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fix: remove unsafe exec() in tracer.go #90

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fix: remove unsafe exec() in tracer.go #90

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85c223e
fix: V-003 security vulnerability
orbisai0security May 11, 2026
e3918e5
fix: use AllThreadsSyscall6 for process-wide capability drop
orbisai0security Jun 4, 2026
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35 changes: 35 additions & 0 deletions pkg/trace/tracer.go
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,11 @@ import (
"os"
"sync"
"sync/atomic"
"syscall"
"unsafe"

"github.com/pkg/errors"
"golang.org/x/sys/unix"

"github.com/maxgio92/xcover/internal/settings"
"github.com/maxgio92/xcover/internal/utils"
Expand Down Expand Up @@ -117,6 +120,11 @@ func (t *UserTracer) Run(ctx context.Context) error {
t.logger.Debug().Msg("attaching trace to selected functions")
t.attachProbe(ctx)

// Drop elevated capabilities after BPF programs are loaded and attached.
if err := dropElevatedCapabilities(); err != nil {
t.logger.Warn().Err(err).Msg("failed to drop elevated capabilities after BPF attach")
}

feedCh := make(chan []byte, feedChBufSize)

eventsCh, err := t.probe.InitEventBuf(ctx)
Expand Down Expand Up @@ -281,3 +289,30 @@ func (t *UserTracer) writeReport(reportPath string) error {

return report.WriteReport(file)
}

func dropElevatedCapabilities() error {

@maxgio92 maxgio92 Jun 4, 2026 •
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This doesn't work with the Go scheduler, since it is going to apply only to the current thread - it is persistent with goroutine preemption or new ones scheduled on different runtime threads - unless probably GOMAXPROCS=1

hdr := unix.CapUserHeader{Version: unix.LINUX_CAPABILITY_VERSION_3}
var data [2]unix.CapUserData
if err := unix.Capget(&hdr, &data[0]); err != nil {
return err
}

data[0].Effective &^= uint32(1) << unix.CAP_SYS_ADMIN
data[0].Permitted &^= uint32(1) << unix.CAP_SYS_ADMIN
data[1].Effective &^= uint32(1) << (unix.CAP_BPF - 32)
data[1].Permitted &^= uint32(1) << (unix.CAP_BPF - 32)

// Apply to ALL OS threads in the process, not just the calling thread.
// This is necessary because Go's scheduler can move goroutines between
// threads, and capset() alone only affects the current thread.
_, _, errno := syscall.AllThreadsSyscall6(
unix.SYS_CAPSET,
uintptr(unsafe.Pointer(&hdr)),
uintptr(unsafe.Pointer(&data[0])),
0, 0, 0, 0,
)
if errno != 0 {
return errno
}
return nil
}