tree fa2d21611760b342f76b0a20ae1e29de81718c79
parent 7428b451264df671fcc9345849f44de1ad3dbace
author Gilles Peskine <Gilles.Peskine@arm.com> 1579551170 +0100
committer Gilles Peskine <Gilles.Peskine@arm.com> 1579551170 +0100

mpi_copy: make the 0 case slightly more robust

If Y was constructed through functions in this module, then Y->n == 0
iff Y->p == NULL. However we do not prevent filling mpi structures
manually, and zero may be represented with n=0 and p a valid pointer.
Most of the code can cope with such a representation, but for the
source of mbedtls_mpi_copy, this would cause an integer underflow.
Changing the test for zero from Y->p==NULL to Y->n==0 causes this case
to work at no extra cost.