ecp_curves: Added unit-tests for `secp224k1`

This patch introduces basic unit-testing for the `ecp_mod_p224k1()`.

The method is exposed through the ecp_invasive interface, and
the standard testing data is being provided by the python framework.

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index 4b64d3a..4ebe5de 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -4612,7 +4612,8 @@
 int mbedtls_ecp_mod_p192k1(mbedtls_mpi *);
 #endif
 #if defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
-static int ecp_mod_p224k1(mbedtls_mpi *);
+MBEDTLS_STATIC_TESTABLE
+int ecp_mod_p224k1(mbedtls_mpi *);
 #endif
 #if defined(MBEDTLS_ECP_DP_SECP256K1_ENABLED)
 static int ecp_mod_p256k1(mbedtls_mpi *);
@@ -5628,7 +5629,8 @@
  * Fast quasi-reduction modulo p224k1 = 2^224 - R,
  * with R = 2^32 + 2^12 + 2^11 + 2^9 + 2^7 + 2^4 + 2 + 1 = 0x0100001A93
  */
-static int ecp_mod_p224k1(mbedtls_mpi *N)
+MBEDTLS_STATIC_TESTABLE
+int ecp_mod_p224k1(mbedtls_mpi *N)
 {
     static mbedtls_mpi_uint Rp[] = {
         MBEDTLS_BYTES_TO_T_UINT_8(0x93, 0x1A, 0x00, 0x00, 0x01, 0x00, 0x00,
diff --git a/library/ecp_invasive.h b/library/ecp_invasive.h
index 73b2a56..ae8598d 100644
--- a/library/ecp_invasive.h
+++ b/library/ecp_invasive.h
@@ -179,6 +179,12 @@
 int mbedtls_ecp_mod_p192k1(mbedtls_mpi *N);
 
 #endif /* MBEDTLS_ECP_DP_SECP192K1_ENABLED */
+#if defined(MBEDTLS_ECP_DP_SECP224K1_ENABLED)
+
+MBEDTLS_STATIC_TESTABLE
+int ecp_mod_p224k1(mbedtls_mpi *N);
+
+#endif /* MBEDTLS_ECP_DP_SECP224K1_ENABLED */
 
