fix(skills): harden skill import against DNS rebinding and SSRF TOCTOU (#5986)

* fix(skill-importer): validate URL scheme and improve skills.sh handling

* fix(skill-importer): enhance DNS resolution and SSRF protection in fetch URL handling

* fix(url-safety): add allowed_dist parameter to check_outbound_url for flexible private blocking

* test(skill-importer): add comprehensive tests for URL parsing and outbound checks

* ensure newline at end of file in test_check_outbound_url_allows_public_ip

* fix(skill-importer): improve TLS certificate handling in _get_checked function

* fix(skill-importer): enhance _check_fetch_url to handle both hostnames and full URLs

* fix(skill-importer): enhance parse_skill_source to support skills.sh URLs in path and netloc

* fix(skill-importer): simplify skills.sh hostname check in parse_skill_source

* fix(skill-importer): enhance parse_skill_source to identify skills.sh URLs in path and handle localhost/IP addresses

* fix(skill-importer): enhance _resolve_and_check_url to validate all resolved IP addresses and prevent TOCTOU vulnerabilities

* fix(skill-importer): enhance parse_skill_source to support schemeless GitHub and skills.sh URLs

* fix(memory): resolve CodeQL URL sanitization warning and restore _check_fetch_url test alias

* fix(memory): pin skill fetch sockets without rewriting URLs

* fix(memory): reject unsupported skill wrapper hosts

* refactor(url-safety): remove unused importer exception

* test(memory): keep redirect regression hermetic

* test(dns-rebinding): add test for _PinnedTransport to ensure connection to pinned IP

* fix(skill-importer): enhance skills.sh support to extract GitHub links from page content

* fix(skill-importer): improve URL scheme validation for GitHub and skills.sh links

* fix(skills): reject unusable skill URLs instead of guessing

Resolving a skills.sh link by scraping the first github.com URL out of
the page body cannot work. Skill pages only ever link the repository
root, never the skill's subdirectory, so every skill in a repo resolved
to the same bundle: importing skills.sh/anthropics/skills/pdf walked the
whole monorepo, saturated the 64-file cap, and installed algorithmic-art
behind an ok:true response. Restore the redirect-target unwrap and fail
with a message that says what to do instead.

Also report the real reason a URL is rejected. The scheme check keyed off
"://" appearing anywhere in the string, so a supplied-but-unusable URL
came back as "URL is required", and a schemeless URL carrying "://" in
its query was reported as an unsupported scheme. Key off the parsed
scheme and let opaque schemes (mailto:, javascript:) and a schemeless
host:port fall through to the host check.

* test(skills): tighten the real-socket pinning regression

The handler swallowed its own exceptions, so a failure inside it
surfaced as a confusing assertion on the captured client address.
Record the exception and assert on it, run the thread as a daemon, and
close the listening socket from the test so a hang cannot outlive the
run. Also drop the duplicate ipaddress import and the missing newline.

* fix(skills): require exact GitHub skill URLs

* test(skills): read complete pinned request headers

---------

Co-authored-by: RaresKeY <158580472+RaresKeY@users.noreply.github.com>
Co-authored-by: Léo <leograndcontact@gmail.com>

services/memory/skill_importer.py

@@ -1,16 +1,18 @@
 """Import SKILL.md bundles from public GitHub (or skills.sh → GitHub) URLs."""
 from __future__ import annotations
 
+import ipaddress
 import logging
 import os
-import re
+import time
 from dataclasses import dataclass
-from typing import Dict, List, Optional, Tuple
+from typing import Dict, Iterable, List, Optional, Tuple, cast
 from urllib.parse import quote, urljoin, urlparse
 
+import httpcore
 import httpx
 
-from src.url_safety import check_outbound_url
+from src.url_safety import _default_resolver, check_outbound_url
 
 logger = logging.getLogger(__name__)
 
@@ -25,6 +27,7 @@ TEXT_NAMES = {"skill.md", "license", "license.md", "readme.md"}
 _GITHUB_HOSTS = frozenset({
     "github.com", "www.github.com", "api.github.com", "raw.githubusercontent.com",
 })
+_SKILLS_SH_HOSTS = frozenset({"skills.sh", "www.skills.sh"})
 
 
 def _github_host(url: str) -> str:
@@ -72,18 +75,158 @@ def _is_text_file(name: str) -> bool:
 _MAX_FETCH_REDIRECTS = 5
 
