doc/man7/fips_module.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

 fips_module - OpenSSL fips module guide

 =head1 SYNOPSIS

 See the individual manual pages for details.

 =head1 DESCRIPTION

 This guide details different ways that OpenSSL can be used in conjunction
 with the FIPS module. Which is the correct approach to use will depend on your
 own specific circumstances and what you are attempting to achieve.

 Note that the old functions FIPS_mode() and FIPS_mode_set() are no longer
 present so you must remove them from your application if you use them.

 Applications written to use the OpenSSL 3.0 FIPS module should not use any
 legacy APIs or features that avoid the FIPS module. Specifically this includes:

 =over 4

 =item *

 Low level cryptographic APIs (use the high level APIs, such as EVP, instead)

 =item *

 Engines

 =item *

 Any functions that create or modify custom "METHODS" (for example
 EVP_MD_meth_new(), EVP_CIPHER_meth_new(), EVP_PKEY_meth_new(), RSA_meth_new(),
 EC_KEY_METHOD_new(), etc.)

 =back

 All of the above APIs are deprecated in OpenSSL 3.0 - so a simple rule is to
 avoid using all deprecated functions. See L<migration_guide(7)> for a list of
 deprecated functions.

 =head2 Making all applications use the FIPS module by default

 One simple approach is to cause all applications that are using OpenSSL to only
 use the FIPS module for cryptographic algorithms by default.

 This approach can be done purely via configuration. As long as applications are
 built and linked against OpenSSL 3.0 and do not override the loading of the
 default config file or its settings then they can automatically start using the
 FIPS module without the need for any further code changes.

 To do this the default OpenSSL config file will have to be modified. The
 location of this config file will depend on the platform, and any options that
 were given during the build process. You can check the location of the config
 file by running this command:

     $ openssl version -d
     OPENSSLDIR: "/usr/local/ssl"

 Caution: Many Operating Systems install OpenSSL by default. It is a common error
 to not have the correct version of OpenSSL in your $PATH. Check that you are
 running an OpenSSL 3.0 version like this:

     $ openssl version -v
     OpenSSL 3.0.0-dev xx XXX xxxx (Library: OpenSSL 3.0.0-dev xx XXX xxxx)

 The B<OPENSSLDIR> value above gives the directory name for where the default
 config file is stored. So in this case the default config file will be called
 F</usr/local/ssl/openssl.cnf>.

 Edit the config file to add the following lines near the beginning:

     config_diagnostics = 1
     openssl_conf = openssl_init

     .include /usr/local/ssl/fipsmodule.cnf

     [openssl_init]
     providers = provider_sect

     [provider_sect]
     fips = fips_sect
     base = base_sect

     [base_sect]
     activate = 1

 Obviously the include file location above should match the path and name of the
 FIPS module config file that you installed earlier.
 See L<https://github.com/openssl/openssl/blob/master/README-FIPS.md>.

 For FIPS usage, it is recommended that the B<config_diagnostics> option is
 enabled to prevent accidental use of non-FIPS validated algorithms via broken
 or mistaken configuration.  See L<config(5)>.

 Any applications that use OpenSSL 3.0 and are started after these changes are
 made will start using only the FIPS module unless those applications take
 explicit steps to avoid this default behaviour. Note that this configuration
 also activates the "base" provider. The base provider does not include any
 cryptographic algorithms (and therefore does not impact the validation status of
 any cryptographic operations), but does include other supporting algorithms that
 may be required. It is designed to be used in conjunction with the FIPS module.

 This approach has the primary advantage that it is simple, and no code changes
 are required in applications in order to benefit from the FIPS module. There are
 some disadvantages to this approach:

 =over 4

 =item *

 You may not want all applications to use the FIPS module.

 It may be the case that some applications should and some should not use the
 FIPS module.

 =item *

 If applications take explicit steps to not load the default config file or
 set different settings.

 This method will not work for these cases.

 =item *

 The algorithms available in the FIPS module are a subset of the algorithms
 that are available in the default OpenSSL Provider.

 If any applications attempt to use any algorithms that are not present,
 then they will fail.

 =item *

 Usage of certain deprecated APIs avoids the use of the FIPS module.

