Add documentation for "NULL" cipher and digest algorithms.

Fixes #20340

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/20356)

(cherry picked from commit f7d76c3d7d09d95a9ceb5b69c8f951f53237ef78)

6 files changed, 132 insertions, 1 deletions

diff --git a/doc/build.info b/doc/build.info
index ec8778f2ac..00dc150721 100644
--- a/doc/build.info
+++ b/doc/build.info
@@ -4145,6 +4145,10 @@ DEPEND[html/man7/EVP_CIPHER-IDEA.html]=man7/EVP_CIPHER-IDEA.pod
 GENERATE[html/man7/EVP_CIPHER-IDEA.html]=man7/EVP_CIPHER-IDEA.pod
 DEPEND[man/man7/EVP_CIPHER-IDEA.7]=man7/EVP_CIPHER-IDEA.pod
 GENERATE[man/man7/EVP_CIPHER-IDEA.7]=man7/EVP_CIPHER-IDEA.pod
+DEPEND[html/man7/EVP_CIPHER-NULL.html]=man7/EVP_CIPHER-NULL.pod
+GENERATE[html/man7/EVP_CIPHER-NULL.html]=man7/EVP_CIPHER-NULL.pod
+DEPEND[man/man7/EVP_CIPHER-NULL.7]=man7/EVP_CIPHER-NULL.pod
+GENERATE[man/man7/EVP_CIPHER-NULL.7]=man7/EVP_CIPHER-NULL.pod
 DEPEND[html/man7/EVP_CIPHER-RC2.html]=man7/EVP_CIPHER-RC2.pod
 GENERATE[html/man7/EVP_CIPHER-RC2.html]=man7/EVP_CIPHER-RC2.pod
 DEPEND[man/man7/EVP_CIPHER-RC2.7]=man7/EVP_CIPHER-RC2.pod
@@ -4289,6 +4293,10 @@ DEPEND[html/man7/EVP_MD-MDC2.html]=man7/EVP_MD-MDC2.pod
 GENERATE[html/man7/EVP_MD-MDC2.html]=man7/EVP_MD-MDC2.pod
 DEPEND[man/man7/EVP_MD-MDC2.7]=man7/EVP_MD-MDC2.pod
 GENERATE[man/man7/EVP_MD-MDC2.7]=man7/EVP_MD-MDC2.pod
+DEPEND[html/man7/EVP_MD-NULL.html]=man7/EVP_MD-NULL.pod
+GENERATE[html/man7/EVP_MD-NULL.html]=man7/EVP_MD-NULL.pod
+DEPEND[man/man7/EVP_MD-NULL.7]=man7/EVP_MD-NULL.pod
+GENERATE[man/man7/EVP_MD-NULL.7]=man7/EVP_MD-NULL.pod
 DEPEND[html/man7/EVP_MD-RIPEMD160.html]=man7/EVP_MD-RIPEMD160.pod
 GENERATE[html/man7/EVP_MD-RIPEMD160.html]=man7/EVP_MD-RIPEMD160.pod
 DEPEND[man/man7/EVP_MD-RIPEMD160.7]=man7/EVP_MD-RIPEMD160.pod
@@ -4619,6 +4627,7 @@ html/man7/EVP_CIPHER-CAST.html \
 html/man7/EVP_CIPHER-CHACHA.html \
 html/man7/EVP_CIPHER-DES.html \
 html/man7/EVP_CIPHER-IDEA.html \
+html/man7/EVP_CIPHER-NULL.html \
 html/man7/EVP_CIPHER-RC2.html \
 html/man7/EVP_CIPHER-RC4.html \
 html/man7/EVP_CIPHER-RC5.html \
@@ -4655,6 +4664,7 @@ html/man7/EVP_MD-MD4.html \
 html/man7/EVP_MD-MD5-SHA1.html \
 html/man7/EVP_MD-MD5.html \
 html/man7/EVP_MD-MDC2.html \
+html/man7/EVP_MD-NULL.html \
 html/man7/EVP_MD-RIPEMD160.html \
 html/man7/EVP_MD-SHA1.html \
 html/man7/EVP_MD-SHA2.html \
@@ -4743,6 +4753,7 @@ man/man7/EVP_CIPHER-CAST.7 \
 man/man7/EVP_CIPHER-CHACHA.7 \
 man/man7/EVP_CIPHER-DES.7 \
 man/man7/EVP_CIPHER-IDEA.7 \
+man/man7/EVP_CIPHER-NULL.7 \
 man/man7/EVP_CIPHER-RC2.7 \
 man/man7/EVP_CIPHER-RC4.7 \
 man/man7/EVP_CIPHER-RC5.7 \
@@ -4779,6 +4790,7 @@ man/man7/EVP_MD-MD4.7 \
 man/man7/EVP_MD-MD5-SHA1.7 \
 man/man7/EVP_MD-MD5.7 \
 man/man7/EVP_MD-MDC2.7 \
+man/man7/EVP_MD-NULL.7 \
 man/man7/EVP_MD-RIPEMD160.7 \