 
-def _check_fetch_url(url: str) -> None:
+def _validated_ips(raw_ips: List[str]) -> List[ipaddress._BaseAddress]:
-    """SSRF guard for skill-import fetches (defense-in-depth).
+    """Parse and de-duplicate one resolver snapshot in resolver order."""
+    ips: List[ipaddress._BaseAddress] = []
+    seen = set()
+    for raw in raw_ips:
+        if not isinstance(raw, str):
+            continue
+        try:
+            ip = ipaddress.ip_address(raw.split("%", 1)[0])
+        except ValueError:
+            continue
+        if ip in seen:
+            continue
+        seen.add(ip)
+        ips.append(ip)
+    return ips
 
-    Skill bundles only ever come from public GitHub, never an internal
+
-    address, so block private/loopback/link-local targets on every hop —
+def _resolve_and_check_url(url: str) -> List[ipaddress._BaseAddress]:
-    matching the hardened web-fetch path in
+    """Return the exact address snapshot approved for one fetch hop."""
-    ``services/search/content.py:_get_public_url`` rather than the lenient
+    resolved_ips: List[str] = []
-    default used for admin-configured model endpoints.
+
-    """
+    def _recording_resolver(host: str) -> List[str]:
-    ok, reason = check_outbound_url(url, block_private=True)
+        answers = list(_default_resolver(host))
+        resolved_ips[:] = answers
+        return answers
+
+    ok, reason = check_outbound_url(
+        url,
+        block_private=True,
+        resolver=_recording_resolver,
+    )
     if not ok:
-        raise SkillImportError(reason)
+        raise SkillImportError(f"outbound URL blocked: {reason}")
+
+    pinned_ips = _validated_ips(resolved_ips)
+    if not pinned_ips:
+        raise SkillImportError("outbound URL blocked: host did not resolve to a usable address")
+    return pinned_ips
+
+
+# Backward compatibility alias for tests importing _check_fetch_url directly
+_check_fetch_url = _resolve_and_check_url
+
+
+class _PinnedBackend(httpcore.NetworkBackend):
+    """Connect only to addresses from one validated DNS snapshot."""
+
+    def __init__(self, ips: List[ipaddress._BaseAddress]):
+        self._ips = [str(ip) for ip in ips]
+        self._real = httpcore.SyncBackend()
+
+    def connect_tcp(
+        self,
+        host: str,
+        port: int,
+        timeout: float | None = None,
+        local_address: str | None = None,
+        socket_options=None,
+    ):
+        deadline = None if timeout is None else time.monotonic() + timeout
+        last_exc: Optional[Exception] = None
+        for ip in self._ips:
+            remaining = None if deadline is None else max(0.0, deadline - time.monotonic())
+            try:
+                return self._real.connect_tcp(
+                    ip,
+                    port,
+                    remaining,
+                    local_address,
+                    socket_options,
+                )
+            except (httpcore.ConnectError, httpcore.ConnectTimeout) as exc:
+                last_exc = exc
+                if deadline is not None and time.monotonic() >= deadline:
+                    break
+        if last_exc is not None:
+            raise last_exc
+        raise httpcore.ConnectError("no validated address available")
+
+    def connect_unix_socket(self, path, timeout=None, socket_options=None):
+        return self._real.connect_unix_socket(path, timeout, socket_options)
+
+    def sleep(self, seconds: float) -> None:
+        return self._real.sleep(seconds)
+
+
+_HTTPCORE_TO_HTTPX_EXC = {
+    httpcore.ConnectError: httpx.ConnectError,
+    httpcore.ConnectTimeout: httpx.ConnectTimeout,
+    httpcore.LocalProtocolError: httpx.LocalProtocolError,
+    httpcore.NetworkError: httpx.NetworkError,
+    httpcore.PoolTimeout: httpx.PoolTimeout,
+    httpcore.ProtocolError: httpx.ProtocolError,
+    httpcore.ProxyError: httpx.ProxyError,
+    httpcore.ReadError: httpx.ReadError,
+    httpcore.ReadTimeout: httpx.ReadTimeout,
+    httpcore.RemoteProtocolError: httpx.RemoteProtocolError,
+    httpcore.TimeoutException: httpx.TimeoutException,
+    httpcore.UnsupportedProtocol: httpx.UnsupportedProtocol,
+    httpcore.WriteError: httpx.WriteError,
+    httpcore.WriteTimeout: httpx.WriteTimeout,
+}
+
+
+class _PinnedTransport(httpx.BaseTransport):
+    """Pin socket connects while preserving URL authority, Host, and TLS SNI."""
+
+    def __init__(self, ips: List[ipaddress._BaseAddress]):
+        self._pinned_ips = list(ips)
+        self._pool = httpcore.ConnectionPool(
+            ssl_context=httpx.create_ssl_context(),
+            http1=True,
+            http2=False,
+            network_backend=_PinnedBackend(ips),
+        )
+
+    def handle_request(self, request: httpx.Request) -> httpx.Response:
+        core_request = httpcore.Request(
+            method=request.method,
+            url=httpcore.URL(
+                scheme=request.url.raw_scheme,
+                host=request.url.raw_host,
+                port=request.url.port,
+                target=request.url.raw_path,
+            ),
+            headers=request.headers.raw,
+            content=request.stream,
+            extensions=request.extensions,
+        )
+        core_response = None
+        try:
+            core_response = self._pool.handle_request(core_request)
+            content = b"".join(cast(Iterable[bytes], core_response.stream))
+        except Exception as exc:
+            mapped = _HTTPCORE_TO_HTTPX_EXC.get(type(exc))
+            if mapped is not None:
+                raise mapped(str(exc)) from exc
+            raise
+        finally:
+            if core_response is not None:
+                core_response.close()
+
+        return httpx.Response(
+            status_code=core_response.status,
+            headers=core_response.headers,
+            content=content,
+            extensions=core_response.extensions,
+        )
+
+    def close(self) -> None:
+        self._pool.close()
 
