package main

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"

	"github.com/go-ping/ping"
	"github.com/miekg/dns"

	"git.nemunai.re/srs/adlin/libadlin"
)

const (
	DEFAULT_RESOLVER = "2a01:e0a:2b:2250::1"
	year68           = 1 << 31 // For RFC1982 (Serial Arithmetic) calculations in 32 bits. Taken from miekg/dns
)

var (
	verbose           = false
	verbose2          = false
	domainsHostingMap = map[string]string{}
)

// ICMP

func check_ping(ip string, cb func(pkt *ping.Packet)) (err error) {
	var pinger *ping.Pinger
	pinger, err = ping.NewPinger(ip)
	if err != nil {
		if verbose {
			log.Printf("check_ping: %s: %s", ip, err.Error())
		}
		return
	}
	defer pinger.Stop()

	pinger.Timeout = time.Second * 5
	pinger.Count = 1
	pinger.OnRecv = cb
	pinger.SetPrivileged(true)
	err = pinger.Run()

	return
}

// PORT 53

func get_GLUE(student *adlin.Student) (aaaa net.IP, err error) {
	client := dns.Client{Net: "tcp", Timeout: time.Second * 5}
	domain := student.MyDelegatedDomain()

	dnssrv := "[2a01:e0a:2b:2250::b]:53"
	if strings.HasSuffix(domain, student.MyDelegatedDomainSuffix()) {
		dnssrv = "[2a01:e0a:2b:2250::b]:53"
	} else if v, ok := domainsHostingMap[domain]; ok {
		dnssrv = v
	} else {
		// Looking for root NS
		m := new(dns.Msg)
		m.SetQuestion(".", dns.TypeNS)
		m.RecursionDesired = false
		m.SetEdns0(4096, true)

		var r *dns.Msg
		r, _, err = client.Exchange(m, dnssrv)
		if err != nil {
			return
		}

		if r == nil {
			return nil, errors.New("response is nil during initial recursion")
		}
		if r.Rcode != dns.RcodeSuccess {
			return nil, errors.New("failed to get a valid answer during initial recursion")
		}

		for _, answer := range r.Answer {
			if t, ok := answer.(*dns.NS); ok {
				dnssrv = t.Ns + ":53"
			}
		}
		// Do casual recursion
		i := 0
	recursion:
		for i = 0; i < 10; i++ {
			m := new(dns.Msg)
			m.SetQuestion(domain, dns.TypeNS)
			m.RecursionDesired = false
			m.SetEdns0(4096, true)

			var r *dns.Msg
			r, _, err = client.Exchange(m, dnssrv)
			if err != nil {
				return
			}

			if r == nil {
				return nil, errors.New("response is nil during recursion")
			}
			if r.Rcode != dns.RcodeSuccess {
				return nil, errors.New("failed to get a valid answer during recursion")
			}

			for _, answer := range r.Ns {
				if t, ok := answer.(*dns.NS); ok {
					dnssrv = t.Ns + ":53"
					if t.Header().Name == domain {
						break recursion
					}
				}
			}
		}

		if i >= 10 {
			return nil, fmt.Errorf("too much name recursions")
		} else {
			domainsHostingMap[domain] = dnssrv
		}
	}

	m := new(dns.Msg)
	m.SetQuestion(domain, dns.TypeNS)
	m.RecursionDesired = false
	m.SetEdns0(4096, true)

	var r *dns.Msg
	r, _, err = client.Exchange(m, dnssrv)
	if err != nil {
		return
	}

	if r == nil {
		return nil, errors.New("response is nil")
	}
	if r.Rcode != dns.RcodeSuccess {
		return nil, errors.New("failed to get a valid answer")
	}

	for _, extra := range r.Extra {
		if t, ok := extra.(*dns.AAAA); ok {
			aaaa = t.AAAA
		}
	}

	return
}

func check_dns(domain, ip string) (aaaa net.IP, err error) {
	client := dns.Client{Timeout: time.Second * 5}

