From 2ef0cff6c3d4b55462269e51921641e29f5fa12e Mon Sep 17 00:00:00 2001 From: Hanno Becker Date: Tue, 12 Apr 2022 10:55:34 +0100 Subject: [PATCH] Fix size check in p25519 modular reduction The check was meant to precisely catch an underflow. Signed-off-by: Hanno Becker --- library/ecp_curves.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/library/ecp_curves.c b/library/ecp_curves.c index 718d0d0894..d3a14d6794 100644 --- a/library/ecp_curves.c +++ b/library/ecp_curves.c @@ -5223,7 +5223,7 @@ static int ecp_mod_p255( mbedtls_mpi *N ) /* Helper references for top part of N */ mbedtls_mpi_uint * const NT_p = N->p + P255_WIDTH; const size_t NT_n = N->n - P255_WIDTH; - if( NT_n == 0 || NT_n > P255_WIDTH ) + if( NT_n == 0 || NT_n > N->n ) return( 0 ); /* Split N as N + 2^256 M */