From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Isaac Morland <isaac(dot)morland(at)gmail(dot)com> |
Cc: | Noah Misch <noah(at)leadboat(dot)com>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net> |
Subject: | Re: Is MinMaxExpr really leakproof? |
Date: | 2018-12-31 18:08:08 |
Message-ID: | 17807.1546279688@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
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
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