feat(sso): forward auth improvements

This adds a couple of key improvements to the Forward Auth SSO implementation. Primarily it adds an included cookies setting which allows filtering cookies to the authorization server. Secondly it fixes a bug where the headerCopyIncluded function was case-sensitive. Documentation in the code and on the web UI is clearer to resolve some common questions and issues. Lastly it moves a lot of funcs to the util.go file and adds fairly comprehensive tests.

src/mod/auth/sso/forward/util.go

@@ -0,0 +1,137 @@
+package forward
+
+import (
+	"net"
+	"net/http"
+	"strings"
+)
+
+func scheme(r *http.Request) string {
+	if r.TLS != nil {
+		return "https"
+	}
+
+	return "http"
+}
+
+func headerCookieRedact(r *http.Request, names []string, exclude bool) {
+	if len(names) == 0 {
+		return
+	}
+
+	original := r.Cookies()
+
+	if len(original) == 0 {
+		return
+	}
+
+	var cookies []string
+
+	for _, cookie := range original {
+		if exclude && stringInSlice(cookie.Name, names) {
+			continue
+		} else if !exclude && !stringInSlice(cookie.Name, names) {
+			continue
+		}
+
+		cookies = append(cookies, cookie.String())
+	}
+
+	value := strings.Join(cookies, "; ")
+
+	r.Header.Set(HeaderCookie, value)
+
+	return
+}
+
+func headerCopyExcluded(original, destination http.Header, excludedHeaders []string) {
+	for key, values := range original {
+		// We should never copy the headers in the below list.
+		if stringInSliceFold(key, doNotCopyHeaders) {
+			continue
+		}
+
+		if stringInSliceFold(key, excludedHeaders) {
+			continue
+		}
+
+		destination[key] = append(destination[key], values...)
+	}
+}
+
+func headerCopyIncluded(original, destination http.Header, includedHeaders []string, allIfEmpty bool) {
+	if allIfEmpty && len(includedHeaders) == 0 {
+		headerCopyAll(original, destination)
+	} else {
+		headerCopyIncludedExact(original, destination, includedHeaders)
+	}
+}
+
+func headerCopyAll(original, destination http.Header) {
+	for key, values := range original {
+		// We should never copy the headers in the below list, even if they're in the list provided by a user.
+		if stringInSliceFold(key, doNotCopyHeaders) {
+			continue
+		}
+
+		destination[key] = append(destination[key], values...)
+	}
+}
+
+func headerCopyIncludedExact(original, destination http.Header, keys []string) {
+	for key, values := range original {
+		// We should never copy the headers in the below list, even if they're in the list provided by a user.
+		if stringInSliceFold(key, doNotCopyHeaders) {
+			continue
+		}
+
+		if !stringInSliceFold(key, keys) {
+			continue
+		}
+
+		destination[key] = append(destination[key], values...)
+	}
+}
+
+func stringInSlice(needle string, haystack []string) bool {
+	if len(haystack) == 0 {
+		return false
+	}
+
+	for _, v := range haystack {
+		if needle == v {
+			return true
+		}
+	}
+
+	return false
+}
+
+func stringInSliceFold(needle string, haystack []string) bool {
+	if len(haystack) == 0 {
+		return false
+	}
+
+	for _, v := range haystack {
+		if strings.EqualFold(needle, v) {
+			return true
+		}
+	}
+
+	return false
+}
+
+func rSetForwardedHeaders(r, req *http.Request) {
+	if r.RemoteAddr != "" {
+		before, _, _ := strings.Cut(r.RemoteAddr, ":")
+
+		if ip := net.ParseIP(before); ip != nil {
+			req.Header.Set(HeaderXForwardedFor, ip.String())
+		}
+	}
+
+	req.Header.Set(HeaderXForwardedMethod, r.Method)
+	req.Header.Set(HeaderXForwardedProto, scheme(r))
+	req.Header.Set(HeaderXForwardedHost, r.Host)
+	req.Header.Set(HeaderXForwardedURI, r.URL.Path)
+}