Add generated tests for mpi_gcd()

Signed-off-by: Felix Conway <[email protected]>

scripts/generate_bignum_tests.py

@@ -212,6 +212,72 @@ class BignumInvMod(BignumOperation):
         return [bignum_common.quote_str("{:x}".format(self._result)), "0"]
 
 
+class BignumGCD(BignumOperation):
+    """Test cases for greatest common divisor."""
+    count = 0
+    symbol = "GCD"
+    test_function = "mpi_gcd"
+    test_name = "GCD"
+    # The default values are not very useful here, so clear them.
+    input_values = [] # type: List[str]
+    input_cases = bignum_common.combination_two_lists(
+        # Input values for A
+        [
+            "3c094fd6b36ee4902c8ba84d13a401def90a2130116dad3361",
+            "-3c094fd6b36ee4902c8ba84d13a401def90a2130116dad3361",
+            "b2b06ebe14a185a83d5d2d7bddd1dd0e05e800d6b914fbed4e",
+            "-b2b06ebe14a185a83d5d2d7bddd1dd0e05e800d6b914fbed4e",
+            "203265b387",
+            "-203265b387",
+            "9bc8e63852",
+            "-9bc8e63852",
+            "123456789abcdef",
+            "-123456789abcdef",
+            "50000",
+            "-50000",
+        ],
+        # Input values for B
+        [
+            "63522ef00b3fa4c6773f1116dca45c121ee51b722644d96b63",
+            "-63522ef00b3fa4c6773f1116dca45c121ee51b722644d96b63",
+            "20902ee9da48664a3b9d5d68542405ac0ad0dd90ce79d633c0",
+            "-20902ee9da48664a3b9d5d68542405ac0ad0dd90ce79d633c0",
+            "7e9de225bb",
+            "-7e9de225bb",
+            "4796a42828",
+            "-4796a42828",
+            "123456789abcdef",
+            "-123456789abcdef",
+            "50000",
+            "-50000",
+        ],
+    )
+
+    def __init__(self, val_a: str, val_b: str) -> None:
+        super().__init__(val_a, val_b)
+        # We always expect a positive result.
+        self._result = abs(bignum_common.gcd(self.int_a, self.int_b))
+
+    def description_suffix(self) -> str:
+        suffix = ": "
+        if abs(self.int_a) > abs(self.int_b):
+            suffix += "|A|>|B|"
+        elif abs(self.int_a) < abs(self.int_b):
+            suffix += "|A|<|B|"
+        else:
+            suffix += "|A|=|B|"
+        if self.int_a < 0:
+            suffix += ", A<0"
+        if self.int_b < 0:
+            suffix += ", B<0"
+        suffix += ", A even" if (self.int_a % 2 == 0) else ", A odd"
+        suffix += ", B even" if (self.int_b % 2 == 0) else ", B odd"
+        return suffix
+
+    def result(self) -> List[str]:
+        return [bignum_common.quote_str("{:x}".format(self._result))]
+
+
 class BignumAdd(BignumOperation):
     """Test cases for bignum value addition."""
     count = 0

scripts/mbedtls_framework/bignum_common.py

@@ -30,6 +30,13 @@ def invmod(a: int, n: int) -> int:
         return b
     raise ValueError("Not invertible")
 
+def gcd(a: int, b: int) -> int:
+    """Return the greatest common divisor of two numbers.
+       The result will match the sign of b."""
+    while b:
+        a, b = b, a % b
+    return a
+
 def invmod_positive(a: int, n: int) -> int:
     """Return a non-negative inverse of a to modulo n.