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       config - OpenSSL CONF library configuration files


       This page documents the syntax of OpenSSL configuration files, as parsed by NCONF_load(3)
       and related functions.  This format is used by many of the OpenSSL commands, and to
       initialize the libraries when used by any application.

       The first part describes the general syntax of the configuration files, and subsequent
       sections describe the semantics of individual modules. Other modules are described in
       fips_config(5) and x509v3_config(5).  The syntax for defining ASN.1 values is described in


       A configuration file is a series of lines.  Blank lines, and whitespace between the
       elements of a line, have no significance. A comment starts with a # character; the rest of
       the line is ignored. If the # is the first non-space character in a line, the entire line
       is ignored.

       Two directives can be used to control the parsing of configuration files: .include and

       For compatibility with older versions of OpenSSL, an equal sign after the directive will
       be ignored.  Older versions will treat it as an assignment, so care should be taken if the
       difference in semantics is important.

       A file can include other files using the include syntax:

         .include [=] pathname

       If pathname is a simple filename, that file is included directly at that point.  Included
       files can have .include statements that specify other files.  If pathname is a directory,
       all files within that directory that have a ".cnf" or ".conf" extension will be included.
       (This is only available on systems with POSIX IO support.)  Any sub-directories found
       inside the pathname are ignored.  Similarly, if a file is opened while scanning a
       directory, and that file has an .include directive that specifies a directory, that is
       also ignored.

       As a general rule, the pathname should be an absolute path; this can be enforced with the
       abspath and includedir pragmas, described below.  The environment variable
       OPENSSL_CONF_INCLUDE, if it exists, is prepended to all relative pathnames.  If the
       pathname is still relative, it is interpreted based on the current working directory.

       To require all file inclusions to name absolute paths, use the following directive:

        .pragma [=] abspath:value

       The default behavior, where the value is false or off, is to allow relative paths. To
       require all .include pathnames to be absolute paths, use a value of true or on.

       In these files, the dollar sign, $, is used to reference a variable, as described below.
       On some platforms, however, it is common to treat $ as a regular character in symbol
       names.  Supporting this behavior can be done with the following directive:

        .pragma [=] dollarid:value

       The default behavior, where the value is false or off, is to treat the dollarsign as
       indicating a variable name; "foo$bar" is interpreted as "foo" followed by the expansion of
       the variable "bar". If value is true or on, then "foo$bar" is a single seven-character
       name nad variable expansions must be specified using braces or parentheses.

        .pragma [=] includedir:value

       If a relative pathname is specified in the .include directive, and the
       OPENSSL_CONF_INCLUDE environment variable doesn't exist, then the value of the includedir
       pragma, if it exists, is prepended to the pathname.

       A configuration file is divided into a number of sections.  A section begins with the
       section name in square brackets, and ends when a new section starts, or at the end of the
       file.  The section name can consist of alphanumeric characters and underscores.
       Whitespace between the name and the brackets is removed.

       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 the current or
       named section, and then the default section if necessary.

       The environment is mapped onto a section called ENV.

       Within a section are a series of name/value assignments, described in more detail below.
       As a reminder, the square brackets shown in this example are required, not optional:

        [ section ]
        name1 = This is value1
        name2 = Another value
        [ newsection ]
        name1 = New value1
        name3 = Value 3

       The name can contain any alphanumeric characters as well as a few punctuation symbols such
       as . , ; and _.  Whitespace after the name and before the equal sign is ignored.

       If a name is repeated in the same section, then all but the last value are ignored. In
       certain circumstances, such as with Certificate DNs, the same field may occur multiple
       times.  In order to support this, commands like openssl-req(1) ignore any leading text
       that is preceded with a period. For example:

        1.OU = First OU
        2.OU = Second OU

       The value consists of the string following the = character until end of line with any
       leading and trailing whitespace removed.

       The value string undergoes variable expansion. The text $var or "${var}" inserts the value
       of the named variable from the current section.  To use a value from another section use
       $section::name or "${section::name}".  By using $ENV::name, the value of the specified
       environment variable will be substituted.

       Variables must be defined before their value is referenced, otherwise an error is flagged
       and the file will not load.  This can be worked around by specifying a default value in
       the default section before the variable is used.

       Any name/value settings in an ENV section are available to the configuration file, but are
       not propagated to the environment.

       It is an error if the value ends up longer than 64k.

