fix(prover): copy tracer memory read

NilFoundation · Feb 11, 2025 · 1a1befa · 1a1befa
1 parent 1d52ae9
commit 1a1befa
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Showing 2 changed files with 23 additions and 10 deletions.
diff --git a/nil/services/synccommittee/prover/tracer/copy_tracer.go b/nil/services/synccommittee/prover/tracer/copy_tracer.go
@@ -203,7 +203,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 		if err != nil {
 			return copyEvent{}, err
 		}
-		data := getDataOverflowSafe(code, src, size)
+		data := getFixedSizeDataSafe(code, src, size)
 
 		return newFinalizedCopyEvent(CopyEvent{
 			From: CopyParticipant{
@@ -234,7 +234,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 		if err != nil {
 			return copyEvent{}, err
 		}
-		data := getDataOverflowSafe(code, src, size)
+		data := getFixedSizeDataSafe(code, src, size)
 
 		return newFinalizedCopyEvent(CopyEvent{
 			From: CopyParticipant{
@@ -256,7 +256,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 			dst  = tCtx.stack.PopUint64()
 			src  = tCtx.stack.PopUint64()
 			size = tCtx.stack.PopUint64()
-			data = getDataOverflowSafe(tCtx.vmCtx.CallInput(), src, size)
+			data = getFixedSizeDataSafe(tCtx.vmCtx.CallInput(), src, size)
 		)
 
 		return newFinalizedCopyEvent(CopyEvent{
@@ -278,7 +278,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 		var (
 			src  = tCtx.stack.PopUint64()
 			size = tCtx.stack.PopUint64()
-			data = tCtx.vmCtx.MemoryData()[src : src+size]
+			data = getDataIfStartValid(tCtx.vmCtx.MemoryData(), src, size)
 		)
 
 		return newFinalizedCopyEvent(CopyEvent{
@@ -327,7 +327,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 			_    = tCtx.stack.Pop() // value
 			src  = tCtx.stack.PopUint64()
 			size = tCtx.stack.PopUint64()
-			data = tCtx.vmCtx.MemoryData()[src : src+size]
+			data = getDataIfStartValid(tCtx.vmCtx.MemoryData(), src, size)
 		)
 		return newCopyEventWithFinalizer(CopyEvent{
 			From: CopyParticipant{
@@ -352,7 +352,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 			_    = tCtx.stack.Pop() // value
 			src  = tCtx.stack.PopUint64()
 			size = tCtx.stack.PopUint64()
-			data = tCtx.vmCtx.MemoryData()[src : src+size]
+			data = getDataIfStartValid(tCtx.vmCtx.MemoryData(), src, size)
 		)
 
 		return newCopyEventWithFinalizer(CopyEvent{
@@ -382,7 +382,7 @@ var copyEventExtractors = map[vm.OpCode]copyEventExtractor{
 		var (
 			src  = tCtx.stack.PopUint64()
 			size = tCtx.stack.PopUint64()
-			data = tCtx.vmCtx.MemoryData()[src : src+size]
+			data = getDataIfStartValid(tCtx.vmCtx.MemoryData(), src, size)
 		)
 
 		return newCopyEventWithFinalizer(CopyEvent{
@@ -427,7 +427,7 @@ func newLogCopyEvent(tCtx copyEventTraceContext) (copyEvent, error) {
 		return newEmptyCopyEvent(), nil
 	}
 
-	data := tCtx.vmCtx.MemoryData()[src : src+size]
+	data := getDataIfStartValid(tCtx.vmCtx.MemoryData(), src, size)
 
 	return newFinalizedCopyEvent(CopyEvent{
 		From: CopyParticipant{

diff --git a/nil/services/synccommittee/prover/tracer/utils.go b/nil/services/synccommittee/prover/tracer/utils.go
@@ -2,11 +2,11 @@ package tracer
 
 import "github.com/NilFoundation/nil/nil/common"
 
-// getDataOverflowSafe returns a slice from the data based on the start and size and pads
+// getFixedSizeDataSafe returns a slice from the data based on the start and size and pads
 // up to size with zero's
 // This function is borrowed from EVM impl to process some opcodes
 // (CODECOPY, EXTCODECOPY, CALLDATACOPY) the same way as it does
-func getDataOverflowSafe(data []byte, start uint64, size uint64) []byte {
+func getFixedSizeDataSafe(data []byte, start uint64, size uint64) []byte {
 	length := uint64(len(data))
 	if start > length {
 		start = length
@@ -17,3 +17,16 @@ func getDataOverflowSafe(data []byte, start uint64, size uint64) []byte {
 	}
 	return common.RightPadBytes(data[start:end], int(size))
 }
+
+// getDataIfStartValid returns a slice from `data` starting at `start` with a length of `size` bytes.
+// It returns nil if `size` is zero or if `start` is out of bounds.
+// Note: It does not check if `start+size` exceeds `data` length.
+func getDataIfStartValid(data []byte, start uint64, size uint64) []byte {
+	if size == 0 {
+		return nil
+	}
+	if len(data) < int(start+size) {
+		return nil
+	}
+	return data[start : start+size]
+}