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eth/tracers: do the JSON serialization via .js to capture C faults #22857

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merged 1 commit into from May 11, 2021
Merged

eth/tracers: do the JSON serialization via .js to capture C faults #22857

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24 changes: 19 additions & 5 deletions eth/tracers/tracer.go
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Expand Up @@ -505,7 +505,7 @@ func (jst *Tracer) Stop(err error) {

// call executes a method on a JS object, catching any errors, formatting and
// returning them as error objects.
func (jst *Tracer) call(method string, args ...string) (json.RawMessage, error) {
func (jst *Tracer) call(noret bool, method string, args ...string) (json.RawMessage, error) {
// Execute the JavaScript call and return any error
jst.vm.PushString(method)
for _, arg := range args {
Expand All @@ -519,7 +519,21 @@ func (jst *Tracer) call(method string, args ...string) (json.RawMessage, error)
return nil, errors.New(err)
}
// No error occurred, extract return value and return
return json.RawMessage(jst.vm.JsonEncode(-1)), nil
if noret {
return nil, nil
}
// Push a JSON marshaller onto the stack. We can't marshal from the out-
// side because duktape can crash on large nestings and we can't catch
// C++ exceptions ourselves from Go. TODO(karalabe): Yuck, why wrap?!
jst.vm.PushString("(JSON.stringify)")
jst.vm.Eval()

jst.vm.Swap(-1, -2)
if code = jst.vm.Pcall(1); code != 0 {
err := jst.vm.SafeToString(-1)
return nil, errors.New(err)
}
return json.RawMessage(jst.vm.SafeToString(-1)), nil
}

func wrapError(context string, err error) error {
Expand Down Expand Up @@ -578,7 +592,7 @@ func (jst *Tracer) CaptureState(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost
*jst.errorValue = err.Error()
}

if _, err := jst.call("step", "log", "db"); err != nil {
if _, err := jst.call(true, "step", "log", "db"); err != nil {
jst.err = wrapError("step", err)
}
}
Expand All @@ -592,7 +606,7 @@ func (jst *Tracer) CaptureFault(env *vm.EVM, pc uint64, op vm.OpCode, gas, cost
jst.errorValue = new(string)
*jst.errorValue = err.Error()

if _, err := jst.call("fault", "log", "db"); err != nil {
if _, err := jst.call(true, "fault", "log", "db"); err != nil {
jst.err = wrapError("fault", err)
}
}
Expand Down Expand Up @@ -640,7 +654,7 @@ func (jst *Tracer) GetResult() (json.RawMessage, error) {
jst.vm.PutPropString(jst.stateObject, "ctx")

// Finalize the trace and return the results
result, err := jst.call("result", "ctx", "db")
result, err := jst.call(false, "result", "ctx", "db")
if err != nil {
jst.err = wrapError("result", err)
}
Expand Down
14 changes: 9 additions & 5 deletions eth/tracers/tracer_test.go
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Expand Up @@ -78,7 +78,7 @@ func runTrace(tracer *Tracer, vmctx *vmContext) (json.RawMessage, error) {
}

func TestTracer(t *testing.T) {
execTracer := func(code string) []byte {
execTracer := func(code string) ([]byte, string) {
t.Helper()
ctx := &vmContext{blockCtx: vm.BlockContext{BlockNumber: big.NewInt(1)}, txCtx: vm.TxContext{GasPrice: big.NewInt(100000)}}
tracer, err := New(code, ctx.txCtx)
Expand All @@ -87,13 +87,14 @@ func TestTracer(t *testing.T) {
}
ret, err := runTrace(tracer, ctx)
if err != nil {
t.Fatal(err)
return nil, err.Error() // Stringify to allow comparison without nil checks
}
return ret
return ret, ""
}
for i, tt := range []struct {
code string
want string
fail string
}{
{ // tests that we don't panic on bad arguments to memory access
code: "{depths: [], step: function(log) { this.depths.push(log.memory.slice(-1,-2)); }, fault: function() {}, result: function() { return this.depths; }}",
Expand All @@ -116,10 +117,13 @@ func TestTracer(t *testing.T) {
}, { // tests intrinsic gas
code: "{depths: [], step: function() {}, fault: function() {}, result: function(ctx) { return ctx.gasPrice+'.'+ctx.gasUsed+'.'+ctx.intrinsicGas; }}",
want: `"100000.6.21000"`,
}, { // tests too deep object / serialization crash
code: "{step: function() {}, fault: function() {}, result: function() { var o={}; var x=o; for (var i=0; i<1000; i++){ o.foo={}; o=o.foo; } return x; }}",
fail: "RangeError: json encode recursion limit in server-side tracer function 'result'",
},
} {
if have := execTracer(tt.code); tt.want != string(have) {
t.Errorf("testcase %d: expected return value to be %s got %s\n\tcode: %v", i, tt.want, string(have), tt.code)
if have, err := execTracer(tt.code); 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)
}
}
}
Expand Down