commit 75ed58723e93a45455ba2412d1d523931de0d978
author Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Tue Jun 18 12:52:45 2024 +0200
committer Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com> Tue Jun 18 12:52:45 2024 +0200
tree 3aada12b9783b90463602122b01585f3db1db003
parent 8fb5df859c3b6a6d6b43bcfcad32385a3f2cbd8f

Add optionally unsafe variant of exp_mod for perf

Attempt to partially solve the performance regression in 3.6.0 without
adding too much code size.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>

library/bignum.c

diff --git a/library/bignum.c b/library/bignum.c
index c45fd5b..4db2b10 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -1610,9 +1610,9 @@
     return 0;
 }
 
-int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
-                        const mbedtls_mpi *E, const mbedtls_mpi *N,
-                        mbedtls_mpi *prec_RR)
+int mbedtls_mpi_exp_mod_optionally_safe(mbedtls_mpi *X, const mbedtls_mpi *A,
+                                        const mbedtls_mpi *E, const mbedtls_mpi *N,
+                                        mbedtls_mpi *prec_RR, int E_public)
 {
     int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
 
@@ -1695,7 +1695,15 @@
     {
         mbedtls_mpi_uint mm = mbedtls_mpi_core_montmul_init(N->p);
         mbedtls_mpi_core_to_mont_rep(X->p, X->p, N->p, N->n, mm, RR.p, T);
-        mbedtls_mpi_core_exp_mod(X->p, X->p, N->p, N->n, E->p, E->n, RR.p, T);
+        mbedtls_mpi_core_exp_mod_optionally_safe(X->p,
+                                                 X->p,
+                                                 N->p,
+                                                 N->n,
+                                                 E->p,
+                                                 E->n,
+                                                 RR.p,
+                                                 T,
+                                                 E_public);
         mbedtls_mpi_core_from_mont_rep(X->p, X->p, N->p, N->n, mm, T);
     }
 
@@ -1720,6 +1728,13 @@
     return ret;
 }
 
+int mbedtls_mpi_exp_mod(mbedtls_mpi *X, const mbedtls_mpi *A,
+                        const mbedtls_mpi *E, const mbedtls_mpi *N,
+                        mbedtls_mpi *prec_RR)
+{
+    return mbedtls_mpi_exp_mod_optionally_safe(X, A, E, N, prec_RR, MBEDTLS_MPI_IS_SECRET);
+}
+
 /*
  * Greatest common divisor: G = gcd(A, B)  (HAC 14.54)
  */