smack: introduce new SmackProcessLabel option

In service file, if the file has some of special SMACK label in
ExecStart= and systemd has no permission for the special SMACK label
then permission error will occurred. To resolve this, systemd should
be able to set its SMACK label to something accessible of ExecStart=.
So introduce new SmackProcessLabel. If label is specified with
SmackProcessLabel= then the child systemd will set its label to
that. To successfully execute the ExecStart=, accessible label should
be specified with SmackProcessLabel=.
Additionally, by SMACK policy, if the file in ExecStart= has no
SMACK64EXEC then the executed process will have given label by
SmackProcessLabel=. But if the file has SMACK64EXEC then the
SMACK64EXEC label will be overridden.

[zj: reword man page]

1 files changed, 50 insertions, 0 deletions

diff --git a/src/core/load-fragment.c b/src/core/load-fragment.c
index 2ee16bdef9..4309121649 100644
--- a/src/core/load-fragment.c
+++ b/src/core/load-fragment.c
@@ -1313,6 +1313,56 @@ int config_parse_exec_apparmor_profile(
         return 0;
 }
 
+int config_parse_exec_smack_process_label(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+
+        ExecContext *c = data;
+        Unit *u = userdata;
+        bool ignore;
+        char *k;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(data);
+
+        if (isempty(rvalue)) {
+                free(c->smack_process_label);
+                c->smack_process_label = NULL;
+                c->smack_process_label_ignore = false;
+                return 0;
+        }
+
+        if (rvalue[0] == '-') {
+                ignore = true;
+                rvalue++;
+        } else
+                ignore = false;
+
+        r = unit_name_printf(u, rvalue, &k);
+        if (r < 0) {
+                log_syntax(unit, LOG_ERR, filename, line, -r,
+                           "Failed to resolve specifiers, ignoring: %s", strerror(-r));
+                return 0;
+        }
+
+        free(c->smack_process_label);
+        c->smack_process_label = k;
+        c->smack_process_label_ignore = ignore;
+
+        return 0;
+}
+
 int config_parse_timer(const char *unit,
                        const char *filename,
                        unsigned line,