DropPrivs: Improve comments

Git-Dch: ignore

apt-pkg/contrib/fileutl.cc

@@ -2175,7 +2175,7 @@ bool Popen(const char* Args[], FileFd &Fd, pid_t &Child, FileFd::OpenMode Mode)
 
 bool DropPrivs()
 {
-   /* uid will be 0 in the end, but gid might be different anyway */
+   // uid will be 0 in the end, but gid might be different anyway
    uid_t old_uid = getuid();
    gid_t old_gid = getgid();
 
@@ -2195,7 +2195,7 @@ bool DropPrivs()
    if(ret < 0)
       _error->Warning("PR_SET_NO_NEW_PRIVS failed with %i", ret);
 #endif
-
+   // Do not change the order here, it might break things
    if (setgroups(1, &pw->pw_gid))
       return _error->Errno("setgroups", "Failed to setgroups");
 
@@ -2207,27 +2207,27 @@ bool DropPrivs()
 
    if (setuid(pw->pw_uid) != 0)
       return _error->Errno("setuid", "Failed to setuid");
+
    // the seteuid() is probably uneeded (at least thats what the linux
    // man-page says about setuid(2)) but we cargo culted it anyway
-
-
    if (seteuid(pw->pw_uid) != 0)
       return _error->Errno("seteuid", "Failed to seteuid");
 
-   /* Try changing GID/EGID */
+   // Check that uid and gid changes do not work anymore
    if (pw->pw_gid != old_gid && (setgid(old_gid) != -1 || setegid(old_gid) != -1))
       return _error->Error("Could restore a gid to root, privilege dropping did not work");
 
    if (pw->pw_uid != old_uid && (setuid(old_uid) != -1 || seteuid(old_uid) != -1))
       return _error->Error("Could restore a uid to root, privilege dropping did not work");
 
-   /* Verify the list of supplementary groups is what we expected */
+   // Verify that the user has only a single group, and the correct one
    gid_t groups[1];
    if (getgroups(1, groups) != 1)
       return _error->Errno("getgroups", "Could not get new groups");
    if (groups[0] != pw->pw_gid)
       return _error->Error("Could not switch group");
-   /* Verify gid, egid, uid, and euid */
+
+   // Verify that gid, egid, uid, and euid changed
    if (getgid() != pw->pw_gid)
       return _error->Error("Could not switch group");
    if (getegid() != pw->pw_gid)
@@ -2257,6 +2257,5 @@ bool DropPrivs()
       return _error->Error("Could not switch saved set-group-ID");
 #endif
 
-   /* TODO: Check saved uid/saved gid as well */
    return true;
 }