Fix deprecation notices for OpenSSL 3 and failure to build on GCC12

Tested with libssl 3.0.10-1ubuntu2.1 (Ubuntu 23.10) and 1.1.1f-1ubuntu2.20
(Ubuntu 20.04).

Signed-off-by: Loïc Gomez <bip@animanova.fr>

src/connection.c

@@ -1171,6 +1171,7 @@ static connection_t *connection_init(int anti_flood, int ssl, time_t timeout,
 static int ctx_set_dh(SSL_CTX *ctx)
 {
 	/* Return ephemeral DH parameters. */
+#if OPENSSL_VERSION_NUMBER < 0x30000000L /* 3.0.0 */
 	DH *dh = NULL;
 	FILE *f;
 	long ret;
@@ -1203,7 +1204,31 @@ static int ctx_set_dh(SSL_CTX *ctx)
 		      ERR_error_string(ERR_get_error(), NULL));
 		return 0;
 	}
+#else
+    BIO *pbio = BIO_new_file(conf_client_dh_file, "r");
+    if (!pbio) {
+	    mylog(LOG_ERROR, "Unable to open DH parameters, BIO_new_file(%s): %s",
+                conf_client_dh_file, ERR_error_string(ERR_get_error(), NULL));
+        return 0;
+    }
 
+    EVP_PKEY *param = PEM_read_bio_Parameters(pbio, NULL);
+    BIO_free(pbio);
+    if (!param) {
+	    mylog(LOG_ERROR, "TLS DH Error: PEM_read_bio_Parameters(%s): %s",
+                conf_client_dh_file, ERR_error_string(ERR_get_error(), NULL));
+        return 0;
+    }
+
+    if (SSL_CTX_set0_tmp_dh_pkey(ctx, param) != 1) {
+        EVP_PKEY_free(param);
+	    mylog(LOG_ERROR, "TLS DH Error: SSL_CTX_set0_tmp_dh_pkey(%s): %s",
+                conf_client_dh_file, ERR_error_string(ERR_get_error(), NULL));
+        return 0;
+    }
+#endif
+	mylog(LOG_DEBUG, "TLS: succesfully set up DH params %s",
+            conf_client_dh_file);
 	return 1;
 }
 #endif