	m := new(dns.Msg)
	m.SetQuestion(domain, dns.TypeAAAA)

	var r *dns.Msg
	r, _, err = client.Exchange(m, fmt.Sprintf("[%s]:53", ip))
	if err != nil {
		return
	}

	if r == nil {
		err = errors.New("response is nil")
		return
	}
	if r.Rcode != dns.RcodeSuccess {
		err = errors.New("failed to get a valid answer")
		return
	}

	for _, answer := range r.Answer {
		if t, ok := answer.(*dns.AAAA); ok {
			aaaa = t.AAAA
		}
	}

	return
}

func check_dnssec(domain, ip string) (err error) {
	client := dns.Client{Net: "tcp", Timeout: time.Second * 10}

	// Get DNSKEY
	m := new(dns.Msg)
	m.SetEdns0(4096, true)
	m.SetQuestion(domain, dns.TypeDNSKEY)

	var r *dns.Msg
	r, _, err = client.Exchange(m, fmt.Sprintf("[%s]:53", ip))
	if err != nil {
		return
	}

	if r == nil {
		return errors.New("response is nil")
	}
	if r.Rcode != dns.RcodeSuccess {
		return errors.New("failed to get a valid answer when getting DNSKEY")
	}

	var rrs []dns.RR
	var dnskeys []*dns.DNSKEY
	var dnskeysig *dns.RRSIG
	for _, answer := range r.Answer {
		if t, ok := answer.(*dns.DNSKEY); ok {
			dnskeys = append(dnskeys, t)
			rrs = append(rrs, dns.RR(t))
		} else if t, ok := answer.(*dns.RRSIG); ok {
			dnskeysig = t
		}
	}

	if dnskeysig == nil {
		return fmt.Errorf("Unable to verify DNSKEY record signature: No RRSIG found for DNSKEY record.")
	}

	found := false
	for _, dnskey := range dnskeys {
		if err = dnskeysig.Verify(dnskey, rrs); err == nil {
			found = true
			break
		}
	}

	if !found {
		return fmt.Errorf("Unable to verify DNSKEY record signature: %w", err)
	}

	// Check AAAA validity
	m = new(dns.Msg)
	m.SetEdns0(4096, true)
	m.SetQuestion(domain, dns.TypeAAAA)

	r, _, err = client.Exchange(m, fmt.Sprintf("[%s]:53", ip))
	if err != nil {
		return
	}

	if r == nil {
		return errors.New("response is nil")
	}
	if r.Rcode != dns.RcodeSuccess {
		return errors.New("failed to get a valid answer when getting AAAA records")
	}

	rrs = []dns.RR{}
	var aaaas []*dns.AAAA
	var aaaasig *dns.RRSIG
	for _, answer := range r.Answer {
		if t, ok := answer.(*dns.AAAA); ok {
			aaaas = append(aaaas, t)
			rrs = append(rrs, t)
		} else if t, ok := answer.(*dns.RRSIG); ok {
			aaaasig = t
		}
	}

	if len(aaaas) == 0 {
		return errors.New("Something odd happen: no AAAA record found.")
	}

	if aaaasig == nil {
		return fmt.Errorf("Unable to verify AAAA record signature: No RRSIG found for AAAA record.")
	}

	found = false
	for _, dnskey := range dnskeys {
		if err = aaaasig.Verify(dnskey, rrs); err == nil {
			found = true

			if !aaaasig.ValidityPeriod(time.Now()) {
				utc := time.Now().UTC().Unix()

				modi := (int64(aaaasig.Inception) - utc) / year68
				ti := int64(aaaasig.Inception) + modi*year68

				mode := (int64(aaaasig.Expiration) - utc) / year68
				te := int64(aaaasig.Expiration) + mode*year68

				if ti > utc {
					return fmt.Errorf("Unable to verify AAAA record signature: signature not yet valid")
				} else if utc > te {
					return fmt.Errorf("Unable to verify AAAA record signature: signature expired")
				} else {
					return fmt.Errorf("Unable to verify AAAA record signature: signature expired or not yet valid")
				}
			}

			break
		}
	}

	if !found {
		return fmt.Errorf("Unable to verify AAAA record signature: %w", err)
	}

