util.c: [ref] move group find/copy into new functions

Move the logic from clean_supplementary_groups into the following new
functions:

* find_group
* copy_group_ifcont

These will be reused later.

Misc: The latter function's signature is based on getgrouplist(2), which
is used on clean_supplementary_groups.

1 files changed, 26 insertions, 11 deletions

diff --git a/src/firejail/util.c b/src/firejail/util.c
index 55dcdc246..6fc8a663f 100644
--- a/src/firejail/util.c
+++ b/src/firejail/util.c
@@ -103,6 +103,30 @@ void errLogExit(char* fmt, ...) {
         exit(1);
 }
 
+static int find_group(gid_t group, const gid_t *groups, int ngroups) {
+        int i;
+        for (i = 0; i < ngroups; i++) {
+                if (group == groups[i])
+                        return i;
+        }
+
+        return -1;
+}
+
+// Gets group from "groupname" and adds it to "new_groups" if it exists on
+// "groups".  Always returns the current value of new_ngroups.
+static int copy_group_ifcont(const char *groupname,
+                             const gid_t *groups, int ngroups,
+                             gid_t *new_groups, int *new_ngroups) {
+        gid_t g = get_group_id(groupname);
+        if (g && find_group(g, groups, ngroups) >= 0) {
+                new_groups[*new_ngroups] = g;
+                (*new_ngroups)++;
+        }
+
+        return *new_ngroups;
+}
+
 static void clean_supplementary_groups(gid_t gid) {
         assert(cfg.username);
         gid_t groups[MAX_GROUPS];
@@ -126,17 +150,8 @@ static void clean_supplementary_groups(gid_t gid) {
 
         int i = 0;
         while (allowed[i]) {
-                gid_t g = get_group_id(allowed[i]);
-                if (g) {
-                        int j;
-                        for (j = 0; j < ngroups; j++) {
-                                if (g == groups[j]) {
-                                        new_groups[new_ngroups] = g;
-                                        new_ngroups++;
-                                        break;
-                                }
-                        }
-                }
+                copy_group_ifcont(allowed[i], groups, ngroups,
+                                  new_groups, &new_ngroups);
                 i++;
         }