journalctl: give a nice hint about group membership based on ACLs of /var/log/journal

If we notice that we unprivileged and not in any of the groups which
have access to /var/log/journal, print a nice message about which groups
do.

This checks and prints all groups that are in the default ACL for
/var/log/journal, which is not necessarily correct for all journal
files, but pretty close.

1 files changed, 21 insertions, 10 deletions

diff --git a/src/shared/strv.c b/src/shared/strv.c
index 7bcfabbf1a..e57e0ee7bf 100644
--- a/src/shared/strv.c
+++ b/src/shared/strv.c
@@ -387,32 +387,43 @@ fail:
         return NULL;
 }
 
-int strv_extend(char ***l, const char *value) {
+int strv_push(char ***l, char *value) {
         char **c;
-        char *v;
         unsigned n;
 
         if (!value)
                 return 0;
 
-        v = strdup(value);
-        if (!v)
-                return -ENOMEM;
-
         n = strv_length(*l);
         c = realloc(*l, sizeof(char*) * (n + 2));
-        if (!c) {
-                free(v);
+        if (!c)
                 return -ENOMEM;
-        }
 
-        c[n] = v;
+        c[n] = value;
         c[n+1] = NULL;
 
         *l = c;
         return 0;
 }
 
+int strv_extend(char ***l, const char *value) {
+        char *v;
+        int r;
+
+        if (!value)
+                return 0;
+
+        v = strdup(value);
+        if (!v)
+                return -ENOMEM;
+
+        r = strv_push(l, v);
+        if (r < 0)
+                free(v);
+
+        return r;
+}
+
 char **strv_uniq(char **l) {
         char **i;