 man/man7/EVP_MD-SHA1.7 \
 man/man7/EVP_MD-SHA2.7 \
diff --git a/doc/man7/EVP_CIPHER-NULL.pod b/doc/man7/EVP_CIPHER-NULL.pod
new file mode 100644
index 0000000000..44e07dcf1b
--- /dev/null
+++ b/doc/man7/EVP_CIPHER-NULL.pod
@@ -0,0 +1,72 @@
+=pod
+
+=head1 NAME
+
+EVP_CIPHER-NULL - The NULL EVP_CIPHER implementation
+
+=head1 DESCRIPTION
+
+Support for a NULL symmetric encryption using the B<EVP_CIPHER> API.
+This is used when the TLS cipher suite is TLS_NULL_WITH_NULL_NULL.
+This does no encryption (just copies the data) and has a mac size of zero.
+
+=head2 Algorithm Name
+
+The following algorithm is available in the default provider:
+
+=over 4
+
+=item "NULL"
+
+=back
+
+=head2 Parameters
+
+This implementation supports the following parameters:
+
+=head3 Gettable EVP_CIPHER parameters
+
+See L<EVP_EncryptInit(3)/Gettable EVP_CIPHER parameters>
+
+=head3 Gettable EVP_CIPHER_CTX parameters
+
+=over 4
+
+=item "keylen" (B<OSSL_CIPHER_PARAM_KEYLEN>) <unsigned integer>
+
+=item "ivlen" (B<OSSL_CIPHER_PARAM_IVLEN> and <B<OSSL_CIPHER_PARAM_AEAD_IVLEN>) <unsigned integer>
+
+=item "tls-mac" (B<OSSL_CIPHER_PARAM_TLS_MAC>) <octet ptr>
+
+=back
+
+See L<EVP_EncryptInit(3)/PARAMETERS> for further information.
+
+=head3 Settable EVP_CIPHER_CTX parameters
+
+=over 4
+
+=item "tls-mac-size" (B<OSSL_CIPHER_PARAM_TLS_MAC_SIZE>) <unsigned integer>
+
+=back
+
+See L<EVP_EncryptInit(3)/PARAMETERS> for further information.
+
+=head1 CONFORMING TO
+
+RFC 5246 section-6.2.3.1
+
+=head1 SEE ALSO
+
+L<provider-cipher(7)>, L<OSSL_PROVIDER-default(7)>
+
+=head1 COPYRIGHT
+
+Copyright 2023 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/EVP_MD-NULL.pod b/doc/man7/EVP_MD-NULL.pod
new file mode 100644
index 0000000000..bce399a1e1
--- /dev/null
+++ b/doc/man7/EVP_MD-NULL.pod
@@ -0,0 +1,42 @@
+=pod
+
+=head1 NAME
+
+EVP_MD-NULL - The NULL EVP_MD implementation
+
+=head1 DESCRIPTION
+
+Support for a NULL digest through the B<EVP_MD> API.
+This algorithm does nothing and returns 1 for its init,
+update and final methods.
+
+=head2 Algorithm Name
+
+The following algorithm is available in the default provider:
+
+=over 4
+
+=item "NULL"
+
+=back
+
+=head2 Gettable Parameters
+
+This implementation supports the common gettable parameters described
+in L<EVP_MD-common(7)>.
+
+=head1 SEE ALSO
+
+L<EVP_MD_CTX_set_params(3)>, L<provider-digest(7)>,
+L<OSSL_PROVIDER-default(7)>
+
+=head1 COPYRIGHT
+
+Copyright 2023 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/OSSL_PROVIDER-default.pod b/doc/man7/OSSL_PROVIDER-default.pod
index 43ba0ef02d..3be5c59319 100644
--- a/doc/man7/OSSL_PROVIDER-default.pod
+++ b/doc/man7/OSSL_PROVIDER-default.pod
@@ -71,6 +71,8 @@ The OpenSSL default provider supports these operations and algorithms:
 
