Improve testing of mbedtls_mpi_gcd() and mbedtls_mpi_inv_mod()
Signed-off-by: Felix Conway <felix.conway@arm.com>
diff --git a/include/mbedtls/bignum.h b/include/mbedtls/bignum.h
index 1e1c063..ed0c4e7 100644
--- a/include/mbedtls/bignum.h
+++ b/include/mbedtls/bignum.h
@@ -988,10 +988,13 @@
* \brief Compute the modular inverse: X = A^-1 mod N
*
* \param X The destination MPI. This must point to an initialized MPI.
+ * The value returned on success will be between [1, N-1].
* \param A The MPI to calculate the modular inverse of. This must point
- * to an initialized MPI.
+ * to an initialized MPI. This value can be negative, in which
+ * case a positive answer will still be returned in \p X.
* \param N The base of the modular inversion. This must point to an
- * initialized MPI.
+ * initialized MPI. If this points to the same MPI as \p X,
+ * then the value returned in \p X will be incorrect.
*
* \return \c 0 if successful.
* \return #MBEDTLS_ERR_MPI_ALLOC_FAILED if a memory allocation failed.
diff --git a/tests/suites/test_suite_bignum.function b/tests/suites/test_suite_bignum.function
index 36f1476..c94e7cc 100644
--- a/tests/suites/test_suite_bignum.function
+++ b/tests/suites/test_suite_bignum.function
@@ -390,12 +390,23 @@
mbedtls_mpi A, X, Y, Z;
mbedtls_mpi_init(&A); mbedtls_mpi_init(&X); mbedtls_mpi_init(&Y); mbedtls_mpi_init(&Z);
- TEST_ASSERT(mbedtls_test_read_mpi(&X, input_X) == 0);
- TEST_ASSERT(mbedtls_test_read_mpi(&Y, input_Y) == 0);
- TEST_ASSERT(mbedtls_test_read_mpi(&A, input_A) == 0);
- TEST_ASSERT(mbedtls_mpi_gcd(&Z, &X, &Y) == 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&X, input_X), 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&Y, input_Y), 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&A, input_A), 0);
+ TEST_EQUAL(mbedtls_mpi_gcd(&Z, &X, &Y), 0);
TEST_ASSERT(sign_is_valid(&Z));
- TEST_ASSERT(mbedtls_mpi_cmp_mpi(&Z, &A) == 0);
+ TEST_EQUAL(mbedtls_mpi_cmp_mpi(&Z, &A), 0);
+
+ mbedtls_mpi *Z_alias_X = &X;
+ TEST_EQUAL(mbedtls_mpi_gcd(Z_alias_X, &X, &Y), 0);
+ TEST_ASSERT(sign_is_valid(Z_alias_X));
+ TEST_EQUAL(mbedtls_mpi_cmp_mpi(Z_alias_X, &A), 0);
+
+ mbedtls_mpi *Z_alias_Y = &Y;
+ TEST_EQUAL(mbedtls_mpi_gcd(Z_alias_Y, &X, &Y), 0);
+ TEST_ASSERT(sign_is_valid(Z_alias_Y));
+ TEST_EQUAL(mbedtls_mpi_cmp_mpi(Z_alias_Y, &A), 0);
+
exit:
mbedtls_mpi_free(&A); mbedtls_mpi_free(&X); mbedtls_mpi_free(&Y); mbedtls_mpi_free(&Z);
@@ -1134,14 +1145,32 @@
int res;
mbedtls_mpi_init(&X); mbedtls_mpi_init(&Y); mbedtls_mpi_init(&Z); mbedtls_mpi_init(&A);
- TEST_ASSERT(mbedtls_test_read_mpi(&X, input_X) == 0);
- TEST_ASSERT(mbedtls_test_read_mpi(&Y, input_Y) == 0);
- TEST_ASSERT(mbedtls_test_read_mpi(&A, input_A) == 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&X, input_X), 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&Y, input_Y), 0);
+ TEST_EQUAL(mbedtls_test_read_mpi(&A, input_A), 0);
res = mbedtls_mpi_inv_mod(&Z, &X, &Y);
- TEST_ASSERT(res == div_result);
+ TEST_EQUAL(res, div_result);
if (res == 0) {
TEST_ASSERT(sign_is_valid(&Z));
- TEST_ASSERT(mbedtls_mpi_cmp_mpi(&Z, &A) == 0);
+ TEST_EQUAL(mbedtls_mpi_cmp_mpi(&Z, &A), 0);
+ }
+
+ mbedtls_mpi *Z_alias_X = &X;
+ res = mbedtls_mpi_inv_mod(Z_alias_X, &X, &Y);
+ TEST_EQUAL(res, div_result);
+ if (res == 0) {
+ TEST_ASSERT(sign_is_valid(Z_alias_X));
+ TEST_EQUAL(mbedtls_mpi_cmp_mpi(Z_alias_X, &A), 0);
+ }
+
+ /* When Z is an alias of Y, the answer returned in Z is normally incorrect. */
+ mbedtls_mpi *Z_alias_Y = &Y;
+ res = mbedtls_mpi_inv_mod(Z_alias_Y, &X, &Y);
+ TEST_EQUAL(res, div_result);
+ if (res == 0) {
+ TEST_ASSERT(sign_is_valid(Z_alias_Y));
+ /* Testing if Z_alias_Y == &A is not useful as it is true sometimes, but is
+ often false. */
}
exit:
diff --git a/tests/suites/test_suite_bignum.misc.data b/tests/suites/test_suite_bignum.misc.data
index 2e3ff1e..d4c7300 100644
--- a/tests/suites/test_suite_bignum.misc.data
+++ b/tests/suites/test_suite_bignum.misc.data
@@ -1504,6 +1504,9 @@
Test GCD: 0 < A = B
mpi_gcd:"109fe45714866e56fdd4ad9b6b686df27224afb7868cf4f0cbb794526932853cbf0beea61594166654d13cd9fe0d9da594a97ee20230f12fb5434de73fb4f8102725a01622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af":"109fe45714866e56fdd4ad9b6b686df27224afb7868cf4f0cbb794526932853cbf0beea61594166654d13cd9fe0d9da594a97ee20230f12fb5434de73fb4f8102725a01622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af":"109fe45714866e56fdd4ad9b6b686df27224afb7868cf4f0cbb794526932853cbf0beea61594166654d13cd9fe0d9da594a97ee20230f12fb5434de73fb4f8102725a01622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af"
+Test GCD: A = B < 0
+mpi_gcd:"-9986dabb54d13cd9fe0d9da594a97e8372ab26ed98ff622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af":"-9986dabb54d13cd9fe0d9da594a97e8372ab26ed98ff622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af":"9986dabb54d13cd9fe0d9da594a97e8372ab26ed98ff622b31b1ea42e3a265019039ac1df31869bd97930d792fb72cdaa971d8a8015af"
+
Base test mbedtls_mpi_inv_mod #1
mpi_inv_mod:"3":"b":"4":0