From 0fd5bf66e8da32f866c0ee7f4af0eeccd60dc250 Mon Sep 17 00:00:00 2001
From: Ashvin <76151462+ashvinctrl@users.noreply.github.com>
Date: Mon, 27 Jul 2026 18:27:08 +0530
Subject: [PATCH] fix: block SSRF / local-file reads via report image URLs
 during PDF generation (#2908)

* fix: block SSRF and local-file reads via report image URLs in PDF generation

save_pdf_report() rendered scraped profile image URLs (ids_data['image'])
straight into xhtml2pdf, which fetches <img src> while building the PDF.
The image field is attacker-influenced and pisaDocument ran with no
link_callback, so a profile carrying image = "file:///etc/passwd" or an
intranet/metadata URL turned report generation into a local file read or
an SSRF from the machine running maigret. In the web UI this is
server-side and fires on every search, since save_pdf_report is always
called.

Add a link_callback that only lets public http(s) images through and
diverts everything else (file://, data:, other schemes, and hosts that
resolve to loopback/private/link-local/reserved addresses) to a bundled
1x1 placeholder, so no fetch or read happens. Diverting rather than
raising keeps report generation working when a scanned profile carries a
hostile image URL.

Tests cover the URL classifier, the callback's placeholder diversion, and
an end-to-end check that PDF generation does not fetch an internal image.

* fix: use is_global to also block CGNAT (100.64.0.0/10) report image hosts

The flag chain missed 100.64.0.0/10, which is neither is_private nor
is_global and is routable inside many cloud and k8s networks. is_global
covers it along with private, loopback, link-local and unspecified.

Multicast and reserved stay explicit: both are still is_global on
CPython, and 64:ff9b::/96 reaches IPv4 through a NAT64 gateway.
---
 maigret/report.py           |  70 ++++++++++++++++++++-
 maigret/resources/blank.png | Bin 0 -> 70 bytes
 tests/test_report.py        | 119 ++++++++++++++++++++++++++++++++++++
 3 files changed, 188 insertions(+), 1 deletion(-)
 create mode 100644 maigret/resources/blank.png

diff --git a/maigret/report.py b/maigret/report.py
index 2429ecf..4711aa6 100644
--- a/maigret/report.py
+++ b/maigret/report.py
@@ -1,11 +1,14 @@
 import ast
 import csv
 import io
+import ipaddress
 import json
 import logging
 import os
+import socket
 from datetime import datetime
 from typing import Dict, Any
+from urllib.parse import urlparse
 
 import xmind  # type: ignore[import-untyped]
 from dateutil.tz import gettz
@@ -83,6 +86,66 @@ PDF_EXTRA_HINT = (
     "Install it with: pip install 'maigret[pdf]'"
 )
 
