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Add function to validate difficulty changes

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The rule against difficulty adjustments changing by more than a factor of 4 can
be helpful for anti-DoS measures in contexts where we lack a full headers
chain, so expose this functionality separately and in the narrow case where we
only know the height, new value, and old value.

Includes fuzz test by Martin Zumsande.
This commit is contained in:
Suhas Daftuar
2022-05-25 10:16:56 -04:00
parent 2bd9aa5a44
commit 1d4cfa4272
4 changed files with 125 additions and 4 deletions
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27
src/test/pow_tests.cpp
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@@ -20,7 +20,14 @@ BOOST_AUTO_TEST_CASE(get_next_work)
pindexLast.nHeight = 32255;
pindexLast.nTime = 1262152739; // Block #32255
pindexLast.nBits = 0x1d00ffff;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), 0x1d00d86aU);
// Here (and below): expected_nbits is calculated in
// CalculateNextWorkRequired(); redoing the calculation here would be just
// reimplementing the same code that is written in pow.cpp. Rather than
// copy that code, we just hardcode the expected result.
unsigned int expected_nbits = 0x1d00d86aU;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), expected_nbits);
BOOST_CHECK(PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, expected_nbits));
}
/* Test the constraint on the upper bound for next work */
@@ -32,7 +39,9 @@ BOOST_AUTO_TEST_CASE(get_next_work_pow_limit)
pindexLast.nHeight = 2015;
pindexLast.nTime = 1233061996; // Block #2015
pindexLast.nBits = 0x1d00ffff;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), 0x1d00ffffU);
unsigned int expected_nbits = 0x1d00ffffU;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), expected_nbits);
BOOST_CHECK(PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, expected_nbits));
}
/* Test the constraint on the lower bound for actual time taken */
@@ -44,7 +53,12 @@ BOOST_AUTO_TEST_CASE(get_next_work_lower_limit_actual)
pindexLast.nHeight = 68543;
pindexLast.nTime = 1279297671; // Block #68543
pindexLast.nBits = 0x1c05a3f4;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), 0x1c0168fdU);
unsigned int expected_nbits = 0x1c0168fdU;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), expected_nbits);
BOOST_CHECK(PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, expected_nbits));
// Test that reducing nbits further would not be a PermittedDifficultyTransition.
unsigned int invalid_nbits = expected_nbits-1;
BOOST_CHECK(!PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, invalid_nbits));
}
/* Test the constraint on the upper bound for actual time taken */
@@ -56,7 +70,12 @@ BOOST_AUTO_TEST_CASE(get_next_work_upper_limit_actual)
pindexLast.nHeight = 46367;
pindexLast.nTime = 1269211443; // Block #46367
pindexLast.nBits = 0x1c387f6f;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), 0x1d00e1fdU);
unsigned int expected_nbits = 0x1d00e1fdU;
BOOST_CHECK_EQUAL(CalculateNextWorkRequired(&pindexLast, nLastRetargetTime, chainParams->GetConsensus()), expected_nbits);
BOOST_CHECK(PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, expected_nbits));
// Test that increasing nbits further would not be a PermittedDifficultyTransition.
unsigned int invalid_nbits = expected_nbits+1;
BOOST_CHECK(!PermittedDifficultyTransition(chainParams->GetConsensus(), pindexLast.nHeight+1, pindexLast.nBits, invalid_nbits));
}
BOOST_AUTO_TEST_CASE(CheckProofOfWork_test_negative_target)