Merge pull request #7482 from gabor-mezei-arm/6029_use_core_api_in_ecp_mod_koblitz
[Bignum] Use core API in ecp_mod_koblitz()
diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index f0a3e6e..db35e96 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -25,6 +25,8 @@
#include "mbedtls/platform_util.h"
#include "mbedtls/error.h"
+#include "mbedtls/platform.h"
+
#include "bn_mul.h"
#include "bignum_core.h"
#include "ecp_invasive.h"
@@ -5525,6 +5527,7 @@
#if defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED) || \
defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED) || \
defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
+
/*
* Fast quasi-reduction modulo P = 2^s - R,
* with R about 33 bits, used by the Koblitz curves.
@@ -5532,69 +5535,101 @@
* Write N as A0 + 2^224 A1, return A0 + R * A1.
* Actually do two passes, since R is big.
*/
-#define P_KOBLITZ_MAX (256 / 8 / sizeof(mbedtls_mpi_uint)) // Max limbs in P
#define P_KOBLITZ_R (8 / sizeof(mbedtls_mpi_uint)) // Limbs in R
-static inline int ecp_mod_koblitz(mbedtls_mpi *N, mbedtls_mpi_uint *Rp, size_t p_limbs,
- size_t adjust, size_t shift, mbedtls_mpi_uint mask)
-{
- int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
- mbedtls_mpi M, R;
- mbedtls_mpi_uint Mp[P_KOBLITZ_MAX + P_KOBLITZ_R + 1];
- if (N->n < p_limbs) {
- return 0;
+static inline int ecp_mod_koblitz(mbedtls_mpi_uint *X,
+ size_t X_limbs,
+ mbedtls_mpi_uint *R,
+ size_t bits)
+{
+ int ret = 0;
+
+ /* Determine if A1 is aligned to limb bitsize. If not then the used limbs
+ * of P, A0 and A1 must be set accordingly and there is a middle limb
+ * which is shared by A0 and A1 and need to handle accordingly.
+ */
+ size_t shift = bits % biL;
+ size_t adjust = (shift + biL - 1) / biL;
+ size_t P_limbs = bits / biL + adjust;
+
+ mbedtls_mpi_uint *A1 = mbedtls_calloc(P_limbs, ciL);
+ if (A1 == NULL) {
+ return MBEDTLS_ERR_ECP_ALLOC_FAILED;
}
- /* Init R */
- R.s = 1;
- R.p = Rp;
- R.n = P_KOBLITZ_R;
+ /* Create a buffer to store the value of `R * A1` */
+ size_t R_limbs = P_KOBLITZ_R;
+ size_t M_limbs = P_limbs + R_limbs;
+ mbedtls_mpi_uint *M = mbedtls_calloc(M_limbs, ciL);
+ if (M == NULL) {
+ ret = MBEDTLS_ERR_ECP_ALLOC_FAILED;
+ goto cleanup;
+ }
- /* Common setup for M */
- M.s = 1;
- M.p = Mp;
+ mbedtls_mpi_uint mask = 0;
+ if (adjust != 0) {
+ mask = ((mbedtls_mpi_uint) 1 << shift) - 1;
+ }
for (size_t pass = 0; pass < 2; pass++) {
- /* M = A1 */
- M.n = N->n - (p_limbs - adjust);
- if (M.n > p_limbs + adjust) {
- M.n = p_limbs + adjust;
- }
- memset(Mp, 0, sizeof(Mp));
- memcpy(Mp, N->p + p_limbs - adjust, M.n * sizeof(mbedtls_mpi_uint));
+ /* Copy A1 */
+ memcpy(A1, X + P_limbs - adjust, P_limbs * ciL);
+
+ /* Shift A1 to be aligned */
if (shift != 0) {
- MBEDTLS_MPI_CHK(mbedtls_mpi_shift_r(&M, shift));
+ mbedtls_mpi_core_shift_r(A1, P_limbs, shift);
}
- M.n += R.n; /* Make room for multiplication by R */
- /* N = A0 */
+ /* Zeroize the A1 part of the shared limb */
if (mask != 0) {
- N->p[p_limbs - 1] &= mask;
- }
- for (size_t i = p_limbs; i < N->n; i++) {
- N->p[i] = 0;
+ X[P_limbs - 1] &= mask;
}
- /* N = A0 + R * A1 */
- MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&M, &M, &R));
- MBEDTLS_MPI_CHK(mbedtls_mpi_add_abs(N, N, &M));
+ /* X = A0
+ * Zeroize the A1 part of X to keep only the A0 part.