+# 1x1 transparent PNG substituted for any report image URL that isn't a safe
+# public http(s) resource (see _is_safe_report_image_url).
+_BLANK_IMAGE_PATH = os.path.join(
+    os.path.dirname(os.path.realpath(__file__)), "resources", "blank.png"
+)
+
+
+def _is_safe_report_image_url(uri) -> bool:
+    """Whether ``uri`` is a public http(s) image safe to fetch during PDF render.
+
+    Report images come from scraped profile data (``ids_data['image']``), which
+    is attacker-influenced. xhtml2pdf resolves ``<img src>`` while building the
+    PDF, so an intranet or cloud-metadata URL is a request made by the machine
+    running maigret (server-side in the web UI). A src with no scheme at all is
+    worse than a URL: xhtml2pdf falls back to treating it as a local path and
+    opens it. Only allow http(s) hosts that resolve to public addresses.
+    """
+    if not isinstance(uri, str):
+        return False
+    parsed = urlparse(uri.strip())
+    if parsed.scheme not in ("http", "https"):
+        return False
+    host = parsed.hostname
+    if not host:
+        return False
+    try:
+        infos = socket.getaddrinfo(host, None)
+    except (socket.gaierror, UnicodeError, ValueError):
+        return False
+    if not infos:
+        return False
+    for info in infos:
+        try:
+            ip = ipaddress.ip_address(info[4][0])
+        except ValueError:
+            return False
+        mapped = getattr(ip, "ipv4_mapped", None)
+        if mapped is not None:
+            ip = mapped
+        # is_global is False for private, loopback, link-local, unspecified and
+        # CGNAT (100.64.0.0/10) addresses. Multicast and reserved ranges are
+        # still is_global on CPython, so they stay explicit: 64:ff9b::/96 is
+        # reserved but routes to IPv4 through a NAT64 gateway.
+        if not ip.is_global or ip.is_multicast or ip.is_reserved:
+            return False
+    return True
+
+
+def _pdf_report_link_callback(uri, rel):
+    """xhtml2pdf resource resolver: let safe public images through, and divert
+    everything else to a local blank placeholder so no fetch/read happens.
+
+    Returning a local path (rather than raising) keeps report generation working
+    even when a scanned profile carries a hostile image URL — a raise would abort
+    the whole PDF.
+    """
+    if _is_safe_report_image_url(uri):
+        return uri
+    return _BLANK_IMAGE_PATH
+
 
 def save_pdf_report(filename: str, context: dict):
     # Imported lazily so that users without the optional 'pdf' extra
@@ -96,7 +159,12 @@ def save_pdf_report(filename: str, context: dict):
     filled_template = template.render(**context)
 
     with open(filename, "w+b") as f:
-        pisa.pisaDocument(io.StringIO(filled_template), dest=f, default_css=css)
+        pisa.pisaDocument(
+            io.StringIO(filled_template),
+            dest=f,
+            default_css=css,
+            link_callback=_pdf_report_link_callback,
+        )
 
 
 def save_json_report(filename: str, username: str, results: dict, report_type: str):
diff --git a/maigret/resources/blank.png b/maigret/resources/blank.png
new file mode 100644
index 0000000000000000000000000000000000000000..145a07dbcb5cf07a4a8560492854177f3d6ce292
GIT binary patch
literal 70
zcmeAS@N?(olHy`uVBq!ia0vp^j3CUx1|;Q0k92}1TpU9x<|HQo0g%hez_|3As{@e5
N;OXk;vd$@?2>_B<4XpqG

literal 0
HcmV?d00001

diff --git a/tests/test_report.py b/tests/test_report.py
index 50603ce..10c6d71 100644
--- a/tests/test_report.py
+++ b/tests/test_report.py
@@ -31,6 +31,9 @@ from maigret.report import (
     generate_json_report,
     get_plaintext_report,
     _graph_to_cypher,
+    _is_safe_report_image_url,
+    _pdf_report_link_callback,
+    _BLANK_IMAGE_PATH,
 )
 from maigret.errors import CheckError
 from maigret.result import MaigretCheckResult, MaigretCheckStatus
@@ -651,6 +654,122 @@ def test_xhtml2pdf_is_not_module_level_dependency():
     assert 'pisa' not in module_globals
 