 
 def _get_checked(
@@ -100,49 +243,76 @@ def _get_checked(
     hand lets us re-validate every hop, closing that blind-SSRF gap.
     """
     current = url
-    with httpx.Client(follow_redirects=False, timeout=timeout) as client:
+    for _ in range(_MAX_FETCH_REDIRECTS + 1):
-        for _ in range(_MAX_FETCH_REDIRECTS + 1):
+        pinned_ips = _resolve_and_check_url(current)
-            _check_fetch_url(current)
+        with httpx.Client(
+            transport=_PinnedTransport(pinned_ips),
+            follow_redirects=False,
+            timeout=timeout,
+        ) as client:
             r = client.get(current, headers=headers)
-            if r.status_code in (301, 302, 303, 307, 308):
+
-                location = r.headers.get("location")
+        if r.status_code in (301, 302, 303, 307, 308):
-                if not location:
+            location = r.headers.get("location")
-                    return r
+            if not location:
-                current = urljoin(str(r.url), location)
+                return r
-                continue
+            current = urljoin(str(r.url), location)
-            return r
+            continue
+        return r
     raise SkillImportError("too many redirects while fetching skill bundle")
 
 
 def parse_skill_source(url: str) -> ResolvedSource:
     """Normalize skills.sh / GitHub web URLs into owner/repo/ref/path."""
-    raw = (url or "").strip()
+    url = (url or "").strip()
-    if not raw:
+    if not url:
         raise SkillImportError("URL is required")
 
