CONFIG(5) OpenSSL CONFIG(5)
NAME
config - OpenSSL CONF library configuration files
DESCRIPTION
The OpenSSL CONF library can be used to read configuration files. It
is used for the OpenSSL master configuration file openssl.cnf and in a
few other places like SPKAC files and certificate extension files for
the x509 utility. OpenSSL applications can also use the CONF library
for their own purposes.
A configuration file is divided into a number of sections. Each section
starts with a line [ section_name ] and ends when a new section is
started or end of file is reached. A section name can consist of
alphanumeric characters and underscores.
The first section of a configuration file is special and is referred to
as the default section. This section is usually unnamed and spans from
the start of file until the first named section. When a name is being
looked up it is first looked up in a named section (if any) and then
the default section.
The environment is mapped onto a section called ENV.
Comments can be included by preceding them with the # character
Other files can be included using the .include directive followed by a
path. If the path points to a directory all files with names ending
with .cnf or .conf are included from the directory. Recursive
inclusion of directories from files in such directory is not supported.
That means the files in the included directory can also contain
.include directives but only inclusion of regular files is supported
there. The inclusion of directories is not supported on systems without
POSIX IO support.
It is strongly recommended to use absolute paths with the .include
directive. Relative paths are evaluated based on the application
current working directory so unless the configuration file containing
the .include directive is application specific the inclusion will not
work as expected.
There can be optional = character and whitespace characters between
.include directive and the path which can be useful in cases the
configuration file needs to be loaded by old OpenSSL versions which do
not support the .include syntax. They would bail out with error if the
= character is not present but with it they just ignore the include.
Each section in a configuration file consists of a number of name and
value pairs of the form name=value
The name string can contain any alphanumeric characters as well as a
few punctuation symbols such as . , ; and _.
The value string consists of the string following the = character until
end of line with any leading and trailing white space removed.
The value string undergoes variable expansion. This can be done by
including the form $var or ${var}: this will substitute the value of
the named variable in the current section. It is also possible to
substitute a value from another section using the syntax $section::name
or ${section::name}. By using the form $ENV::name environment variables
can be substituted. It is also possible to assign values to environment
variables by using the name ENV::name, this will work if the program
looks up environment variables using the CONF library instead of
calling getenv() directly. The value string must not exceed 64k in
length after variable expansion. Otherwise an error will occur.
It is possible to escape certain characters by using any kind of quote
or the \ character. By making the last character of a line a \ a value
string can be spread across multiple lines. In addition the sequences
\n, \r, \b and \t are recognized.
All expansion and escape rules as described above that apply to value
also apply to the path of the .include directive.
OPENSSL LIBRARY CONFIGURATION
Applications can automatically configure certain aspects of OpenSSL
using the master OpenSSL configuration file, or optionally an
alternative configuration file. The openssl utility includes this
functionality: any sub command uses the master OpenSSL configuration
file unless an option is used in the sub command to use an alternative
configuration file.
To enable library configuration the default section needs to contain an
appropriate line which points to the main configuration section. The
default name is openssl_conf which is used by the openssl utility.
Other applications may use an alternative name such as
myapplication_conf. All library configuration lines appear in the
default section at the start of the configuration file.
The configuration section should consist of a set of name value pairs
which contain specific module configuration information. The name
represents the name of the configuration module. The meaning of the
value is module specific: it may, for example, represent a further
configuration section containing configuration module specific
information. E.g.:
# This must be in the default section
openssl_conf = openssl_init
[openssl_init]
oid_section = new_oids
engines = engine_section
[new_oids]
... new oids here ...
[engine_section]
... engine stuff here ...
The features of each configuration module are described below.
ASN1 Object Configuration Module
This module has the name oid_section. The value of this variable points
to a section containing name value pairs of OIDs: the name is the OID
short and long name, the value is the numerical form of the OID.
Although some of the openssl utility sub commands already have their
own ASN1 OBJECT section functionality not all do. By using the ASN1
OBJECT configuration module all the openssl utility sub commands can
see the new objects as well as any compliant applications. For example:
[new_oids]
some_new_oid = 1.2.3.4
some_other_oid = 1.2.3.5
It is also possible to set the value to the long name followed by a
comma and the numerical OID form. For example:
shortName = some object long name, 1.2.3.4
Engine Configuration Module
This ENGINE configuration module has the name engines. The value of
this variable points to a section containing further ENGINE
configuration information.
