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Initial cut for auto enable sigma rules #406

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merged 3 commits into from
Apr 3, 2024
Merged

Initial cut for auto enable sigma rules #406

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b9fd709
Initial cut for auto enable sigma rules
defensivedepth Apr 2, 2024
00bfb0d
Add config option to auto-enable specific Sigma rules
defensivedepth Apr 3, 2024
36c1fcb
Refactored for unit test
defensivedepth Apr 3, 2024
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18 changes: 17 additions & 1 deletion server/modules/elastalert/elastalert.go
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Original file line number Diff line number Diff line change
Expand Up @@ -61,6 +61,7 @@ type ElastAlertEngine struct {
elastAlertRulesFolder string
rulesFingerprintFile string
sigmaRulePackages []string
autoEnabledSigmaRules []string
rulesRepos []*module.RuleRepo
reposFolder string
isRunning bool
Expand All @@ -74,6 +75,19 @@ type ElastAlertEngine struct {
IOManager
}

func checkRulesetEnabled(e *ElastAlertEngine, det *model.Detection) {

det.IsEnabled = false
metaCombined := *det.Ruleset + "+" + string(det.Severity)
for _, rule := range e.autoEnabledSigmaRules {
if rule == metaCombined {
det.IsEnabled = true
break
}
}

}

func NewElastAlertEngine(srv *server.Server) *ElastAlertEngine {
return &ElastAlertEngine{
srv: srv,
Expand All @@ -94,6 +108,7 @@ func (e *ElastAlertEngine) Init(config module.ModuleConfig) (err error) {
e.elastAlertRulesFolder = module.GetStringDefault(config, "elastAlertRulesFolder", "/opt/sensoroni/elastalert")
e.rulesFingerprintFile = module.GetStringDefault(config, "rulesFingerprintFile", "/opt/sensoroni/fingerprints/sigma.fingerprint")
e.autoUpdateEnabled = module.GetBoolDefault(config, "autoUpdateEnabled", false)
e.autoEnabledSigmaRules = module.GetStringArrayDefault(config, "autoEnabledSigmaRules", []string{"securityonion-resources+critical", "securityonion-resources+high"})

pkgs := module.GetStringArrayDefault(config, "sigmaRulePackages", []string{"core", "emerging_threats_addon"})
e.parseSigmaPackages(pkgs)
Expand Down Expand Up @@ -836,7 +851,8 @@ func (e *ElastAlertEngine) syncCommunityDetections(ctx context.Context, detectio
results.Unchanged++
}
} else {
det.IsEnabled = false

checkRulesetEnabled(e, det)

_, err = e.srv.Detectionstore.CreateDetection(ctx, det)
if err != nil {
Expand Down
28 changes: 28 additions & 0 deletions server/modules/elastalert/elastalert_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,34 @@ import (
"gopkg.in/yaml.v3"
)

func TestCheckAutoEnabledSigmaRule(t *testing.T) {
e := &ElastAlertEngine{
autoEnabledSigmaRules: []string{"securityonion-resources+high", "core+critical"},
}

tests := []struct {
name string
ruleset string
severity model.Severity
expected bool
}{
{"securityonion-resources rule with high severity, rule enabled", "securityonion-resources", model.SeverityHigh, true},
{"core rule with critical severity, rule enabled", "core", model.SeverityCritical, true},
{"core rule with high severity, rule not enabled", "core", model.SeverityHigh, false},
}

for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
det := &model.Detection{
Ruleset: util.Ptr(tt.ruleset),
Severity: tt.severity,
}
checkRulesetEnabled(e, det)
assert.Equal(t, tt.expected, det.IsEnabled)
})
}
}

func TestElastAlertModule(t *testing.T) {
srv := &server.Server{
DetectionEngines: map[model.EngineName]server.DetectionEngine{},
Expand Down
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