Add a null provider which implements no algorithms.

By loading the null provider into the default context, it is possible
to verify that it is not accidentally being used.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/11488)

1 files changed, 35 insertions, 0 deletions

diff --git a/doc/man7/OSSL_PROVIDER-null.pod b/doc/man7/OSSL_PROVIDER-null.pod
new file mode 100644
index 0000000000..10ce5844f1
--- /dev/null
+++ b/doc/man7/OSSL_PROVIDER-null.pod
@@ -0,0 +1,35 @@
+=pod
+
+=head1 NAME
+
+OSSL_PROVIDER-null - OpenSSL null provider
+
+=head1 DESCRIPTION
+
+The OpenSSL null provider supplies no algorithms.
+
+It can used to guarantee that the default library context and a fallback
+provider will not be accidentally accessed.
+
+=head2 Properties
+
+The null provider defines no properties.
+
+=head1 OPERATIONS AND ALGORITHMS
+
+The OpenSSL null provider supports no operations and algorithms.
+
+=head1 SEE ALSO
+
+L<provider(7)>
+
+=head1 COPYRIGHT
+
+Copyright 2020 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