The section pointed to by engines is a table of engine names (though
see engine_id below) and further sections containing configuration
information specific to each ENGINE.
Each ENGINE specific section is used to set default algorithms, load
dynamic, perform initialization and send ctrls. The actual operation
performed depends on the command name which is the name of the name
value pair. The currently supported commands are listed below.
For example:
[engine_section]
# Configure ENGINE named "foo"
foo = foo_section
# Configure ENGINE named "bar"
bar = bar_section
[foo_section]
... foo ENGINE specific commands ...
[bar_section]
... "bar" ENGINE specific commands ...
The command engine_id is used to give the ENGINE name. If used this
command must be first. For example:
[engine_section]
# This would normally handle an ENGINE named "foo"
foo = foo_section
[foo_section]
# Override default name and use "myfoo" instead.
engine_id = myfoo
The command dynamic_path loads and adds an ENGINE from the given path.
It is equivalent to sending the ctrls SO_PATH with the path argument
followed by LIST_ADD with value 2 and LOAD to the dynamic ENGINE. If
this is not the required behaviour then alternative ctrls can be sent
directly to the dynamic ENGINE using ctrl commands.
The command init determines whether to initialize the ENGINE. If the
value is 0 the ENGINE will not be initialized, if 1 and attempt it made
to initialized the ENGINE immediately. If the init command is not
present then an attempt will be made to initialize the ENGINE after all
commands in its section have been processed.
The command default_algorithms sets the default algorithms an ENGINE
will supply using the functions ENGINE_set_default_string().
If the name matches none of the above command names it is assumed to be
a ctrl command which is sent to the ENGINE. The value of the command is
the argument to the ctrl command. If the value is the string EMPTY then
no value is sent to the command.
For example:
[engine_section]
# Configure ENGINE named "foo"
foo = foo_section
[foo_section]
# Load engine from DSO
dynamic_path = /some/path/fooengine.so
# A foo specific ctrl.
some_ctrl = some_value
# Another ctrl that doesn't take a value.
other_ctrl = EMPTY
# Supply all default algorithms
default_algorithms = ALL
EVP Configuration Module
This modules has the name alg_section which points to a section
containing algorithm commands.
Currently the only algorithm command supported is fips_mode whose value
can only be the boolean string off. If fips_mode is set to on, an error
occurs as this library version is not FIPS capable.
SSL Configuration Module
This module has the name ssl_conf which points to a section containing
SSL configurations.
Each line in the SSL configuration section contains the name of the
configuration and the section containing it.
Each configuration section consists of command value pairs for
SSL_CONF. Each pair will be passed to a SSL_CTX or SSL structure if it
calls SSL_CTX_config() or SSL_config() with the appropriate
configuration name.
Note: any characters before an initial dot in the configuration section
are ignored so the same command can be used multiple times.
For example:
ssl_conf = ssl_sect
[ssl_sect]
server = server_section
[server_section]
RSA.Certificate = server-rsa.pem
ECDSA.Certificate = server-ecdsa.pem
Ciphers = ALL:!RC4
The system default configuration with name system_default if present
will be applied during any creation of the SSL_CTX structure.
Example of a configuration with the system default:
ssl_conf = ssl_sect
[ssl_sect]
system_default = system_default_sect
[system_default_sect]
MinProtocol = TLSv1.2
MinProtocol = DTLSv1.2
NOTES
If a configuration file attempts to expand a variable that doesn't
exist then an error is flagged and the file will not load. This can
happen if an attempt is made to expand an environment variable that
doesn't exist. For example in a previous version of OpenSSL the default
OpenSSL master configuration file used the value of HOME which may not
be defined on non Unix systems and would cause an error.
This can be worked around by including a default section to provide a
default value: then if the environment lookup fails the default value
will be used instead. For this to work properly the default value must
be defined earlier in the configuration file than the expansion. See
the EXAMPLES section for an example of how to do this.
If the same variable exists in the same section then all but the last
value will be silently ignored. In certain circumstances such as with
DNs the same field may occur multiple times. This is usually worked
around by ignoring any characters before an initial . e.g.
