Add migration guide for 3.0

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14710)

8 files changed, 2273 insertions, 16 deletions

diff --git a/doc/build.info b/doc/build.info
index 02882af91e..f64919a7c4 100644
--- a/doc/build.info
+++ b/doc/build.info
@@ -4292,6 +4292,10 @@ DEPEND[html/man7/evp.html]=man7/evp.pod
 GENERATE[html/man7/evp.html]=man7/evp.pod
 DEPEND[man/man7/evp.7]=man7/evp.pod
 GENERATE[man/man7/evp.7]=man7/evp.pod
+DEPEND[html/man7/fips_module.html]=man7/fips_module.pod
+GENERATE[html/man7/fips_module.html]=man7/fips_module.pod
+DEPEND[man/man7/fips_module.7]=man7/fips_module.pod
+GENERATE[man/man7/fips_module.7]=man7/fips_module.pod
 DEPEND[html/man7/life_cycle-kdf.html]=man7/life_cycle-kdf.pod
 GENERATE[html/man7/life_cycle-kdf.html]=man7/life_cycle-kdf.pod
 DEPEND[man/man7/life_cycle-kdf.7]=man7/life_cycle-kdf.pod
@@ -4304,6 +4308,10 @@ DEPEND[html/man7/life_cycle-rand.html]=man7/life_cycle-rand.pod
 GENERATE[html/man7/life_cycle-rand.html]=man7/life_cycle-rand.pod
 DEPEND[man/man7/life_cycle-rand.7]=man7/life_cycle-rand.pod
 GENERATE[man/man7/life_cycle-rand.7]=man7/life_cycle-rand.pod
+DEPEND[html/man7/migration_guide.html]=man7/migration_guide.pod
+GENERATE[html/man7/migration_guide.html]=man7/migration_guide.pod
+DEPEND[man/man7/migration_guide.7]=man7/migration_guide.pod
+GENERATE[man/man7/migration_guide.7]=man7/migration_guide.pod
 DEPEND[html/man7/openssl-core.h.html]=man7/openssl-core.h.pod
 GENERATE[html/man7/openssl-core.h.html]=man7/openssl-core.h.pod
 DEPEND[man/man7/openssl-core.h.7]=man7/openssl-core.h.pod
@@ -4496,9 +4504,11 @@ html/man7/crypto.html \
 html/man7/ct.html \
 html/man7/des_modes.html \
 html/man7/evp.html \
+html/man7/fips_module.html \
 html/man7/life_cycle-kdf.html \
 html/man7/life_cycle-mac.html \
 html/man7/life_cycle-rand.html \
+html/man7/migration_guide.html \
 html/man7/openssl-core.h.html \
 html/man7/openssl-core_dispatch.h.html \
 html/man7/openssl-core_names.h.html \
@@ -4599,9 +4609,11 @@ man/man7/crypto.7 \
 man/man7/ct.7 \
 man/man7/des_modes.7 \
 man/man7/evp.7 \
+man/man7/fips_module.7 \
 man/man7/life_cycle-kdf.7 \
 man/man7/life_cycle-mac.7 \
 man/man7/life_cycle-rand.7 \
+man/man7/migration_guide.7 \
 man/man7/openssl-core.h.7 \
 man/man7/openssl-core_dispatch.h.7 \
 man/man7/openssl-core_names.h.7 \
diff --git a/doc/man3/DH_size.pod b/doc/man3/DH_size.pod
index cb30b27ff5..e4b7e429a0 100644
--- a/doc/man3/DH_size.pod
+++ b/doc/man3/DH_size.pod
@@ -9,26 +9,26 @@ security bits
 
  #include <openssl/dh.h>
 
- int DH_bits(const DH *dh);
-
 Deprecated since OpenSSL 3.0, can be hidden entirely by defining
 B<OPENSSL_API_COMPAT> with a suitable version value, see
 L<openssl_user_macros(7)>:
 
+ int DH_bits(const DH *dh);
+
  int DH_size(const DH *dh);
 
  int DH_security_bits(const DH *dh);
 
 =head1 DESCRIPTION
 
+The functions described on this page are deprecated.
+Applications should instead use L<EVP_PKEY_bits(3)>,
+L<EVP_PKEY_security_bits(3)> and L<EVP_PKEY_size(3)>.
+
 DH_bits() returns the number of significant bits.
 
 B<dh> and B<dh-E<gt>p> must not be B<NULL>.
 
-The remaining functions described on this page are deprecated.
-Applications should instead use L<EVP_PKEY_security_bits(3)> and
-L<EVP_PKEY_size(3)>.
-
 DH_size() returns the Diffie-Hellman prime size in bytes. It can be used
 to determine how much memory must be allocated for the shared secret
 computed by L<DH_compute_key(3)>.
@@ -55,9 +55,7 @@ L<BN_num_bits(3)>
 
 =head1 HISTORY
 
-The DH_size() and DH_security_bits() functions were deprecated in OpenSSL 3.0.
-
-The DH_bits() function was added in OpenSSL 1.1.0.
+All functions were deprecated in OpenSSL 3.0.
 