 If any applications use those APIs then the FIPS module will not be used.

 =back

 =head2 Selectively making applications use the FIPS module by default

 A variation on the above approach is to do the same thing on an individual
 application basis. The default OpenSSL config file depends on the compiled in
 value for B<OPENSSLDIR> as described in the section above. However it is also
 possible to override the config file to be used via the B<OPENSSL_CONF>
 environment variable. For example the following, on Unix, will cause the
 application to be executed with a non-standard config file location:

     $ OPENSSL_CONF=/my/nondefault/openssl.cnf myapplication

 Using this mechanism you can control which config file is loaded (and hence
 whether the FIPS module is loaded) on an application by application basis.

 This removes the disadvantage listed above that you may not want all
 applications to use the FIPS module. All the other advantages and disadvantages
 still apply.

 =head2 Programmatically loading the FIPS module (default library context)

 Applications may choose to load the FIPS provider explicitly rather than relying
 on config to do this. The config file is still necessary in order to hold the
 FIPS module config data (such as its self test status and integrity data). But
 in this case we do not automatically activate the FIPS provider via that config
 file.

 To do things this way configure as per
 L</Making all applications use the FIPS module by default> above, but edit the
 F<fipsmodule.cnf> file to remove or comment out the line which says
 C<activate = 1> (note that setting this value to 0 is I<not> sufficient).
 This means all the required config information will be available to load the
 FIPS module, but it is not automatically loaded when the application starts. The
 FIPS provider can then be loaded programmatically like this:

     #include <openssl/provider.h>

     int main(void)
     {
         OSSL_PROVIDER *fips;
         OSSL_PROVIDER *base;

         fips = OSSL_PROVIDER_load(NULL, "fips");
         if (fips == NULL) {
             printf("Failed to load FIPS provider\n");
             exit(EXIT_FAILURE);
         }
         base = OSSL_PROVIDER_load(NULL, "base");
         if (base == NULL) {
             OSSL_PROVIDER_unload(fips);
             printf("Failed to load base provider\n");
             exit(EXIT_FAILURE);
         }

         /* Rest of application */

         OSSL_PROVIDER_unload(base);
         OSSL_PROVIDER_unload(fips);
         exit(EXIT_SUCCESS);
     }

 Note that this should be one of the first things that you do in your
 application. If any OpenSSL functions get called that require the use of
 cryptographic functions before this occurs then, if no provider has yet been
 loaded, then the default provider will be automatically loaded. If you then
 later explicitly load the FIPS provider then you will have both the FIPS and the
 default provider loaded at the same time. It is undefined which implementation
 of an algorithm will be used if multiple implementations are available and you
 have not explicitly specified via a property query (see below) which one should
 be used.

 Also note that in this example we have additionally loaded the "base" provider.
 This loads a sub-set of algorithms that are also available in the default
 provider - specifically non cryptographic ones which may be used in conjunction
 with the FIPS provider. For example this contains algorithms for encoding and
 decoding keys. If you decide not to load the default provider then you
 will usually want to load the base provider instead.

 In this example we are using the "default" library context. OpenSSL functions
 operate within the scope of a library context. If no library context is
 explicitly specified then the default library context is used. For further
 details about library contexts see the L<OSSL_LIB_CTX(3)> man page.

 =head2 Loading the FIPS module at the same time as other providers

 It is possible to have the FIPS provider and other providers (such as the
 default provider) all loaded at the same time into the same library context. You
 can use a property query string during algorithm fetches to specify which
 implementation you would like to use.

 For example to fetch an implementation of SHA256 which conforms to FIPS
 standards you can specify the property query C<fips=yes> like this:

     EVP_MD *sha256;

     sha256 = EVP_MD_fetch(NULL, "SHA2-256", "fips=yes");

 If no property query is specified, or more than one implementation matches the
 property query then it is undefined which implementation of a particular
 algorithm will be returned.

 This example shows an explicit request for an implementation of SHA256 from the
 default provider:

     EVP_MD *sha256;

     sha256 = EVP_MD_fetch(NULL, "SHA2-256", "provider=default");

 It is also possible to set a default property query string. The following
 example sets the default property query of C<fips=yes> for all fetches within
 the default library context:

     EVP_set_default_properties(NULL, "fips=yes");

 If a fetch function has both an explicit property query specified, and a
 default property query is defined then the two queries are merged together and
 both apply. The local property query overrides the default properties if the
 same property name is specified in both.