	// Check DS
	m = new(dns.Msg)
	m.SetQuestion(domain, dns.TypeDS)
	m.RecursionDesired = false
	m.SetEdns0(4096, true)

	r, _, err = client.Exchange(m, "[2a01:e0a:2b:2250::b]:53")
	if err != nil {
		return
	}

	if r == nil {
		return errors.New("response is nil")
	}
	if r.Rcode != dns.RcodeSuccess {
		return errors.New("failed to get a valid answer when getting DS records in parent server")
	}

	found = false
	for _, answer := range r.Answer {
		if t, ok := answer.(*dns.DS); ok {
			for _, dnskey := range dnskeys {
				expectedDS := dnskey.ToDS(dns.SHA256)
				if expectedDS.KeyTag == t.KeyTag && expectedDS.Algorithm == t.Algorithm && expectedDS.DigestType == t.DigestType && expectedDS.Digest == t.Digest {
					found = true
					err = nil
					break
				} else {
					err = fmt.Errorf("DS record found in parent zone differs from DNSKEY %v vs. %v.", expectedDS, t)
				}
			}
		}
	}

	if !found {
		if err == nil {
			return fmt.Errorf("Unable to find a valid DS record in parent zone (if you use your own domain (ie. not given by maatma), this can be due to a previously cached response, you should wait).")
		} else {
			return err
		}
	}

	return
}

// PORT 80

func check_http(ip, dn string) (err error) {
	client := &http.Client{
		CheckRedirect: func(req *http.Request, via []*http.Request) error {
			return http.ErrUseLastResponse
		},
	}

	req, errr := http.NewRequest("GET", fmt.Sprintf("http://[%s]/", ip), nil)
	if errr != nil {
		return errr
	}

	if dn != "" {
		req.Header.Add("Host", strings.TrimSuffix(dn, "."))
	}

	var resp *http.Response
	resp, err = client.Do(req)
	if err != nil {
		return
	}
	defer resp.Body.Close()

	if dn != "" && resp.StatusCode >= 400 {
		return fmt.Errorf("Bad status, got: %d (%s)", resp.StatusCode, resp.Status)
	}

	_, err = ioutil.ReadAll(resp.Body)
	return
}

// PORT 443

func check_https(domain, ip string) (err error) {
	var resp *http.Response
	resp, err = http.Get(fmt.Sprintf("https://%s/", strings.TrimSuffix(domain, ".")))
	if err != nil {
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 && resp.StatusCode < 400 {
		loc := resp.Header.Get("Location")
		if loc != "" && strings.HasSuffix(dns.Fqdn(loc), domain) {
			if dns.Fqdn(loc) == domain {
				return fmt.Errorf("Redirection loop %s redirect to %s", domain, loc)
			} else if err = check_https(dns.Fqdn(loc), ip); err != nil {
				return fmt.Errorf("Error after following redirection to %s: %w", loc, err)
			} else {
				return
			}
		}
	}

	if resp.StatusCode >= 300 {
		return fmt.Errorf("Bad status, got: %d (%s)", resp.StatusCode, resp.Status)
	}

	_, err = ioutil.ReadAll(resp.Body)
	return
}

// MATRIX

type matrix_result struct {
	WellKnownResult struct {
		Server string `json:"m.server"`
		Result string `json:"result"`
	}
	DNSResult struct {
		SRVError *struct {
			Message string
		}
	}
	ConnectionReports map[string]struct {
		Errors []string
	}
	ConnectionErrors map[string]struct {
		Message string
	}
	Version struct {
		Name    string `json:"name"`
		Version string `json:"version"`
	}
	FederationOK bool `json:"FederationOK"`
}

