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Fix information leak in ecp_gen_keypair_base

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The function mbedtls_ecp_gen_keypair_base did not wipe the stack buffer used to
hold the private exponent before returning. This commit fixes this by not using
a stack buffer in the first place but instead calling mpi_fill_random directly
to acquire the necessary random MPI.
This commit is contained in:
Hanno Becker 2017-10-17 15:19:38 +01:00
parent 073c199224
commit 7c8cb9c28b
1 changed files with 1 additions and 3 deletions
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4
library/ecp.c
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@ -1953,7 +1953,6 @@ int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
{
/* SEC1 3.2.1: Generate d such that 1 <= n < N */
int count = 0;
unsigned char rnd[MBEDTLS_ECP_MAX_BYTES];
/*
* Match the procedure given in RFC 6979 (deterministic ECDSA):
@ -1964,8 +1963,7 @@ int mbedtls_ecp_gen_keypair_base( mbedtls_ecp_group *grp,
*/
do
{
MBEDTLS_MPI_CHK( f_rng( p_rng, rnd, n_size ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( d, rnd, n_size ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( d, n_size, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( d, 8 * n_size - grp->nbits ) );
/*