Make default_method mostly compile-time

Document thread-safety issues

Cherry-pick from 076fc55527a1499391fa6de109c8387895199ee9 but
keeps the RSA_null method.

Reviewed-by: Geoff Thorpe <geoff@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3146)

3 files changed, 18 insertions, 6 deletions

diff --git a/doc/crypto/DH_set_method.pod b/doc/crypto/DH_set_method.pod
index cd75a9b549..2100608674 100644
--- a/doc/crypto/DH_set_method.pod
+++ b/doc/crypto/DH_set_method.pod
@@ -31,8 +31,11 @@ Initially, the default DH_METHOD is the OpenSSL internal implementation, as
 returned by DH_OpenSSL().
 
 DH_set_default_method() makes B<meth> the default method for all DH
-structures created later. B<NB>: This is true only whilst no ENGINE has been set
+structures created later.
+B<NB>: This is true only whilst no ENGINE has been set
 as a default for DH, so this function is no longer recommended.
+This function is not thread-safe and should not be called at the same time
+as other OpenSSL functions.
 
 DH_get_default_method() returns a pointer to the current default DH_METHOD.
 However, the meaningfulness of this result is dependent on whether the ENGINE
diff --git a/doc/crypto/DSA_set_method.pod b/doc/crypto/DSA_set_method.pod
index a64725f7e4..d870f56f26 100644
--- a/doc/crypto/DSA_set_method.pod
+++ b/doc/crypto/DSA_set_method.pod
@@ -31,8 +31,11 @@ Initially, the default DSA_METHOD is the OpenSSL internal implementation,
 as returned by DSA_OpenSSL().
 
 DSA_set_default_method() makes B<meth> the default method for all DSA
-structures created later. B<NB>: This is true only whilst no ENGINE has
+structures created later.
+B<NB>: This is true only whilst no ENGINE has
 been set as a default for DSA, so this function is no longer recommended.
+This function is not thread-safe and should not be called at the same time
+as other OpenSSL functions.
 
 DSA_get_default_method() returns a pointer to the current default
 DSA_METHOD. However, the meaningfulness of this result is dependent on
diff --git a/doc/crypto/RSA_set_method.pod b/doc/crypto/RSA_set_method.pod
index 7e7d27cf93..668ad7a16b 100644
--- a/doc/crypto/RSA_set_method.pod
+++ b/doc/crypto/RSA_set_method.pod
@@ -3,7 +3,7 @@
 =head1 NAME
 
 RSA_set_default_method, RSA_get_default_method, RSA_set_method,
-RSA_get_method, RSA_PKCS1_OpenSSL, RSA_null_method, RSA_flags,
+RSA_get_method, RSA_PKCS1_OpenSSL, RSA_flags,
 RSA_new_method - select RSA method
 
 =head1 SYNOPSIS
@@ -20,8 +20,6 @@ RSA_new_method - select RSA method
 
  RSA_METHOD *RSA_PKCS1_OpenSSL(void);
 
- RSA_METHOD *RSA_null_method(void);
-
  int RSA_flags(const RSA *rsa);
 
  RSA *RSA_new_method(ENGINE *engine);
@@ -38,8 +36,11 @@ Initially, the default RSA_METHOD is the OpenSSL internal implementation,
 as returned by RSA_PKCS1_OpenSSL().
 
 RSA_set_default_method() makes B<meth> the default method for all RSA
-structures created later. B<NB>: This is true only whilst no ENGINE has
+structures created later.
+B<NB>: This is true only whilst no ENGINE has
 been set as a default for RSA, so this function is no longer recommended.
+This function is not thread-safe and should not be called at the same time
+as other OpenSSL functions.
 
 RSA_get_default_method() returns a pointer to the current default
 RSA_METHOD. However, the meaningfulness of this result is dependent on
@@ -168,6 +169,11 @@ not currently exist).
 
 L<RSA_new(3)>
 
+=head1 HISTORY
+
+The RSA_null_method(), which was a partial attempt to avoid patent issues,
+was replaced to always return NULL in OpenSSL 1.1.0f.
+
 =head1 COPYRIGHT
 
 Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.