       It is possible to escape certain characters by using a single ' or double " quote around
       the value, or using a backslash \ before 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.

       The expansion and escape rules as described above that apply to value also apply to the
       pathname of the .include directive.


       The sections below use the informal term module to refer to a part of the OpenSSL
       functionality. This is not the same as the formal term FIPS module, for example.

       The OpenSSL configuration looks up the value of openssl_conf in the default section and
       takes that as the name of a section that specifies how to configure any modules in the
       library. It is not an error to leave any module in its default configuration. An
       application can specify a different name by calling CONF_modules_load_file(), for example,

       OpenSSL also looks up the value of config_diagnostics.  If this exists and has a nonzero
       numeric value, any error suppressing flags passed to CONF_modules_load() will be ignored.
       This is useful for diagnosing misconfigurations but its use in production requires
       additional consideration.  With this option enabled, a configuration error will completely
       prevent access to a service.  Without this option and in the presence of a configuration
       error, access will be allowed but the desired configuration will not be used.

        # These must be in the default section
        config_diagnostics = 1
        openssl_conf = openssl_init

        oid_section = oids
        providers = providers
        alg_section = evp_properties
        ssl_conf = ssl_configuration
        engines = engines
        random = random

        ... new oids here ...

        ... provider stuff here ...

        ... EVP properties here ...

        ... SSL/TLS configuration properties here ...

        ... engine properties here ...

        ... random properties here ...

       The semantics of each module are described below. The phrase "in the initialization
       section" refers to the section identified by the openssl_conf or other name (given as
       openssl_init in the example above).  The examples below assume the configuration above is
       used to specify the individual sections.

   ASN.1 Object Identifier Configuration
       The name oid_section in the initialization section names the section containing name/value
       pairs of OID's.  The name is the short name; the value is an optional long name followed
       by a comma, and the numeric value.  While some OpenSSL commands have their own section for
       specifying OID's, this section makes them available to all commands and applications.

        shortName = a very long OID name,
        newoid1 =
        some_other_oid =

       If a full configuration with the above fragment is in the file example.cnf, then the
       following command line:

        OPENSSL_CONF=example.cnf openssl asn1parse -genstr OID:

       will output:

        0:d=0  hl=2 l=   4 prim: OBJECT            :newoid1

       showing that the OID "newoid1" has been added as "".

   Provider Configuration
       The name providers in the initialization section names the section containing
       cryptographic provider configuration. The name/value assignments in this section each name
       a provider, and point to the configuration section for that provider. The provider-
       specific section is used to specify how to load the module, activate it, and set other

       Within a provider section, the following names have meaning:

           This is used to specify an alternate name, overriding the default name specified in
           the list of providers.  For example:

            foo = foo_provider

            identity = my_fips_module

           Specifies the pathname of the module (typically a shared library) to load.

           If present, the module is activated. The value assigned to this name is not

       All parameters in the section as well as sub-sections are made available to the provider.

       Default provider and its activation

       If no providers are activated explicitly, the default one is activated implicitly.  See
       OSSL_PROVIDER-default(7) for more details.

       If you add a section explicitly activating any other provider(s), you most probably need
       to explicitly activate the default provider, otherwise it becomes unavailable in openssl.
       It may make the system remotely unavailable.

   EVP Configuration
       The name alg_section in the initialization section names the section containing
       algorithmic properties when using the EVP API.

       Within the algorithm properties section, the following names have meaning:

           The value may be anything that is acceptable as a property query string for

       fips_mode (deprecated)
           The value is a boolean that can be yes or no.  If the value is yes, this is exactly
           equivalent to:

            default_properties = fips=yes

           If the value is no, nothing happens. Using this name is deprecated, and if used, it
           must be the only name in the section.

   SSL Configuration
       The name ssl_conf in the initialization section names the section containing the list of
       SSL/TLS configurations.  As with the providers, each name in this section identifies a
       section with the configuration for that name. For example:

        server = server_tls_config
        client = client_tls_config
        system_default = tls_system_default

        ... configuration for SSL/TLS servers ...

        ... configuration for SSL/TLS clients ...