-    # skills.sh often links to GitHub; try to unwrap ?url= or redirect target later.
+    # ``urlparse`` only reports an unambiguous scheme when the URL carries the
-    if "skills.sh" in raw and "github.com" not in raw:
+    # ``scheme://`` form. Opaque schemes (``mailto:``, ``javascript:``) and a
-        r = _get_checked(raw, timeout=20.0)
+    # schemeless ``host:port`` both parse a "scheme" that is not one, so they
+    # fall through to the host check below and are rejected on the host instead.
+    scheme = urlparse(url).scheme.lower()
+    if scheme not in ("http", "https"):
+        if scheme and url.lower().startswith(f"{scheme}://"):
+            raise SkillImportError(f"unsupported URL scheme: {scheme}")
+        # Schemeless "github.com/owner/repo" — accept only a supported host.
+        rough_host = (urlparse("//" + url).hostname or "").lower()
+        if rough_host not in _GITHUB_HOSTS and rough_host not in _SKILLS_SH_HOSTS:
+            raise SkillImportError("Only GitHub or skills.sh URLs are supported")
+        url = "https://" + url
+
+    parsed = urlparse(url)
+    hostname = (parsed.hostname or "").lower()
+    if hostname not in _GITHUB_HOSTS and hostname not in _SKILLS_SH_HOSTS:
+        raise SkillImportError("Only GitHub or skills.sh URLs are supported")
+
+    # A skills.sh link is only usable if it redirects to an exact supported
+    # GitHub host. Scraping the page body for a github.com link cannot work:
+    # skill pages only ever link the repository root, never the skill's
+    # subdirectory, so the scrape resolves every skill in a repo to the same
+    # (wrong) bundle. Fail with an actionable message instead.
+    if hostname in _SKILLS_SH_HOSTS:
+        r = _get_checked(url, timeout=20.0)
         if r.status_code >= 400:
             raise _github_response_error(r)
         final = str(r.url)
-        _assert_github_url(final, context="redirect target")
+        if _github_host(final) not in _GITHUB_HOSTS:
-        # Page may embed a github link; prefer final URL if redirected.
+            raise SkillImportError(
-        if "github.com" in final:
+                "skills.sh did not redirect to GitHub — open the skill's "
-            raw = final
+                "repository on GitHub, navigate to the exact skill folder or "
-        else:
+                "SKILL.md file, and paste that URL; the repository-root link "
-            m = re.search(r"https?://github\.com/[^\s\"')]+", r.text or "")
+                "alone is not sufficient"
-            if m:
+            )
-                raw = m.group(0).rstrip(".,)")
+        url = final
 
-    parsed = urlparse(raw)
+    # Update parsed and hostname to reflect the new GitHub URL
-    host = _github_host(raw)
+    parsed = urlparse(url)
-    if host not in _GITHUB_HOSTS:
+    hostname = (parsed.hostname or "").lower()
-        raise SkillImportError(
-            "Only GitHub URLs are supported (https://github.com/... or raw.githubusercontent.com/...)"
-        )
 
-    if host == "raw.githubusercontent.com":
+    _assert_github_url(url)
+
+    if hostname == "raw.githubusercontent.com":
         # /owner/repo/ref/path/to/file
         bits = [p for p in parsed.path.split("/") if p]
         if len(bits) < 4:

tests/test_skill_importer.py

@@ -1,4 +1,6 @@
 """Skill URL importer — GitHub path parsing."""
+import ipaddress
+
 import pytest
 
 from services.memory.skill_importer import (
@@ -11,6 +13,13 @@ from services.memory.skill_importer import (
 )
 
 
+def _allow_fetch(monkeypatch):
+    monkeypatch.setattr(
+        "services.memory.skill_importer._resolve_and_check_url",
+        lambda url: [ipaddress.ip_address("93.184.216.34")],
+    )
+
+
 def test_parse_github_blob_skill_md():
     src = parse_skill_source(
         "https://github.com/anthropics/skills/blob/main/skills/pdf/SKILL.md"
@@ -69,10 +78,7 @@ def test_fetch_bytes_rejects_cross_host_redirect(monkeypatch):
             return _Resp()
 
     monkeypatch.setattr("services.memory.skill_importer.httpx.Client", _Client)
-    monkeypatch.setattr(
+    _allow_fetch(monkeypatch)
-        "services.memory.skill_importer.check_outbound_url",
-        lambda url, **kwargs: (True, ""),
-    )
     with pytest.raises(SkillImportError, match="redirect target"):
         _fetch_bytes("https://raw.githubusercontent.com/o/r/main/SKILL.md")
 
