To prevent screwing up terminal settings when printing to
the terminal, for ASCII and UTF-8, escape bytes not forming characters and
bytes forming non-printable characters with vis(3) VIS_OCTAL. For other
character sets, abort printing of the current string in these cases. In
particular, * let scp(1) respect the local user's LC_CTYPE locale(1); *
sanitize data received from the remote host; * sanitize filenames, usernames,
and similar data even locally; * take character display widths into account
for the progressmeter.
This is believed to be sufficient to keep the local terminal safe
on OpenBSD, but bad things can still happen on other systems with
state-dependent locales because many places in the code print
unencoded ASCII characters into the output stream.
Using feedback from djm@ and martijn@,
various aspects discussed with many others.
deraadt@ says it should go in now, i probably already hesitated too long
Upstream-ID: e66afbc94ee396ddcaffd433b9a3b80f387647e0