 There are two important built-in properties that you should be aware of:

 The "provider" property enables you to specify which provider you want an
 implementation to be fetched from, e.g. C<provider=default> or C<provider=fips>.
 All algorithms implemented in a provider have this property set on them.

 There is also the C<fips> property. All FIPS algorithms match against the
 property query C<fips=yes>. There are also some non-cryptographic algorithms
 available in the default and base providers that also have the C<fips=yes>
 property defined for them. These are the encoder and decoder algorithms that
 can (for example) be used to write out a key generated in the FIPS provider to a
 file. The encoder and decoder algorithms are not in the FIPS module itself but
 are allowed to be used in conjunction with the FIPS algorithms.

 It is possible to specify default properties within a config file. For example
 the following config file automatically loads the default and FIPS providers and
 sets the default property value to be C<fips=yes>. Note that this config file
 does not load the "base" provider. All supporting algorithms that are in "base"
 are also in "default", so it is unnecessary in this case:

     config_diagnostics = 1
     openssl_conf = openssl_init

     .include /usr/local/ssl/fipsmodule.cnf

     [openssl_init]
     providers = provider_sect
     alg_section = algorithm_sect

     [provider_sect]
     fips = fips_sect
     default = default_sect

     [default_sect]
     activate = 1

     [algorithm_sect]
     default_properties = fips=yes

 =head2 Programmatically loading the FIPS module (nondefault library context)

 In addition to using properties to separate usage of the FIPS module from other
 usages this can also be achieved using library contexts. In this example we
 create two library contexts. In one we assume the existence of a config file
 called F<openssl-fips.cnf> that automatically loads and configures the FIPS and
 base providers. The other library context will just use the default provider.

     OSSL_LIB_CTX *fips_libctx, *nonfips_libctx;
     OSSL_PROVIDER *defctxnull = NULL;
     EVP_MD *fipssha256 = NULL, *nonfipssha256 = NULL;
     int ret = 1;

     /*
      * Create two nondefault library contexts. One for fips usage and
      * one for non-fips usage
      */
     fips_libctx = OSSL_LIB_CTX_new();
     nonfips_libctx = OSSL_LIB_CTX_new();
     if (fips_libctx == NULL || nonfips_libctx == NULL)
         goto err;

     /* Prevent anything from using the default library context */
     defctxnull = OSSL_PROVIDER_load(NULL, "null");

     /*
      * Load config file for the FIPS library context. We assume that
      * this config file will automatically activate the FIPS and base
      * providers so we don't need to explicitly load them here.
      */
     if (!OSSL_LIB_CTX_load_config(fips_libctx, "openssl-fips.cnf"))
         goto err;

     /*
      * We don't need to do anything special to load the default
      * provider into nonfips_libctx. This happens automatically if no
      * other providers are loaded.
      * Because we don't call OSSL_LIB_CTX_load_config() explicitly for
      * nonfips_libctx it will just use the default config file.
      */

     /* As an example get some digests */

     /* Get a FIPS validated digest */
     fipssha256 = EVP_MD_fetch(fips_libctx, "SHA2-256", NULL);
     if (fipssha256 == NULL)
         goto err;

     /* Get a non-FIPS validated digest */
     nonfipssha256 = EVP_MD_fetch(nonfips_libctx, "SHA2-256", NULL);
     if (nonfipssha256 == NULL)
         goto err;

     /* Use the digests */

     printf("Success\n");
     ret = 0;

     err:
     EVP_MD_free(fipssha256);
     EVP_MD_free(nonfipssha256);
     OSSL_LIB_CTX_free(fips_libctx);
     OSSL_LIB_CTX_free(nonfips_libctx);
     OSSL_PROVIDER_unload(defctxnull);

     return ret;

 Note that we have made use of the special "null" provider here which we load
 into the default library context. We could have chosen to use the default
 library context for FIPS usage, and just create one additional library context
 for other usages - or vice versa. However if code has not been converted to use
 library contexts then the default library context will be automatically used.
 This could be the case for your own existing applications as well as certain
 parts of OpenSSL itself. Not all parts of OpenSSL are library context aware. If
 this happens then you could "accidentally" use the wrong library context for a
 particular operation. To be sure this doesn't happen you can load the "null"
 provider into the default library context. Because a provider has been
 explicitly loaded, the default provider will not automatically load. This means
 code using the default context by accident will fail because no algorithms will
 be available.

