Provided by: openssl_1.1.1-1ubuntu2.1~18.04.23_amd64 
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.
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
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.
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 an 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 2000-2018 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>.