From 598d1cc41b14556bb85d36f31df1f11c4a83fc33 Mon Sep 17 00:00:00 2001 From: Josh Rickmar Date: Mon, 11 Nov 2024 18:18:15 +0000 Subject: [PATCH] mixclient: Sort roots for slot assignment The purpose of the SR (slot reservation) mix is to determine unique anonymous slot positions for the DC-net (xor) mix. However, there was a missing check by non-root-solving peers that the published roots are in the proper order. This could result in a malicious actor publishing roots in a different order, disrupting mixes by causing non-root-solving peers to unknowingly perform the DC-net in the wrong slots, and causing the wrong peers to be blamed for disrupting the mix. Prevent this by requiring roots to be sorted before slots are discovered. This also matches the root-sorting that occurred in the older client-server design. This change is not compatible with previous mixclient versions, as the DC-net mix would occur with peers writing messages into different slots. The pairing version included in PR messages is updated to reflect this. --- mixing/mixclient/client.go | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/mixing/mixclient/client.go b/mixing/mixclient/client.go index a1131cdfc..13b42353e 100644 --- a/mixing/mixclient/client.go +++ b/mixing/mixclient/client.go @@ -37,7 +37,7 @@ import ( // MinPeers is the minimum number of peers required for a mix run to proceed. const MinPeers = 4 -const pairingFlags byte = 0 +const pairingVersion byte = 1 const ( timeoutDuration = 30 * time.Second @@ -725,7 +725,7 @@ func (c *Client) Dicemix(ctx context.Context, cj *CoinJoin) error { pr, err := wire.NewMsgMixPairReq(*p.id, cj.prExpiry, cj.mixValue, string(mixing.ScriptClassP2PKHv0), cj.tx.Version, cj.tx.LockTime, cj.mcount, cj.inputValue, cj.prUTXOs, - cj.change, prFlags, pairingFlags) + cj.change, prFlags, pairingVersion) if err != nil { return err } @@ -1731,6 +1731,9 @@ func (c *Client) roots(ctx context.Context, seenSRs []chainhash.Hash, close(publishedRoots) return nil, errTriggeredBlame } + sort.Slice(roots, func(i, j int) bool { + return roots[i].Cmp(roots[j]) == -1 + }) rootBytes := make([][]byte, len(roots)) for i, root := range roots { rootBytes[i] = root.Bytes() @@ -1802,6 +1805,12 @@ func (c *Client) roots(ctx context.Context, seenSRs []chainhash.Hash, roots = append(roots, root) } } + sorted := sort.SliceIsSorted(roots, func(i, j int) bool { + return roots[i].Cmp(roots[j]) == -1 + }) + if !sorted { + continue + } if len(roots) == len(a)-1 { return roots, nil }