       The configuration name system_default has a special meaning.  If it exists, it is applied
       whenever an SSL_CTX object is created.  For example, to impose system-wide minimum TLS and
       DTLS protocol versions:

        MinProtocol = TLSv1.2
        MinProtocol = DTLSv1.2

       The minimum TLS protocol is applied to SSL_CTX objects that are TLS-based, and the minimum
       DTLS protocol to those are DTLS-based.  The same applies also to maximum versions set with

       Each configuration section consists of name/value pairs that are parsed by
       SSL_CONF_cmd(3), which will be called by SSL_CTX_config() or SSL_config(), appropriately.
       Note that any characters before an initial dot in the configuration section are ignored,
       so that the same command can be used multiple times. This probably is most useful for
       loading different key types, as shown here:

        RSA.Certificate = server-rsa.pem
        ECDSA.Certificate = server-ecdsa.pem

   Engine Configuration
       The name engines in the initialization section names the section containing the list of
       ENGINE configurations.  As with the providers, each name in this section identifies an
       engine with the configuration for that engine.  The engine-specific section is used to
       specify how to load the engine, activate it, and set other parameters.

       Within an engine section, the following names have meaning:

           This is used to specify an alternate name, overriding the default name specified in
           the list of engines. If present, it must be first.  For example:

            foo = foo_engine

            engine_id = myfoo

           This 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.

           This specifies whether to initialize the ENGINE. If the value is 0 the ENGINE will not
           be initialized, if the value is 1 an attempt is made to initialize 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.

           This sets the default algorithms an ENGINE will supply using the function

       All other names are taken to be the name of a ctrl command that is sent to the ENGINE, and
       the value is the argument passed with the command.  The special value EMPTY means no value
       is sent with the command.  For example:

        foo = foo_engine

        dynamic_path = /some/path/
        some_ctrl = some_value
        default_algorithms = ALL
        other_ctrl = EMPTY

   Random Configuration
       The name random in the initialization section names the section containing the random
       number generater settings.

       Within the random section, the following names have meaning:

           This is used to specify the random bit generator.  For example:

            random = CTR-DRBG

           The available random bit generators are:

           This specifies what cipher a CTR-DRBG random bit generator will use.  Other random bit
           generators ignore this name.  The default value is AES-256-CTR.

           This specifies what digest the HASH-DRBG or HMAC-DRBG random bit generators will use.
           Other random bit generators ignore this name.

           This sets the property query used when fetching the random bit generator and any
           underlying algorithms.

           This sets the randomness source that should be used.  By default SEED-SRC will be used
           outside of the FIPS provider.  The FIPS provider uses call backs to access the same
           randomness sources from outside the validated boundary.

           This sets the property query used when fetching the randomness source.


       This example shows how to use quoting and escaping.

        # This is the default section.
        HOME = /temp
        configdir = $ENV::HOME/config

        [ 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 example shows how to expand environment variables safely.  In this example, the
       variable tempfile is intended to refer to a temporary file, and the environment variable
       TEMP or TMP, if present, specify the directory where the file should be put.  Since the
       default section is checked if a variable does not exist, it is possible to set TMP to
       default to /tmp, and TEMP to default to TMP.

        # These two lines must be in the default section.
        TMP = /tmp
        TEMP = $ENV::TMP

        # This can be used anywhere
        tmpfile = ${ENV::TEMP}/tmp.filename

       This example shows how to enforce FIPS mode for the application sample.

        sample = fips_config

        alg_section = evp_properties

        default_properties = "fips=yes"


           The path to the config file, or the empty string for none.  Ignored in set-user-ID and
           set-group-ID programs.

           The path to the engines directory.  Ignored in set-user-ID and set-group-ID programs.

           The path to the directory with OpenSSL modules, such as providers.  Ignored in set-
           user-ID and set-group-ID programs.

           The optional path to prepend to all .include paths.


       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.

       The limit that only one directory can be opened and read at a time can be considered a bug
       and should be fixed.


       An undocumented API, NCONF_WIN32(), used a slightly different set of parsing rules there
       were intended to be tailored to the Microsoft Windows platform.  Specifically, the
       backslash character was not an escape character and could be used in pathnames, only the
       double-quote character was recognized, and comments began with a semi-colon.  This
       function was deprecated in OpenSSL 3.0; applications with configuration files using that
       syntax will have to be modified.


       openssl-x509(1), openssl-req(1), openssl-ca(1), openssl-fipsinstall(1),
       ASN1_generate_nconf(3), EVP_set_default_properties(3), CONF_modules_load(3),
       CONF_modules_load_file(3), fips_config(5), and x509v3_config(5).


       Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (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 <>.