Add better support for using deprecated symbols internally

OPENSSL_SUPPRESS_DEPRECATED only does half the job, in telling the
deprecation macros not to add the warning attribute.  However, with
'no-deprecated', the symbols are still removed entirely, while we
might still want to use them internally.

The solution is to permit <openssl/opensslconf.h> macros to be
modified internally, such as undefining OPENSSL_NO_DEPRECATED in this
case.

However, with the way <openssl/opensslconf.h> includes
<openssl/macros.h>, that's easier said than done.  That's solved by
generating <openssl/configuration.h> instead, and add a new
<openssl/opensslconf.h> that includes <openssl/configuration.h> as
well as <openssl/macros.h>, thus allowing to replace an inclusion of
<openssl/opensslconf.h> with this:

    #include <openssl/configuration.h>

    #undef OPENSSL_NO_DEPRECATED
    #define OPENSSL_SUPPRESS_DEPRECATED

    #include <openssl/macros.h>

Or simply add the following prior to any other openssl inclusion:

    #include <openssl/configuration.h>

    #undef OPENSSL_NO_DEPRECATED
    #define OPENSSL_SUPPRESS_DEPRECATED

Note that undefining OPENSSL_NO_DEPRECATED must never be done by
applications, since the symbols must still be exported by the
library.  Internal test programs are excempt of this rule, though.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/10608)

1 files changed, 20 insertions, 0 deletions

diff --git a/CHANGES b/CHANGES
index e0b15b35f6..45f97e6740 100644
--- a/CHANGES
+++ b/CHANGES
@@ -9,6 +9,26 @@
 
  Changes between 1.1.1 and 3.0.0 [xx XXX xxxx]
 
+  *) Removed include/openssl/opensslconf.h.in and replaced it with
+     include/openssl/configuration.h.in, which differs in not including
+     <openssl/macros.h>.  A short header include/openssl/opensslconf.h
+     was added to include both.
+
+     This allows internal hacks where one might need to modify the set
+     of configured macros, for example this if deprecated symbols are
+     still supposed to be available internally:
+
+         #include <openssl/configuration.h>
+
+         #undef OPENSSL_NO_DEPRECATED
+         #define OPENSSL_SUPPRESS_DEPRECATED
+
+         #include <openssl/macros.h>
+
+     This should not be used by applications that use the exported
+     symbols, as that will lead to linking errors.
+     [Richard Levitte]
+
   *) Fixed an an overflow bug in the x64_64 Montgomery squaring procedure
      used in exponentiation with 512-bit moduli. No EC algorithms are
      affected. Analysis suggests that attacks against 2-prime RSA1024,