122 lines
2.2 KiB
Go
122 lines
2.2 KiB
Go
package cachet
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import (
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"net"
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"regexp"
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"strings"
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"github.com/Sirupsen/logrus"
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"github.com/miekg/dns"
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)
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type DNSAnswer struct {
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Regex string
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regexp *regexp.Regexp
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Exact string
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}
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type DNSMonitor struct {
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AbstractMonitor `mapstructure:",squash"`
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// IP:port format or blank to use system defined DNS
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DNS string
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// A(default), AAAA, MX, ...
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Question string
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question uint16
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Answers []DNSAnswer
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}
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func (monitor *DNSMonitor) Validate() []string {
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errs := monitor.AbstractMonitor.Validate()
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if len(monitor.DNS) == 0 {
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config, _ := dns.ClientConfigFromFile("/etc/resolv.conf")
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if len(config.Servers) > 0 {
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monitor.DNS = net.JoinHostPort(config.Servers[0], config.Port)
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}
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}
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if len(monitor.DNS) == 0 {
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monitor.DNS = "8.8.8.8:53"
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}
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if len(monitor.Question) == 0 {
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monitor.Question = "A"
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}
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monitor.Question = strings.ToUpper(monitor.Question)
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monitor.question = findDNSType(monitor.Question)
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if monitor.question == 0 {
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errs = append(errs, "Could not look up DNS question type")
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}
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for i, a := range monitor.Answers {
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if len(a.Regex) > 0 {
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monitor.Answers[i].regexp, _ = regexp.Compile(a.Regex)
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}
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}
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return errs
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}
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func (monitor *DNSMonitor) test() bool {
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m := new(dns.Msg)
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m.SetQuestion(dns.Fqdn(monitor.Target), monitor.question)
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m.RecursionDesired = true
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c := new(dns.Client)
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r, _, err := c.Exchange(m, monitor.DNS)
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if err != nil {
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logrus.Warnf("DNS error: %v", err)
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return false
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}
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if r.Rcode != dns.RcodeSuccess {
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return false
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}
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for _, check := range monitor.Answers {
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found := false
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for _, answer := range r.Answer {
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found = matchAnswer(answer, check)
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if found {
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break
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}
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}
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if !found {
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logrus.Warnf("DNS check failed: %v. Not found in any of %v", check, r.Answer)
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return false
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}
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}
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return true
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}
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func findDNSType(t string) uint16 {
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for rr, strType := range dns.TypeToString {
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if t == strType {
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return rr
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}
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}
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return 0
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}
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func matchAnswer(answer dns.RR, check DNSAnswer) bool {
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fields := []string{}
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for i := 0; i < dns.NumField(answer); i++ {
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fields = append(fields, dns.Field(answer, i+1))
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}
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str := strings.Join(fields, " ")
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if check.regexp != nil {
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return check.regexp.Match([]byte(str))
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}
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return str == check.Exact
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}
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