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fix(policy): correctly wire subrequest mode through CEL/path checkers (#1630)

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* fix(policy): correctly wire subrequest mode through CEL/path checkers

Previously Anubis only checked for the X-Original-Url when using
subrequest mode. This header is used by the example nginx config to pass
the request path through from the original client request to Anubis in
order to do path-based filtering.

According to facts and circumstances, Traefik hardcodes its own
headers[1]:

```text
httpdebug-1  | GET /.within.website/x/cmd/anubis/api/check
httpdebug-1  | X-Forwarded-Method: GET
httpdebug-1  | X-Forwarded-Proto: http
httpdebug-1  | X-Forwarded-Server: b9a5d299c929
httpdebug-1  | X-Forwarded-Port: 8080
httpdebug-1  | X-Forwarded-Uri: /
httpdebug-1  | X-Real-Ip: 172.18.0.1
httpdebug-1  | Accept-Encoding: gzip
httpdebug-1  | User-Agent: curl/8.20.0
httpdebug-1  | Accept: */*
httpdebug-1  | X-Forwarded-For: 172.18.0.1
httpdebug-1  | X-Forwarded-Host: localhost:8080
```

As a result, this means that path-based filtering did not work.

This commit fixes this issue by amending how path based checking logic
works:

* For CEL based checks, this pipes through the `subrequestMode` flag from
  main and alters the behaviour if either `X-Original-Url` or
  `X-Forwarded-Url` are found. These values are currently hardcoded for
  convenience but probably need to be made configurable in the policy
  file at a future date.
* For path-based checks, this uses the existing `subrequestMode` flag
  from main and adds `X-Forwarded-Url` to the list of headers it checks.

A smoke test was added to make sure that traefik in this mode continues
to work. Thank you https://github.com/flifloo for filing a detailed
issue with the relevant configuration fragments. Those configuration
fragments formed the core of this smoke test.

[1]: https://doc.traefik.io/traefik/v3.4/middlewares/http/forwardauth/

Closes: https://github.com/TecharoHQ/anubis/issues/1628
Signed-off-by: Xe Iaso <me@xeiaso.net>
Co-Authored-By: flifloo <flifloo@gmail.com>