func check_matrix_federation(domain string) (version string, err error) {
	var resp *http.Response
	resp, err = http.Get(fmt.Sprintf("https://federation-tester.adlin.nemunai.re/api/report?server_name=%s", strings.TrimSuffix(domain, ".")))
	if err != nil {
		return
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 {
		return "", fmt.Errorf("Sorry, the federation tester is broken. Check on https://federationtester.matrix.org/#%s", strings.TrimSuffix(domain, "."))
	}

	var federationTest matrix_result
	if err = json.NewDecoder(resp.Body).Decode(&federationTest); err != nil {
		log.Printf("Error in check_matrix_federation, when decoding json: %s", err.Error())
		return "", fmt.Errorf("Sorry, the federation tester is broken. Check on https://federationtester.matrix.org/#%s", strings.TrimSuffix(domain, "."))
	} else if federationTest.FederationOK {
		version = federationTest.Version.Name + " " + federationTest.Version.Version
		return version, nil
	} else if federationTest.DNSResult.SRVError != nil && federationTest.WellKnownResult.Result != "" {
		return "", fmt.Errorf("%s OR %s", federationTest.DNSResult.SRVError.Message, federationTest.WellKnownResult.Result)
	} else if len(federationTest.ConnectionErrors) > 0 {
		var msg strings.Builder
		for srv, cerr := range federationTest.ConnectionErrors {
			if msg.Len() > 0 {
				msg.WriteString("; ")
			}
			msg.WriteString(srv)
			msg.WriteString(": ")
			msg.WriteString(cerr.Message)
		}
		return "", fmt.Errorf("Connection errors: %s", msg.String())
	} else if federationTest.WellKnownResult.Server != strings.TrimSuffix(domain, ".") {
		return "", fmt.Errorf("Bad homeserver_name: got %s, expected %s.", federationTest.WellKnownResult.Server, strings.TrimSuffix(domain, "."))
	} else {
		return "", fmt.Errorf("An unimplemented error occurs. Please report to nemunaire. But know that federation seems to be broken. Check https://federationtester.matrix.org/#%s", strings.TrimSuffix(domain, "."))
	}
}

type matrix_wk_client struct {
	Homeserver struct {
		BaseURL string `json:"base_url"`
	} `json:"m.homeserver"`
	IdentityServer struct {
		BaseURL string `json:"base_url"`
	} `json:"m.identity_server"`
}

type matrix_client_versions struct {
	Versions         []string        `json:"versions"`
	UnstableFeatures map[string]bool `json:"unstable_features"`
}

func check_matrix_client(domain string) (version string, err error) {
	var resp *http.Response
	resp, err = http.Get(fmt.Sprintf("https://%s/.well-known/matrix/client", strings.TrimSuffix(domain, ".")))
	if err != nil {
		return
	}
	defer resp.Body.Close()

	var HomeserverBase = fmt.Sprintf("https://%s", strings.TrimSuffix(domain, "."))

	if resp.StatusCode < 300 {
		var wellknown matrix_wk_client
		if err = json.NewDecoder(resp.Body).Decode(&wellknown); err != nil {
			log.Printf("Error in check_matrix_client, when decoding json: %s", err.Error())
			return "", fmt.Errorf("File at https://%s/.well-known/matrix/client is invalid: JSON parse error", strings.TrimSuffix(domain, "."))
		} else if wellknown.Homeserver.BaseURL != "" {
			if baseurl, err := url.Parse(wellknown.Homeserver.BaseURL); err != nil {
				return "", fmt.Errorf("File at https://%s/.well-known/matrix/client is invalid: Bad homeserver URL: %s", strings.TrimSuffix(domain, "."), err.Error())
			} else if !strings.HasSuffix(strings.TrimSuffix(baseurl.Host, "."), strings.TrimSuffix(domain, ".")) {
				return "", fmt.Errorf("Your homeserver base_url is not under %s", strings.TrimSuffix(domain, "."))
			} else if strings.TrimSuffix(baseurl.Host, ".") == strings.TrimSuffix(domain, ".") {
				// This test can be optional
				return "", fmt.Errorf("Your homeserver should be on its own subdomain")
			} else {
				HomeserverBase = wellknown.Homeserver.BaseURL
			}
		}
	}