@@ -89,10 +95,7 @@ def test_list_github_dir_accepts_api_github_response(monkeypatch):
         "services.memory.skill_importer._fetch_text",
         lambda url: "# skill\n",
     )
-    monkeypatch.setattr(
+    _allow_fetch(monkeypatch)
-        "services.memory.skill_importer.check_outbound_url",
-        lambda url, **kwargs: (True, ""),
-    )
 
     class _Resp:
         url = "https://api.github.com/repos/o/r/contents?ref=main"
@@ -144,10 +147,7 @@ def _mock_httpx_client(monkeypatch, response):
             return response
 
     monkeypatch.setattr("services.memory.skill_importer.httpx.Client", _Client)
-    monkeypatch.setattr(
+    _allow_fetch(monkeypatch)
-        "services.memory.skill_importer.check_outbound_url",
-        lambda url, **kwargs: (True, ""),
-    )
 
 
 def test_list_github_dir_surfaces_rate_limit(monkeypatch):

tests/test_skill_importer_dns_pinning.py

@@ -0,0 +1,217 @@
+"""Deterministic regressions for skill-import DNS validation and pinning."""
+
+import gzip
+import ipaddress
+import socket
+import threading
+
+import httpcore
+import httpx
+
+from services.memory import skill_importer
+
+
+PUBLIC_A = ipaddress.ip_address("93.184.216.34")
+PUBLIC_B = ipaddress.ip_address("1.1.1.1")
+
+
+def test_validation_snapshot_is_the_only_connect_destination(monkeypatch):
+    answers = iter([
+        [str(PUBLIC_A)],
+        ["127.0.0.1"],
+    ])
+    resolver_calls = []
+
+    def _flipping_resolver(host):
+        resolver_calls.append(host)
+        return next(answers)
+
+    monkeypatch.setattr(skill_importer, "_default_resolver", _flipping_resolver)
+    pinned_ips = skill_importer._check_fetch_url("https://rebind.example/skill")
+
+    connected = []
+
+    class _RecordingBackend:
+        def connect_tcp(self, host, port, timeout, local_address, socket_options):
+            connected.append((host, port))
+            return object()
+
+    backend = skill_importer._PinnedBackend(pinned_ips)
+    backend._real = _RecordingBackend()
+    backend.connect_tcp("rebind.example", 443, timeout=1.0)
+
+    assert resolver_calls == ["rebind.example"]
+    assert pinned_ips == [PUBLIC_A]
+    assert connected == [(str(PUBLIC_A), 443)]
+
+
+def test_pinned_backend_falls_back_only_within_validated_snapshot():
+    attempts = []
+
+    class _FallbackBackend:
+        def connect_tcp(self, host, port, timeout, local_address, socket_options):
+            attempts.append((host, timeout))
+            if host == str(PUBLIC_A):
+                raise httpcore.ConnectError("first address unavailable")
+            return "connected"
+
+    backend = skill_importer._PinnedBackend([PUBLIC_A, PUBLIC_B])
+    backend._real = _FallbackBackend()
+
+    assert backend.connect_tcp("rebind.example", 443, timeout=1.0) == "connected"
+    assert [host for host, _ in attempts] == [str(PUBLIC_A), str(PUBLIC_B)]
+    assert all(timeout is not None and 0 <= timeout <= 1.0 for _, timeout in attempts)
+
+
+def test_transport_preserves_request_authority_and_response_url():
+    recorded = []
+
+    class _CoreResponse:
+        status = 200
+        headers = [(b"content-type", b"text/plain")]
+        stream = [b"ok"]
+        extensions = {}
+
+        def close(self):
+            return None
+
+    class _RecordingPool:
+        def handle_request(self, request):
+            recorded.append(request)
+            return _CoreResponse()
+
+        def close(self):
+            return None
+
+    transport = skill_importer._PinnedTransport([PUBLIC_A])
+    transport._pool.close()
+    transport._pool = _RecordingPool()
+
+    url = "https://github.com:444/octocat/repo?q=1"
+    with httpx.Client(transport=transport) as client:
+        response = client.get(url)
+
+    core_request = recorded[0]
+    assert core_request.url.host == b"github.com"
+    assert core_request.url.port == 444
+    assert core_request.url.target == b"/octocat/repo?q=1"
+    assert (b"host", b"github.com:444") in [
+        (name.lower(), value) for name, value in core_request.headers
+    ]
+    assert str(response.url) == url
+
+
+def test_get_checked_uses_fresh_transport_per_redirect_hop(monkeypatch):
+    first = "https://github.com/owner/repo"
