/
challenge_management.go
247 lines (209 loc) · 6.33 KB
/
challenge_management.go
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package pairing
import (
"bytes"
"crypto/rand"
"fmt"
"io/ioutil"
"net"
"net/http"
"github.com/btcsuite/btcutil/base58"
"github.com/gorilla/sessions"
"go.uber.org/zap"
)
const (
// Session names
sessionChallenge = "challenge"
sessionBlocked = "blocked"
)
type ChallengeError struct {
Text string
HTTPCode int
}
func (ce *ChallengeError) Error() string {
return fmt.Sprintf("%s : %d", ce.Text, ce.HTTPCode)
}
func makeCookieStore() (*sessions.CookieStore, error) {
auth := make([]byte, 64)
_, err := rand.Read(auth)
if err != nil {
return nil, err
}
enc := make([]byte, 32)
_, err = rand.Read(enc)
if err != nil {
return nil, err
}
return sessions.NewCookieStore(auth, enc), nil
}
// ChallengeGiver is responsible for generating challenges and checking challenge responses
type ChallengeGiver struct {
cookieStore *sessions.CookieStore
encryptor *PayloadEncryptor
logger *zap.Logger
authedIP net.IP
}
func NewChallengeGiver(e *PayloadEncryptor, logger *zap.Logger) (*ChallengeGiver, error) {
cs, err := makeCookieStore()
if err != nil {
return nil, err
}
return &ChallengeGiver{
cookieStore: cs,
encryptor: e.Renew(),
logger: logger,
}, nil
}
func (cg *ChallengeGiver) getIP(r *http.Request) (net.IP, error) {
h, _, err := net.SplitHostPort(r.RemoteAddr)
if err != nil {
cg.logger.Error("getIP: h, _, err := net.SplitHostPort(r.RemoteAddr)", zap.Error(err), zap.String("r.RemoteAddr", r.RemoteAddr))
return nil, &ChallengeError{"error", http.StatusInternalServerError}
}
return net.ParseIP(h), nil
}
func (cg *ChallengeGiver) registerClientIP(r *http.Request) error {
IP, err := cg.getIP(r)
if err != nil {
return err
}
cg.authedIP = IP
return nil
}
func (cg *ChallengeGiver) validateClientIP(r *http.Request) error {
// If we haven't registered yet register the IP
if cg.authedIP == nil || len(cg.authedIP) == 0 {
err := cg.registerClientIP(r)
if err != nil {
return err
}
}
// Then compare the current req RemoteIP with the authed IP
IP, err := cg.getIP(r)
if err != nil {
return err
}
if !cg.authedIP.Equal(IP) {
cg.logger.Error(
"request RemoteAddr does not match authedIP: expected '%s', received '%s'",
zap.String("expected", cg.authedIP.String()),
zap.String("received", IP.String()),
)
return &ChallengeError{"forbidden", http.StatusForbidden}
}
return nil
}
func (cg *ChallengeGiver) getSession(r *http.Request) (*sessions.Session, error) {
s, err := cg.cookieStore.Get(r, sessionChallenge)
if err != nil {
cg.logger.Error("checkChallengeResponse: cg.cookieStore.Get(r, sessionChallenge)", zap.Error(err), zap.String("sessionChallenge", sessionChallenge))
return nil, &ChallengeError{"error", http.StatusInternalServerError}
}
return s, nil
}
func (cg *ChallengeGiver) generateNewChallenge(s *sessions.Session, w http.ResponseWriter, r *http.Request) ([]byte, error) {
challenge := make([]byte, 64)
_, err := rand.Read(challenge)
if err != nil {
cg.logger.Error("regenerateNewChallenge: _, err = rand.Read(challenge)", zap.Error(err))
return nil, &ChallengeError{"error", http.StatusInternalServerError}
}
s.Values[sessionChallenge] = challenge
err = s.Save(r, w)
if err != nil {
cg.logger.Error("regenerateNewChallenge: err = s.Save(r, w)", zap.Error(err))
return nil, &ChallengeError{"error", http.StatusInternalServerError}
}
return challenge, nil
}
func (cg *ChallengeGiver) block(s *sessions.Session, w http.ResponseWriter, r *http.Request) error {
s.Values[sessionBlocked] = true
err := s.Save(r, w)
if err != nil {
cg.logger.Error("block: err = s.Save(r, w)", zap.Error(err))
return &ChallengeError{"error", http.StatusInternalServerError}
}
return &ChallengeError{"forbidden", http.StatusForbidden}
}
func (cg *ChallengeGiver) checkChallengeResponse(w http.ResponseWriter, r *http.Request) error {
err := cg.validateClientIP(r)
if err != nil {
return err
}
s, err := cg.getSession(r)
if err != nil {
return err
}
blocked, ok := s.Values[sessionBlocked].(bool)
if ok && blocked {
return &ChallengeError{"forbidden", http.StatusForbidden}
}
// If the request header doesn't include a challenge don't punish the client, just throw a 403
clientChallengeResp := r.Header.Get(sessionChallenge)
if clientChallengeResp == "" {
return &ChallengeError{"forbidden", http.StatusForbidden}
}
dcr, err := cg.encryptor.decryptPlain(base58.Decode(clientChallengeResp))
if err != nil {
cg.logger.Error("checkChallengeResponse: cg.encryptor.decryptPlain(base58.Decode(clientChallengeResp))", zap.Error(err), zap.String("clientChallengeResp", clientChallengeResp))
return &ChallengeError{"error", http.StatusInternalServerError}
}
// If the challenge is not in the session store don't punish the client, just throw a 403
challenge, ok := s.Values[sessionChallenge].([]byte)
if !ok {
return &ChallengeError{"forbidden", http.StatusForbidden}
}
// Only if we have both a challenge in the session store and in the request header
// do we entertain blocking the client. Because then we know someone is trying to be sneaky.
if !bytes.Equal(dcr, challenge) {
return cg.block(s, w, r)
}
// If every is ok, generate a new challenge for the next req
_, err = cg.generateNewChallenge(s, w, r)
return err
}
func (cg *ChallengeGiver) getChallenge(w http.ResponseWriter, r *http.Request) ([]byte, error) {
err := cg.validateClientIP(r)
if err != nil {
return nil, err
}
s, err := cg.getSession(r)
if err != nil {
return nil, err
}
challenge, ok := s.Values[sessionChallenge].([]byte)
if !ok {
challenge, err = cg.generateNewChallenge(s, w, r)
if err != nil {
return nil, err
}
}
return challenge, nil
}
// ChallengeTaker is responsible for storing and performing server challenges
type ChallengeTaker struct {
encryptor *PayloadEncryptor
serverChallenge []byte
}
func NewChallengeTaker(e *PayloadEncryptor) *ChallengeTaker {
return &ChallengeTaker{
encryptor: e.Renew(),
}
}
func (ct *ChallengeTaker) SetChallenge(resp *http.Response) error {
challenge, err := ioutil.ReadAll(resp.Body)
if err != nil {
return err
}
ct.serverChallenge = challenge
return nil
}
func (ct *ChallengeTaker) DoChallenge(req *http.Request) error {
if ct.serverChallenge != nil {
ec, err := ct.encryptor.encryptPlain(ct.serverChallenge)
if err != nil {
return err
}
req.Header.Set(sessionChallenge, base58.Encode(ec))
}
return nil
}