On 6/18/25 11:53, Paul Eggert wrote:
On 2025-06-17 20:27, Jacob Bachmeyer via Gcrypt-devel wrote:
It is a size_t so it is unsigned.
Then the checks are correct as written.
Not on oddball platforms where SIZE_MAX <= INT_MAX, because in that
case it's signed integer overflow and behavior is undefined. POSIX
allows such platforms.
Maybe gcrypt should have a static_assert (INT_MAX < SIZE_MAX)? That
might be easier than adjusting all its size_t-calculating code to be
portable to oddball platforms. Unless there's a goal to be fully POSIX
portable.
More important, the checks are not valid on platforms like x86-64
where UINT_MAX < SIZE_MAX, because mpi_set_opaque takes an unsigned
int arg.
I was about to say that I thought amd64 would trip that static assert,
since "int" is 32-bit but "long int" and "size_t" are 64-bit.
This looks like a real bug, at least just from local inspection.
So the checks are indeed incorrect...
I advocate for defense-in-depth
Although this defense is needed it's not defense in depth, as there's
no guarantee malloc will fail with sizes close to SIZE_MAX.
... and the checks are also needed. "Fun."
-- Jacob
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