+    second = "https://raw.githubusercontent.com/owner/repo/main/SKILL.md"
+    snapshots = {
+        first: [PUBLIC_A],
+        second: [PUBLIC_B],
+    }
+    clients = []
+    requested = []
+
+    monkeypatch.setattr(
+        skill_importer,
+        "_resolve_and_check_url",
+        lambda url: snapshots[url],
+    )
+
+    class _Client:
+        def __init__(self, *, transport, follow_redirects, timeout):
+            assert follow_redirects is False
+            clients.append((transport._pinned_ips, timeout))
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *args):
+            return False
+
+        def get(self, url, headers=None):
+            requested.append((url, headers))
+            request = httpx.Request("GET", url)
+            if url == first:
+                return httpx.Response(
+                    302,
+                    headers={"location": second},
+                    request=request,
+                )
+            return httpx.Response(200, content=b"ok", request=request)
+
+    monkeypatch.setattr(skill_importer.httpx, "Client", _Client)
+
+    response = skill_importer._get_checked(first, headers={"Accept": "text/plain"})
+
+    assert [ips for ips, _ in clients] == [[PUBLIC_A], [PUBLIC_B]]
+    assert requested == [
+        (first, {"Accept": "text/plain"}),
+        (second, {"Accept": "text/plain"}),
+    ]
+    assert str(response.url) == second
+
+
+def test_dns_rebinding_pinned_transport_dials_pinned_ip():
+    """The real pool must dial the pinned IP and keep the logical request intact.
+
+    Everything above this test replaces the pool or the backend, so this is the
+    only case that exercises ``httpcore.ConnectionPool`` end to end: the socket
+    goes to the pinned address while URL, ``Host``, and the decoded body stay on
+    the original hostname.
+    """
+    server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+    server_socket.bind(("127.0.0.1", 0))
+    server_socket.listen(1)
+    port = server_socket.getsockname()[1]
+
+    captured_request = b""
+    client_address = None
+    server_error = None
+
+    def handle_client():
+        nonlocal captured_request, client_address, server_error
+        try:
+            conn, client_address = server_socket.accept()
+            with conn:
+                conn.settimeout(2.0)
+                while b"\r\n\r\n" not in captured_request:
+                    if len(captured_request) >= 16_384:
+                        raise AssertionError("request headers exceeded 16 KiB")
+                    chunk = conn.recv(min(4096, 16_384 - len(captured_request)))
+                    if not chunk:
+                        break
+                    captured_request += chunk
+                if b"\r\n\r\n" not in captured_request:
+                    raise AssertionError(
+                        "connection closed before request headers completed"
+                    )
+                body = gzip.compress(b"successfully decoded gzip body")
+                conn.sendall(
+                    b"HTTP/1.1 200 OK\r\n"
+                    b"Content-Encoding: gzip\r\n"
+                    b"Content-Length: " + str(len(body)).encode() + b"\r\n"
+                    b"\r\n" + body
+                )
+        except Exception as exc:  # surfaced by the assertion below
+            server_error = exc
+
+    server_thread = threading.Thread(target=handle_client, daemon=True)
+    server_thread.start()
+
+    # Any hostname works: only the pinned snapshot decides where the socket goes.
+    url = f"http://rebind.example:{port}/secret-metadata"
+    try:
+        with httpx.Client(
+            transport=skill_importer._PinnedTransport([ipaddress.ip_address("127.0.0.1")])
+        ) as client:
+            response = client.get(url)
+        server_thread.join(timeout=5.0)
+    finally:
+        server_socket.close()
+
+    assert server_error is None, server_error
+    assert not server_thread.is_alive()
+    assert client_address is not None and client_address[0] == "127.0.0.1"
+    assert f"host: rebind.example:{port}".encode() in captured_request.lower()
+    assert str(response.url) == url
+    assert response.text == "successfully decoded gzip body"

