Escape all non-printable characters in strings fetched from the network

[matsduf]

TXT records can easily contain non-printable ASCII characters, but also non-ASCII characters (eighth bit set), and those can mess the terminal up. Other records with TXT like content can give the same problem. And even domain names can contain unwanted characters.

zonemaster-cli should check all strings and domain names fetched from the network before printing out. Non-printable ASCII characters and non-ASCII characters should be escaped or replaced.

One escaping option is to use same mechanism as Bind. ESC character is printed as \027 (decimal representation, always three digits).

[marc-vanderwal]

I can confirm that a specially-crafted version.bind string can be used to inject escape sequences in a terminal. In this case, aphrodite.x0r.fr has a string that contains the ANSI escape sequence ESC [ 3 4 m, turning the remainder of the output blue.

[matsduf]

And that could have been a specially-craftet SPF TXT record instead.

[marc-vanderwal]

In Zone11, Zonemaster does not reproduce the SPF policy that it obtained in its messages, so we are safe. Only Nameserver15 is affected.