 =head1 COPYRIGHT
 
diff --git a/doc/man3/PEM_read_CMS.pod b/doc/man3/PEM_read_CMS.pod
index 6c24c437e5..4024b3219c 100644
--- a/doc/man3/PEM_read_CMS.pod
+++ b/doc/man3/PEM_read_CMS.pod
@@ -85,7 +85,7 @@ L<openssl_user_macros(7)>:
 =head1 DESCRIPTION
 
 All of the functions described on this page are deprecated.
-Applications should use OSSL_ENCODER_to_bio() and OSSL_ENCODER_from_bio()
+Applications should use OSSL_ENCODER_to_bio() and OSSL_DECODER_from_bio()
 instead.
 
 In the description below, B<I<TYPE>> is used
diff --git a/doc/man3/PEM_read_bio_PrivateKey.pod b/doc/man3/PEM_read_bio_PrivateKey.pod
index 2addbb4d61..c053d03a21 100644
--- a/doc/man3/PEM_read_bio_PrivateKey.pod
+++ b/doc/man3/PEM_read_bio_PrivateKey.pod
@@ -194,7 +194,7 @@ L<openssl_user_macros(7)>:
 
 All of the functions described on this page that have a I<TYPE> of B<DH>, B<DSA>
 and B<RSA> are deprecated. Applications should use OSSL_ENCODER_to_bio() and
-OSSL_ENCODER_from_bio() instead.
+OSSL_DECODER_from_bio() instead.
 
 The PEM functions read or write structures in PEM format. In
 this sense PEM format is simply base64 encoded data surrounded
diff --git a/doc/man7/OSSL_PROVIDER-legacy.pod b/doc/man7/OSSL_PROVIDER-legacy.pod
index 86ac3fa9a0..1fa86ab2cd 100644
--- a/doc/man7/OSSL_PROVIDER-legacy.pod
+++ b/doc/man7/OSSL_PROVIDER-legacy.pod
@@ -64,7 +64,8 @@ Not all of these symmetric cipher algorithms are enabled by default.
 
 =item DES
 
-=item IDEA
+The algorithm names are: DES_ECB, DES_CBC, DES_OFB, DES_CFB, DES_CFB1, DES_CFB8
+and DESX_CBC.
 
 =item RC2
 
@@ -83,8 +84,6 @@ Disabled by default. Use I<enable-rc5> config option to enable.
 When algorithms for other operations start appearing, the
 following =head2 titles are appropriate to use:
 
-- Symmetric Ciphers
-
 - Message Authentication Code (MAC)
 
 - Key Derivation Function (KDF)
@@ -108,7 +107,7 @@ L<provider(7)>
 
 =head1 COPYRIGHT
 
-Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
+Copyright 2020-2021 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
diff --git a/doc/man7/crypto.pod b/doc/man7/crypto.pod
index 9db62e5aab..b45404cce0 100644
--- a/doc/man7/crypto.pod
+++ b/doc/man7/crypto.pod
@@ -75,6 +75,7 @@ Similarly when the application exits the default library context is
 automatically destroyed. No explicit de-initialisation steps need to be taken.
 
 See L<OSSL_LIB_CTX(3)> for more information about library contexts.
+See also L</ALGORITHM FETCHING>.
 
 =head2 Multi-threaded applications
 
@@ -303,7 +304,7 @@ provider can also be selected with the property "fips=yes". The FIPS provider
 may also contain non-approved algorithm implementations and these can be
 selected with the property "fips=no".
 
-See L<OSSL_PROVIDER-FIPS(7)>.
+See L<OSSL_PROVIDER-FIPS(7)> and L<fips_module(7)>.
 
