91 lines
2.0 KiB
Go
91 lines
2.0 KiB
Go
package resolvers
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import (
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"bytes"
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"errors"
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"fmt"
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"io/ioutil"
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"net/http"
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"net/url"
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"time"
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"github.com/miekg/dns"
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)
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// DOHResolver represents the config options for setting up a DOH based resolver.
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type DOHResolver struct {
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client *http.Client
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servers []string
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}
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type DOHResolverOpts struct {
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Timeout time.Duration
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}
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// NewDOHResolver accepts a list of nameservers and configures a DOH based resolver.
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func NewDOHResolver(servers []string, opts DOHResolverOpts) (Resolver, error) {
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if len(servers) == 0 {
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return nil, errors.New(`no DOH server specified`)
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}
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for _, s := range servers {
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u, err := url.ParseRequestURI(s)
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if err != nil {
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return nil, fmt.Errorf("%s is not a valid HTTPS nameserver", s)
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}
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if u.Scheme != "https" {
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return nil, fmt.Errorf("missing https in %s", s)
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}
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}
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httpClient := &http.Client{
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Timeout: opts.Timeout,
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}
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return &DOHResolver{
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client: httpClient,
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servers: servers,
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}, nil
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}
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func (d *DOHResolver) Lookup(questions []dns.Question) ([]Response, error) {
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var (
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messages = prepareMessages(questions)
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responses []Response
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)
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for _, msg := range messages {
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// get the DNS Message in wire format.
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b, err := msg.Pack()
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if err != nil {
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return nil, err
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}
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for _, srv := range d.servers {
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now := time.Now()
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// Make an HTTP POST request to the DNS server with the DNS message as wire format bytes in the body.
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resp, err := d.client.Post(srv, "application/dns-message", bytes.NewBuffer(b))
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if err != nil {
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return nil, err
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}
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if resp.StatusCode != http.StatusOK {
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return nil, fmt.Errorf("error from nameserver %s", resp.Status)
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}
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rtt := time.Since(now)
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// extract the binary response in DNS Message.
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body, err := ioutil.ReadAll(resp.Body)
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if err != nil {
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return nil, err
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}
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err = msg.Unpack(body)
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if err != nil {
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return nil, err
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}
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rsp := Response{
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Message: msg,
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RTT: rtt,
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Nameserver: srv,
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}
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responses = append(responses, rsp)
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}
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}
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return responses, nil
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}
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