[digest] Add commands for all enabled digest algorithms

Add "sha256sum", "sha512sum", and similar commands.  Include these new
commands only when DIGEST_CMD is enabled in config/general.h and the
corresponding algorithm is enabled in config/crypto.h.

Leave "mdsum" and "sha1sum" included whenever only DIGEST_CMD is
enabled, to avoid potentially breaking backwards compatibility with
builds that disabled MD5 or SHA-1 as a TLS or X.509 digest algorithm,
but would still have expected those commands to be present.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/config/config_digest_cmd.c

@@ -0,0 +1,61 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ *
+ * You can also choose to distribute this program under the terms of
+ * the Unmodified Binary Distribution Licence (as given in the file
+ * COPYING.UBDL), provided that you have satisfied its requirements.
+ */
+
+FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
+
+#include <config/crypto.h>
+
+/** @file
+ *
+ * Digest command configuration
+ *
+ */
+
+PROVIDE_REQUIRING_SYMBOL();
+
+/* MD4 */
+#if defined ( CRYPTO_DIGEST_MD4 )
+REQUIRE_OBJECT ( cmd_md4 );
+#endif
+
+/* MD5 is present by default for historical reasons */
+
+/* SHA-1 is present by default for historical reasons */
+
+/* SHA-224 */
+#if defined ( CRYPTO_DIGEST_SHA224 )
+REQUIRE_OBJECT ( cmd_sha224 );
+#endif
+
+/* SHA-256 */
+#if defined ( CRYPTO_DIGEST_SHA256 )
+REQUIRE_OBJECT ( cmd_sha256 );
+#endif
+
+/* SHA-384 */
+#if defined ( CRYPTO_DIGEST_SHA384 )
+REQUIRE_OBJECT ( cmd_sha384 );
+#endif
+
+/* SHA-512 */
+#if defined ( CRYPTO_DIGEST_SHA512 )
+REQUIRE_OBJECT ( cmd_sha512 );
+#endif