 =head2 Legacy provider
 
diff --git a/doc/man7/fips_module.pod b/doc/man7/fips_module.pod
new file mode 100644
index 0000000000..b8a343eb09
--- /dev/null
+++ b/doc/man7/fips_module.pod
@@ -0,0 +1,443 @@
+=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:
+
+- Low level cryptographic APIs (use the high level APIs, such as EVP, instead)
+- Engines
+- 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.)
+
+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 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
+`/usr/local/ssl/openssl.cnf`
+
+Edit the config file to add the following lines near the beginning:
+
+    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>.
+
+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 OPENSSLDIR as described in the section above. However it is also
+possible to override the config file to be used via the `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
+`fipsmodule.cnf` file to remove or comment out the line which says
+`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 `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 "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. `provider=default` or `provider=fips`.
+All algorithms implemented in a provider have this property set on them.
+
+There is also the `fips` property. All FIPS algorithms match against the
+property query `fips=yes`. There are also some non-cryptographic algorithms
+available in the default and base providers that also have the `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 `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:
+
+    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 "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 "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_provider(3)>.
+To extract the name from the B<OSSL_PROVIDER>, use L<OSSL_PROVIDER_name(3)>.
+
+=head1 SEE ALSO
+
+L<migration_guide(7)>,
+L<crypto(7)>
+
+=head1 COPYRIGHT
+
+Copyright 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut
diff --git a/doc/man7/migration_guide.pod b/doc/man7/migration_guide.pod
new file mode 100644
index 0000000000..58260860de
--- /dev/null
+++ b/doc/man7/migration_guide.pod
@@ -0,0 +1,1804 @@
+=pod
+
+=head1 NAME
+
+migration_guide - OpenSSL migration guide
+
+=head1 SYNOPSIS
+
+See the individual manual pages for details.
+
+=head1 DESCRIPTION
+
+This guide details the changes required to migrate to new versions of OpenSSL.
+Currently this covers OpenSSL 3.0. For earlier versions refer to
+L<https://github.com/openssl/openssl/blob/master/CHANGES.md>.
+For an overview of some of the key concepts introduced in OpenSSL 3.0 see
+L<crypto(7)>.
+
+=head1 OPENSSL 3_0
+
+=head2 Main Changes from OpenSSL 1.1.1
+
+=head3 Major Release
+
+OpenSSL 3.0 is a major release and consequently any application that currently
+uses an older version of OpenSSL will at the very least need to be recompiled in
+order to work with the new version. It is the intention that the large majority
+of applications will work unchanged with OpenSSL 3.0 if those applications
+previously worked with OpenSSL 1.1.1. However this is not guaranteed and some
+changes may be required in some cases. Changes may also be required if
+applications need to take advantage of some of the new features available in
+OpenSSL 3.0 such as the availability of the FIPS module.
+
+=head3 License Change
+
+In previous versions, OpenSSL was licensed under the L<dual OpenSSL and SSLeay
+licenses|https://www.openssl.org/source/license-openssl-ssleay.txt>
+(both licenses apply). From OpenSSL 3.0 this is replaced by the
+L<Apache License v2|https://www.openssl.org/source/apache-license-2.0.txt>.
+
+=head3 Providers and FIPS support
+
+One of the key changes from OpenSSL 1.1.1 is the introduction of the Provider
+concept. Providers collect together and make available algorithm implementations.
+With OpenSSL 3.0 it is possible to specify, either programmatically or via a
+config file, which providers you want to use for any given application.
+OpenSSL 3.0 comes with 5 different providers as standard. Over time third
+parties may distribute additional providers that can be plugged into OpenSSL.
+All algorithm implementations available via providers are accessed through the
+"high level" APIs (for example those functions prefixed with "EVP"). They cannot
+be accessed using the L</Low Level APIs>.
+One of the standard providers available is the FIPS provider. This makes
+available FIPS validated cryptographic algorithms.
+The FIPS provider is disabled by default and needs to be enabled explicitly
+at configuration time using the `enable-fips` option. If it is enabled,
+the FIPS provider gets built and installed in addition to the other standard
+providers. No separate installation procedure is necessary.
+There is however a dedicated `install_fips` make target, which serves the
+special purpose of installing only the FIPS provider into an existing
+OpenSSL installation.
+
+See also L</Legacy Algorithms> for information on the legacy provider.
+
+See also L</Completing the installation of the FIPS Module> and
+L</Using the FIPS Module in applications>.
+
+=head3 Low Level APIs
+
+OpenSSL has historically provided two sets of APIs for invoking cryptographic
+algorithms: the "high level" APIs (such as the "EVP" APIs) and the "low level"
+APIs. The high level APIs are typically designed to work across all algorithm