	var resp2 *http.Response
	resp2, err = http.Get(fmt.Sprintf("%s/_matrix/client/versions", HomeserverBase))
	if err != nil {
		return
	}
	defer resp2.Body.Close()

	if resp2.StatusCode != http.StatusOK {
		return "", fmt.Errorf("Unable to fetch your homeserver versions at %s/_matrix/client/versions: %s", HomeserverBase, resp2.Status)
	}

	var clientTest matrix_client_versions
	if err = json.NewDecoder(resp2.Body).Decode(&clientTest); err != nil {
		log.Printf("Error in check_matrix_client, when decoding versions json: %s", err.Error())
		return "", fmt.Errorf("File at %s/_matrix/client/versions is invalid: JSON parse error: %s", HomeserverBase, err.Error())
	} else if len(clientTest.Versions) == 0 {
		return "", fmt.Errorf("File at %s/_matrix/client/versions is invalid: no protocol version supported", HomeserverBase)
	} else {
		return clientTest.Versions[len(clientTest.Versions)-1], nil
	}
}

// Main

func minTunnelVersion(std *adlin.Student, suffixip int) (int, error) {
	tunnels, err := std.GetTunnelTokens()
	if err != nil {
		return 0, err
	}

	var minversion int = 2147483647
	for _, tunnel := range tunnels {
		if tunnel.Version == 0 {
			continue
		}

		if tunnel.Dump != nil && tunnel.Version < minversion && suffixip == tunnel.SuffixIP {
			minversion = tunnel.Version
		}
	}

	return minversion, nil
}

func studentChecker(std *adlin.Student, also_check_matrix bool, offline bool) {
	tuns, err := std.GetActivesTunnels()
	if err != nil {
		if offline {
			tuns, err = std.GetDefaultTunnels()
			if err != nil {
				if verbose {
					log.Printf("SKip %s as I'm unable to generate default tunnels: %s", std.Login, err.Error())
				}
				return
			}
		} else {
			if verbose2 {
				log.Printf("SKip %s due to error when getting active tunnels: %s", std.Login, err.Error())
			}
			return
		}
	}
	if verbose2 && len(tuns) == 0 {
		log.Printf("%s has no active tunnels: %s", std.Login, err.Error())
	}

	for _, tun := range tuns {
		stdIP := tun.GetStudentIP()
		if verbose2 {
			log.Printf("Tests %s on %s...", std.Login, stdIP)
		}
		// Check ping
		err = check_ping(stdIP, func(pkt *ping.Packet) {
			tunnel_version, err := minTunnelVersion(std, tun.SuffixIP)
			if verbose {
				log.Printf("%s PONG (on %x); version=%d (%v)\n", std.Login, tun.SuffixIP, tunnel_version, err)
			}
			std.OnPong(true)

			if !offline && (tunnel_version == 2147483647 || tunnel_version == 0) {
				log.Printf("%s unknown tunnel version: %d skipping tests (%v)", std.Login, tunnel_version, err)
				return
			}

			// PingResolver
			if tunnel_version == 3 {
				tmp := strings.Split(stdIP, ":")
				tmp[len(tmp)-1] = "2"
				stdResolverIP := strings.Join(tmp, ":")
				go check_ping(stdResolverIP, func(_ *ping.Packet) {
					if verbose {
						log.Printf("%s resolver PONG", std.Login)
					}
					if _, err := std.UnlockChallenge(CheckMap[tunnel_version][PingResolver], ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}
				})
			}

			dnsIP := stdIP
			var glueErr error
			// Is GLUE defined?
			if glueIP, err := get_GLUE(std); glueIP != nil {
				dnsIP = glueIP.String()

				if verbose {
					log.Printf("%s has defined GLUE: %s\n", std.Login, dnsIP)
				}
			} else if err != nil {
				log.Printf("%s and GLUE: %s\n", std.Login, err)
				glueErr = err
			}

