From 6f12bfaf30ae730744fee5ed8b719274b04f632f Mon Sep 17 00:00:00 2001
From: Oleg Kovalov <hey@olegk.dev>
Date: Wed, 18 Sep 2024 16:46:51 +0200
Subject: [PATCH] feat(verify): remove height check in Verify (#216)

Remove `heightThreshold` check in `Verify` func.
---
 headertest/verify_test.go | 15 ++++++++++-----
 p2p/exchange.go           |  2 +-
 sync/sync_head.go         |  8 +-------
 verify.go                 | 31 +++++++++++--------------------
 4 files changed, 23 insertions(+), 33 deletions(-)

diff --git a/headertest/verify_test.go b/headertest/verify_test.go
index 2774c056..07d233e5 100644
--- a/headertest/verify_test.go
+++ b/headertest/verify_test.go
@@ -87,17 +87,22 @@ func TestVerify(t *testing.T) {
 		},
 		{
 			prepare: func() *DummyHeader {
-				untrusted := next()
-				untrusted.HeightI += 100000
-				return untrusted
+				return zero
 			},
-			err: header.ErrHeightFromFuture,
+			err: header.ErrZeroHeader,
+		},
+		{
+			trusted: zero,
+			prepare: func() *DummyHeader {
+				return next()
+			},
+			err: header.ErrZeroHeader,
 		},
 	}
 
 	for i, test := range tests {
 		t.Run(strconv.Itoa(i), func(t *testing.T) {
-			err := header.Verify(trusted, test.prepare(), 0)
+			err := header.Verify(test.trusted, test.prepare())
 			if test.err != nil {
 				var verErr *header.VerifyError
 				assert.ErrorAs(t, err, &verErr)
diff --git a/p2p/exchange.go b/p2p/exchange.go
index 3f6a6572..900b06a8 100644
--- a/p2p/exchange.go
+++ b/p2p/exchange.go
@@ -182,7 +182,7 @@ func (ex *Exchange[H]) Head(ctx context.Context, opts ...header.HeadOption[H]) (
 			}
 			// if tracked (untrusted) peers were requested, verify head
 			if useTrackedPeers {
-				err = header.Verify[H](reqParams.TrustedHead, headers[0], header.DefaultHeightThreshold)
+				err = header.Verify[H](reqParams.TrustedHead, headers[0])
 				if err != nil {
 					var verErr *header.VerifyError
 					if errors.As(err, &verErr) && verErr.SoftFailure {
diff --git a/sync/sync_head.go b/sync/sync_head.go
index a5a97a3a..93642cab 100644
--- a/sync/sync_head.go
+++ b/sync/sync_head.go
@@ -167,13 +167,7 @@ func (s *Syncer[H]) verify(ctx context.Context, newHead H) (bool, error) {
 		return true, &header.VerifyError{Reason: err, SoftFailure: true}
 	}
 
-	var heightThreshold uint64
-	if s.Params.TrustingPeriod != 0 && s.Params.blockTime != 0 {
-		buffer := time.Hour * 48 / s.Params.blockTime // generous buffer to account for variable block time
-		heightThreshold = uint64(s.Params.TrustingPeriod/s.Params.blockTime + buffer)
-	}
-
-	err = header.Verify(sbjHead, newHead, heightThreshold)
+	err = header.Verify(sbjHead, newHead)
 	if err == nil {
 		return false, nil
 	}
diff --git a/verify.go b/verify.go
index 0c1f3e9e..c9840014 100644
--- a/verify.go
+++ b/verify.go
@@ -13,11 +13,11 @@ const DefaultHeightThreshold uint64 = 80000 // ~ 14 days of 15 second headers
 // Verify verifies untrusted Header against trusted following general Header checks and
 // custom user-specific checks defined in Header.Verify
 //
-// If heightThreshold is zero, uses DefaultHeightThreshold.
+// Given headers must be non-zero
 // Always returns VerifyError.
-func Verify[H Header[H]](trstd, untrstd H, heightThreshold uint64) error {
+func Verify[H Header[H]](trstd, untrstd H) error {
 	// general mandatory verification
-	err := verify[H](trstd, untrstd, heightThreshold)
+	err := verify[H](trstd, untrstd)
 	if err != nil {
 		return &VerifyError{Reason: err}
 	}
@@ -45,11 +45,10 @@ func Verify[H Header[H]](trstd, untrstd H, heightThreshold uint64) error {
 
 // verify is a little bro of Verify yet performs mandatory Header checks
 // for any Header implementation.
-func verify[H Header[H]](trstd, untrstd H, heightThreshold uint64) error {
-	if heightThreshold == 0 {
-		heightThreshold = DefaultHeightThreshold
+func verify[H Header[H]](trstd, untrstd H) error {
+	if trstd.IsZero() {
+		return ErrZeroHeader
 	}
-
 	if untrstd.IsZero() {
 		return ErrZeroHeader
 	}
@@ -71,24 +70,16 @@ func verify[H Header[H]](trstd, untrstd H, heightThreshold uint64) error {
 	if known {
 		return fmt.Errorf("%w: '%d' <= current '%d'", ErrKnownHeader, untrstd.Height(), trstd.Height())
 	}
-	// reject headers with height too far from the future
-	// this is essential for headers failed non-adjacent verification
-	// yet taken as sync target
-	adequateHeight := untrstd.Height()-trstd.Height() < heightThreshold
-	if !adequateHeight {
-		return fmt.Errorf("%w: '%d' - current '%d' >= threshold '%d'", ErrHeightFromFuture, untrstd.Height(), trstd.Height(), heightThreshold)
-	}
 
 	return nil
 }
 
 var (
-	ErrZeroHeader       = errors.New("zero header")
-	ErrWrongChainID     = errors.New("wrong chain id")
-	ErrUnorderedTime    = errors.New("unordered headers")
-	ErrFromFuture       = errors.New("header is from the future")
-	ErrKnownHeader      = errors.New("known header")
-	ErrHeightFromFuture = errors.New("header height is far from future")
+	ErrZeroHeader    = errors.New("zero header")
+	ErrWrongChainID  = errors.New("wrong chain id")
+	ErrUnorderedTime = errors.New("unordered headers")
+	ErrFromFuture    = errors.New("header is from the future")
+	ErrKnownHeader   = errors.New("known header")
 )
 
 // VerifyError is thrown if a Header failed verification.