* chore: spelling

Signed-off-by: Xe Iaso <me@xeiaso.net>

---------

Signed-off-by: Xe Iaso <me@xeiaso.net>
Co-authored-by: flifloo <flifloo@gmail.com>
This commit is contained in:
Xe Iaso
2026-05-14 21:37:02 -04:00
committed by GitHub
parent 9f479f578a
commit 276b537776
15 changed files with 354 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
.github/actions/spelling/allow.txt
+2
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@@ -39,3 +39,5 @@ wenet
qwertiko
setuplistener
mba
xfu
xou
.github/workflows/smoke-tests.yml
+1
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@@ -27,6 +27,7 @@ jobs:
- palemoon/amd64
#- palemoon/i386
- robots_txt
- traefik
runs-on: ubuntu-latest
steps:
- name: Checkout code
docs/docs/CHANGELOG.md
+1
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@@ -28,6 +28,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
- Fix a bug in the dataset poisoning maze that could allow denial of service [#1580](https://github.com/TecharoHQ/anubis/issues/1580).
- Add config option to add ASN to logs/metrics.
- Log weight when issuing challenge
- Fix `path_regex` and CEL `path` rules not matching when using Traefik `forwardAuth` middleware. Anubis now checks `X-Forwarded-Uri` (Traefik) in addition to `X-Original-URI` (nginx) when resolving the request path in subrequest mode ([#1628](https://github.com/TecharoHQ/anubis/issues/1628)).
## v1.25.0: Necron
lib/policy/celchecker.go
+13 -2
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@@ -15,9 +15,10 @@ import (
type CELChecker struct {
program cel.Program
src string
subRequestMode bool
}
func NewCELChecker(cfg *config.ExpressionOrList, dnsObj *dns.Dns) (*CELChecker, error) {
func NewCELChecker(cfg *config.ExpressionOrList, dnsObj *dns.Dns, subRequestMode bool) (*CELChecker, error) {
env, err := expressions.BotEnvironment(dnsObj)
if err != nil {
return nil, err
@@ -31,6 +32,7 @@ func NewCELChecker(cfg *config.ExpressionOrList, dnsObj *dns.Dns) (*CELChecker,
return &CELChecker{
src: cfg.String(),
program: program,
subRequestMode: subRequestMode,
}, nil
}
@@ -39,7 +41,7 @@ func (cc *CELChecker) Hash() string {
}
func (cc *CELChecker) Check(r *http.Request) (bool, error) {
result, _, err := cc.program.ContextEval(r.Context(), &CELRequest{r})
result, _, err := cc.program.ContextEval(r.Context(), &CELRequest{r, cc.subRequestMode})
if err != nil {
return false, err
@@ -54,6 +56,7 @@ func (cc *CELChecker) Check(r *http.Request) (bool, error) {
type CELRequest struct {
*http.Request
subRequestMode bool
}
func (cr *CELRequest) Parent() cel.Activation { return nil }
@@ -71,6 +74,14 @@ func (cr *CELRequest) ResolveName(name string) (any, bool) {
case "userAgent":
return cr.UserAgent(), true
case "path":
if cr.subRequestMode {
if xou := cr.Header.Get("X-Original-URI"); xou != "" {
return xou, true
}
if xfu := cr.Header.Get("X-Forwarded-Uri"); xfu != "" {
return xfu, true
}
}
return cr.URL.Path, true
case "query":
return expressions.URLValues{Values: cr.URL.Query()}, true
lib/policy/celchecker_test.go
+75 -1
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@@ -23,7 +23,7 @@ func TestCELChecker_MapIterationWrappers(t *testing.T) {
Expression: `headers.exists(k, k == "Accept") && query.exists(k, k == "format")`,
}
checker, err := NewCELChecker(cfg, newTestDNS(t))
checker, err := NewCELChecker(cfg, newTestDNS(t), false)
if err != nil {
t.Fatalf("creating CEL checker failed: %v", err)
}
@@ -42,3 +42,77 @@ func TestCELChecker_MapIterationWrappers(t *testing.T) {
t.Fatal("expected expression to evaluate true")
}
}
func TestCELChecker_PathWithForwardedUri(t *testing.T) {
tests := []struct {
name string
expression string
xForwardedUri string
urlPath string
subRequestMode bool
want bool
}{
{
name: "path matches X-Forwarded-Uri in subrequest mode",
expression: `path.startsWith("/admin")`,
xForwardedUri: "/admin/secret",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "path with query string",
expression: `path.startsWith("/api/secret")`,
xForwardedUri: "/api/secret?token=abc",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "path falls back to url path when no header",