			snicheck1 := false
			snicheck1_tested := false

			// Check DNS
			if addr, err := check_dns(std.MyDelegatedDomain(), dnsIP); err == nil {
				if addr == nil {
					dnsAt := " at " + dnsIP
					if glueErr != nil {
						dnsAt = " + there is a problem with the GLUE record: " + glueErr.Error()
					}
					if errreg := std.RegisterChallengeError(CheckMap[tunnel_version][DNSDelegation], fmt.Errorf("%s: empty response from the server%s", std.MyDelegatedDomain(), dnsAt)); errreg != nil {
						log.Printf("Unable to register challenge error for %s: %s\n", std.Login, errreg)
					}
				} else {
					if verbose {
						log.Printf("%s just unlocked DNS challenge\n", std.Login)
					}
					if _, err := std.UnlockChallenge(CheckMap[tunnel_version][DNSDelegation], addr.String()); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}

					// Check HTTP with DNS
					if glueErr != nil {
						std.RegisterChallengeError(CheckMap[tunnel_version][HTTPonDelegatedDomain], fmt.Errorf("Unable to perform the test due to GLUE problem: %w", glueErr))
					} else if err := check_http(addr.String(), std.MyDelegatedDomain()); err == nil {
						if verbose {
							log.Printf("%s just unlocked HTTP challenge\n", std.Login)
						}
						if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPonDelegatedDomain], ""); err != nil {
							log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
						}
					} else {
						std.RegisterChallengeError(CheckMap[tunnel_version][HTTPonDelegatedDomain], err)
						if verbose {
							log.Printf("%s and HTTP (with DNS ip=%s): %s\n", std.Login, addr.String(), err)
						}
					}

					// Check HTTPs with DNS
					if glueErr != nil {
						std.RegisterChallengeError(CheckMap[tunnel_version][HTTPSonDelegatedDomain], fmt.Errorf("Unable to perform the test due to GLUE problem: %w", glueErr))
					} else if err := check_https(std.MyDelegatedDomain(), addr.String()); err == nil {
						snicheck1 = true
						snicheck1_tested = true
						if verbose {
							log.Printf("%s just unlocked HTTPS challenge\n", std.Login)
						}
						if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPSonDelegatedDomain], ""); err != nil {
							log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
						}
					} else {
						snicheck1_tested = true
						std.RegisterChallengeError(CheckMap[tunnel_version][HTTPSonDelegatedDomain], err)
						if verbose {
							log.Printf("%s and HTTPS (with DNS ip=%s): %s\n", std.Login, addr.String(), err)
						}
					}

					// Check Matrix (only if GLUE Ok and defer contraint)
					if glueErr == nil && also_check_matrix {
						// Check Matrix Federation first
						if v, err := check_matrix_federation(std.MyDelegatedDomain()); err == nil {
							if verbose {
								log.Printf("%s just unlocked Matrix federation challenge\n", std.Login)
							}
							if _, err := std.UnlockChallenge(CheckMap[tunnel_version][MatrixSrv], v); err != nil {
								log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
							}
						} else {
							std.RegisterChallengeError(CheckMap[tunnel_version][MatrixSrv], err)
							if verbose {
								log.Printf("%s and Matrix federation: %s\n", std.Login, err)
							}
						}

						// Check Matrix Client
						if v, err := check_matrix_client(std.MyDelegatedDomain()); err == nil {
							if verbose {
								log.Printf("%s just unlocked Matrix client challenge\n", std.Login)
							}
							if _, err := std.UnlockChallenge(CheckMap[tunnel_version][MatrixClt], v); err != nil {
								log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
							}
						} else {
							std.RegisterChallengeError(CheckMap[tunnel_version][MatrixClt], err)
							if verbose {
								log.Printf("%s and Matrix client: %s\n", std.Login, err)
							}
						}
					}

