commit 02b35bd00a0b2c100975b0b0575a74ec5250324b
author Hanno Becker <hanno.becker@arm.com> Sat Jan 01 06:54:25 2022 +0000
committer Hanno Becker <hanno.becker@arm.com> Sat Jan 01 06:54:25 2022 +0000
tree 8474f7ee4073b9952be8c848189d14436381a1a9
parent 5c8ea307b878a9860996972c5890c53d8655c525

Introduce wrapper for modular multiplication with single-width const

Signed-off-by: Hanno Becker <hanno.becker@arm.com>

library/ecp.c

diff --git a/library/ecp.c b/library/ecp.c
index ba6e8f3..0fd570e 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1138,6 +1138,19 @@
     return( ret );
 }
 
+static inline int mbedtls_mpi_mul_int_mod( const mbedtls_ecp_group *grp,
+                                           mbedtls_mpi *X,
+                                           const mbedtls_mpi *A,
+                                           mbedtls_mpi_uint c )
+{
+    int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+
+    MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int( X, A, c ) );
+    MOD_ADD( *X );
+cleanup:
+    return( ret );
+}
+
 #if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED) && \
     !( defined(MBEDTLS_ECP_NO_FALLBACK) && \
        defined(MBEDTLS_ECP_DOUBLE_JAC_ALT) && \
@@ -1372,17 +1385,17 @@
     if( grp->A.p == NULL )
     {
         /* M = 3(X + Z^2)(X - Z^2) */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod( grp, &S,  &P->Z,  &P->Z   ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_add_mod( grp, &T,  &P->X,  &S      ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mod( grp, &U,  &P->X,  &S      ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod( grp, &S,  &T,     &U      ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int( &M,  &S,     3       ) ); MOD_ADD( M );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod(     grp, &S,  &P->Z,  &P->Z   ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_add_mod(     grp, &T,  &P->X,  &S      ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mod(     grp, &U,  &P->X,  &S      ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod(     grp, &S,  &T,     &U      ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int_mod( grp, &M,  &S,     3       ) );
     }
     else
     {
         /* M = 3.X^2 */
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod( grp, &S,  &P->X,  &P->X   ) );
-        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int( &M,  &S,     3       ) ); MOD_ADD( M );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mod    ( grp, &S,  &P->X,  &P->X   ) );
+        MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int_mod( grp, &M,  &S,     3       ) );
 
         /* Optimize away for "koblitz" curves with A = 0 */
         if( mbedtls_mpi_cmp_int( &grp->A, 0 ) != 0 )