commit 8cdb6064de78582a3bed86524bb342a393e19150
author Janos Follath <janos.follath@arm.com> Tue Jan 09 09:28:48 2024 +0000
committer Dave Rodgman <dave.rodgman@arm.com> Mon Jan 22 15:58:57 2024 +0000
tree 06483e10071035c5771631e15615fc3131abe453
parent f10bfbbe744ecffeb88ac8518390e432b2d1bb2a

Align Montgomery init with development

The signature and naming of the Montgomrey initialisation function in
development and in the LTS was different. Align them for easier
readability and maintenance.

Signed-off-by: Janos Follath <janos.follath@arm.com>

library/bignum.c

diff --git a/library/bignum.c b/library/bignum.c
index 50da6b3..74f10af 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1907,19 +1907,17 @@
 /*
  * Fast Montgomery initialization (thanks to Tom St Denis)
  */
-void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N)
+mbedtls_mpi_uint mbedtls_mpi_montmul_init(const mbedtls_mpi_uint *N)
 {
-    mbedtls_mpi_uint x, m0 = N->p[0];
-    unsigned int i;
+    mbedtls_mpi_uint x = N[0];
 
-    x  = m0;
-    x += ((m0 + 2) & 4) << 1;
+    x += ((N[0] + 2) & 4) << 1;
 
-    for (i = biL; i >= 8; i /= 2) {
-        x *= (2 - (m0 * x));
+    for (unsigned int i = biL; i >= 8; i /= 2) {
+        x *= (2 - (N[0] * x));
     }
 
-    *mm = ~x + 1;
+    return ~x + 1;
 }
 
 void mbedtls_mpi_montmul(mbedtls_mpi *A,
@@ -2069,7 +2067,7 @@
     /*
      * Init temps and window size
      */
-    mbedtls_mpi_montg_init(&mm, N);
+    mm = mbedtls_mpi_montmul_init(N->p);
     mbedtls_mpi_init(&RR); mbedtls_mpi_init(&T);
     mbedtls_mpi_init(&Apos);
     mbedtls_mpi_init(&WW);

library/bignum_internal.h

diff --git a/library/bignum_internal.h b/library/bignum_internal.h
index f14c294..5435ebb 100644
--- a/library/bignum_internal.h
+++ b/library/bignum_internal.h
@@ -30,14 +30,14 @@
 
 /**
  * \brief Calculate initialisation value for fast Montgomery modular
- *        multiplication.
+ *        multiplication
  *
- * \param[out] mm   The initialisation value for fast Montgomery modular
- *                  multiplication.
- * \param[in]  N    Little-endian presentation of the modulus. This must have
- *                  at least one limb.
+ * \param[in] N  Little-endian presentation of the modulus. This must have
+ *               at least one limb.
+ *
+ * \return       The initialisation value for fast Montgomery modular multiplication
  */
-void mbedtls_mpi_montg_init(mbedtls_mpi_uint *mm, const mbedtls_mpi *N);
+mbedtls_mpi_uint mbedtls_mpi_montmul_init(const mbedtls_mpi_uint *N);
 
 /** Montgomery multiplication: A = A * B * R^-1 mod N  (HAC 14.36)
  *

library/rsa.c

diff --git a/library/rsa.c b/library/rsa.c
index 23fe843..0a0c2e3 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -815,8 +815,7 @@
     const size_t nlimbs = N->n;
     const size_t tlimbs = 2 * (nlimbs + 1);
 
-    mbedtls_mpi_uint mm;
-    mbedtls_mpi_montg_init(&mm, N);
+    mbedtls_mpi_uint mm = mbedtls_mpi_montmul_init(N->p);
 
     mbedtls_mpi RR, M_T;