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chargen.go
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chargen.go
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// Copyright 2017 Capsule8, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sensor
import (
"fmt"
api "github.com/capsule8/capsule8/api/v0"
"github.com/capsule8/capsule8/pkg/expression"
"github.com/capsule8/capsule8/pkg/sys"
"github.com/capsule8/capsule8/pkg/sys/perf"
"google.golang.org/genproto/googleapis/rpc/code"
)
var chargenEventTypes = expression.FieldTypeMap{
"index": expression.ValueTypeUnsignedInt64,
"characters": expression.ValueTypeString,
}
type chargenFilter struct {
sensor *Sensor
}
func (c *chargenFilter) decodeChargenEvent(
sample *perf.SampleRecord,
data perf.TraceEventSampleData,
) (interface{}, error) {
e := c.sensor.NewEvent()
e.Event = &api.TelemetryEvent_Chargen{
Chargen: &api.ChargenEvent{
Index: data["index"].(uint64),
Characters: data["characters"].(string),
},
}
return e, nil
}
func generateCharacters(start, length uint64) string {
bytes := make([]byte, length)
for i := uint64(0); i < length; i++ {
bytes[i] = ' ' + byte((start+i)%95)
}
return string(bytes)
}
func registerChargenEvents(
sensor *Sensor,
subscr *subscription,
events []*api.ChargenEventFilter,
) {
f := chargenFilter{sensor: sensor}
eventID, err := sensor.Monitor.RegisterExternalEvent("chargen",
f.decodeChargenEvent)
if err != nil {
subscr.logStatus(
code.Code_UNKNOWN,
fmt.Sprintf("Could not register chargen event: %v", err))
return
}
done := make(chan struct{})
nchargens := 0
for _, e := range events {
// XXX there should be a maximum bound here too ...
if e.Length == 0 || e.Length > 1<<16 {
subscr.logStatus(
code.Code_INVALID_ARGUMENT,
fmt.Sprintf("Chargen length out of range (%d)", e.Length))
continue
}
nchargens++
go func() {
index := uint64(0)
length := e.Length
for {
select {
case <-done:
return
default:
monoNow := sys.CurrentMonotonicRaw()
sampleID := perf.SampleID{
Time: uint64(monoNow),
}
s := generateCharacters(index, length)
data := perf.TraceEventSampleData{
"index": index,
"characters": s,
}
index += length
sensor.Monitor.EnqueueExternalSample(
eventID, sampleID, data)
}
}
}()
}
if nchargens == 0 {
sensor.Monitor.UnregisterEvent(eventID)
} else {
es, _ := subscr.addEventSink(eventID, nil, chargenEventTypes)
es.unregister = func(es *eventSink) {
sensor.Monitor.UnregisterEvent(es.eventID)
close(done)
}
}
}