CONFIG(5) OpenSSL CONFIG(5)NAMEconfig - 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 getenv() 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
In OpenSSL 0.9.8 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
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 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
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 ALSOx509(1), req(1), ca(1)1.0.1e 2013-02-11 CONFIG(5)
