name B<ENV::name>, this will work
68 if the program looks up environment variables using the B<CONF> library
69 instead of calling getenv() directly. The value string must not exceed 64k in
70 length after variable expansion. Otherwise an error will occur.
72 It is possible to escape certain characters by using any kind of quote
73 or the B<\> character. By making the last character of a line a B<\>
74 a B<value> string can be spread across multiple lines. In addition
75 the sequences B<\n>, B<\r>, B<\b> and B<\t> are recognized.
77 All expansion and escape rules as described above that apply to B<value>
78 also apply to the path of the B<.include> directive.
80 =head1 OPENSSL LIBRARY CONFIGURATION
82 Applications can automatically configure certain
83 aspects of OpenSSL using the master OpenSSL configuration file, or optionally
84 an alternative configuration file. The B<openssl> utility includes this
85 functionality: any sub command uses the master OpenSSL configuration file
86 unless an option is used in the sub command to use an alternative configuration
89 To enable library configuration the default section needs to contain an
90 appropriate line which points to the main configuration section. The default
91 name is B<openssl_conf> which is used by the B<openssl> utility. Other
92 applications may use an alternative name such as B<myapplication_conf>.
93 All library configuration lines appear in the default section at the start
94 of the configuration file.
96 The configuration section should consist of a set of name value pairs which
97 contain specific module configuration information. The B<name> represents
98 the name of the I<configuration module>. The meaning of the B<value> is
99 module specific: it may, for example, represent a further configuration
100 section containing configuration module specific information. E.g.:
102 # This must be in the default section
103 openssl_conf = openssl_init
107 oid_section = new_oids
108 engines = engine_section
112 ... new oids here ...
116 ... engine stuff here ...
118 The features of each configuration module are described below.
120 =head2 ASN1 Object Configuration Module
122 This module has the name B<oid_section>. The value of this variable points
123 to a section containing name value pairs of OIDs: the name is the OID short
124 and long name, the value is the numerical form of the OID. Although some of
125 the B<openssl> utility sub commands already have their own ASN1 OBJECT section
126 functionality not all do. By using the ASN1 OBJECT configuration module
127 B<all> the B<openssl> utility sub commands can see the new objects as well
128 as any compliant applications. For example:
132 some_new_oid = 1.2.3.4
133 some_other_oid = 1.2.3.5
135 It is also possible to set the value to the long name followed
136 by a comma and the numerical OID form. For example:
138 shortName = some object long name, 1.2.3.4
140 =head2 Engine Configuration Module
142 This ENGINE configuration module has the name B<engines>. The value of this
143 variable points to a section containing further ENGINE configuration
146 The section pointed to by B<engines> is a table of engine names (though see
147 B<engine_id> below) and further sections containing configuration information
148 specific to each ENGINE.
150 Each ENGINE specific section is used to set default algorithms, load
151 dynamic, perform initialization and send ctrls. The actual operation performed
152 depends on the I<command> name which is the name of the name value pair. The
153 currently supported commands are listed below.
159 # Configure ENGINE named "foo"
161 # Configure ENGINE named "bar"
165 ... foo ENGINE specific commands ...
168 ... "bar" ENGINE specific commands ...
170 The command B<engine_id> is used to give the ENGINE name. If used this
171 command must be first. For example:
174 # This would normally handle an ENGINE named "foo"
178 # Override default name and use "myfoo" instead.
181 The command B<dynamic_path> loads and adds an ENGINE from the given path. It
182 is equivalent to sending the ctrls B<SO_PATH> with the path argument followed
183 by B<LIST_ADD> with value 2 and B<LOAD> to the dynamic ENGINE. If this is
184 not the required behaviour then alternative ctrls can be sent directly
185 to the dynamic ENGINE using ctrl commands.
187 The command B<init> determines whether to initialize the ENGINE. If the value
188 is B<0> the ENGINE will not be initialized, if B<1> and attempt it made to
189 initialized the ENGINE immediately. If the B<init> command is not present
190 then an attempt will be made to initialize the ENGINE after all commands in
191 its section have been processed.
193 The command B<default_algorithms> sets the default algorithms an ENGINE will
194 supply using the functions ENGINE_set_default_string().
196 If the name matches none of the above command names it is assumed to be a
197 ctrl command which is sent to the ENGINE. The value of the command is the
198 argument to the ctrl command. If the value is the string B<EMPTY> then no
199 value is sent to the command.
206 # Configure ENGINE named "foo"
210 # Load engine from DSO
211 dynamic_path = /some/path/fooengine.so
212 # A foo specific ctrl.
213 some_ctrl = some_value
214 # Another ctrl that doesn't take a value.
216 # Supply all default algorithms
217 default_algorithms = ALL
219 =head2 EVP Configuration Module
221 This modules has the name B<alg_section> which points to a section containing
224 Currently the only algorithm command supported is B<fips_mode> whose
225 value can only be the boolean string B<off>. If B<fips_mode> is set to B<on>,
226 an error occurs as this library version is not FIPS capable.
228 =head2 SSL Configuration Module
230 This module has the name B<ssl_conf> which points to a section containing
233 Each line in the SSL configuration section contains the name of the
234 configuration and the section containing it.
236 Each configuration section consists of command value pairs for B<SSL_CONF>.
237 Each pair will be passed to a B<SSL_CTX> or B<SSL> structure if it calls
238 SSL_CTX_config() or SSL_config() with the appropriate configuration name.
240 Note: any characters before an initial dot in the configuration section are
241 ignored so the same command can be used multiple times.
