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
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 ...
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
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
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
should be a boolean string such as
on or
off. If the value is
on this attempt to enter FIPS mode. If the call fails or the library is
not FIPS capable then an error occurs.
For example:
alg_section = evp_settings
[evp_settings]
fips_mode = on
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
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 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".
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
openssl_x509(1),
openssl_req(1),
openssl_ca(1)