Backport 2.28: Fix undefined behavior in bignum: NULL+0 and -most-negative-sint #6618
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Since they're part of the public API (even if only through a few functions), they should be documented. I deliberately skipped documenting how to configure the size of the type. Right now, MBEDTLS_HAVE_INT32 and MBEDTLS_HAVE_INT64 have no Doxygen documentation, so it's ambiguous whether they're part of the public API. Resolving this ambiguity is out of scope of my current work. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Fix undefined behavior (typically harmless in practice) of mbedtls_mpi_add_mpi(), mbedtls_mpi_add_abs() and mbedtls_mpi_add_int() when both operands are 0 and the left operand is represented with 0 limbs. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
When x is the most negative value of a two's complement type, `(unsigned_type)(-x)` has undefined behavior, whereas `-(unsigned_type)x` has well-defined behavior and does what was intended. Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
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| /** \typedef mbedtls_mpi_sint | ||
| * \brief The signed type corresponding to #mbedtls_mpi_uint. | ||
| * | ||
| * This is always an signed integer type with no padding bits. The size |
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Grr, missed this in the original. Up to you whether you fix :)
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| * This is always an signed integer type with no padding bits. The size | |
| * This is always a signed integer type with no padding bits. The size |
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This hinders neither comprehension nor grepping so I'd prefer to merge if the CI is happy.
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I gave an approval anyway...
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Nov 17, 2022
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Fix two kinds of typically harmless undefined behavior in bignum. Trivial backport of #6609.
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