+types. The "low level" APIs are targeted at a specific algorithm implementation.
+For example, the EVP APIs provide the functions L<EVP_EncryptInit_ex(3)>,
+L<EVP_EncryptUpdate(3)> and L<EVP_EncryptFinal(3)> to perform symmetric
+encryption. Those functions can be used with the algorithms AES, CHACHA, 3DES etc.
+On the other hand, to do AES encryption using the low level APIs you would have
+to call AES specific functions such as L<AES_set_encrypt_key(3)>,
+L<AES_encrypt(3)>, and so on. The functions for 3DES are different.
+Use of the low level APIs has been informally discouraged by the OpenSSL
+development team for a long time. However in OpenSSL 3.0 this is made more
+formal. All such low level APIs have been deprecated. You may still use them in
+your applications, but you may start to see deprecation warnings during
+compilation (dependent on compiler support for this). Deprecated APIs may be
+removed from future versions of OpenSSL so you are strongly encouraged to update
+your code to use the high level APIs instead.
+
+This is described in more detail in L</Deprecation of Low Level Functions>
+
+=head3 Legacy Algorithms
+
+Some cryptographic algorithms such as B<MD2> and B<DES> that were available via
+the EVP APIs are now considered legacy and their use is strongly discouraged.
+These legacy EVP algorithms are still available in OpenSSL 3.0 but not by
+default. If you want to use them then you must load the legacy provider.
+This can be as simple as a config file change, or can be done programmatically.
+See L<OSSL_PROVIDER-legacy(7)> for a complete list of algorithms.
+Applications using the EVP APIs to access these algorithms should instead use
+more modern algorithms. If that is not possible then these applications
+should ensure that the legacy provider has been loaded. This can be achieved
+either programmatically or via configuration. See L<crypto(7)> man page for
+more information about providers.
+
+=head3 Engines and "METHOD" APIs
+
+The refactoring to support Providers conflicts internally with the APIs used to
+support engines, including the ENGINE API and any function that creates or
+modifies custom "METHODS" (for example L<EVP_MD_meth_new(3)>,
+L<EVP_CIPHER_meth_new(3)>, L<EVP_PKEY_meth_new(3)>, L<RSA_meth_new(3)>,
+L<EC_KEY_METHOD_new(3)>, etc.). These functions are being deprecated in
+OpenSSL 3.0, and users of these APIs should know that their use can likely
+bypass provider selection and configuration, with unintended consequences.
+This is particularly relevant for applications written to use the OpenSSL 3.0
+FIPS module, as detailed below. Authors and maintainers of external engines are
+strongly encouraged to refactor their code transforming engines into providers
+using the new Provider API and avoiding deprecated methods. 
+
+=head3 Versioning Scheme
+
+The OpenSSL versioning scheme has changed with the OpenSSL 3.0 release. The new
+versioning scheme has this format:
+
+MAJOR.MINOR.PATCH
+
+For OpenSSL 1.1.1 and below, different patch levels were indicated by a letter
+at the end of the release version number. This will no longer be used and
+instead the patch level is indicated by the final number in the version. A
+change in the second (MINOR) number indicates that new features may have been
+added. OpenSSL versions with the same major number are API and ABI compatible.
+If the major number changes then API and ABI compatibility is not guaranteed. 
+
+=head3 Other major new features
+
+=head4 Certificate Management Protocol (CMP, RFC 4210)
+
+This also covers CRMF (RFC 4211) and HTTP transfer (RFC 6712)
+See L<openssl-cmp(1)> and L<OSSL_CMP_exec_certreq(3)> as starting points.
+
+=head4 HTTP(S) client
+
+A proper HTTP(S) client that supports GET and POST, redirection, plain and
+ASN.1-encoded contents, proxies, and timeouts.
+
+=head4 Key Derivation Function API (EVP_KDF)
+
+This simplifies the process of adding new KDF and PRF implementations.
+
+Previously KDF algorithms had been shoe-horned into using the EVP_PKEY object
+which was not a logical mapping.
+Existing applications that use KDF algorithms using EVP_PKEY
+(scrypt, TLS1 PRF and HKDF) may be slower as they use an EVP_KDF bridge
+internally.
+All new applications should use the new L<EVP_KDF(3)> interface.
+See also L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)> and
+L<OSSL_PROVIDER-FIPS(7)/Key Derivation Function (KDF)>.
+
+=head4 Message Authentication Code API (EVP_MAC)
+
+This simplifies the process of adding MAC implementations.
+
+This includes a generic EVP_PKEY to EVP_MAC bridge, to facilitate the continued
+use of MACs through raw private keys in functionality such as
+L<EVP_DigestSign(3)> and L<EVP_DigestVerify(3)>.
+
+All new applications should use the new L<EVP_MAC(3)> interface.
+See also L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)>
+and L<OSSL_PROVIDER-FIPS(7)/Message Authentication Code (MAC)>.
+
+=head4 Support for Linux Kernel TLS
+
+In order to use KTLS, support for it must be compiled in using the 'enable-ktls'
+compile time option. It must also be enabled at run time using the
+B<SSL_OP_ENABLE_KTLS> option.
+
+=head4 New Algorithms
+
+=over 4
+
+=item KDF algorithms "SINGLE STEP" and "SSH"
+
+See L<EVP_KDF-SS(7)> and L<EVP_KDF-SSHKDF(7)>
+
+=item MAC Algorithms "GMAC" and "KMAC"
+
+See L<EVP_MAC-GMAC(7)> and L<EVP_MAC-KMAC(7)>.
+
+=item KEM Algorithm "RSASVE"