dexorder

lib_openzeppelin_contracts/certora/specs/EnumerableSet.spec

@@ -0,0 +1,246 @@
+import "helpers/helpers.spec";
+
+methods {
+    // library
+    function add(bytes32)      external returns (bool)    envfree;
+    function remove(bytes32)   external returns (bool)    envfree;
+    function contains(bytes32) external returns (bool)    envfree;
+    function length()          external returns (uint256) envfree;
+    function at_(uint256)      external returns (bytes32) envfree;
+
+    // FV
+    function _positionOf(bytes32) external returns (uint256) envfree;
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Helpers                                                                                                             │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+definition sanity() returns bool =
+    length() < max_uint256;
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Invariant: All indexed keys are contained                                                                           │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+invariant indexedContained(uint256 index)
+    index < length() => contains(at_(index))
+    {
+        preserved {
+            requireInvariant consistencyIndex(index);
+            requireInvariant consistencyIndex(require_uint256(length() - 1));
+        }
+    }
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Invariant: A value can only be stored at a single location                                                          │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+invariant atUniqueness(uint256 index1, uint256 index2)
+    index1 == index2 <=> at_(index1) == at_(index2)
+    {
+        preserved remove(bytes32 key) {
+            requireInvariant atUniqueness(index1, require_uint256(length() - 1));
+            requireInvariant atUniqueness(index2, require_uint256(length() - 1));
+        }
+    }
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Invariant: index <> key relationship is consistent                                                                  │
+│                                                                                                                     │
+│ Note that the two consistencyXxx invariants, put together, prove that at_ and _positionOf are inverse of one        │
+│ another. This proves that we have a bijection between indices (the enumerability part) and keys (the entries that   │
+│ are added and removed from the EnumerableSet).                                                                      │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+invariant consistencyIndex(uint256 index)
+    index < length() => _positionOf(at_(index)) == require_uint256(index + 1)
+    {
+        preserved remove(bytes32 key) {
+            requireInvariant consistencyIndex(require_uint256(length() - 1));
+        }
+    }
+
+invariant consistencyKey(bytes32 key)
+    contains(key) => (
+        _positionOf(key) > 0 &&
+        _positionOf(key) <= length() &&
+        at_(require_uint256(_positionOf(key) - 1)) == key
+    )
+    {
+        preserved remove(bytes32 otherKey) {
+            requireInvariant consistencyKey(otherKey);
+            requireInvariant atUniqueness(
+                require_uint256(_positionOf(key) - 1),
+                require_uint256(_positionOf(otherKey) - 1)
+            );
+        }
+    }
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: state only changes by adding or removing elements                                                             │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule stateChange(env e, bytes32 key) {
+    require sanity();
+    requireInvariant consistencyKey(key);
+
+    uint256 lengthBefore   = length();
+    bool    containsBefore = contains(key);
+
+    method f;
+    calldataarg args;
+    f(e, args);
+
+    uint256 lengthAfter   = length();
+    bool    containsAfter = contains(key);
+
+    assert lengthBefore != lengthAfter => (
+        (f.selector == sig:add(bytes32).selector    && lengthAfter == require_uint256(lengthBefore + 1)) ||
+        (f.selector == sig:remove(bytes32).selector && lengthAfter == require_uint256(lengthBefore - 1))
+    );
+
+    assert containsBefore != containsAfter => (
+        (f.selector == sig:add(bytes32).selector    && containsAfter) ||
+        (f.selector == sig:remove(bytes32).selector && containsBefore)
+    );
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: check liveness of view functions.                                                                             │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule liveness_1(bytes32 key) {
+    requireInvariant consistencyKey(key);
+
+    // contains never revert
+    contains@withrevert(key);
+    assert !lastReverted;
+}
+
+rule liveness_2(uint256 index) {
+    requireInvariant consistencyIndex(index);
+
+    // length never revert
+    uint256 length = length@withrevert();
+    assert !lastReverted;
+
+    // at reverts iff the index is out of bound
+    at_@withrevert(index);
+    assert !lastReverted <=> index < length;
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: add key to EnumerableSet if not already contained                                                             │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule add(bytes32 key, bytes32 otherKey) {
+    require sanity();
+
+    uint256 lengthBefore        = length();
+    bool    containsBefore      = contains(key);
+    bool    containsOtherBefore = contains(otherKey);
+
+    bool added = add@withrevert(key);
+    bool success = !lastReverted;
+
+    assert success && contains(key),
+        "liveness & immediate effect";
+
+    assert added <=> !containsBefore,
+        "return value: added iff not contained";
+
+    assert length() == require_uint256(lengthBefore + to_mathint(added ? 1 : 0)),
+        "effect: length increases iff added";
+
+    assert added => at_(lengthBefore) == key,
+        "effect: add at the end";
+
+    assert containsOtherBefore != contains(otherKey) => (added && key == otherKey),
+        "side effect: other keys are not affected";
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: remove key from EnumerableSet if already contained                                                            │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule remove(bytes32 key, bytes32 otherKey) {
+    requireInvariant consistencyKey(key);
+    requireInvariant consistencyKey(otherKey);
+
+    uint256 lengthBefore        = length();
+    bool    containsBefore      = contains(key);
+    bool    containsOtherBefore = contains(otherKey);
+
+    bool removed = remove@withrevert(key);
+    bool success = !lastReverted;
+
+    assert success && !contains(key),
+        "liveness & immediate effect";
+
+    assert removed <=> containsBefore,
+        "return value: removed iff contained";
+
+    assert length() == require_uint256(lengthBefore - to_mathint(removed ? 1 : 0)),
+        "effect: length decreases iff removed";
+
+    assert containsOtherBefore != contains(otherKey) => (removed && key == otherKey),
+        "side effect: other keys are not affected";
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: when adding a new key, the other keys remain in set, at the same index.                                       │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule addEnumerability(bytes32 key, uint256 index) {
+    require sanity();
+
+    bytes32 atBefore = at_(index);
+    add(key);
+    bytes32 atAfter = at_@withrevert(index);
+    bool atAfterSuccess = !lastReverted;
+
+    assert atAfterSuccess;
+    assert atBefore == atAfter;
+}
+
+/*
+┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
+│ Rule: when removing a existing key, the other keys remain in set, at the same index (except for the last one).      │
+└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+*/
+rule removeEnumerability(bytes32 key, uint256 index) {
+    uint256 last = require_uint256(length() - 1);
+
+    requireInvariant consistencyKey(key);
+    requireInvariant consistencyIndex(index);
+    requireInvariant consistencyIndex(last);
+
+    bytes32 atBefore = at_(index);
+    bytes32 lastBefore = at_(last);
+
+    remove(key);
+
+    // can't read last value (length decreased)
+    bytes32 atAfter = at_@withrevert(index);
+    assert lastReverted <=> index == last;
+
+    // One value that is allowed to change is if previous value was removed,
+    // in that case the last value before took its place.
+    assert (
+        index != last &&
+        atBefore != atAfter
+    ) => (
+        atBefore == key &&
+        atAfter == lastBefore
+    );
+}