These are not valid outside of UTF-16 so seeing them in a UTF-8 sequence
means that something is wrong with that sequence. Best to filter them
out rather than letting them propagate and have unknown effects.

We should handle this in the low-level protocol code as much as possible
to avoid mistakes. This way the rest of the code can assume that strings
are always UTF-8 with \n line endings.

These will always be byte streams at heart, so let's try to keep them
with a proper type. Should make it clearer how they will be used.

An assert will kill the entire server, which is overly harsh when there
is a problem with a single connection. Instead, throw an exception which
will just disconnect that specific client.

Addresses the following AVC denial:

type=PROCTITLE msg=audit(01/12/2023 02:58:12.648:696) : proctitle=/usr/sbin/vncsession fedora :1
type=PATH msg=audit(01/12/2023 02:58:12.648:696) : item=1 name=/home/fedora/.vnc nametype=CREATE cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 cap_frootid=0
type=PATH msg=audit(01/12/2023 02:58:12.648:696) : item=0 name=/home/fedora/ inode=262145 dev=fc:02 mode=dir,700 ouid=fedora ogid=fedora rdev=00:00 obj=unconfined_u:object_r:user_home_dir_t:s0 nametype=PARENT cap_fp=none cap_fi=none cap_fe=0 cap_fver=0 cap_frootid=0
type=CWD msg=audit(01/12/2023 02:58:12.648:696) : cwd=/home/fedora
type=SYSCALL msg=audit(01/12/2023 02:58:12.648:696) : arch=x86_64 syscall=mkdir success=no exit=EACCES(Permission denied) a0=0x7fff47d52540 a1=0755 a2=0x0 a3=0x0 items=2 ppid=2869 pid=2880 auid=fedora uid=fedora gid=fedora euid=fedora suid=fedora fsuid=fedora egid=fedora sgid=fedora fsgid=fedora tty=(none) ses=8 comm=vncsession exe=/usr/sbin/vncsession subj=system_u:system_r:vnc_session_t:s0 key=(null)
type=AVC msg=audit(01/12/2023 02:58:12.648:696) : avc:  denied  { create } for  pid=2880 comm=vncsession name=.vnc scontext=system_u:system_r:vnc_session_t:s0 tcontext=system_u:object_r:vnc_home_t:s0 tclass=dir permissive=0

Resolves: rhbz#2143704

Clipboard functions may run on connections that are not yet at
RFBSTATE_NORMAL. Due to recent hardening of the accessCheck() function,
it is important to validate that the state is RFBSTATE_NORMAL before
calling accessCheck().

Fixes #1599.

It's a type specific to that class, so let's keep them close for
clarity.

Make sure we don't send a bogus request to the X server in the (common)
case that we don't actually have anything to restore.

It is much more natural than custom methods for this very common
operation.

It is easy to get confused if these methods modify the existing object,
or return a new one. So let's mark the return value as critical so the
compiler can help out if someone gets it wrong.

This can have unexpected consequences as some code may rely on it being
a simple variable. Instead to what we do in Socket, which is to define a
unique name for getting socket error numbers.

It doesn't use any exceptions, so stop including the header for it.

These files don't use anything from this header, so remove the include.

This exposes some missing includes in other places, though. So add an
explicit include in the files that were relying on an indirect
inclusion.

This matches the naming in STL, which is what we are mostly mimicing now
that we are using std::string for these functions.

It's just confusing that we have our own variety that isn't compatible.

It has now been replaced, mostly by std::string, so remove the actual
type definition.

Avoids a bit of complexity by delegating that handling to a string
object.

Let's use a more common type instead of something homegrown. Should be
more familiar to new developers.

It's more standard and familiar than our custom CharArray type, and it
still gives us automatic freeing of the buffer.

We could probably have used std::unique_ptr instead, but we are
currently targeting older compilers where C++11 isn't standard yet.

It's extreme overkill to inherit from CharArray just to get the
automatic freeing of the buffer when the object is destroyed.

Get rid of all the magical re-allocation and shuffling and instead just
return a new set of strings that is fully splitted. Will consume a bit
more memory, but is a lot safer to use as there is less confusion about
ownership of memory.

We mostly use classical C strings, but the memory management around them
can get confusing and error prone. Let's use std::string for the cases
where we need to return a newly allocated string.

The compiler doesn't enforce this, but it at least documents the
expected array size.

We know the needed space here, so let's keep it simple with a constant
size string buffer.

It should return a path to the directory itself, just like its sister
function getuserhomedir().

All library functions should be in a proper namespace.

A blank string might be very confusing, depending on where this will be
used. Let's give something more visible back in the cases where we
cannot get the proper name for the peer.

This mimics how some system functions (like inet_ntop()) work, and
avoids complexity around ownership of the returned string buffer.

The downside is that the string must be consumed directly as it will be
overwritten on the next call, but that is not an issue with the current
usage.

Use the same indentation we use in all other files.

These don't need to be changed, so let's just keep it simple with a
constant string literal.

It's unclear why this was initially added. The function takes string
constants, so it is not going to modify these.

Avoid complicating things by moving things in to a second buffer here as
there is no need for it.

We don't need to make extra copies of the string in most cases, so let's
simplify the code and access the string directly when we can.

We never use Windows' "UNICODE" mode anyway, so let's get rid of this
complexity.

This makes memory management more clear and robust when using these
helper functions.

Let the string helpers call the more fancy setParam(). This makes sure
we can avoid duplicating things.

Otherwise the old length is preserved, which will result in NULL pointer
dereferencing if the parameter is ever accessed.

This is explicitly a byte sequence, so let's try to keep a consistent
typing.

These are used here and there so let's make them more general rather
than hiding them in the stream classes.

Avoid our own custom types in favour of what's already included with
C++.

Avoid having our own custom stuff and instead use the modern, standard
types, for familiarity.

Avoid preprocessor magic and instead rely on templating to generate
optimized functions for performance critical code.

This should have been removed with the code using these defines in
03ca975.

Everything else uses LF line endings, so fix up the few stray ones.