Fix [-Wdeprecated-declarations] warning in ERR_load_BIO_strings when building YDBEncrypt with OpenSSL 3.0

Background

• When building YDBEncrypt on a Ubuntu 22.04 system (which has OpenSSL 3.0), we noticed the following warning.

  gtm_tls_impl.c:523:9: warning: 'ERR_load_BIO_strings' is deprecated: Since OpenSSL 3.0 [-Wdeprecated-declarations]
    523 |         ERR_load_BIO_strings();
        |         ^~~~~~~~~~~~~~~~~~~~
  In file included from /usr/include/openssl/cryptoerr.h:17,
                   from /usr/include/openssl/crypto.h:38,
                   from /usr/include/openssl/bio.h:30,
                   from /usr/include/openssl/err.h:29,
                   from gtm_tls_impl.c:29:
  /usr/include/openssl/cryptoerr_legacy.h:31:27: note: declared here
     31 | OSSL_DEPRECATEDIN_3_0 int ERR_load_BIO_strings(void);
        |                           ^~~~~~~~~~~~~~~~~~~~

Issue

• https://www.openssl.org/docs/man3.0/man7/migration_guide.html#Deprecated-function-mappings says the following about warnings in ERR_load_BIO_strings.

  • ERR_load_*(), ERR_func_error_string(), ERR_get_error_line(), ERR_get_error_line_data(), ERR_get_state()
  • OpenSSL now loads error strings automatically so these functions are not needed.

Fix

• The ERR_load_BIO_strings() invocation is now done only if OPENSSL_VERSION_MAJOR is less than 3.

Notes

• Note that there were a total of 3 warnings when building YDBEncrypt using OpenSSL 3.0. Only 1 of them is fixed in this commit. The other 2 will be fixed in later commits as they involve non-trivial changes. Those warnings are pasted below for reference.

• Warning that SSL_set_tmp_dh_callback is deprecated.

  gtm_tls_impl.c: In function 'gtm_tls_socket':
  gtm_tls_impl.c:1350:25: warning: 'SSL_set_tmp_dh_callback' is deprecated: Since OpenSSL 3.0 [-Wdeprecated-declarations]
   1350 |                         SSL_set_tmp_dh_callback(ssl, tmp_dh_callback);
        |                         ^~~~~~~~~~~~~~~~~~~~~~~
  In file included from gtm_tls_impl.c:30:
  /usr/include/openssl/ssl.h:2220:6: note: declared here
   2220 | void SSL_set_tmp_dh_callback(SSL *ssl,
        |      ^~~~~~~~~~~~~~~~~~~~~~~

• Warning that PEM_read_bio_DHparams is deprecated.

  gtm_tls_impl.c: In function 'read_dhparams':
  gtm_tls_impl.c:444:9: warning: 'PEM_read_bio_DHparams' is deprecated: Since OpenSSL 3.0 [-Wdeprecated-declarations]
    444 |         if (NULL == (dh = (PEM_read_bio_DHparams(bio, NULL, NULL, NULL))))
        |         ^~
  In file included from /usr/include/openssl/ssl.h:36,
                   from gtm_tls_impl.c:30:
  /usr/include/openssl/pem.h:469:1: note: declared here
    469 | DECLARE_PEM_rw_attr(OSSL_DEPRECATEDIN_3_0, DHparams, DH)
        | ^~~~~~~~~~~~~~~~~~~