249 server = server_section
253 RSA.Certificate = server-rsa.pem
254 ECDSA.Certificate = server-ecdsa.pem
257 The system default configuration with name B<system_default> if present will
258 be applied during any creation of the B<SSL_CTX> structure.
260 Example of a configuration with the system default:
265 system_default = system_default_sect
267 [system_default_sect]
268 MinProtocol = TLSv1.2
269 MinProtocol = DTLSv1.2
273 If a configuration file attempts to expand a variable that doesn't exist
274 then an error is flagged and the file will not load. This can happen
275 if an attempt is made to expand an environment variable that doesn't
276 exist. For example in a previous version of OpenSSL the default OpenSSL
277 master configuration file used the value of B<HOME> which may not be
278 defined on non Unix systems and would cause an error.
280 This can be worked around by including a B<default> section to provide
281 a default value: then if the environment lookup fails the default value
282 will be used instead. For this to work properly the default value must
283 be defined earlier in the configuration file than the expansion. See
284 the B<EXAMPLES> section for an example of how to do this.
286 If the same variable exists in the same section then all but the last
287 value will be silently ignored. In certain circumstances such as with
288 DNs the same field may occur multiple times. This is usually worked
289 around by ignoring any characters before an initial B<.> e.g.
296 Here is a sample configuration file using some of the features
299 # This is the default section.
302 RANDFILE= ${ENV::HOME}/.rnd
303 configdir=$ENV::HOME/config
307 # We are now in section one.
309 # Quotes permit leading and trailing whitespace
310 any = " any variable name "
312 other = A string that can \
313 cover several lines \
314 by including \\ characters
316 message = Hello World\n
320 greeting = $section_one::message
322 This next example shows how to expand environment variables safely.
324 Suppose you want a variable called B<tmpfile> to refer to a
325 temporary filename. The directory it is placed in can determined by
326 the B<TEMP> or B<TMP> environment variables but they may not be
327 set to any value at all. If you just include the environment variable
328 names and the variable doesn't exist then this will cause an error when
329 an attempt is made to load the configuration file. By making use of the
330 default section both values can be looked up with B<TEMP> taking
331 priority and B</tmp> used if neither is defined:
334 # The above value is used if TMP isn't in the environment
336 # The above value is used if TEMP isn't in the environment
337 tmpfile=${ENV::TEMP}/tmp.filename
339 Simple OpenSSL library configuration example to enter FIPS mode:
341 # Default appname: should match "appname" parameter (if any)
342 # supplied to CONF_modules_load_file et al.
343 openssl_conf = openssl_conf_section
345 [openssl_conf_section]
346 # Configuration module list
347 alg_section = evp_sect
350 # Set to "yes" to enter FIPS mode if supported
353 Note: in the above example you will get an error in non FIPS capable versions
356 Simple OpenSSL library configuration to make TLS 1.2 and DTLS 1.2 the
357 system-default minimum TLS and DTLS versions, respectively:
359 # Toplevel section for openssl (including libssl)
360 openssl_conf = default_conf_section
362 [default_conf_section]
363 # We only specify configuration for the "ssl module"
364 ssl_conf = ssl_section
367 system_default = system_default_section
369 [system_default_section]
370 MinProtocol = TLSv1.2
371 MinProtocol = DTLSv1.2
373 The minimum TLS protocol is applied to B<SSL_CTX> objects that are TLS-based,
374 and the minimum DTLS protocol to those are DTLS-based.
375 The same applies also to maximum versions set with B<MaxProtocol>.
377 More complex OpenSSL library configuration. Add OID and don't enter FIPS mode:
379 # Default appname: should match "appname" parameter (if any)
380 # supplied to CONF_modules_load_file et al.
381 openssl_conf = openssl_conf_section
383 [openssl_conf_section]
384 # Configuration module list
385 alg_section = evp_sect
386 oid_section = new_oids
389 # This will have no effect as FIPS mode is off by default.
390 # Set to "yes" to enter FIPS mode, if supported
394 # New OID, just short name
396 # New OID shortname and long name
397 newoid2 = New OID 2 long name, 1.2.3.4.2
399 The above examples can be used with any application supporting library
400 configuration if "openssl_conf" is modified to match the appropriate "appname".
402 For example if the second sample file above is saved to "example.cnf" then
405 OPENSSL_CONF=example.cnf openssl asn1parse -genstr OID:1.2.3.4.1
409 0:d=0 hl=2 l= 4 prim: OBJECT :newoid1
411 showing that the OID "newoid1" has been added as "1.2.3.4.1".
417 =item B<OPENSSL_CONF>
419 The path to the config file.
420 Ignored in set-user-ID and set-group-ID programs.
422 =item B<OPENSSL_ENGINES>
424 The path to the engines directory.
425 Ignored in set-user-ID and set-group-ID programs.
431 Currently there is no way to include characters using the octal B<\nnn>
432 form. Strings are all null terminated so nulls cannot form part of
435 The escaping isn't quite right: if you want to use sequences like B<\n>
436 you can't use any quote escaping on the same line.
438 Files are loaded in a single pass. This means that a variable expansion
439 will only work if the variables referenced are defined earlier in the
444 L<x509(1)>, L<req(1)>, L<ca(1)>
448 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
450 Licensed under the OpenSSL license (the "License"). You may not use
451 this file except in compliance with the License. You can obtain a copy
452 in the file LICENSE in the source distribution or at
453 L<https://www.openssl.org/source/license.html>.