tests/test_skill_importer_security.py

@@ -0,0 +1,155 @@
+import re
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+from services.memory.skill_importer import (
+    ResolvedSource,
+    SkillImportError,
+    check_outbound_url,
+    parse_skill_source,
+)
+
+## 1. Tests for Hostname Dispatch & Substring Spoofing
+
+@pytest.mark.parametrize(
+    "url",
+    [
+        "https://skills.sh.attacker.com/owner/repo",
+        "https://evilskills.sh/owner/repo",
+        "https://notskills.sh/owner/repo",
+        "https://api.skills.sh/owner/repo",
+        "https://1.1.1.1/skills.sh/owner/repo",
+        "http://localhost/skills.sh/owner/repo",
+    ],
+)
+def test_parse_skill_source_rejects_unsupported_host_before_fetch(url):
+    """Unsupported authorities must never reach the network unwrap path."""
+    with patch("services.memory.skill_importer._get_checked") as mock_get:
+        with pytest.raises(SkillImportError):
+            parse_skill_source(url)
+    mock_get.assert_not_called()
+
+
+@pytest.mark.parametrize("entry", ["https://skills.sh/my-skill", "https://www.skills.sh/my-skill"])
+def test_parse_skill_source_unwraps_skills_sh_redirect_to_github(entry):
+    """Both skills.sh spellings unwrap when the fetch lands on a GitHub host."""
+    with patch("services.memory.skill_importer._get_checked") as mock_get:
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.url = "https://github.com/test-owner/test-repo"
+        mock_get.return_value = mock_response
+
+        source = parse_skill_source(entry)
+        assert source.owner == "test-owner"
+        assert source.repo == "test-repo"
+
+
+def test_parse_skill_source_rejects_skills_sh_page_that_never_reaches_github():
+    """A skills.sh page that does not redirect to GitHub must fail loudly.
+
+    The live site serves the skill page from ``www.skills.sh`` and only ever
+    links the repository root, never the skill's subdirectory. Scraping a
+    ``github.com`` link out of the body therefore resolves every skill in a
+    repo to the same bundle, so the importer must refuse rather than guess.
+    """
+    body = '<html><body><a href="https://github.com/test-owner/test-repo">Repository</a></body></html>'
+    with patch("services.memory.skill_importer._get_checked") as mock_get:
+        mock_response = MagicMock()
+        mock_response.status_code = 200
+        mock_response.url = "https://www.skills.sh/anthropics/skills/pdf"
+        mock_response.text = body
+        mock_get.return_value = mock_response
+
+        with pytest.raises(
+            SkillImportError, match="did not redirect to GitHub"
+        ) as exc_info:
+            parse_skill_source("https://skills.sh/anthropics/skills/pdf")
+
+    message = str(exc_info.value)
+    assert "exact skill folder or SKILL.md file" in message
+    assert "repository-root link alone is not sufficient" in message
+
+
+@pytest.mark.parametrize(
+    ("url", "expected"),
+    [
+        ("ftp://github.com/o/r", "unsupported URL scheme: ftp"),
+        ("file:///etc/passwd", "unsupported URL scheme: file"),
+        ("gopher://github.com/o/r", "unsupported URL scheme: gopher"),
+        ("javascript:alert(1)", "Only GitHub or skills.sh URLs are supported"),
+        ("mailto:x@y.z", "Only GitHub or skills.sh URLs are supported"),
+        ("data:text/html,<b>x</b>", "Only GitHub or skills.sh URLs are supported"),
+        ("https://evil.example/o/r", "Only GitHub or skills.sh URLs are supported"),
+    ],
+)
+def test_parse_skill_source_reports_the_real_reason_for_rejection(url, expected):
+    """A supplied-but-unusable URL must not be reported as a missing URL."""
+    with patch("services.memory.skill_importer._get_checked") as mock_get:
+        with pytest.raises(SkillImportError, match=re.escape(expected)):
+            parse_skill_source(url)
+    mock_get.assert_not_called()
+
+
+@pytest.mark.parametrize(
+    ("url", "owner", "repo"),
+    [
+        ("github.com/octocat/Hello-World", "octocat", "Hello-World"),
+        ("HTTPS://github.com/octocat/Hello-World", "octocat", "Hello-World"),
+        ("github.com:443/octocat/Hello-World", "octocat", "Hello-World"),
+        ("github.com/octocat/Hello-World?q=a://b", "octocat", "Hello-World"),
+    ],
+)
+def test_parse_skill_source_accepts_schemeless_and_uppercase_github(url, owner, repo):
+    """A schemeless host, an uppercase scheme, and a ``://`` in the query all parse."""
+    source = parse_skill_source(url)
+    assert (source.owner, source.repo) == (owner, repo)
+
+
+def test_parse_skill_source_valid_github():
+    """Ensure standard GitHub URLs parse into the correct ResolvedSource fields."""
+    source = parse_skill_source("https://github.com/octocat/Hello-World/tree/main/docs")
+    assert isinstance(source, ResolvedSource)
+    assert source.owner == "octocat"
+    assert source.repo == "Hello-World"
+    assert source.ref == "main"
+    assert source.path == "docs"
+
+
+## 2. Tests for SSRF Guard & CGNAT
+
+def test_check_outbound_url_blocks_cgnat():
+    """Ensure Carrier-Grade NAT (RFC 6598) block 100.64.0.0/10 is blocked."""
+    def mock_resolver(host):
+        return ["100.64.5.10"]
+
+    ok, reason = check_outbound_url("http://example.com", block_private=True, resolver=mock_resolver)
+    assert not ok
+    assert "private/shared/loopback" in reason  # Updated to match your codebase's error string
+
+def test_check_outbound_url_blocks_loopback():
+    """Ensure loopback IPs (127.0.0.1) are blocked by default."""
+    def mock_resolver(host):
+        return ["127.0.0.1"]
+
+    ok, reason = check_outbound_url("http://localhost", block_private=True, resolver=mock_resolver)
+    assert not ok
+
+
+def test_check_outbound_url_blocks_metadata():
+    """Ensure cloud metadata endpoints (169.254.169.254) are blocked."""
+    def mock_resolver(host):
+        return ["169.254.169.254"]
+
+    ok, reason = check_outbound_url("http://metadata.google.internal", block_private=True, resolver=mock_resolver)
+    assert not ok
+
+
+def test_check_outbound_url_allows_public_ip():
+    """Ensure public routable IPs pass successfully."""
+    def mock_resolver(host):
+        return ["93.184.216.34"]
+
+    ok, reason = check_outbound_url("http://example.com", block_private=True, resolver=mock_resolver)
+    assert ok
+    assert reason == "ok"

