Re: Is MinMaxExpr really leakproof?

Isaac Morland <isaac(dot)morland(at)gmail(dot)com> writes:
> On Mon, 31 Dec 2018 at 12:26, Noah Misch <noah(at)leadboat(dot)com> wrote:
>> bttextcmp() and other varstr_cmp() callers fall afoul of the same
>> restriction with their "could not convert string to UTF-16" errors

> I'm confused. What characters cannot be represented in UTF-16?

What's actually being reported there is failure of Windows'
MultiByteToWideChar function. Probable causes could include
invalid data (not valid UTF8), or conditions such as out-of-memory
which might have nothing at all to do with the input.

There are similar, equally nonspecific, error messages in the
non-Windows code path.

In principle, an attacker might be able to find out the existence
of extremely long strings in a column by noting out-of-memory
failures in this code, but that doesn't seem like a particularly
interesting information leak ...

regards, tom lane