 /** Initialise a modulus with hard-coded const curve data.
  *
diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index 8a711ce..94ecdfe 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -552,3 +552,68 @@
     @property
     def is_valid(self) -> bool:
         return True
+
+
+class EcpP224K1Raw(bignum_common.ModOperationCommon,
+                   EcpTarget):
+    """Test cases for ECP P224 fast reduction."""
+    symbol = "-"
+    test_function = "ecp_mod_p224k1"
+    test_name = "ecp_mod_p224k1"
+    input_style = "fixed"
+    arity = 1
+    dependencies = ["MBEDTLS_ECP_DP_SECP224K1_ENABLED"]
+
+    moduli = ["fffffffffffffffffffffffffffffffffffffffffffffffeffffe56d"] # type: List[str]
+
+    input_values = [
+        "0", "1",
+
+        # Modulus - 1
+        "fffffffffffffffffffffffffffffffffffffffffffffffeffffe56c",
+
+        # Modulus + 1
+        "fffffffffffffffffffffffffffffffffffffffffffffffeffffe56e",
+
+        # 2^224 - 1
+        "ffffffffffffffffffffffffffffffffffffffffffffffffffffffff",
+
+        # Maximum canonical P224 multiplication result
+        ("fffffffffffffffffffffffffffffffffffffffffffffffdffffcad8"
+         "00000000000000000000000000000000000000010000352802c26590"),
+
+        # First 8 number generated by random.getrandbits(448) - seed(2,2)
+        ("da94e3e8ab73738fcf1822ffbc6887782b491044d5e341245c6e4337"
+         "15ba2bdd177219d30e7a269fd95bafc8f2a4d27bdcf4bb99f4bea973"),
+        ("cdbd47d364be8049a372db8f6e405d93ffed9235288bc781ae662675"
+         "94c9c9500925e4749b575bd13653f8dd9b1f282e4067c3584ee207f8"),
+        ("defc044a09325626e6b58de744ab6cce80877b6f71e1f6d2ef8acd12"
+         "8b4f2fc15f3f57ebf30b94fa82523e86feac7eb7dc38f519b91751da"),
+        ("2d6c797f8f7d9b782a1be9cd8697bbd0e2520e33e44c50556c71c4a6"
+         "6148a86fe8624fab5186ee32ee8d7ee9770348a05d300cb90706a045"),
+        ("8f54f8ceacaab39e83844b40ffa9b9f15c14bc4a829e07b0829a48d4"
+         "22fe99a22c70501e533c91352d3d854e061b90303b08c6e33c729578"),
+        ("97eeab64ca2ce6bc5d3fd983c34c769fe89204e2e8168561867e5e15"
+         "bc01bfce6a27e0dfcbf8754472154e76e4c11ab2fec3f6b32e8d4b8a"),
+        ("a7a83ee0761ebfd2bd143fa9b714210c665d7435c1066932f4767f26"
+         "294365b2721dea3bf63f23d0dbe53fcafb2147df5ca495fa5a91c89b"),
+        ("74667bffe202849da9643a295a9ac6decbd4d3e2d4dec9ef83f0be4e"
+         "80371eb97f81375eecc1cb6347733e847d718d733ff98ff387c56473"),
+
+        # Next 2 number generated by random.getrandbits(224)
+        ("eb9ac688b9d39cca91551e8259cc60b17604e4b4e73695c3e652c71a"),
+        ("f0caeef038c89b38a8acb5137c9260dc74e088a9b9492f258ebdbfe3"),
+    ]
+
+    @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)
+
+    def result(self) -> List[str]:
+        result = self.int_a % self.int_n
+        return [self.format_result(result)]
+
+    @property
+    def is_valid(self) -> bool:
+        return True
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index bcd8e61..6630c59 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -1394,6 +1394,50 @@
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_TEST_HOOKS:MBEDTLS_ECP_DP_SECP224K1_ENABLED */
+void ecp_mod_p224k1(char *input_N,
+                    char *input_X,
+                    char *result)
+{
+    mbedtls_mpi X;
+    mbedtls_mpi_uint *N = NULL;
+    mbedtls_mpi_uint *res = NULL;
+    size_t limbs_N;
+    size_t limbs_res;
+
+    mbedtls_mpi_mod_modulus m;
+    mbedtls_mpi_init(&X);
+    mbedtls_mpi_mod_modulus_init(&m);
+
+    TEST_EQUAL(mbedtls_test_read_mpi(&X, input_X), 0);
+    TEST_EQUAL(mbedtls_test_read_mpi_core(&N,   &limbs_N,   input_N), 0);
+    TEST_EQUAL(mbedtls_test_read_mpi_core(&res, &limbs_res, result),  0);
+
+    size_t limbs = limbs_N;
+    size_t bytes = limbs * sizeof(mbedtls_mpi_uint);
+
+    TEST_EQUAL(X.s,  1);
+    TEST_LE_U(X.n, 448 / biL);
+    TEST_EQUAL(limbs_res, limbs);
+
+    TEST_EQUAL(mbedtls_mpi_mod_modulus_setup(
+                   &m, N, limbs,
+                   MBEDTLS_MPI_MOD_REP_MONTGOMERY), 0);
+
+    TEST_EQUAL(mbedtls_ecp_mod_p224k1(&X), 0);
+    TEST_LE_U(mbedtls_mpi_core_bitlen(X.p, X.n), 224);
+    mbedtls_mpi_mod_raw_fix_quasi_reduction(X.p, &m);
+    ASSERT_COMPARE(X.p, bytes, res, bytes);
+
+exit:
+    mbedtls_mpi_free(&X);
+    mbedtls_free(res);
+
+    mbedtls_mpi_mod_modulus_free(&m);
+    mbedtls_free(N);
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:MBEDTLS_TEST_HOOKS */
 void ecp_mod_setup(char *input_A, int id, int ctype, int iret)
 {