From 9bb5effc3298265f829878825d9bd38478e67514 Mon Sep 17 00:00:00 2001
From: Sachin Parekh <sachin.parekh@espressif.com>
Date: Wed, 5 Jan 2022 15:23:44 +0530
Subject: [PATCH] ecp: Add support for hardware implementation of ECP routines

ESP32C2 has a hardware ECC accelerator that supports NIST P-192 and NIST P-256 curves,
which can increase the performance of the point multiplication and point
verification operation.

Provision is also added to fallback to software implementation in
case the curve is not from the supported curves
---
 library/ecp.c | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/library/ecp.c b/library/ecp.c
index 0212069c83..0e32396b91 100644
--- a/library/ecp.c
+++ b/library/ecp.c
@@ -1210,6 +1210,7 @@ cleanup:
 #endif /* !defined(MBEDTLS_ECP_NO_FALLBACK) || !defined(MBEDTLS_ECP_NORMALIZE_JAC_ALT) */
 }
 
+#if !defined(MBEDTLS_ECP_MUL_ALT)
 /*
  * Normalize jacobian coordinates of an array of (pointers to) points,
  * using Montgomery's trick to perform only one inversion mod P.
@@ -1333,6 +1334,7 @@ cleanup:
 
     return( ret );
 }
+#endif /* MBEDTLS_ECP_MUL_ALT */
 
 /*
  * Point doubling R = 2 P, Jacobian coordinates
@@ -1533,6 +1535,7 @@ cleanup:
 #endif /* !defined(MBEDTLS_ECP_NO_FALLBACK) || !defined(MBEDTLS_ECP_ADD_MIXED_ALT) */
 }
 
+#if !defined(MBEDTLS_ECP_MUL_ALT)
 /*
  * Randomize jacobian coordinates:
  * (X, Y, Z) -> (l^2 X, l^3 Y, l Z) for random l
@@ -2232,6 +2235,8 @@ cleanup:
     return( ret );
 }
 
+#endif /* MBEDTLS_ECP_MUL_ALT */
+
 #endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
 
 #if defined(MBEDTLS_ECP_MONTGOMERY_ENABLED)
@@ -2243,6 +2248,7 @@ cleanup:
  * For scalar multiplication, we'll use a Montgomery ladder.
  */
 
+#if !defined(MBEDTLS_ECP_MUL_ALT)
 /*
  * Normalize Montgomery x/z coordinates: X = X/Z, Z = 1
  * Cost: 1M + 1I
@@ -2441,8 +2447,10 @@ cleanup:
     return( ret );
 }
 
+#endif /* MBEDTLS_ECP_MUL_ALT */
 #endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
 
+#if !defined(MBEDTLS_ECP_MUL_ALT)
 /*
  * Restartable multiplication R = m * P
  *
@@ -2453,6 +2461,7 @@ static int ecp_mul_restartable_internal( mbedtls_ecp_group *grp, mbedtls_ecp_poi
              const mbedtls_mpi *m, const mbedtls_ecp_point *P,
              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
              mbedtls_ecp_restart_ctx *rs_ctx )
+#endif
 {
     int ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
 #if defined(MBEDTLS_ECP_INTERNAL_ALT)
@@ -2510,13 +2519,22 @@ cleanup:
     return( ret );
 }
 
+#if !defined(MBEDTLS_ECP_MUL_ALT)
 /*
  * Restartable multiplication R = m * P
  */
+
+#if defined(MBEDTLS_ECP_MUL_ALT_SOFT_FALLBACK)
+int mbedtls_ecp_mul_restartable_soft( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
+             const mbedtls_mpi *m, const mbedtls_ecp_point *P,
+             int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
+             mbedtls_ecp_restart_ctx *rs_ctx )
+#else
 int mbedtls_ecp_mul_restartable( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
              const mbedtls_mpi *m, const mbedtls_ecp_point *P,
              int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
              mbedtls_ecp_restart_ctx *rs_ctx )
+#endif
 {
     ECP_VALIDATE_RET( grp != NULL );
     ECP_VALIDATE_RET( R   != NULL );
@@ -2528,6 +2546,7 @@ int mbedtls_ecp_mul_restartable( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
 
     return( ecp_mul_restartable_internal( grp, R, m, P, f_rng, p_rng, rs_ctx ) );
 }
+#endif /* MBEDTLS_ECP_MUL_ALT */
 
 /*
  * Multiplication R = m * P
@@ -2543,7 +2562,10 @@ int mbedtls_ecp_mul( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
     return( mbedtls_ecp_mul_restartable( grp, R, m, P, f_rng, p_rng, NULL ) );
 }
 
+#if !defined(MBEDTLS_ECP_VERIFY_ALT)
+
 #if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
+
 /*
  * Check that an affine point is valid as a public key,
  * short weierstrass curves (SEC1 3.2.3.1)
@@ -2592,6 +2614,7 @@ cleanup:
     return( ret );
 }
 #endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
+#endif /* MBEDTLS_ECP_VERIFY_ALT */
 
 #if defined(MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED)
 /*
@@ -2745,6 +2768,8 @@ int mbedtls_ecp_muladd( mbedtls_ecp_group *grp, mbedtls_ecp_point *R,
 }
 #endif /* MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
 
+#if !defined(MBEDTLS_ECP_VERIFY_ALT)
+
 #if defined(MBEDTLS_ECP_MONTGOMERY_ENABLED)
 #if defined(MBEDTLS_ECP_DP_CURVE25519_ENABLED)
 #define ECP_MPI_INIT(s, n, p) {s, (n), (mbedtls_mpi_uint *)(p)}
@@ -2858,11 +2883,19 @@ static int ecp_check_pubkey_mx( const mbedtls_ecp_group *grp, const mbedtls_ecp_
 }
 #endif /* MBEDTLS_ECP_MONTGOMERY_ENABLED */
 
+#endif /* MBEDTLS_ECP_VERIFY_ALT */
+
+#if !defined(MBEDTLS_ECP_VERIFY_ALT)
 /*
  * Check that a point is valid as a public key
  */
+#if defined(MBEDTLS_ECP_VERIFY_ALT_SOFT_FALLBACK)
+int mbedtls_ecp_check_pubkey_soft( const mbedtls_ecp_group *grp,
+                              const mbedtls_ecp_point *pt )
+#else
 int mbedtls_ecp_check_pubkey( const mbedtls_ecp_group *grp,
                               const mbedtls_ecp_point *pt )
+#endif
 {
     ECP_VALIDATE_RET( grp != NULL );
     ECP_VALIDATE_RET( pt  != NULL );
@@ -2881,6 +2914,7 @@ int mbedtls_ecp_check_pubkey( const mbedtls_ecp_group *grp,
 #endif
     return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
 }
+#endif /* MBEDTLS_ECP_VERIFY_ALT */
 
 /*
  * Check that an mbedtls_mpi is valid as a private key