 See L<migration_guide(7)/Library Context> for additional information about the
 Library Context.

 =head2 Using Encoders and Decoders with the FIPS module

 Encoders and decoders are used to read and write keys or parameters from or to
 some external format (for example a PEM file). If your application generates
 keys or parameters that then need to be written into PEM or DER format
 then it is likely that you will need to use an encoder to do this. Similarly
 you need a decoder to read previously saved keys and parameters. In most cases
 this will be invisible to you if you are using APIs that existed in
 OpenSSL 1.1.1 or earlier such as L<i2d_PrivateKey(3)>. However the appropriate
 encoder/decoder will need to be available in the library context associated with
 the key or parameter object. The built-in OpenSSL encoders and decoders are
 implemented in both the default and base providers and are not in the FIPS
 module boundary. However since they are not cryptographic algorithms themselves
 it is still possible to use them in conjunction with the FIPS module, and
 therefore these encoders/decoders have the C<fips=yes> property against them.
 You should ensure that either the default or base provider is loaded into the
 library context in this case.

 =head2 Using the FIPS module in SSL/TLS

 Writing an application that uses libssl in conjunction with the FIPS module is
 much the same as writing a normal libssl application. If you are using global
 properties and the default library context to specify usage of FIPS validated
 algorithms then this will happen automatically for all cryptographic algorithms
 in libssl. If you are using a nondefault library context to load the FIPS
 provider then you can supply this to libssl using the function
 L<SSL_CTX_new_ex(3)>. This works as a drop in replacement for the function
 L<SSL_CTX_new(3)> except it provides you with the capability to specify the
 library context to be used. You can also use the same function to specify
 libssl specific properties to use.

 In this first example we create two SSL_CTX objects using two different library
 contexts.

     /*
      * We assume that a nondefault library context with the FIPS
      * provider loaded has been created called fips_libctx.
      */
     SSL_CTX *fips_ssl_ctx = SSL_CTX_new_ex(fips_libctx, NULL, TLS_method());
     /*
      * We assume that a nondefault library context with the default
      * provider loaded has been created called non_fips_libctx.
      */
     SSL_CTX *non_fips_ssl_ctx = SSL_CTX_new_ex(non_fips_libctx, NULL,
                                                TLS_method());

 In this second example we create two SSL_CTX objects using different properties
 to specify FIPS usage:

     /*
      * The "fips=yes" property includes all FIPS approved algorithms
      * as well as encoders from the default provider that are allowed
      * to be used. The NULL below indicates that we are using the
      * default library context.
      */
     SSL_CTX *fips_ssl_ctx = SSL_CTX_new_ex(NULL, "fips=yes", TLS_method());
     /*
      * The "provider!=fips" property allows algorithms from any
      * provider except the FIPS provider
      */
     SSL_CTX *non_fips_ssl_ctx = SSL_CTX_new_ex(NULL, "provider!=fips",
                                                TLS_method());

 =head2 Confirming that an algorithm is being provided by the FIPS module

 A chain of links needs to be followed to go from an algorithm instance to the
 provider that implements it. The process is similar for all algorithms. Here the
 example of a digest is used.

 To go from an B<EVP_MD_CTX> to an B<EVP_MD>, use L<EVP_MD_CTX_md(3)> .
 To go from the B<EVP_MD> to its B<OSSL_PROVIDER>,
 use L<EVP_MD_get0_provider(3)>.
 To extract the name from the B<OSSL_PROVIDER>, use
 L<OSSL_PROVIDER_get0_name(3)>.

 =head1 SEE ALSO

 L<migration_guide(7)>, L<crypto(7)>, L<fips_config(5)>

 =head1 COPYRIGHT

 Copyright 2021-2022 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
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

	fips_module - OpenSSL fips module guide

	=head1 SYNOPSIS

	See the individual manual pages for details.

