MOTD "safe_print" prints control characters

[Victor Engmark]

/etc/update-motd.d/50-motd-news contains a function called "safe_print". Its documentation says it does not print control characters, but this is false. If you look at the `tr` command it prints \012 (Device Control 2 aka. DC2 aka. ␒) and \015 (Negative Acknowledge aka. NAK aka. ␕) from the source. I don't know why it would do that, or whether it could possibly be a security issue, especially since it makes the code more complex than it should be (`tr -d '\000-\011\013\014\016-\037'` vs `tr -d '\000-\037'`). A quick `/etc/update-motd.d/50-motd-news --force | grep $'\x12\|\x15'` returned exit code 1, so it's not part of the current MOTD.

[Victor Engmark (victor-engmark)]

Correction: That's of course *octal* 012 and 015, aka. Line Feed and Carriage Return. That should probably be explicit in the documentation.