initial release

authenticate/middleware.go

@@ -0,0 +1,98 @@
+package authenticate // import "github.com/pomerium/pomerium/authenticate"
+
+import (
+	"crypto/hmac"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/pomerium/pomerium/internal/httputil"
+)
+
+// validateRedirectURI checks the redirect uri in the query parameters and ensures that
+// the url's domain is one in the list of proxy root domains.
+func validateRedirectURI(f http.HandlerFunc, proxyRootDomains []string) http.HandlerFunc {
+	return func(rw http.ResponseWriter, req *http.Request) {
+		err := req.ParseForm()
+		if err != nil {
+			httputil.ErrorResponse(rw, req, err.Error(), http.StatusBadRequest)
+			return
+		}
+		redirectURI := req.Form.Get("redirect_uri")
+		if !validRedirectURI(redirectURI, proxyRootDomains) {
+			httputil.ErrorResponse(rw, req, "Invalid redirect parameter", http.StatusBadRequest)
+			return
+		}
+
+		f(rw, req)
+	}
+}
+
+func validRedirectURI(uri string, rootDomains []string) bool {
+	redirectURL, err := url.Parse(uri)
+	if uri == "" || err != nil || redirectURL.Host == "" {
+		return false
+	}
+	for _, domain := range rootDomains {
+		if strings.HasSuffix(redirectURL.Hostname(), domain) {
+			return true
+		}
+	}
+	return false
+}
+
+func validateSignature(f http.HandlerFunc, proxyClientSecret string) http.HandlerFunc {
+	return func(rw http.ResponseWriter, req *http.Request) {
+		err := req.ParseForm()
+		if err != nil {
+			httputil.ErrorResponse(rw, req, err.Error(), http.StatusBadRequest)
+			return
+		}
+		redirectURI := req.Form.Get("redirect_uri")
+		sigVal := req.Form.Get("sig")
+		timestamp := req.Form.Get("ts")
+		if !validSignature(redirectURI, sigVal, timestamp, proxyClientSecret) {
+			httputil.ErrorResponse(rw, req, "Invalid redirect parameter", http.StatusBadRequest)
+			return
+		}
+
+		f(rw, req)
+	}
+}
+
+func validSignature(redirectURI, sigVal, timestamp, secret string) bool {
+	if redirectURI == "" || sigVal == "" || timestamp == "" || secret == "" {
+		return false
+	}
+	_, err := url.Parse(redirectURI)
+	if err != nil {
+		return false
+	}
+	requestSig, err := base64.URLEncoding.DecodeString(sigVal)
+	if err != nil {
+		return false
+	}
+	i, err := strconv.ParseInt(timestamp, 10, 64)
+	if err != nil {
+		return false
+	}
+	tm := time.Unix(i, 0)
+	ttl := 5 * time.Minute
+	if time.Now().Sub(tm) > ttl {
+		return false
+	}
+	localSig := redirectURLSignature(redirectURI, tm, secret)
+	return hmac.Equal(requestSig, localSig)
+}
+
+func redirectURLSignature(rawRedirect string, timestamp time.Time, secret string) []byte {
+	h := hmac.New(sha256.New, []byte(secret))
+	h.Write([]byte(rawRedirect))
+	h.Write([]byte(fmt.Sprint(timestamp.Unix())))
+	return h.Sum(nil)
+}