+ */
+ for (size_t i = P_limbs; i < X_limbs; i++) {
+ X[i] = 0;
+ }
+
+ /* X = A0 + R * A1 */
+ mbedtls_mpi_core_mul(M, A1, P_limbs, R, R_limbs);
+ (void) mbedtls_mpi_core_add(X, X, M, P_limbs + R_limbs);
+
+ /* Carry can not be generated since R is a 33-bit value and stored in
+ * 64 bits. The result value of the multiplication is at most
+ * P length + 33 bits in length and the result value of the addition
+ * is at most P length + 34 bits in length. So the result of the
+ * addition always fits in P length + 64 bits.
+ */
}
cleanup:
+ mbedtls_free(M);
+ mbedtls_free(A1);
+
return ret;
}
+
#endif /* MBEDTLS_ECP_DP_SECP192K1_ENABLED) ||
MBEDTLS_ECP_DP_SECP224K1_ENABLED) ||
MBEDTLS_ECP_DP_SECP256K1_ENABLED) */
#if defined(MBEDTLS_ECP_DP_SECP192K1_ENABLED)
+
/*
* Fast quasi-reduction modulo p192k1 = 2^192 - R,
- * with R = 2^32 + 2^12 + 2^8 + 2^7 + 2^6 + 2^3 + 1 = 0x0100001119
+ * with R = 2^32 + 2^12 + 2^8 + 2^7 + 2^6 + 2^3 + 1 = 0x01000011C9
*/
static int ecp_mod_p192k1(mbedtls_mpi *N)
{
- return mbedtls_ecp_mod_p192k1(N);
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ size_t expected_width = 2 * ((192 + biL - 1) / biL);
+ MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
+ ret = mbedtls_ecp_mod_p192k1(N);
+
+cleanup:
+ return ret;
}
MBEDTLS_STATIC_TESTABLE
@@ -5605,16 +5640,22 @@
0x00)
};
- return ecp_mod_koblitz(N, Rp, 192 / 8 / sizeof(mbedtls_mpi_uint), 0, 0,
- 0);
+ return ecp_mod_koblitz(N->p, N->n, Rp, 192);
}
+
#endif /* MBEDTLS_ECP_DP_SECP192K1_ENABLED */
#if defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
static int ecp_mod_p224k1(mbedtls_mpi *N)
{
- return mbedtls_ecp_mod_p224k1(N);
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ size_t expected_width = 2 * 224 / biL;
+ MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
+ ret = mbedtls_ecp_mod_p224k1(N);
+
+cleanup:
+ return ret;
}
/*
@@ -5629,12 +5670,7 @@
0x00)
};
-#if defined(MBEDTLS_HAVE_INT64)
- return ecp_mod_koblitz(N, Rp, 4, 1, 32, 0xFFFFFFFF);
-#else
- return ecp_mod_koblitz(N, Rp, 224 / 8 / sizeof(mbedtls_mpi_uint), 0, 0,
- 0);
-#endif
+ return ecp_mod_koblitz(N->p, N->n, Rp, 224);
}
#endif /* MBEDTLS_ECP_DP_SECP224K1_ENABLED */
@@ -5643,7 +5679,13 @@
static int ecp_mod_p256k1(mbedtls_mpi *N)
{
- return mbedtls_ecp_mod_p256k1(N);
+ int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
+ size_t expected_width = 2 * ((256 + biL - 1) / biL);
+ MBEDTLS_MPI_CHK(mbedtls_mpi_grow(N, expected_width));
+ ret = mbedtls_ecp_mod_p256k1(N);
+
+cleanup:
+ return ret;
}
/*
@@ -5657,8 +5699,7 @@
MBEDTLS_BYTES_TO_T_UINT_8(0xD1, 0x03, 0x00, 0x00, 0x01, 0x00, 0x00,
0x00)
};
- return ecp_mod_koblitz(N, Rp, 256 / 8 / sizeof(mbedtls_mpi_uint), 0, 0,
- 0);
+ return ecp_mod_koblitz(N->p, N->n, Rp, 256);
}
#endif /* MBEDTLS_ECP_DP_SECP256K1_ENABLED */
diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index f9f27fa..2dae703 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -672,8 +672,7 @@
@property
def arg_a(self) -> str:
- hex_digits = bignum_common.hex_digits_for_limb(448 // self.bits_in_limb, self.bits_in_limb)
- return super().format_arg('{:x}'.format(self.int_a)).zfill(hex_digits)
+ return super().format_arg('{:x}'.format(self.int_a)).zfill(2 * self.hex_digits)
def result(self) -> List[str]:
result = self.int_a % self.int_n