build-sys: fix build with libgrcypt disabled

- Move gcrypt.h include inside grcrypt-util.h.
- Allow gcrypt-util.[ch] to be compiled even without gcrypt.
This allows the logic in files using gcrypt to be simplified.

- Fix compilation of systemd-resolve without gcrypt.
systemd-resolved already supported that.

Fixes #2711.

Makefile.am

@@ -4262,7 +4262,9 @@ libsystemd_journal_internal_la_SOURCES = \
 	src/journal/mmap-cache.h \
 	src/journal/compress.c \
 	src/journal/audit-type.h \
-	src/journal/audit-type.c
+	src/journal/audit-type.c \
+	src/shared/gcrypt-util.h \
+	src/shared/gcrypt-util.c
 
 nodist_libsystemd_journal_internal_la_SOURCES = \
 	src/journal/audit_type-to-name.h
@@ -4294,9 +4296,7 @@ libsystemd_journal_internal_la_SOURCES += \
 	src/journal/journal-authenticate.c \
 	src/journal/journal-authenticate.h \
 	src/journal/fsprg.c \
-	src/journal/fsprg.h \
-	src/shared/gcrypt-util.c \
-	src/shared/gcrypt-util.h
+	src/journal/fsprg.h
 
 libsystemd_journal_internal_la_LIBADD += \
 	$(GCRYPT_LIBS)

src/resolve/resolve-tool.c

@@ -17,7 +17,6 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include <gcrypt.h>
 #include <getopt.h>
 #include <net/if.h>
 
@@ -863,7 +862,7 @@ static int resolve_openpgp(sd_bus *bus, const char *address) {
         }
         domain++;
 
-        r = string_hashsum(address, domain - 1 - address, GCRY_MD_SHA224, &hashed);
+        r = string_hashsum_sha224(address, domain - 1 - address, &hashed);
         if (r < 0)
                 return log_error_errno(r, "Hashing failed: %m");
 

src/shared/gcrypt-util.c

@@ -19,10 +19,11 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#ifdef HAVE_GCRYPT
 #include <gcrypt.h>
 
-#include "hexdecoct.h"
 #include "gcrypt-util.h"
+#include "hexdecoct.h"
 
 void initialize_libgcrypt(bool secmem) {
         const char *p;
@@ -67,3 +68,4 @@ int string_hashsum(const char *s, size_t len, int md_algorithm, char **out) {
         *out = enc;
         return 0;
 }
+#endif

src/shared/gcrypt-util.h

@@ -19,7 +19,21 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
+#include <errno.h>
 #include <stdbool.h>
+#include <stddef.h>
+
+#ifdef HAVE_GCRYPT
+#include <gcrypt.h>
 
 void initialize_libgcrypt(bool secmem);
 int string_hashsum(const char *s, size_t len, int md_algorithm, char **out);
+#endif
+
+static inline int string_hashsum_sha224(const char *s, size_t len, char **out) {
+#ifdef HAVE_GCRYPT
+        return string_hashsum(s, len, GCRY_MD_SHA224, out);
+#else
+        return -EOPNOTSUPP;
+#endif
+}