1.OU="My first OU"
2.OU="My Second OU"
EXAMPLES
Here is a sample configuration file using some of the features
mentioned above.
# This is the default section.
HOME=/temp
RANDFILE= ${ENV::HOME}/.rnd
configdir=$ENV::HOME/config
[ section_one ]
# We are now in section one.
# Quotes permit leading and trailing whitespace
any = " any variable name "
other = A string that can \
cover several lines \
by including \\ characters
message = Hello World\n
[ section_two ]
greeting = $section_one::message
This next example shows how to expand environment variables safely.
Suppose you want a variable called tmpfile to refer to a temporary
filename. The directory it is placed in can determined by the TEMP or
TMP environment variables but they may not be set to any value at all.
If you just include the environment variable names and the variable
doesn't exist then this will cause an error when an attempt is made to
load the configuration file. By making use of the default section both
values can be looked up with TEMP taking priority and /tmp used if
neither is defined:
TMP=/tmp
# The above value is used if TMP isn't in the environment
TEMP=$ENV::TMP
# The above value is used if TEMP isn't in the environment
tmpfile=${ENV::TEMP}/tmp.filename
Simple OpenSSL library configuration example to enter FIPS mode:
# Default appname: should match "appname" parameter (if any)
# supplied to CONF_modules_load_file et al.
openssl_conf = openssl_conf_section
[openssl_conf_section]
# Configuration module list
alg_section = evp_sect
[evp_sect]
# Set to "yes" to enter FIPS mode if supported
fips_mode = yes
Note: in the above example you will get an error in non FIPS capable
versions of OpenSSL.
Simple OpenSSL library configuration to make TLS 1.2 and DTLS 1.2 the
system-default minimum TLS and DTLS versions, respectively:
# Toplevel section for openssl (including libssl)
openssl_conf = default_conf_section
[default_conf_section]
# We only specify configuration for the "ssl module"
ssl_conf = ssl_section
[ssl_section]
system_default = system_default_section
[system_default_section]
MinProtocol = TLSv1.2
MinProtocol = DTLSv1.2
The minimum TLS protocol is applied to SSL_CTX objects that are TLS-
based, and the minimum DTLS protocol to those are DTLS-based. The same
applies also to maximum versions set with MaxProtocol.
More complex OpenSSL library configuration. Add OID and don't enter
FIPS mode:
# Default appname: should match "appname" parameter (if any)
# supplied to CONF_modules_load_file et al.
openssl_conf = openssl_conf_section
[openssl_conf_section]
# Configuration module list
alg_section = evp_sect
oid_section = new_oids
[evp_sect]
# This will have no effect as FIPS mode is off by default.
# Set to "yes" to enter FIPS mode, if supported
fips_mode = no
[new_oids]
# New OID, just short name
newoid1 = 1.2.3.4.1
# New OID shortname and long name
newoid2 = New OID 2 long name, 1.2.3.4.2
The above examples can be used with any application supporting library
configuration if "openssl_conf" is modified to match the appropriate
"appname".
For example if the second sample file above is saved to "example.cnf"
then the command line:
OPENSSL_CONF=example.cnf openssl asn1parse -genstr OID:1.2.3.4.1
will output:
0:d=0 hl=2 l= 4 prim: OBJECT :newoid1
showing that the OID "newoid1" has been added as "1.2.3.4.1".
ENVIRONMENT
OPENSSL_CONF
The path to the config file. Ignored in set-user-ID and set-group-
ID programs.
OPENSSL_ENGINES
The path to the engines directory. Ignored in set-user-ID and set-
group-ID programs.
BUGS
Currently there is no way to include characters using the octal \nnn
form. Strings are all null terminated so nulls cannot form part of the
value.
The escaping isn't quite right: if you want to use sequences like \n
you can't use any quote escaping on the same line.
Files are loaded in a single pass. This means that a variable expansion
will only work if the variables referenced are defined earlier in the
file.
SEE ALSO
x509(1), req(1), ca(1)
COPYRIGHT
Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy
in the file LICENSE in the source distribution or at
<https://www.openssl.org/source/license.html>;.
1.1.1k 2021-03-25 CONFIG(5)
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