mirror of
https://github.com/kairos-io/kcrypt-challenger.git
synced 2025-04-27 19:05:23 +00:00
311b8adda0
because tpm has nothing to do with mdns. TODO: Remove the functions from tpm helpers and bump the module here Signed-off-by: Dimitris Karakasilis <dimitris@karakasilis.me>
86 lines
2.7 KiB
Go
86 lines
2.7 KiB
Go
package client
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import (
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"fmt"
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"net/url"
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"strconv"
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"strings"
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"time"
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"github.com/hashicorp/mdns"
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)
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const (
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MDNSServiceType = "_kcrypt._tcp"
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MDNSTimeout = 15 * time.Second
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)
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// queryMDNS will make an mdns query on local network to find a kcrypt challenger server
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// instance. If none is found, the original URL is returned and no additional headers.
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// If a response is received, the IP address and port from the response will be returned// and an additional "Host" header pointing to the original host.
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func queryMDNS(originalURL string) (string, map[string]string, error) {
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additionalHeaders := map[string]string{}
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var err error
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parsedURL, err := url.Parse(originalURL)
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if err != nil {
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return originalURL, additionalHeaders, fmt.Errorf("parsing the original host: %w", err)
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}
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host := parsedURL.Host
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if !strings.HasSuffix(host, ".local") { // sanity check
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return "", additionalHeaders, fmt.Errorf("domain should end in \".local\" when using mdns")
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}
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mdnsIP, mdnsPort := discoverMDNSServer(host)
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if mdnsIP == "" { // no reply
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logToFile("no reply from mdns\n")
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return originalURL, additionalHeaders, nil
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}
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additionalHeaders["Host"] = parsedURL.Host
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newURL := strings.ReplaceAll(originalURL, host, mdnsIP)
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// Remove any port in the original url
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if port := parsedURL.Port(); port != "" {
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newURL = strings.ReplaceAll(newURL, port, "")
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}
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// Add any possible port from the mdns response
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if mdnsPort != "" {
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newURL = strings.ReplaceAll(newURL, mdnsIP, fmt.Sprintf("%s:%s", mdnsIP, mdnsPort))
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}
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return newURL, additionalHeaders, nil
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}
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// discoverMDNSServer performs an mDNS query to discover any running kcrypt challenger
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// servers on the same network that matches the given hostname.
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// If a response if received, the IP address and the Port from the response are returned.
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func discoverMDNSServer(hostname string) (string, string) {
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// Make a channel for results and start listening
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entriesCh := make(chan *mdns.ServiceEntry, 4)
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defer close(entriesCh)
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logToFile("Will now wait for some mdns server to respond\n")
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// Start the lookup. It will block until we read from the chan.
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mdns.Lookup(MDNSServiceType, entriesCh)
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expectedHost := hostname + "." // FQDN
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// Wait until a matching server is found or we reach a timeout
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for {
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select {
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case entry := <-entriesCh:
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logToFile("mdns response received\n")
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if entry.Host == expectedHost {
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logToFile("%s matches %s\n", entry.Host, expectedHost)
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return entry.AddrV4.String(), strconv.Itoa(entry.Port) // TODO: v6?
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} else {
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logToFile("%s didn't match %s\n", entry.Host, expectedHost)
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}
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case <-time.After(MDNSTimeout):
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logToFile("timed out waiting for mdns\n")
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return "", ""
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}
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}
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}
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