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perf(yara): Limit YARA mmap scans #436

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Merged
rabbitstack merged 1 commit into from
Feb 15, 2025
Merged

perf(yara): Limit YARA mmap scans #436

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19 changes: 16 additions & 3 deletions pkg/yara/scanner.go
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Original file line number Diff line number Diff line change
Expand Up @@ -72,7 +72,8 @@ type scanner struct {

psnap ps.Snapshotter

rwxs map[uint32]va.Address // contains scanned and matched RWX process allocations
rwxs map[uint32]va.Address // contains scanned and matched RWX process allocations
mmaps map[uint32]va.Address // contains scanned and matched suspicious memory mappings
}

// NewScanner creates a new YARA scanner.
Expand Down Expand Up @@ -141,6 +142,7 @@ func NewScanner(psnap ps.Snapshotter, config config.Config) (Scanner, error) {
config: config,
psnap: psnap,
rwxs: make(map[uint32]va.Address),
mmaps: make(map[uint32]va.Address),
}, nil
}

Expand Down Expand Up @@ -173,7 +175,9 @@ func (s scanner) CanEnqueue() bool { return false }
func (s *scanner) ProcessEvent(evt *kevent.Kevent) (bool, error) {
if evt.IsTerminateProcess() {
// cleanup
delete(s.rwxs, evt.Kparams.MustGetPid())
pid := evt.Kparams.MustGetPid()
delete(s.rwxs, pid)
delete(s.mmaps, pid)
}
return s.Scan(evt)
}
Expand Down Expand Up @@ -292,7 +296,7 @@ func (s scanner) Scan(e *kevent.Kevent) (bool, error) {
pid := e.Kparams.MustGetPid()
prot := e.Kparams.MustGetUint32(kparams.MemProtect)
size := e.Kparams.MustGetUint64(kparams.FileViewSize)
if e.PID != 4 && size >= 4096 && ((prot&sys.SectionRX) != 0 && (prot&sys.SectionRWX) != 0) {
if e.PID != 4 && size >= 4096 && ((prot&sys.SectionRX) != 0 && (prot&sys.SectionRWX) != 0) && !s.isMmapMatched(pid) {
filename := e.GetParamAsString(kparams.FilePath)
// skip mappings of signed images
addr := e.Kparams.MustGetUint64(kparams.FileViewBase)
Expand All @@ -314,6 +318,9 @@ func (s scanner) Scan(e *kevent.Kevent) (bool, error) {
e.GetParamAsString(kparams.FileViewBase))
matches, err = s.scan(pid)
}
if len(matches) > 0 {
s.mmaps[pid] = va.Address(addr)
}
mmapScans.Add(1)
isScanned = true
}
Expand Down Expand Up @@ -462,3 +469,9 @@ func (s *scanner) isRwxMatched(pid uint32) (ok bool) {
_, ok = s.rwxs[pid]
return ok
}

// isMmapMatched returns true if the process already triggered suspicious mmap rule match.
func (s *scanner) isMmapMatched(pid uint32) (ok bool) {
_, ok = s.mmaps[pid]
return ok
}