	=head1 DESCRIPTION

	This guide details different ways that OpenSSL can be used in conjunction
	with the FIPS module. Which is the correct approach to use will depend on your
	own specific circumstances and what you are attempting to achieve.

	Note that the old functions FIPS_mode() and FIPS_mode_set() are no longer
	present so you must remove them from your application if you use them.

	Applications written to use the OpenSSL 3.0 FIPS module should not use any
	legacy APIs or features that avoid the FIPS module. Specifically this includes:

	=over 4

	=item *

	Low level cryptographic APIs (use the high level APIs, such as EVP, instead)

	=item *

	Engines

	=item *

	Any functions that create or modify custom "METHODS" (for example
	EVP_MD_meth_new(), EVP_CIPHER_meth_new(), EVP_PKEY_meth_new(), RSA_meth_new(),
	EC_KEY_METHOD_new(), etc.)

	=back

	All of the above APIs are deprecated in OpenSSL 3.0 - so a simple rule is to
	avoid using all deprecated functions. See L<migration_guide(7)> for a list of
	deprecated functions.

	=head2 Making all applications use the FIPS module by default

	One simple approach is to cause all applications that are using OpenSSL to only
	use the FIPS module for cryptographic algorithms by default.

	This approach can be done purely via configuration. As long as applications are
	built and linked against OpenSSL 3.0 and do not override the loading of the
	default config file or its settings then they can automatically start using the
	FIPS module without the need for any further code changes.

	To do this the default OpenSSL config file will have to be modified. The
	location of this config file will depend on the platform, and any options that
	were given during the build process. You can check the location of the config
	file by running this command:

	$ openssl version -d
	OPENSSLDIR: "/usr/local/ssl"

	Caution: Many Operating Systems install OpenSSL by default. It is a common error
	to not have the correct version of OpenSSL in your $PATH. Check that you are
	running an OpenSSL 3.0 version like this:

	$ openssl version -v
	OpenSSL 3.0.0-dev xx XXX xxxx (Library: OpenSSL 3.0.0-dev xx XXX xxxx)

	The B<OPENSSLDIR> value above gives the directory name for where the default
	config file is stored. So in this case the default config file will be called
	F</usr/local/ssl/openssl.cnf>.

	Edit the config file to add the following lines near the beginning:

	config_diagnostics = 1
	openssl_conf = openssl_init

	.include /usr/local/ssl/fipsmodule.cnf

	[openssl_init]
	providers = provider_sect

	[provider_sect]
	fips = fips_sect
	base = base_sect

	[base_sect]
	activate = 1

	Obviously the include file location above should match the path and name of the
	FIPS module config file that you installed earlier.
	See L<https://github.com/openssl/openssl/blob/master/README-FIPS.md>.

	For FIPS usage, it is recommended that the B<config_diagnostics> option is
	enabled to prevent accidental use of non-FIPS validated algorithms via broken
	or mistaken configuration. See L<config(5)>.

	Any applications that use OpenSSL 3.0 and are started after these changes are
	made will start using only the FIPS module unless those applications take
	explicit steps to avoid this default behaviour. Note that this configuration
	also activates the "base" provider. The base provider does not include any
	cryptographic algorithms (and therefore does not impact the validation status of
	any cryptographic operations), but does include other supporting algorithms that
	may be required. It is designed to be used in conjunction with the FIPS module.

	This approach has the primary advantage that it is simple, and no code changes
	are required in applications in order to benefit from the FIPS module. There are
	some disadvantages to this approach:

	=over 4

	=item *

	You may not want all applications to use the FIPS module.

	It may be the case that some applications should and some should not use the
	FIPS module.

	=item *

	If applications take explicit steps to not load the default config file or
	set different settings.

	This method will not work for these cases.

	=item *

	The algorithms available in the FIPS module are a subset of the algorithms
	that are available in the default OpenSSL Provider.

	If any applications attempt to use any algorithms that are not present,
	then they will fail.

	=item *

	Usage of certain deprecated APIs avoids the use of the FIPS module.

	If any applications use those APIs then the FIPS module will not be used.

