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Fix ECDSA signature verification edge-case

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For R and S equal to 1, ensure the public key is checked
for validity.

Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
This commit is contained in:
Dave Rodgman 2022-08-10 11:26:24 +01:00
parent 1fdb8e8c17
commit c947751a5f
1 changed files with 3 additions and 0 deletions
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3
library/ecp.c
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@ -2666,14 +2666,17 @@ static int mbedtls_ecp_mul_shortcuts( mbedtls_ecp_group *grp,
if( mbedtls_mpi_cmp_int( m, 0 ) == 0 ) if( mbedtls_mpi_cmp_int( m, 0 ) == 0 )
{ {
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, P ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_set_zero( R ) ); MBEDTLS_MPI_CHK( mbedtls_ecp_set_zero( R ) );
} }
else if( mbedtls_mpi_cmp_int( m, 1 ) == 0 ) else if( mbedtls_mpi_cmp_int( m, 1 ) == 0 )
{ {
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, P ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_copy( R, P ) ); MBEDTLS_MPI_CHK( mbedtls_ecp_copy( R, P ) );
} }
else if( mbedtls_mpi_cmp_int( m, -1 ) == 0 ) else if( mbedtls_mpi_cmp_int( m, -1 ) == 0 )
{ {
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, P ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_copy( R, P ) ); MBEDTLS_MPI_CHK( mbedtls_ecp_copy( R, P ) );
MPI_ECP_NEG( &R->Y ); MPI_ECP_NEG( &R->Y );
} }