enodia-sentinal/go-agent/internal/enrich/enrich.go

// SPDX-License-Identifier: GPL-3.0-or-later

// Package enrich builds bounded, no-I/O post-alert context from data already
// captured for a snapshot. Filesystem hashing, package ownership, and integrity
// collectors are intentionally excluded from this hot-path stage.
package enrich

import (
	"crypto/sha256"
	"encoding/hex"
	"io"
	"os"
	"regexp"
	"sort"
	"strings"
	"syscall"

	"codeberg.org/anassaeneroi/enodia-sentinal/go-agent/internal/model"
	"codeberg.org/anassaeneroi/enodia-sentinal/go-agent/internal/netutil"
)

const (
	maxAlerts     = 128
	maxProcesses  = 64
	maxIndicators = 128
	MaxHashBytes  = int64(8 << 20)
)

var (
	ipv4Pattern = regexp.MustCompile(`(?:[0-9]{1,3}\.){3}[0-9]{1,3}`)
	pathPattern = regexp.MustCompile(`/[^\s,\])]+`)
)

type Process struct {
	PID      int
	Comm     string
	Exe      string
	PPID     int
	PPIDComm string
}

// SlowResult contains bounded filesystem enrichment collected away from the
// alert-emission path. A file larger than MaxHashBytes is described but not
// hashed, avoiding unbounded worker time or memory use.
type SlowResult struct {
	Processes map[int]map[string]any
	Files     map[string]map[string]any
}

func CollectSlow(processes []Process, paths []string) SlowResult {
	result := SlowResult{Processes: map[int]map[string]any{}, Files: map[string]map[string]any{}}
	for _, process := range processes {
		exe := cleanPath(process.Exe)
		if exe == "" {
			continue
		}
		result.Processes[process.PID] = map[string]any{"exe_sha256": boundedHash(exe)}
	}
	for _, path := range paths {
		result.Files[path] = fileMetadata(path)
	}
	return result
}

func boundedHash(path string) any {
	info, err := os.Stat(path)
	if err != nil || !info.Mode().IsRegular() || info.Size() > MaxHashBytes {
		return nil
	}
	file, err := os.Open(path)
	if err != nil {
		return nil
	}
	defer file.Close()
	hash := sha256.New()
	if _, err := io.Copy(hash, io.LimitReader(file, MaxHashBytes+1)); err != nil {
		return nil
	}
	return hex.EncodeToString(hash.Sum(nil))
}

func fileMetadata(path string) map[string]any {
	info, err := os.Lstat(path)
	if err != nil {
		return map[string]any{"exists": false, "mode": nil, "uid": nil, "gid": nil}
	}
	mode, uid, gid := int(info.Mode().Perm()), -1, -1
	if stat, ok := info.Sys().(*syscall.Stat_t); ok {
		uid, gid = int(stat.Uid), int(stat.Gid)
	}
	return map[string]any{"exists": true, "mode": mode, "uid": uid, "gid": gid}
}

// Build returns the stable Python enrichment keys without invoking any slow
// collectors. Input and indicator caps keep attacker-controlled details from
// causing unbounded snapshot work or output.
func Build(alerts []model.Alert, processes []Process, lineage []int) map[string]any {
	return map[string]any{
		"source":        "enodia-sentinel-go",
		"processes":     processContext(processes),
		"remotes":       remoteContext(alerts),
		"files":         fileCandidates(alerts),
		"recent_writes": []string{},
		"lineage":       lineageContext(processes, lineage),
		"integrity":     map[string]any{},
	}
}

func processContext(processes []Process) []map[string]any {
	if len(processes) > maxProcesses {
		processes = processes[:maxProcesses]
	}
	result := make([]map[string]any, 0, len(processes))
	for _, process := range processes {
		chain := []map[string]any{}
		if process.PPID > 0 {
			chain = append(chain, map[string]any{
				"pid": process.PPID, "comm": process.PPIDComm, "ppid": 0,
			})
		}
		result = append(result, map[string]any{
			"pid": process.PID, "comm": process.Comm,
			"exe": cleanPath(process.Exe), "package_owner": nil,
			"exe_sha256": nil, "parent_chain": chain,
		})
	}
	return result
}

func remoteContext(alerts []model.Alert) []map[string]any {
	values := map[string]bool{}
	for _, alert := range cappedAlerts(alerts) {
		for _, value := range ipv4Pattern.FindAllString(alert.Detail, -1) {
			if len(values) >= maxIndicators {
				break
			}
			values[value] = true
		}
	}
	keys := sortedKeys(values)
	result := make([]map[string]any, 0, len(keys))
	for _, value := range keys {
		classification := "reserved"
		address, ok := netutil.ParseAddr(value)
		if !ok {
			classification = "invalid"
		} else if netutil.IsPublicIP(value) {
			classification = "public"
		} else if address.IsLoopback() {
			classification = "loopback"
		} else if address.IsPrivate() {
			classification = "private"
		} else if address.IsLinkLocalUnicast() {
			classification = "link-local"
		}
		result = append(result, map[string]any{"ip": value, "classification": classification})
	}
	return result
}

func fileCandidates(alerts []model.Alert) []map[string]any {
	values := map[string]bool{}
	for _, alert := range cappedAlerts(alerts) {
		for _, text := range []string{alert.Detail, alert.Key} {
			for _, value := range pathPattern.FindAllString(text, -1) {
				if len(values) >= maxIndicators {
					break
				}
				values[cleanPath(strings.TrimSuffix(value, ":"))] = true
			}
		}
	}
	keys := sortedKeys(values)
	result := make([]map[string]any, 0, len(keys))
	for _, value := range keys {
		// Existence/ownership is unknown until the deferred collector runs.
		result = append(result, map[string]any{
			"path": value, "exists": nil, "mode": nil, "uid": nil,
			"gid": nil, "package_owner": nil,
		})
	}
	return result
}

func lineageContext(processes []Process, lineage []int) []map[string]any {
	known := map[int]string{}
	for _, process := range processes {
		known[process.PID] = process.Comm
		if process.PPID > 0 && known[process.PPID] == "" {
			known[process.PPID] = process.PPIDComm
		}
	}
	values := append([]int(nil), lineage...)
	sort.Ints(values)
	if len(values) > maxProcesses*4 {
		values = values[:maxProcesses*4]
	}
	result := make([]map[string]any, 0, len(values))
	for _, pid := range values {
		comm, present := known[pid]
		result = append(result, map[string]any{"pid": pid, "comm": comm, "present": present})
	}
	return result
}

func cappedAlerts(alerts []model.Alert) []model.Alert {
	if len(alerts) > maxAlerts {
		return alerts[:maxAlerts]
	}
	return alerts
}

func sortedKeys(values map[string]bool) []string {
	result := make([]string, 0, len(values))
	for value := range values {
		if value != "" {
			result = append(result, value)
		}
	}
	sort.Strings(result)
	return result
}

func cleanPath(value string) string { return strings.ReplaceAll(value, " (deleted)", "") }