	=back

	=head2 Selectively making applications use the FIPS module by default

	A variation on the above approach is to do the same thing on an individual
	application basis. The default OpenSSL config file depends on the compiled in
	value for B<OPENSSLDIR> as described in the section above. However it is also
	possible to override the config file to be used via the B<OPENSSL_CONF>
	environment variable. For example the following, on Unix, will cause the
	application to be executed with a non-standard config file location:

	$ OPENSSL_CONF=/my/nondefault/openssl.cnf myapplication

	Using this mechanism you can control which config file is loaded (and hence
	whether the FIPS module is loaded) on an application by application basis.

	This removes the disadvantage listed above that you may not want all
	applications to use the FIPS module. All the other advantages and disadvantages
	still apply.

	=head2 Programmatically loading the FIPS module (default library context)

	Applications may choose to load the FIPS provider explicitly rather than relying
	on config to do this. The config file is still necessary in order to hold the
	FIPS module config data (such as its self test status and integrity data). But
	in this case we do not automatically activate the FIPS provider via that config
	file.

	To do things this way configure as per
	L</Making all applications use the FIPS module by default> above, but edit the
	F<fipsmodule.cnf> file to remove or comment out the line which says
	C<activate = 1> (note that setting this value to 0 is I<not> sufficient).
	This means all the required config information will be available to load the
	FIPS module, but it is not automatically loaded when the application starts. The
	FIPS provider can then be loaded programmatically like this:

	#include <openssl/provider.h>

	int main(void)
	{
	OSSL_PROVIDER *fips;
	OSSL_PROVIDER *base;

	fips = OSSL_PROVIDER_load(NULL, "fips");
	if (fips == NULL) {
	printf("Failed to load FIPS provider\n");
	exit(EXIT_FAILURE);
	}
	base = OSSL_PROVIDER_load(NULL, "base");
	if (base == NULL) {
	OSSL_PROVIDER_unload(fips);
	printf("Failed to load base provider\n");
	exit(EXIT_FAILURE);
	}

	/* Rest of application */

	OSSL_PROVIDER_unload(base);
	OSSL_PROVIDER_unload(fips);
	exit(EXIT_SUCCESS);
	}

	Note that this should be one of the first things that you do in your
	application. If any OpenSSL functions get called that require the use of
	cryptographic functions before this occurs then, if no provider has yet been
	loaded, then the default provider will be automatically loaded. If you then
	later explicitly load the FIPS provider then you will have both the FIPS and the
	default provider loaded at the same time. It is undefined which implementation
	of an algorithm will be used if multiple implementations are available and you
	have not explicitly specified via a property query (see below) which one should
	be used.

	Also note that in this example we have additionally loaded the "base" provider.
	This loads a sub-set of algorithms that are also available in the default
	provider - specifically non cryptographic ones which may be used in conjunction
	with the FIPS provider. For example this contains algorithms for encoding and
	decoding keys. If you decide not to load the default provider then you
	will usually want to load the base provider instead.

	In this example we are using the "default" library context. OpenSSL functions
	operate within the scope of a library context. If no library context is
	explicitly specified then the default library context is used. For further
	details about library contexts see the L<OSSL_LIB_CTX(3)> man page.

	=head2 Loading the FIPS module at the same time as other providers

	It is possible to have the FIPS provider and other providers (such as the
	default provider) all loaded at the same time into the same library context. You
	can use a property query string during algorithm fetches to specify which
	implementation you would like to use.

	For example to fetch an implementation of SHA256 which conforms to FIPS
	standards you can specify the property query C<fips=yes> like this:

	EVP_MD *sha256;

	sha256 = EVP_MD_fetch(NULL, "SHA2-256", "fips=yes");

	If no property query is specified, or more than one implementation matches the
	property query then it is undefined which implementation of a particular
	algorithm will be returned.

	This example shows an explicit request for an implementation of SHA256 from the
	default provider:

	EVP_MD *sha256;

	sha256 = EVP_MD_fetch(NULL, "SHA2-256", "provider=default");

	It is also possible to set a default property query string. The following
	example sets the default property query of C<fips=yes> for all fetches within
	the default library context:

	EVP_set_default_properties(NULL, "fips=yes");

	If a fetch function has both an explicit property query specified, and a
	default property query is defined then the two queries are merged together and
	both apply. The local property query overrides the default properties if the
	same property name is specified in both.

