From 81f4b11010097d578e81df49927a3743c4cfa210 Mon Sep 17 00:00:00 2001
From: Minos Galanakis <minos.galanakis@arm.com>
Date: Thu, 10 Nov 2022 14:40:38 +0000
Subject: [PATCH] bignum_mod: Added `mbedtls_mpi_mod_read/write()` IO functions

This patch adds input and ouput fucntions in the `bignum_mod` layer.
The data will be automatically converted between Cannonical and
Montgomery representation if required.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
---
 library/bignum_mod.c | 47 ++++++++++++++++++++++++++++++++++++++++++++
 library/bignum_mod.h | 44 +++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)

diff --git a/library/bignum_mod.c b/library/bignum_mod.c
index 13108c51f1..a4ed32b6a3 100644
--- a/library/bignum_mod.c
+++ b/library/bignum_mod.c
@@ -209,7 +209,54 @@ exit:
 /* END MERGE SLOT 6 */
 
 /* BEGIN MERGE SLOT 7 */
+int mbedtls_mpi_mod_read( mbedtls_mpi_mod_residue *r,
+                          mbedtls_mpi_mod_modulus *m,
+                          unsigned char *buf,
+                          size_t buflen )
+{
+    int ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
 
+    if ( r == NULL || m == NULL )
+        goto cleanup;
+
+    if ( r->p == NULL || m->p == NULL || r->limbs > m->limbs ||\
+         r->limbs == 0 || m->limbs == 0 )
+        goto cleanup;
+
+    ret = mbedtls_mpi_mod_raw_read( r->p, m, buf, buflen );
+
+    if( ret != 0 )
+        goto cleanup;
+
+    if (m->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY)
+       ret = mbedtls_mpi_mod_raw_to_mont_rep(r->p, m);
+
+cleanup:
+    return ( ret );
+}
+
+int mbedtls_mpi_mod_write( mbedtls_mpi_mod_residue *r,
+                           mbedtls_mpi_mod_modulus *m,
+                           unsigned char *buf,
+                           size_t buflen )
+{
+    int ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA;
+
+    if ( r == NULL || m == NULL )
+        goto cleanup;
+
+    if ( r->p == NULL || m->p == NULL || r->limbs > m->limbs ||\
+         r->limbs == 0 || m->limbs == 0 )
+        goto cleanup;
+
+    if ( m->int_rep == MBEDTLS_MPI_MOD_REP_MONTGOMERY)
+        ret = mbedtls_mpi_mod_raw_from_mont_rep( r->p, m );
+
+    ret = mbedtls_mpi_mod_raw_write( r->p, m, buf, buflen );
+
+cleanup:
+    return ( ret );
+}
 /* END MERGE SLOT 7 */
 
 /* BEGIN MERGE SLOT 8 */
diff --git a/library/bignum_mod.h b/library/bignum_mod.h
index 29c26f2ef9..9378aabacd 100644
--- a/library/bignum_mod.h
+++ b/library/bignum_mod.h
@@ -173,7 +173,51 @@ void mbedtls_mpi_mod_modulus_free( mbedtls_mpi_mod_modulus *m );
 /* END MERGE SLOT 6 */
 
 /* BEGIN MERGE SLOT 7 */
+/** Read public representation data stored in a buffer into a residue structure.
+ *
+ * The `mbedtls_mpi_mod_residue` and `mbedtls_mpi_mod_modulus` structures must
+ * be compatible. The data will be automatically converted into the appropriate
+ * representation based on the value of `m->int_rep field`.
+ *
+ * \param r      The address of the residue related to \p m. It must have as
+ *               many limbs as the modulus \p m.
+ * \param m      The address of the modulus.
+ * \param buf    The input buffer to import from.
+ * \param buflen The length in bytes of \p buf.
+ *
+ * \return       \c 0 if successful.
+ * \return       #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p X isn't
+ *               large enough to hold the value in \p buf.
+ * \return       #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the external representation
+ *               of \p m is invalid or \p X is not less than \p m.
+ */
+int mbedtls_mpi_mod_read( mbedtls_mpi_mod_residue *r,
+                          mbedtls_mpi_mod_modulus *m,
+                          unsigned char *buf,
+                          size_t buflen );
 
+/** Write residue data onto a buffer using public representation data.
+ *
+ * The `mbedtls_mpi_mod_residue` and `mbedtls_mpi_mod_modulus` structures must
+ * be compatible. The data will be automatically converted into the appropriate
+ * representation based on the value of `m->int_rep field`.
+ *
+ * \param r      The address of the residue related to \p m. It must have as
+ *               many limbs as the modulus \p m.
+ * \param m      The address of the modulus.
+ * \param buf    The output buffer to export to.
+ * \param buflen The length in bytes of \p buf.
+ *
+ * \return       \c 0 if successful.
+ * \return       #MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL if \p buf isn't
+ *               large enough to hold the value of \p X.
+ * \return       #MBEDTLS_ERR_MPI_BAD_INPUT_DATA if the external representation
+ *               of \p m is invalid.
+ */
+int mbedtls_mpi_mod_write( mbedtls_mpi_mod_residue *r,
+                           mbedtls_mpi_mod_modulus *m,
+                           unsigned char *buf,
+                           size_t buflen );
 /* END MERGE SLOT 7 */
 
 /* BEGIN MERGE SLOT 8 */