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package directives
import (
"errors"
"fmt"
"net"
"net/http"
"time"
"github.com/caddyserver/caddy/v2"
"github.com/caddyserver/caddy/v2/modules/caddyhttp"
"github.com/golang-jwt/jwt/v5"
"github.com/google/uuid"
"github.com/invopop/ctxi18n/i18n"
"github.com/sjtug/cerberus/core"
"github.com/sjtug/cerberus/internal/ipblock"
"github.com/sjtug/cerberus/internal/randpool"
"github.com/sjtug/cerberus/web"
"go.uber.org/zap"
)
// Middleware is the actual middleware that will be used to challenge requests.
type Middleware struct {
// The base URL for the challenge. It must be the same as the deployed endpoint route.
BaseURL string `json:"base_url,omitempty"`
// If true, the middleware will not perform any challenge. It will only block known bad IPs.
BlockOnly bool `json:"block_only,omitempty"`
instance *core.Instance
logger *zap.Logger
}
func getClientIP(r *http.Request) string {
address := caddyhttp.GetVar(r.Context(), caddyhttp.ClientIPVarKey).(string)
clientIP, _, err := net.SplitHostPort(address)
if err != nil {
clientIP = address // no port
}
return clientIP
}
func (m *Middleware) invokeAuth(w http.ResponseWriter, r *http.Request) error {
c := m.instance
// Make sure the response is not cached so that users always see the latest challenge.
w.Header().Set("Cache-Control", "no-cache")
ipBlockRaw := caddyhttp.GetVar(r.Context(), core.VarIPBlock)
if ipBlockRaw != nil {
ipBlock := ipBlockRaw.(ipblock.IPBlock)
count := c.IncPending(ipBlock)
if count > c.MaxPending {
m.logger.Info(
"Max failed/active challenges reached for IP block, rejecting",
zap.String("ip", ipBlock.ToIPNet(c.PrefixCfg).String()),
)
c.InsertBlocklist(ipBlock)
c.RemovePending(ipBlock)
return respondFailure(w, r, &c.Config, "IP blocked", true, http.StatusForbidden, m.BaseURL)
}
}
clearCookie(w, c.CookieName)
challenge, err := challengeFor(r, c)
if err != nil {
m.logger.Error("failed to calculate challenge", zap.Error(err))
return err
}
nonce := randpool.ReadUint32()
ts := time.Now().Unix()
signature := calcSignature(challenge, nonce, ts, c)
w.Header().Set(c.HeaderName, "CHALLENGE")
return renderTemplate(w, r, &c.Config, m.BaseURL, i18n.T(r.Context(), "challenge.title"), web.Challenge(challenge, c.Difficulty, nonce, ts, signature))
}
func (m *Middleware) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
r = setupRequestID(r)
r, err := setupLocale(r)
if err != nil {
return err
}
c := m.instance
if ipBlock, err := ipblock.NewIPBlock(net.ParseIP(getClientIP(r)), c.PrefixCfg); err == nil {
caddyhttp.SetVar(r.Context(), core.VarIPBlock, ipBlock)
if c.ContainsBlocklist(ipBlock) {
m.logger.Debug("IP is blocked", zap.String("ip", ipBlock.ToIPNet(c.PrefixCfg).String()))
return respondFailure(w, r, &c.Config, "", true, http.StatusForbidden, m.BaseURL)
}
}
if m.BlockOnly {
// If block only mode is enabled, we don't need to perform any challenge.
// Continue to the next handler.
w.Header().Set(c.HeaderName, "DISABLED")
return next.ServeHTTP(w, r)
}
// Get the "cerberus-auth" cookie
cookie, err := r.Cookie(c.CookieName)
if err != nil {
m.logger.Debug("cookie not found", zap.Error(err))
return m.invokeAuth(w, r)
}
if err := validateCookie(cookie); err != nil {
m.logger.Debug("invalid cookie", zap.Error(err))
return m.invokeAuth(w, r)
}
token, err := jwt.ParseWithClaims(cookie.Value, jwt.MapClaims{}, func(_ *jwt.Token) (interface{}, error) {
return c.GetPublicKey(), nil
}, jwt.WithValidMethods([]string{jwt.SigningMethodEdDSA.Alg()}))
if err != nil {
m.logger.Debug("invalid token", zap.Error(err))
}
if err := validateToken(token); err != nil {
m.logger.Debug("invalid token", zap.Error(err))
return m.invokeAuth(w, r)
}
// Metadata structure correct. Now we need to check the approval.
claims := token.Claims.(jwt.MapClaims)
// First we check approval state.
approvalIDRaw, ok := claims["approval_id"].(string)
if !ok {
m.logger.Debug("token does not contain valid approval_id claim")
return m.invokeAuth(w, r)
}
approvalID, err := uuid.Parse(approvalIDRaw)
if err != nil {
m.logger.Debug("invalid approval_id", zap.String("approval_id", approvalIDRaw), zap.Error(err))
return m.invokeAuth(w, r)
}
approved := c.DecApproval(approvalID)
if !approved {
m.logger.Debug("approval not found", zap.String("approval_id", approvalIDRaw))
return m.invokeAuth(w, r)
}
// Then we check user fingerprint matches the challenge to prevent cookie reuse.
challenge, ok := claims["challenge"].(string)
if !ok {
m.logger.Debug("token does not contain valid challenge claim")
return m.invokeAuth(w, r)
}
expected, err := challengeFor(r, c)
if err != nil {
m.logger.Error("failed to calculate challenge", zap.Error(err))
return err
}
if challenge != expected {
m.logger.Debug("challenge mismatch", zap.String("expected", expected), zap.String("actual", challenge))
return m.invokeAuth(w, r)
}
// OK: Continue to the next handler
w.Header().Set(c.HeaderName, "PASS")
return next.ServeHTTP(w, r)
}
func (m *Middleware) Provision(ctx caddy.Context) error {
m.logger = ctx.Logger()
appRaw, err := ctx.App("cerberus")
if err != nil {
return err
}
app := appRaw.(*App)
instance := app.GetInstance()
if instance == nil {
return errors.New("no global cerberus app found")
}
m.instance = instance
return nil
}
func (m *Middleware) Validate() error {
if m.BaseURL == "" {
return fmt.Errorf("base_url is required")
}
return nil
}
func (Middleware) CaddyModule() caddy.ModuleInfo {
return caddy.ModuleInfo{
ID: "http.handlers.cerberus",
New: func() caddy.Module { return new(Middleware) },
}
}
var (
_ caddy.Provisioner = (*Middleware)(nil)
_ caddy.Validator = (*Middleware)(nil)
_ caddyhttp.MiddlewareHandler = (*Middleware)(nil)
)
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