analyze-security: include an actual syscall name in the message

This information was already available in the debug output, but I think it
is good to include it in the message in the table. This makes it easier to wrap
one's head around the allowlist/denylist filtering.

src/analyze/analyze-security.c

@@ -493,7 +493,7 @@ static int assess_system_call_architectures(
 
 #if HAVE_SECCOMP
 
-static bool syscall_names_in_filter(Set *s, bool allow_list, const SyscallFilterSet *f) {
+static bool syscall_names_in_filter(Set *s, bool allow_list, const SyscallFilterSet *f, const char **ret_offending_syscall) {
         const char *syscall;
 
         NULSTR_FOREACH(syscall, f->value) {
@@ -503,7 +503,7 @@ static bool syscall_names_in_filter(Set *s, bool allow_list, const SyscallFilter
                         const SyscallFilterSet *g;
 
                         assert_se(g = syscall_filter_set_find(syscall));
-                        if (syscall_names_in_filter(s, allow_list, g))
+                        if (syscall_names_in_filter(s, allow_list, g, ret_offending_syscall))
                                 return true; /* bad! */
 
                         continue;
@@ -516,10 +516,13 @@ static bool syscall_names_in_filter(Set *s, bool allow_list, const SyscallFilter
 
                 if (set_contains(s, syscall) == allow_list) {
                         log_debug("Offending syscall filter item: %s", syscall);
+                        if (ret_offending_syscall)
+                                *ret_offending_syscall = syscall;
                         return true; /* bad! */
                 }
         }
 
+        *ret_offending_syscall = NULL;
         return false;
 }
 
@@ -530,42 +533,48 @@ static int assess_system_call_filter(
                 uint64_t *ret_badness,
                 char **ret_description) {
 
-        const SyscallFilterSet *f;
-        char *d = NULL;
-        uint64_t b;
-
         assert(a);
         assert(info);
         assert(ret_badness);
         assert(ret_description);
 
         assert(a->parameter < _SYSCALL_FILTER_SET_MAX);
-        f = syscall_filter_sets + a->parameter;
+        const SyscallFilterSet *f = syscall_filter_sets + a->parameter;
+
+        char *d = NULL;
+        uint64_t b;
 
         if (!info->system_call_filter_allow_list && set_isempty(info->system_call_filter)) {
                 d = strdup("Service does not filter system calls");
                 b = 10;
         } else {
                 bool bad;
+                const char *offender = NULL;
 
                 log_debug("Analyzing system call filter, checking against: %s", f->name);
-                bad = syscall_names_in_filter(info->system_call_filter, info->system_call_filter_allow_list, f);
+                bad = syscall_names_in_filter(info->system_call_filter, info->system_call_filter_allow_list, f, &offender);
                 log_debug("Result: %s", bad ? "bad" : "good");
 
                 if (info->system_call_filter_allow_list) {
                         if (bad) {
-                                (void) asprintf(&d, "System call allow list defined for service, and %s is included", f->name);
+                                (void) asprintf(&d, "System call allow list defined for service, and %s is included "
+                                                "(e.g. %s is allowed)",
+                                                f->name, offender);
                                 b = 9;
                         } else {
-                                (void) asprintf(&d, "System call allow list defined for service, and %s is not included", f->name);
+                                (void) asprintf(&d, "System call allow list defined for service, and %s is not included",
+                                                f->name);
                                 b = 0;
                         }
                 } else {
                         if (bad) {
-                                (void) asprintf(&d, "System call deny list defined for service, and %s is not included", f->name);
+                                (void) asprintf(&d, "System call deny list defined for service, and %s is not included "
+                                                "(e.g. %s is allowed)",
+                                                f->name, offender);
                                 b = 10;
                         } else {
-                                (void) asprintf(&d, "System call deny list defined for service, and %s is included", f->name);
+                                (void) asprintf(&d, "System call deny list defined for service, and %s is included",
+                                                f->name);
                                 b = 0;
                         }
                 }