eth/tracers/native: prevent panic for LOG edge-cases (#26848)

This PR fixes OOM panic in the callTracer as well as panicing on
opcode validation errors (e.g. stack underflow) in callTracer and
prestateTracer.

Co-authored-by: Martin Holst Swende <martin@swende.se>

eth/tracers/js/goja.go

@@ -32,10 +32,6 @@ import (
 	jsassets "github.com/ethereum/go-ethereum/eth/tracers/js/internal/tracers"
 )
 
-const (
-	memoryPadLimit = 1024 * 1024
-)
-
 var assetTracers = make(map[string]string)
 
 // init retrieves the JavaScript transaction tracers included in go-ethereum.
@@ -571,14 +567,10 @@ func (mo *memoryObj) slice(begin, end int64) ([]byte, error) {
 	if end < begin || begin < 0 {
 		return nil, fmt.Errorf("tracer accessed out of bound memory: offset %d, end %d", begin, end)
 	}
-	mlen := mo.memory.Len()
-	if end-int64(mlen) > memoryPadLimit {
-		return nil, fmt.Errorf("tracer reached limit for padding memory slice: end %d, memorySize %d", end, mlen)
+	slice, err := tracers.GetMemoryCopyPadded(mo.memory, begin, end-begin)
+	if err != nil {
+		return nil, err
 	}
-	slice := make([]byte, end-begin)
-	end = min(end, int64(mo.memory.Len()))
-	ptr := mo.memory.GetPtr(begin, end-begin)
-	copy(slice[:], ptr[:])
 	return slice, nil
 }
 
@@ -959,10 +951,3 @@ func (l *steplog) setupObject() *goja.Object {
 	o.Set("contract", l.contract.setupObject())
 	return o
 }
-
-func min(a, b int64) int64 {
-	if a < b {
-		return a
-	}
-	return b
-}

eth/tracers/js/tracer_test.go

@@ -150,12 +150,12 @@ func TestTracer(t *testing.T) {
 		}, {
 			code:     "{res: [], step: function(log) { if (log.op.toString() === 'STOP') { this.res.push(log.memory.slice(5, 1025 * 1024)) } }, fault: function() {}, result: function() { return this.res }}",
 			want:     "",
-			fail:     "tracer reached limit for padding memory slice: end 1049600, memorySize 32 at step (<eval>:1:83(20))    in server-side tracer function 'step'",
+			fail:     "reached limit for padding memory slice: 1049568 at step (<eval>:1:83(20))    in server-side tracer function 'step'",
 			contract: []byte{byte(vm.PUSH1), byte(0xff), byte(vm.PUSH1), byte(0x00), byte(vm.MSTORE8), byte(vm.STOP)},
 		},
 	} {
 		if have, err := execTracer(tt.code, tt.contract); tt.want != string(have) || tt.fail != err {
-			t.Errorf("testcase %d: expected return value to be '%s' got '%s', error to be '%s' got '%s'\n\tcode: %v", i, tt.want, string(have), tt.fail, err, tt.code)
+			t.Errorf("testcase %d: expected return value to be \n'%s'\n\tgot\n'%s'\nerror to be\n'%s'\n\tgot\n'%s'\n\tcode: %v", i, tt.want, string(have), tt.fail, err, tt.code)
 		}
 	}
 }