	There are two important built-in properties that you should be aware of:

	The "provider" property enables you to specify which provider you want an
	implementation to be fetched from, e.g. C<provider=default> or C<provider=fips>.
	All algorithms implemented in a provider have this property set on them.

	There is also the C<fips> property. All FIPS algorithms match against the
	property query C<fips=yes>. There are also some non-cryptographic algorithms
	available in the default and base providers that also have the C<fips=yes>
	property defined for them. These are the encoder and decoder algorithms that
	can (for example) be used to write out a key generated in the FIPS provider to a
	file. The encoder and decoder algorithms are not in the FIPS module itself but
	are allowed to be used in conjunction with the FIPS algorithms.

	It is possible to specify default properties within a config file. For example
	the following config file automatically loads the default and FIPS providers and
	sets the default property value to be C<fips=yes>. Note that this config file
	does not load the "base" provider. All supporting algorithms that are in "base"
	are also in "default", so it is unnecessary in this case:

	config_diagnostics = 1
	openssl_conf = openssl_init

	.include /usr/local/ssl/fipsmodule.cnf

	[openssl_init]
	providers = provider_sect
	alg_section = algorithm_sect

	[provider_sect]
	fips = fips_sect
	default = default_sect

	[default_sect]
	activate = 1

	[algorithm_sect]
	default_properties = fips=yes

	=head2 Programmatically loading the FIPS module (nondefault library context)

	In addition to using properties to separate usage of the FIPS module from other
	usages this can also be achieved using library contexts. In this example we
	create two library contexts. In one we assume the existence of a config file
	called F<openssl-fips.cnf> that automatically loads and configures the FIPS and
	base providers. The other library context will just use the default provider.

	OSSL_LIB_CTX fips_libctx, nonfips_libctx;
	OSSL_PROVIDER *defctxnull = NULL;
	EVP_MD fipssha256 = NULL, nonfipssha256 = NULL;
	int ret = 1;

	/*
	* Create two nondefault library contexts. One for fips usage and
	* one for non-fips usage
	*/
	fips_libctx = OSSL_LIB_CTX_new();
	nonfips_libctx = OSSL_LIB_CTX_new();
	if (fips_libctx == NULL \|\| nonfips_libctx == NULL)
	goto err;

	/* Prevent anything from using the default library context */
	defctxnull = OSSL_PROVIDER_load(NULL, "null");

	/*
	* Load config file for the FIPS library context. We assume that
	* this config file will automatically activate the FIPS and base
	* providers so we don't need to explicitly load them here.
	*/
	if (!OSSL_LIB_CTX_load_config(fips_libctx, "openssl-fips.cnf"))
	goto err;

	/*
	* We don't need to do anything special to load the default
	* provider into nonfips_libctx. This happens automatically if no
	* other providers are loaded.
	* Because we don't call OSSL_LIB_CTX_load_config() explicitly for
	* nonfips_libctx it will just use the default config file.
	*/

	/* As an example get some digests */

	/* Get a FIPS validated digest */
	fipssha256 = EVP_MD_fetch(fips_libctx, "SHA2-256", NULL);
	if (fipssha256 == NULL)
	goto err;

	/* Get a non-FIPS validated digest */
	nonfipssha256 = EVP_MD_fetch(nonfips_libctx, "SHA2-256", NULL);
	if (nonfipssha256 == NULL)
	goto err;

	/* Use the digests */

	printf("Success\n");
	ret = 0;

	err:
	EVP_MD_free(fipssha256);
	EVP_MD_free(nonfipssha256);
	OSSL_LIB_CTX_free(fips_libctx);
	OSSL_LIB_CTX_free(nonfips_libctx);
	OSSL_PROVIDER_unload(defctxnull);

	return ret;

	Note that we have made use of the special "null" provider here which we load
	into the default library context. We could have chosen to use the default
	library context for FIPS usage, and just create one additional library context
	for other usages - or vice versa. However if code has not been converted to use
	library contexts then the default library context will be automatically used.
	This could be the case for your own existing applications as well as certain
	parts of OpenSSL itself. Not all parts of OpenSSL are library context aware. If
	this happens then you could "accidentally" use the wrong library context for a
	particular operation. To be sure this doesn't happen you can load the "null"
	provider into the default library context. Because a provider has been
	explicitly loaded, the default provider will not automatically load. This means
	code using the default context by accident will fail because no algorithms will
	be available.