 
+# Report images come from scraped profile data and are attacker-influenced;
+# xhtml2pdf resolves <img src> while rendering the PDF, so an intranet URL is a
+# request from the host, and a src with no scheme is opened as a local file.
+def test_is_safe_report_image_url_rejects_dangerous():
+    bad = [
+        "file:///etc/passwd",
+        "file://C:/Windows/win.ini",
+        "data:text/html,<script>",
+        "ftp://example.com/x.png",
+        "http://127.0.0.1/a.png",
+        "http://localhost/a.png",
+        "http://169.254.169.254/latest/meta-data/",
+        "http://10.0.0.5/a.png",
+        "http://192.168.1.1/a.png",
+        "http://172.16.0.1/a.png",
+        "http://[::1]/a.png",
+        "http://0.0.0.0/a.png",
+        "//example.com/a.png",  # scheme-relative, no scheme
+        # No scheme at all: xhtml2pdf treats these as local paths and opens them.
+        "/etc/passwd",
+        "C:/Windows/win.ini",
+        "../../../../etc/shadow",
+        "",
+        None,
+        42,
+    ]
+    for value in bad:
+        assert _is_safe_report_image_url(value) is False, value
+
+
+def test_is_safe_report_image_url_rejects_non_global_ranges():
+    # Ranges that the private/loopback/link-local flags alone do not catch.
+    bad = [
+        # CGNAT / shared address space, common inside cloud and k8s networks.
+        "http://100.64.0.1/a.png",
+        "http://100.127.255.254/a.png",
+        # Multicast and reserved are still is_global on CPython, so a bare
+        # `return ip.is_global` would let these through.
+        "http://224.0.0.1/a.png",
+        "http://239.255.255.250/a.png",
+        "http://[ff02::1]/a.png",
+        # NAT64 well-known prefix: reaches 10.0.0.1 through a NAT64 gateway.
+        "http://[64:ff9b::a00:1]/a.png",
+        # IPv4-mapped IPv6 forms of blocked v4 addresses.
+        "http://[::ffff:127.0.0.1]/a.png",
+        "http://[::ffff:169.254.169.254]/a.png",
+    ]
+    for value in bad:
+        assert _is_safe_report_image_url(value) is False, value
+
+
+def test_is_safe_report_image_url_allows_public_hosts():
+    # IP literals resolve without DNS, so this stays offline and deterministic.
+    assert _is_safe_report_image_url("https://1.1.1.1/avatar.png") is True
+    assert _is_safe_report_image_url("http://8.8.8.8/avatar.png") is True
+
+
+def test_pdf_link_callback_diverts_unsafe_to_local_blank():
+    assert os.path.exists(_BLANK_IMAGE_PATH)
+    # Unsafe URLs resolve to a local placeholder path, so xhtml2pdf never
+    # fetches or reads them.
+    assert _pdf_report_link_callback("file:///etc/passwd", "") == _BLANK_IMAGE_PATH
+    assert (
+        _pdf_report_link_callback("http://169.254.169.254/x", "") == _BLANK_IMAGE_PATH
+    )
+    # Safe public URLs pass through unchanged.
+    url = "https://1.1.1.1/a.png"
+    assert _pdf_report_link_callback(url, "") == url
+
+
+def test_pdf_report_does_not_fetch_unsafe_image(tmp_path):
+    pytest.importorskip("xhtml2pdf")
+    import http.server
+    import socketserver
+    import threading
+
+    hits = []
+
+    class _Handler(http.server.BaseHTTPRequestHandler):
+        def do_GET(self):
+            hits.append(self.path)
+            self.send_response(404)
+            self.end_headers()
+
+        def log_message(self, *args):
+            pass
+
+    srv = socketserver.TCPServer(("127.0.0.1", 0), _Handler)
+    port = srv.server_address[1]
+    threading.Thread(target=srv.serve_forever, daemon=True).start()
+    try:
+        internal = f"http://127.0.0.1:{port}/SSRF-should-not-happen"
+        res = MaigretCheckResult(
+            "alice",
+            "TestSite",
+            "http://testsite/alice",
+            MaigretCheckStatus.CLAIMED,
+            ids_data={"image": internal},
+        )
+        username_results = [
+            (
+                "alice",
+                "username",
+                {"TestSite": {"status": res, "url_user": "http://testsite/alice"}},
+            )
+        ]
+        context = generate_report_context(username_results)
+        target = tmp_path / "report.pdf"
+        save_pdf_report(str(target), context)
+        assert target.exists()
+    finally:
+        srv.shutdown()
+
+    assert hits == [], f"PDF generation fetched a blocked URL: {hits}"
+
+
 def test_import_maigret_without_pdf_extras():
     # End-to-end check: spawn a fresh interpreter with every package in the
     # [pdf] extra blocked before any maigret module is loaded, and confirm