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Prevent possible from_multiplier () function overflow (#2265)

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* Prevent possible from_multiplier () function overflow

* Remove not required asserts

* Add more comments & test with 0 difficulty

* Update zero base difficulty test

* Formatting
This commit is contained in:
Sergey Kroshnin 2019-09-03 10:50:19 +03:00 • committed by Guilherme Lawless
commit 658855f6b4
2 changed files with 61 additions and 1 deletions
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59
nano/core_test/difficulty.cpp
View file

@ -26,6 +26,24 @@ TEST (difficulty, multipliers)
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (expected_multiplier, base));
}
{
uint64_t base = std::numeric_limits<std::uint64_t>::max ();
uint64_t difficulty = 0xffffffffffffff00;
double expected_multiplier = 0.00390625;
ASSERT_NEAR (expected_multiplier, nano::difficulty::to_multiplier (difficulty, base), 1e-10);
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (expected_multiplier, base));
}
{
uint64_t base = 0x8000000000000000;
uint64_t difficulty = 0xf000000000000000;
double expected_multiplier = 8.0;
ASSERT_NEAR (expected_multiplier, nano::difficulty::to_multiplier (difficulty, base), 1e-10);
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (expected_multiplier, base));
}
{
#ifndef NDEBUG
// Causes valgrind to be noisy
@ -46,3 +64,44 @@ TEST (difficulty, network_constants)
{
ASSERT_NEAR (16., nano::difficulty::to_multiplier (nano::network_constants::publish_full_threshold, nano::network_constants::publish_beta_threshold), 1e-10);
}
TEST (difficulty, overflow)
{
// Overflow max (attempt to overflow & receive lower difficulty)
{
uint64_t base = std::numeric_limits<std::uint64_t>::max (); // Max possible difficulty
uint64_t difficulty = std::numeric_limits<std::uint64_t>::max ();
double multiplier = 1.001; // Try to increase difficulty above max
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (multiplier, base));
}
// Overflow min (attempt to overflow & receive higher difficulty)
{
uint64_t base = 1; // Min possible difficulty before 0
uint64_t difficulty = 0;
double multiplier = 0.999; // Decrease difficulty
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (multiplier, base));
}
}
TEST (difficulty, zero)
{
// Tests with base difficulty 0 should return 0 with any multiplier
{
uint64_t base = 0; // Min possible difficulty
uint64_t difficulty = 0;
double multiplier = 0.000000001; // Decrease difficulty
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (multiplier, base));
}
{
uint64_t base = 0; // Min possible difficulty
uint64_t difficulty = 0;
double multiplier = 1000000000.0; // Increase difficulty
ASSERT_EQ (difficulty, nano::difficulty::from_multiplier (multiplier, base));
}
}

3
nano/lib/numbers.cpp
View file

@ -823,7 +823,8 @@ std::string nano::to_string (double const value_a, int const precision_a)
uint64_t nano::difficulty::from_multiplier (double const multiplier_a, uint64_t const base_difficulty_a)
{
assert (multiplier_a > 0.);
return (-static_cast<uint64_t> ((-base_difficulty_a) / multiplier_a));
uint64_t reverse_difficulty (static_cast<uint64_t> ((-base_difficulty_a) / multiplier_a));
return (reverse_difficulty != 0 || base_difficulty_a == 0 || multiplier_a < 1. ? -reverse_difficulty : std::numeric_limits<std::uint64_t>::max ());
}
double nano::difficulty::to_multiplier (uint64_t const difficulty_a, uint64_t const base_difficulty_a)