	See L<migration_guide(7)/Library Context> for additional information about the
	Library Context.

	=head2 Using Encoders and Decoders with the FIPS module

	Encoders and decoders are used to read and write keys or parameters from or to
	some external format (for example a PEM file). If your application generates
	keys or parameters that then need to be written into PEM or DER format
	then it is likely that you will need to use an encoder to do this. Similarly
	you need a decoder to read previously saved keys and parameters. In most cases
	this will be invisible to you if you are using APIs that existed in
	OpenSSL 1.1.1 or earlier such as L<i2d_PrivateKey(3)>. However the appropriate
	encoder/decoder will need to be available in the library context associated with
	the key or parameter object. The built-in OpenSSL encoders and decoders are
	implemented in both the default and base providers and are not in the FIPS
	module boundary. However since they are not cryptographic algorithms themselves
	it is still possible to use them in conjunction with the FIPS module, and
	therefore these encoders/decoders have the C<fips=yes> property against them.
	You should ensure that either the default or base provider is loaded into the
	library context in this case.

	=head2 Using the FIPS module in SSL/TLS

	Writing an application that uses libssl in conjunction with the FIPS module is
	much the same as writing a normal libssl application. If you are using global
	properties and the default library context to specify usage of FIPS validated
	algorithms then this will happen automatically for all cryptographic algorithms
	in libssl. If you are using a nondefault library context to load the FIPS
	provider then you can supply this to libssl using the function
	L<SSL_CTX_new_ex(3)>. This works as a drop in replacement for the function
	L<SSL_CTX_new(3)> except it provides you with the capability to specify the
	library context to be used. You can also use the same function to specify
	libssl specific properties to use.

	In this first example we create two SSL_CTX objects using two different library
	contexts.

	/*
	* We assume that a nondefault library context with the FIPS
	* provider loaded has been created called fips_libctx.
	*/
	SSL_CTX *fips_ssl_ctx = SSL_CTX_new_ex(fips_libctx, NULL, TLS_method());
	/*
	* We assume that a nondefault library context with the default
	* provider loaded has been created called non_fips_libctx.
	*/
	SSL_CTX *non_fips_ssl_ctx = SSL_CTX_new_ex(non_fips_libctx, NULL,
	TLS_method());

	In this second example we create two SSL_CTX objects using different properties
	to specify FIPS usage:

	/*
	* The "fips=yes" property includes all FIPS approved algorithms
	* as well as encoders from the default provider that are allowed
	* to be used. The NULL below indicates that we are using the
	* default library context.
	*/
	SSL_CTX *fips_ssl_ctx = SSL_CTX_new_ex(NULL, "fips=yes", TLS_method());
	/*
	* The "provider!=fips" property allows algorithms from any
	* provider except the FIPS provider
	*/
	SSL_CTX *non_fips_ssl_ctx = SSL_CTX_new_ex(NULL, "provider!=fips",
	TLS_method());

	=head2 Confirming that an algorithm is being provided by the FIPS module

	A chain of links needs to be followed to go from an algorithm instance to the
	provider that implements it. The process is similar for all algorithms. Here the
	example of a digest is used.

	To go from an B<EVP_MD_CTX> to an B<EVP_MD>, use L<EVP_MD_CTX_md(3)> .
	To go from the B<EVP_MD> to its B<OSSL_PROVIDER>,
	use L<EVP_MD_get0_provider(3)>.
	To extract the name from the B<OSSL_PROVIDER>, use
	L<OSSL_PROVIDER_get0_name(3)>.

	=head1 SEE ALSO

	L<migration_guide(7)>, L<crypto(7)>, L<fips_config(5)>

	=head1 COPYRIGHT

	Copyright 2021-2022 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
	L<https://www.openssl.org/source/license.html>.

	=cut