expression: `path == "/public/page"`,
urlPath: "/public/page",
subRequestMode: true,
want: true,
},
{
name: "non-subrequest mode ignores X-Forwarded-Uri",
expression: `path.startsWith("/admin")`,
xForwardedUri: "/admin/secret",
urlPath: "/public/page",
subRequestMode: false,
want: false,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
cfg := &config.ExpressionOrList{
Expression: tt.expression,
}
checker, err := NewCELChecker(cfg, newTestDNS(t), tt.subRequestMode)
if err != nil {
t.Fatalf("NewCELChecker() error: %v", err)
}
req, err := http.NewRequest(http.MethodGet, "http://example.com"+tt.urlPath, nil)
if err != nil {
t.Fatalf("http.NewRequest: %v", err)
}
if tt.xForwardedUri != "" {
req.Header.Set("X-Forwarded-Uri", tt.xForwardedUri)
}
got, err := checker.Check(req)
if err != nil {
t.Fatalf("Check() error: %v", err)
}
if got != tt.want {
t.Errorf("Check() = %v, want %v (subRequestMode=%v, urlPath=%q, X-Forwarded-Uri=%q)",
got, tt.want, tt.subRequestMode, tt.urlPath, tt.xForwardedUri)
}
})
}
}
lib/policy/checker.go
+3
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@@ -110,6 +110,9 @@ func NewPathChecker(rexStr string, subrequestMode bool) (checker.Impl, error) {
func (pc *PathChecker) Check(r *http.Request) (bool, error) {
if pc.subRequestMode {
originalUrl := r.Header.Get("X-Original-URI")
if originalUrl == "" {
originalUrl = r.Header.Get("X-Forwarded-Uri")
}
if originalUrl != "" {
if pc.regexp.MatchString(originalUrl) {
return true, nil
lib/policy/checker_test.go
+116
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@@ -410,3 +410,119 @@ func TestPathChecker_GHSA_6wcg_mqvh_fcvg(t *testing.T) {
})
}
}
func TestPathChecker_XForwardedUri(t *testing.T) {
tests := []struct {
name string
regex string
xForwardedUri string
xOriginalURI string
urlPath string
subRequestMode bool
want bool
}{
{
name: "X-Forwarded-Uri matches regex in subrequest mode",
regex: "^/admin/.*",
xForwardedUri: "/admin/users",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "X-Forwarded-Uri with query string",
regex: "^/admin/.*",
xForwardedUri: "/admin/users?page=1",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "X-Original-URI takes priority over X-Forwarded-Uri",
regex: "^/admin/.*",
xForwardedUri: "/public/page",
xOriginalURI: "/admin/users",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "falls back to X-Forwarded-Uri when no X-Original-URI",
regex: "^/admin/.*",
xForwardedUri: "/admin/dashboard",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: true,
},
{
name: "neither header matches, url path matches",
regex: "^/public/.*",
xForwardedUri: "/admin/users",
urlPath: "/public/page",
subRequestMode: true,
want: true,
},
{
name: "nothing matches",
regex: "^/admin/.*",
xForwardedUri: "/public/page",
urlPath: "/.within.website/x/cmd/anubis/api/check",
subRequestMode: true,
want: false,
},
{
name: "non-subrequest mode ignores X-Forwarded-Uri",
regex: "^/admin/.*",
xForwardedUri: "/admin/users",
urlPath: "/public/page",
subRequestMode: false,
want: false,
},
{
name: "non-subrequest mode uses url path",
regex: "^/admin/.*",
xForwardedUri: "/public/page",
urlPath: "/admin/secret",
subRequestMode: false,
want: true,
},
{
name: "empty X-Forwarded-Uri falls back to url path",
regex: "^/check$",
urlPath: "/check",
subRequestMode: true,
want: true,
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
pc, err := NewPathChecker(tt.regex, tt.subRequestMode)
if err != nil {
t.Fatalf("NewPathChecker(%q, %v) returned error: %v", tt.regex, tt.subRequestMode, err)
}
req, err := http.NewRequest(http.MethodGet, "http://example.com"+tt.urlPath, nil)
if err != nil {
t.Fatalf("http.NewRequest: %v", err)
}
if tt.xForwardedUri != "" {
req.Header.Set("X-Forwarded-Uri", tt.xForwardedUri)
}
if tt.xOriginalURI != "" {
req.Header.Set("X-Original-URI", tt.xOriginalURI)
}
got, err := pc.Check(req)
if err != nil {
t.Fatalf("Check() unexpected error: %v", err)
}
if got != tt.want {
t.Errorf("Check() = %v, want %v (subRequestMode=%v, urlPath=%q, X-Forwarded-Uri=%q, X-Original-URI=%q)",