 =item RIPEMD160, see L<EVP_MD-RIPEMD160(7)>
 
+=item NULL, see L<EVP_MD-NULL(7)>
+
 =back
 
 =head2 Symmetric Ciphers
@@ -93,6 +95,8 @@ The OpenSSL default provider supports these operations and algorithms:
 
 =item ChaCha20-Poly1305, see L<EVP_CIPHER-CHACHA(7)>
 
+=item NULL, see L<EVP_CIPHER-NULL(7)>
+
 =back
 
 =head2 Message Authentication Code (MAC)
diff --git a/doc/man7/provider-cipher.pod b/doc/man7/provider-cipher.pod
index 1faf698107..0124872521 100644
--- a/doc/man7/provider-cipher.pod
+++ b/doc/man7/provider-cipher.pod
@@ -228,7 +228,7 @@ L<EVP_CIPHER-AES(7)>, L<EVP_CIPHER-ARIA(7)>, L<EVP_CIPHER-BLOWFISH(7)>,
 L<EVP_CIPHER-CAMELLIA(7)>, L<EVP_CIPHER-CAST(7)>, L<EVP_CIPHER-CHACHA(7)>,
 L<EVP_CIPHER-DES(7)>, L<EVP_CIPHER-IDEA(7)>, L<EVP_CIPHER-RC2(7)>,
 L<EVP_CIPHER-RC4(7)>, L<EVP_CIPHER-RC5(7)>, L<EVP_CIPHER-SEED(7)>,
-L<EVP_CIPHER-SM4(7)>,
+L<EVP_CIPHER-SM4(7)>, L<EVP_CIPHER-NULL(7)>,
 L<life_cycle-cipher(7)>, L<EVP_EncryptInit(3)>
 
 =head1 HISTORY
diff --git a/doc/man7/provider-digest.pod b/doc/man7/provider-digest.pod
index c96dfe3966..afad428c89 100644
--- a/doc/man7/provider-digest.pod
+++ b/doc/man7/provider-digest.pod
@@ -268,6 +268,7 @@ L<EVP_MD-MD4(7)>, L<EVP_MD-MD5(7)>, L<EVP_MD-MD5-SHA1(7)>,
 L<EVP_MD-MDC2(7)>, L<EVP_MD-RIPEMD160(7)>, L<EVP_MD-SHA1(7)>,
 L<EVP_MD-SHA2(7)>, L<EVP_MD-SHA3(7)>, L<EVP_MD-SHAKE(7)>,
 L<EVP_MD-SM3(7)>, L<EVP_MD-WHIRLPOOL(7)>,
+L<EVP_MD-NULL(7)>,
 L<life_cycle-digest(7)>, L<EVP_DigestInit(3)>
 
 =head1 HISTORY