config - phpMan

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 applica-
tions 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 punctua-
tion 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 alterna-
tive 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 con-
figuration 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 sec-
tion 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, per-
form 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 com-
mands 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 equiv-
alent 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 com-
mand 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 com-
mand.

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 configu-
ration 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 vari-
ables but they may not be set to any value at all. If you just include the environ-
ment 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.