From 3e9f5228c8072ce2821d2158ba8f2e561d5e5c21 Mon Sep 17 00:00:00 2001 From: Gilles Peskine Date: Mon, 20 Jan 2020 21:12:50 +0100 Subject: 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. --- library/bignum.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/library/bignum.c b/library/bignum.c index 6713bcbf..fdf571d2 100644 --- a/library/bignum.c +++ b/library/bignum.c @@ -198,7 +198,7 @@ int mbedtls_mpi_copy( mbedtls_mpi *X, const mbedtls_mpi *Y ) if( X == Y ) return( 0 ); - if( Y->p == NULL ) + if( Y->n == 0 ) { mbedtls_mpi_free( X ); return( 0 ); -- cgit v1.2.3