got, tt.want, tt.subRequestMode, tt.urlPath, tt.xForwardedUri, tt.xOriginalURI)
}
})
}
}
lib/policy/policy.go
+1 -1
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@@ -170,7 +170,7 @@ func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDiffic
}
if b.Expression != nil {
c, err := NewCELChecker(b.Expression, result.Dns)
c, err := NewCELChecker(b.Expression, result.Dns, subrequestMode)
if err != nil {
validationErrs = append(validationErrs, fmt.Errorf("while processing rule %s expressions: %w", b.Name, err))
} else {
test/traefik/anubis.yaml
+16
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@@ -0,0 +1,16 @@
bots:
- name: block-admin-via-regex
path_regex: ^/admin(/.*)?$
action: DENY
- name: block-secret-via-cel
expression:
all:
- 'path.startsWith("/api/secret")'
action: DENY
- import: (data)/meta/default-config.yaml
status_codes:
CHALLENGE: 200
DENY: 403
test/traefik/docker-compose.yaml
+27
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@@ -0,0 +1,27 @@
services:
traefik:
image: traefik:v3.3
restart: always
ports:
- 8080:80
volumes:
- ./traefik.yml:/etc/traefik/traefik.yml:ro
- ./http.yaml:/config/http.yaml:ro
anubis:
image: ko.local/anubis
restart: always
environment:
BIND: ":8080"
TARGET: " "
POLICY_FNAME: /etc/techaro/anubis.yaml
PUBLIC_URL: http://localhost:8080/.within.website/x/cmd/anubis
COOKIE_DOMAIN: localhost
USE_REMOTE_ADDRESS: "true"
volumes:
- ./anubis.yaml:/etc/techaro/anubis.yaml
backend:
image: ghcr.io/xe/x/httpdebug
pull_policy: always
restart: always
test/traefik/http.yaml
+30
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@@ -0,0 +1,30 @@
http:
middlewares:
anubis:
forwardAuth:
address: http://anubis:8080/.within.website/x/cmd/anubis/api/check
trustForwardHeader: true
routers:
anubis-assets:
rule: Host(`localhost`) && PathPrefix(`/.within.website/x/cmd/anubis`)
entryPoints:
- web
service: anubis
backend:
rule: Host(`localhost`)
entryPoints:
- web
service: backend
middlewares:
- anubis
services:
anubis:
loadBalancer:
servers:
- url: http://anubis:8080
backend:
loadBalancer:
servers:
- url: http://backend:3000
test/traefik/test.mjs
+33
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@@ -0,0 +1,33 @@
// Smoke test for https://github.com/TecharoHQ/anubis/issues/1628
//
// Traefik's forwardAuth middleware calls Anubis at the literal path
// /.within.website/x/cmd/anubis/api/check and conveys the original URL in the
// X-Forwarded-Uri header. Path-targeting policy rules must match that header
// (not r.URL.Path), otherwise every request looks like a request to /check.
const BASE = "http://localhost:8080";
const UA = "Mozilla/5.0 (compatible; AnubisTraefikSmoke/1.0)";
const cases = [
{ path: "/", expected: 307, why: "control: no DENY rule, default challenge redirect" },
{ path: "/free", expected: 307, why: "control: no DENY rule, default challenge redirect" },
{ path: "/admin", expected: 403, why: "path_regex must match X-Forwarded-Uri, not 307 or 200" },
{ path: "/admin/users", expected: 403, why: "path_regex must match X-Forwarded-Uri, not 307 or 200" },
{ path: "/api/secret", expected: 403, why: "CEL path must match X-Forwarded-Uri, not 307 or 200" },
];
let failed = false;
for (const c of cases) {
const resp = await fetch(`${BASE}${c.path}`, {
headers: { "User-Agent": UA },
redirect: "manual",
});
const ok = resp.status === c.expected;
console.log(
`${ok ? "PASS" : "FAIL"}: GET ${c.path} → ${resp.status} (want ${c.expected}: ${c.why})`,
);
if (!ok) failed = true;
}
process.exit(failed ? 1 : 0);
test/traefik/test.sh
Executable
+22
View File
@@ -0,0 +1,22 @@
#!/usr/bin/env bash
set -eo pipefail
export VERSION=${GITHUB_SHA:-devel}-test
export KO_DOCKER_REPO=ko.local
set -u
source ../lib/lib.sh
build_anubis_ko
function cleanup() {
docker compose down -t 1 || :
}
trap cleanup EXIT SIGINT
docker compose up -d
backoff-retry --try-count 20 node ./test.mjs
test/traefik/traefik.yml
+8
View File
@@ -0,0 +1,8 @@
entryPoints:
web:
address: ":80"
providers:
file:
directory: /config
watch: false
test/traefik/var/.gitignore
+2
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@@ -0,0 +1,2 @@
*
!.gitignore