					// Check DNSSEC (only if GLUE Ok)
					if glueErr == nil {
						if err := check_dnssec(std.MyDelegatedDomain(), dnsIP); err == nil {
							if verbose {
								log.Printf("%s just unlocked DNSSEC challenge\n", std.Login)
							}
							if _, err := std.UnlockChallenge(CheckMap[tunnel_version][DNSSEC], ""); err != nil {
								log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
							}
						} else {
							std.RegisterChallengeError(CheckMap[tunnel_version][DNSSEC], err)
							if verbose {
								log.Printf("%s and DNSSEC: %s\n", std.Login, err)
							}
						}
					}
				}
			} else {
				if errreg := std.RegisterChallengeError(CheckMap[tunnel_version][DNSDelegation], err); errreg != nil {
					log.Printf("Unable to register challenge error for %s: %s\n", std.Login, errreg)
				}
				if verbose {
					log.Printf("%s and DNS: %s\n", std.Login, err)
				}
			}

			// Check HTTP without DNS
			if err := check_http(stdIP, ""); err == nil {
				if verbose {
					log.Printf("%s just unlocked HTTP IP (without DNS) challenge\n", std.Login)
				}
				if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPonIP], ""); err != nil {
					log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
				}
			} else {
				std.RegisterChallengeError(CheckMap[tunnel_version][HTTPonIP], err)
				if verbose {
					log.Printf("%s and HTTP IP (without DNS): %s\n", std.Login, err)
				}
			}

			// Check DNS for association
			if addr, err := check_dns(std.MyAssociatedDomain(), DEFAULT_RESOLVER); err == nil {
				// Check HTTP on delegated domain
				if err := check_http(addr.String(), std.MyAssociatedDomain()); err == nil {
					if verbose {
						log.Printf("%s just unlocked HTTP (without DNS) challenge\n", std.Login)
					}
					if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPonAssociatedDomain], ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}
				} else {
					std.RegisterChallengeError(CheckMap[tunnel_version][HTTPonAssociatedDomain], err)
					if verbose {
						log.Printf("%s and HTTP (without DNS): %s\n", std.Login, err)
					}
				}

				// Check HTTPs without DNS
				if err := check_https(std.MyAssociatedDomain(), stdIP); err == nil {
					if verbose {
						log.Printf("%s just unlocked HTTPS challenge\n", std.Login)
					}
					if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPSonAssociatedDomain], ""); err != nil {
						log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
					}

					// SNI check: validate if this check + HTTPS on delegation is validated
					if snicheck1 {
						if verbose {
							log.Printf("%s just unlocked HTTPS-SNI challenge\n", std.Login)
						}
						if _, err := std.UnlockChallenge(CheckMap[tunnel_version][HTTPSSNI], ""); err != nil {
							log.Printf("Unable to register challenge for %s: %s\n", std.Login, err.Error())
						}
					}
				} else {
					std.RegisterChallengeError(CheckMap[tunnel_version][HTTPSonAssociatedDomain], err)
					if verbose {
						log.Printf("%s and HTTPS (without DNS): %s\n", std.Login, err)
					}
				}
			}

			if snicheck1_tested && !snicheck1 {
				std.RegisterChallengeError(CheckMap[tunnel_version][HTTPSSNI], fmt.Errorf("associated and delegated domain are not accessible through HTTPS at the same time, see errors for thoses checks"))
				if verbose {
					log.Printf("%s and HTTPS-SNI: %s\n", std.Login, "associated and delegated domains not accessible at the same time through HTTPS")
				}
			}

			return
		})
		if err != nil && verbose {
			log.Printf("%s: Unable to perform ping to %s: %s", std.Login, stdIP, err.Error())
		}
	}
}

func studentsChecker(offline bool) {
	students, err := adlin.GetStudents()
	if err != nil {
		log.Println("Unable to check students:", err)
		return
	}
	check_matrix_for := (time.Now().Second()/30)*5 + time.Now().Minute()%5

	log.Printf("Checking students... (std_matrix%%10=%d)\n", check_matrix_for)

	for istd, s := range students {
		time.Sleep(250 * time.Millisecond)
		go studentChecker(s, istd%10 == check_matrix_for, offline)
	}
}