[build] WITHOUT_LIB_CRYPTO option in code

(not (yet?) an end-user option in the build system)
(If extended to build system, build system should also unset CRYPTO_LIB)

If WITHOUT_LIB_CRYPTO is defined in sys-crypto.h, then non-TLS modules
will have access to MD5() and SHA1() built with lighttpd (algo_md5.[ch]
and algo_sha1.[ch]), but not to other message digest algorithms.

As of this commit, this affects only mod_secdownload with SHA256 digest
and mod_auth* modules using HTTP Digest Auth with digest=SHA-256, which
is not currently well-supported by client browers (besides Opera)

src/rand.c

@@ -64,6 +64,14 @@
 #include <nss/pk11pub.h>
 #endif
 #endif
+#ifndef USE_LIB_CRYPTO
+#undef USE_NETTLE_CRYPTO
+#undef USE_MBEDTLS_CRYPTO
+#undef USE_WOLFSSL_CRYPTO
+#undef USE_OPENSSL_CRYPTO
+#undef USE_GNUTLS_CRYPTO
+#undef USE_NSS_CRYPTO
+#endif
 #ifdef HAVE_GETENTROPY
 #include <sys/random.h>
 #endif

src/sys-crypto.h

@@ -50,4 +50,8 @@
 #define USE_GNUTLS_CRYPTO
 #endif
 
+#ifdef WITHOUT_LIB_CRYPTO
+#undef USE_LIB_CRYPTO
+#endif
+
 #endif