206 lines
4.9 KiB
Go
206 lines
4.9 KiB
Go
package appsec_rule
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import (
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"fmt"
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"hash/fnv"
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"strings"
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)
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type ModsecurityRule struct {
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ids []uint32
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}
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var zonesMap map[string]string = map[string]string{
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"ARGS": "ARGS_GET",
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"ARGS_NAMES": "ARGS_GET_NAMES",
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"BODY_ARGS": "ARGS_POST",
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"BODY_ARGS_NAMES": "ARGS_POST_NAMES",
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"HEADERS_NAMES": "REQUEST_HEADERS_NAMES",
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"HEADERS": "REQUEST_HEADERS",
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"METHOD": "REQUEST_METHOD",
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"PROTOCOL": "REQUEST_PROTOCOL",
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"URI": "REQUEST_URI",
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"RAW_BODY": "REQUEST_BODY",
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"FILENAMES": "FILES",
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}
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var transformMap map[string]string = map[string]string{
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"lowercase": "t:lowercase",
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"uppercase": "t:uppercase",
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"b64decode": "t:base64Decode",
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"hexdecode": "t:hexDecode",
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"length": "t:length",
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}
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var matchMap map[string]string = map[string]string{
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"regex": "@rx",
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"equals": "@streq",
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"startsWith": "@beginsWith",
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"endsWith": "@endsWith",
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"contains": "@contains",
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"libinjectionSQL": "@detectSQLi",
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"libinjectionXSS": "@detectXSS",
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"gt": "@gt",
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"lt": "@lt",
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"gte": "@ge",
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"lte": "@le",
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"eq": "@eq",
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}
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var bodyTypeMatch map[string]string = map[string]string{
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"json": "JSON",
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"xml": "XML",
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"multipart": "MULTIPART",
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"urlencoded": "URLENCODED",
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}
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func (m *ModsecurityRule) Build(rule *CustomRule, appsecRuleName string) (string, []uint32, error) {
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rules, err := m.buildRules(rule, appsecRuleName, false, 0, 0)
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if err != nil {
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return "", nil, err
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}
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//We return the id of the first generated rule, as it's the interesting one in case of chain or skip
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return strings.Join(rules, "\n"), m.ids, nil
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}
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func (m *ModsecurityRule) generateRuleID(rule *CustomRule, appsecRuleName string, depth int) uint32 {
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h := fnv.New32a()
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h.Write([]byte(appsecRuleName))
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h.Write([]byte(rule.Match.Type))
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h.Write([]byte(rule.Match.Value))
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h.Write([]byte(fmt.Sprintf("%d", depth)))
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for _, zone := range rule.Zones {
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h.Write([]byte(zone))
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}
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for _, transform := range rule.Transform {
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h.Write([]byte(transform))
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}
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id := h.Sum32()
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m.ids = append(m.ids, id)
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return id
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}
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func (m *ModsecurityRule) buildRules(rule *CustomRule, appsecRuleName string, and bool, toSkip int, depth int) ([]string, error) {
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ret := make([]string, 0)
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if len(rule.And) != 0 && len(rule.Or) != 0 {
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return nil, fmt.Errorf("cannot have both 'and' and 'or' in the same rule")
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}
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if rule.And != nil {
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for c, andRule := range rule.And {
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depth++
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lastRule := c == len(rule.And)-1 // || len(rule.Or) == 0
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rules, err := m.buildRules(&andRule, appsecRuleName, !lastRule, 0, depth)
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if err != nil {
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return nil, err
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}
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ret = append(ret, rules...)
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}
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}
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if rule.Or != nil {
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for c, orRule := range rule.Or {
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depth++
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skip := len(rule.Or) - c - 1
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rules, err := m.buildRules(&orRule, appsecRuleName, false, skip, depth)
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if err != nil {
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return nil, err
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}
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ret = append(ret, rules...)
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}
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}
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r := strings.Builder{}
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r.WriteString("SecRule ")
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if rule.Zones == nil {
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return ret, nil
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}
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zone_prefix := ""
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variable_prefix := ""
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if rule.Transform != nil {
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for tidx, transform := range rule.Transform {
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if transform == "count" {
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zone_prefix = "&"
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rule.Transform[tidx] = ""
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}
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}
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}
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for idx, zone := range rule.Zones {
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if idx > 0 {
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r.WriteByte('|')
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}
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mappedZone, ok := zonesMap[zone]
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if !ok {
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return nil, fmt.Errorf("unknown zone '%s'", zone)
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}
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if len(rule.Variables) == 0 {
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r.WriteString(mappedZone)
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} else {
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for j, variable := range rule.Variables {
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if j > 0 {
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r.WriteByte('|')
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}
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r.WriteString(fmt.Sprintf("%s%s:%s%s", zone_prefix, mappedZone, variable_prefix, variable))
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}
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}
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}
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r.WriteByte(' ')
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if rule.Match.Type != "" {
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if match, ok := matchMap[rule.Match.Type]; ok {
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prefix := ""
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if rule.Match.Not {
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prefix = "!"
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}
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r.WriteString(fmt.Sprintf(`"%s%s %s"`, prefix, match, rule.Match.Value))
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} else {
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return nil, fmt.Errorf("unknown match type '%s'", rule.Match.Type)
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}
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}
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//Should phase:2 be configurable?
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r.WriteString(fmt.Sprintf(` "id:%d,phase:2,deny,log,msg:'%s',tag:'crowdsec-%s'`, m.generateRuleID(rule, appsecRuleName, depth), appsecRuleName, appsecRuleName))
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if rule.Transform != nil {
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for _, transform := range rule.Transform {
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if transform == "" {
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continue
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}
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r.WriteByte(',')
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if mappedTransform, ok := transformMap[transform]; ok {
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r.WriteString(mappedTransform)
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} else {
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return nil, fmt.Errorf("unknown transform '%s'", transform)
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}
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}
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}
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if rule.BodyType != "" {
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if mappedBodyType, ok := bodyTypeMatch[rule.BodyType]; ok {
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r.WriteString(fmt.Sprintf(",ctl:requestBodyProcessor=%s", mappedBodyType))
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} else {
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return nil, fmt.Errorf("unknown body type '%s'", rule.BodyType)
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}
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}
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if and {
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r.WriteString(",chain")
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}
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if toSkip > 0 {
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r.WriteString(fmt.Sprintf(",skip:%d", toSkip))
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}
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r.WriteByte('"')
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ret = append(ret, r.String())
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return ret, nil
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}
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