tests/test_skill_importer_ssrf_redirect.py

@@ -6,10 +6,12 @@ path in ``services/search/content.py:_get_public_url``. Previously it used
 ``httpx``'s ``follow_redirects=True`` with the lenient guard on the *initial*
 URL only, so a ``3xx`` to an internal/metadata address was still connected to.
 
-These tests are hermetic: every host is an IP literal, so ``check_outbound_url``
+These tests are hermetic: public and internal guard cases use IP literals, while
-resolves them locally (``getaddrinfo`` on a numeric address does no DNS) and no
+the exact ``skills.sh`` case injects its validated address snapshot. The HTTP
-network access is required. The HTTP layer is faked so no real request is made.
+layer is faked, so no real DNS lookup or request is made.
 """
+import ipaddress
+
 import pytest
 
 from services.memory import skill_importer
@@ -108,10 +110,20 @@ def test_fetch_bytes_blocks_redirect_to_internal(monkeypatch, internal):
 
 def test_skills_sh_entry_blocks_redirect_to_metadata(monkeypatch):
     # The skills.sh unwrap path (user-supplied host) must also revalidate hops.
-    raw = "http://1.1.1.1/skills.sh"  # contains "skills.sh", not "github.com"
+    raw = "https://skills.sh/example/skill"
+    checked = []
+
+    def _check_hop(url):
+        checked.append(url)
+        if url == raw:
+            return [ipaddress.ip_address("1.1.1.1")]
+        raise SkillImportError("outbound URL blocked: private target")
+
+    monkeypatch.setattr(skill_importer, "_resolve_and_check_url", _check_hop)
     _install_fake_client(monkeypatch, redirect_from=raw, redirect_to=METADATA)
     with pytest.raises(SkillImportError, match="blocked"):
         parse_skill_source(raw)
+    assert checked == [raw, METADATA]
 
 
 # --- Positive: a legitimate public->public redirect is still followed --------