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|
package netceptor
import (
"fmt"
"reflect"
"regexp"
"strings"
)
type FirewallRuleData map[interface{}]interface{}
type FirewallRule struct {
Action string
FromNode string
ToNode string
FromService string
ToService string
}
func buildComp(field string, pattern string) CompareFunc {
if pattern == "" {
return nil
}
var comp CompareFunc
if strings.HasPrefix(pattern, "/") {
comp, _ = regexCompare(field, pattern)
} else {
comp, _ = stringCompare(field, pattern)
}
return comp
}
func (fr FirewallRule) BuildComps() []CompareFunc {
var comps []CompareFunc
fnc := buildComp("fromnode", fr.FromNode)
if fnc != nil {
comps = append(comps, fnc)
}
tnc := buildComp("tonode", fr.ToNode)
if tnc != nil {
comps = append(comps, tnc)
}
fsc := buildComp("fromservice", fr.FromService)
if fsc != nil {
comps = append(comps, fsc)
}
tsc := buildComp("toservice", fr.ToService)
if tsc != nil {
comps = append(comps, tsc)
}
return comps
}
// ParseFirewallRule takes a single string describing a firewall rule, and returns a FirewallRuleFunc function.
func (frd FirewallRuleData) ParseFirewallRule() (FirewallRuleFunc, error) {
rv := reflect.ValueOf(frd)
if rv.Kind() != reflect.Map {
return nil, fmt.Errorf("invalid firewall rule. see documentation for syntax")
}
fr := FirewallRule{}
for _, key := range rv.MapKeys() {
mkv := rv.MapIndex(key)
key := key.Elem().String()
switch mkv.Interface().(type) {
case string:
// expected
default:
return nil, fmt.Errorf("invalid firewall rule. %s must be a string", key)
}
val := mkv.Elem().String()
switch strings.ToLower(key) {
case "action":
fr.Action = val
case "fromnode":
fr.FromNode = val
case "tonode":
fr.ToNode = val
case "fromservice":
fr.FromService = val
case "toservice":
fr.ToService = val
default:
return nil, fmt.Errorf("invalid filewall rule. unknown key: %s", key)
}
}
comps := fr.BuildComps()
fwr, err := firewallRule(comps, fr.Action)
if err != nil {
return nil, err
}
return fwr, nil
}
// ParseFirewallRules takes a slice of string describing firewall rules, and returns a slice of FirewallRuleFunc functions.
func ParseFirewallRules(rules []FirewallRuleData) ([]FirewallRuleFunc, error) {
results := make([]FirewallRuleFunc, 0)
for i, rule := range rules {
result, err := rule.ParseFirewallRule()
if err != nil {
return nil, fmt.Errorf("error in rule %d: %s", i, err)
}
results = append(results, result)
}
return results, nil
}
type CompareFunc func(md *MessageData) bool
func firewallRule(comparers []CompareFunc, action string) (FirewallRuleFunc, error) {
var result FirewallResult
switch strings.ToLower(action) {
case "accept":
result = FirewallResultAccept
case "reject":
result = FirewallResultReject
case "drop":
result = FirewallResultDrop
default:
return nil, fmt.Errorf("unknown action: %s", action)
}
if len(comparers) == 0 {
return func(md *MessageData) FirewallResult {
return result
}, nil
}
return func(md *MessageData) FirewallResult {
matched := true
for _, comp := range comparers {
matched = matched && comp(md)
}
if matched {
return result
}
return FirewallResultContinue
}, nil
}
func stringCompare(field string, value string) (CompareFunc, error) {
switch strings.ToLower(field) {
case "fromnode":
return func(md *MessageData) bool {
return md.FromNode == value
}, nil
case "fromservice":
return func(md *MessageData) bool {
return md.FromService == value
}, nil
case "tonode":
return func(md *MessageData) bool {
return md.ToNode == value
}, nil
case "toservice":
return func(md *MessageData) bool {
return md.ToService == value
}, nil
}
return nil, fmt.Errorf("unknown field: %s", field)
}
func regexCompare(field string, value string) (CompareFunc, error) {
if value[0] != '/' || value[len(value)-1] != '/' {
return nil, fmt.Errorf("regex not enclosed in //")
}
value = fmt.Sprintf("^%s$", value[1:len(value)-1])
re, err := regexp.Compile(value)
if err != nil {
return nil, fmt.Errorf("regex failed to compile: %s", value)
}
switch strings.ToLower(field) {
case "fromnode":
return func(md *MessageData) bool {
return re.MatchString(md.FromNode)
}, nil
case "fromservice":
return func(md *MessageData) bool {
return re.MatchString(md.FromService)
}, nil
case "tonode":
return func(md *MessageData) bool {
return re.MatchString(md.ToNode)
}, nil
case "toservice":
return func(md *MessageData) bool {
return re.MatchString(md.ToService)
}, nil
}
return nil, fmt.Errorf("unknown field: %s", field)
}
|
