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
is usually unnamed and is 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
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 gtn( directly.
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.
OPENSSL LIBRARY CONFIGURATION
In OpenSSL 0.9.7 and later 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 myapplicaton_conf.
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.
openssl_conf = openssl_init
[openssl_init]
oid_section = new_oids
engines = engine_section
[new_oids]
... new oids here ...
[engine_section]
... engine stuff here ...
Currently there are two configuration modules. One for ASN1 objects another for ENGINE configuration.
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
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 informations 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
EGN_st_dfut_srn(
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
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 = $section_one::message
This next example shows how to expand environment variables safely.
Suppose you want a variable called tmpfile to refer to a temporary filename. The directory it is
placed in can determined by the the TEMP or TMP environment variables but they may not be set to any
value at all. If you just include the environment variable names and the variable doesn't exist then
this will cause an error when an attempt is made to load the configuration file. By making use of the
default section both values can be looked up with TEMP taking priority and /tmp used if neither is
defined:
TMP=/tmp
# The above value is used if TMP isn't in the environment
TEMP=$ENV::TMP
# The above value is used if TEMP isn't in the environment
tmpfile=${ENV::TEMP}/tmp.filename
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)
0.9.7l 2004-03-01 CONFIG(5)
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