Harden remote installer security warning

unsloth_cli/commands/start.py

@@ -49,13 +49,22 @@
 # the wizard's global API-key/model prompts would block the launch and point the
 # user at a different (global) provider than the one Unsloth just configured.
 # Both installers expose a skip flag: `-SkipSetup` (PowerShell) and
-# `--skip-setup` (POSIX; passed to the piped script via `bash -s --`).
+# `--skip-setup` (POSIX; passed to the piped script via `bash -s --`). Pin both
+# the fetched script and the repository checkout it performs to the same full
+# commit so a later change to either upstream branch cannot silently replace
+# code that Unsloth executes with the user's privileges.
+_HERMES_INSTALL_COMMIT = "f1af945f6c576eccb126fa955edc9be258b33020"
+_HERMES_INSTALL_BASE = (
+    "https://raw.githubusercontent.com/NousResearch/hermes-agent/"
+    f"{_HERMES_INSTALL_COMMIT}/scripts"
+)
 _HERMES_WINDOWS_INSTALL_HINT = (
-    "& ([scriptblock]::Create((irm https://hermes-agent.nousresearch.com/install.ps1))) -SkipSetup"
+    f"& ([scriptblock]::Create((irm {_HERMES_INSTALL_BASE}/install.ps1)))"
+    f" -SkipSetup -Commit {_HERMES_INSTALL_COMMIT}"
 )
 _HERMES_POSIX_INSTALL_HINT = (
-    "curl -fsSL https://raw.githubusercontent.com/NousResearch/hermes-agent"
-    "/main/scripts/install.sh | bash -s -- --skip-setup"
+    f"curl -fsSL {_HERMES_INSTALL_BASE}/install.sh | bash -s --"
+    f" --skip-setup --commit {_HERMES_INSTALL_COMMIT}"
 )
 # Hermes refuses to initialize when the model window is under 64,000 tokens; its
 # error message points at the model.context_length / auxiliary.compression
@@ -1121,6 +1130,16 @@ def _install_source(install_hint: str) -> Optional[str]:
     return match.group(0) if match else None
 
 
+def _pinned_raw_github_commit(source: str) -> Optional[str]:
+    """Return the immutable full commit in a raw GitHub URL, if present."""
+    match = re.match(
+        r"^https://raw\.githubusercontent\.com/[^/]+/[^/]+/([0-9a-f]{40})/",
+        source,
+        flags = re.IGNORECASE,
+    )
+    return match.group(1).lower() if match else None
+
+
 def _install_agent(name: str, install_hint: str) -> Optional[str]:
     # Missing agent under --launch: offer to run its documented install command, then
     # re-resolve it on PATH. Consent-based (we never auto-run a remote install script
@@ -1134,12 +1153,27 @@ def _install_agent(name: str, install_hint: str) -> Optional[str]:
     # and nothing checks a signature or hash on the fetched content. Naming the source
     # turns a blind "yes" into informed consent.
     source = _install_source(install_hint)
-    warning = (
-        f"This will download and RUN a script from {source} with your privileges"
-        if source
-        else f"This will RUN `{install_hint}` with your privileges"
-    )
-    typer.secho(f"{warning}; there is no signature or hash check.", fg = "yellow", err = True)
+    if source:
+        pinned_commit = _pinned_raw_github_commit(source)
+        if pinned_commit:
+            warning = (
+                "Security warning: This will download and execute a third-party script "
+                f"from {source} with your privileges. Unsloth pins this content to "
+                f"immutable upstream commit {pinned_commit}, but does not independently "
+                "verify or sandbox it. Continue only if you trust this source and commit."
+            )
+        else:
+            warning = (
+                "Security warning: This will download and execute an unverified third-party "
+                f"script from {source} with your privileges. Unsloth does not pin or verify "
+                "the downloaded content. Continue only if you trust this source."
+            )
+    else:
+        warning = (
+            f"This will RUN `{install_hint}` with your privileges; "
+            "there is no signature or hash check."
+        )
+    typer.secho(warning, fg = "yellow", err = True)
     if not typer.confirm(f"Install `{name}` now with `{install_hint}`?", default = False):
         return None
     # Run each hint through the shell it is written for: PowerShell (irm | iex, or npm)

unsloth_cli/tests/test_start.py

@@ -7,6 +7,7 @@
 
 import json
 import os
+import re
 import shlex
 import sys
 import urllib.error
@@ -128,7 +129,7 @@ def test_install_agent_uses_powershell_on_windows(monkeypatch):
     assert ran == [["powershell", "-NoProfile", "-Command", install_hint]]
 
 
-def test_install_agent_warns_and_names_remote_source(monkeypatch, capsys):
+def test_install_agent_warns_remote_installer_is_unverified_third_party(monkeypatch, capsys):
     # Before the confirm, a remote installer must name the URL it fetches so the
     # user consents to a specific source rather than blindly accepting.
     monkeypatch.setattr(start.os, "name", "nt")
@@ -137,9 +138,23 @@ def test_install_agent_warns_and_names_remote_source(monkeypatch, capsys):
     hint = "& ([scriptblock]::Create((irm https://hermes-agent.nousresearch.com/install.ps1))) -SkipSetup"
     assert start._install_agent("hermes", hint) is None
     err = capsys.readouterr().err
+    assert "Security warning" in err
+    assert "unverified third-party script" in err
     assert "https://hermes-agent.nousresearch.com/install.ps1" in err
-    assert "download and RUN" in err
-    assert "signature or hash" in err
+    assert "Unsloth does not pin or verify the downloaded content" in err
+    assert "Continue only if you trust this source" in err
+
+
+def test_install_agent_reports_immutable_remote_installer_pin(monkeypatch, capsys):
+    monkeypatch.setattr(start.os, "name", "posix")
+    monkeypatch.setattr(start.sys, "stdin", SimpleNamespace(isatty = lambda: True))
+    monkeypatch.setattr(start.typer, "confirm", lambda *a, **k: False)
+    assert start._install_agent("hermes", start._HERMES_POSIX_INSTALL_HINT) is None
+    err = capsys.readouterr().err
+    assert start._HERMES_INSTALL_COMMIT in err
+    assert "immutable upstream commit" in err
+    assert "does not independently verify or sandbox it" in err
+    assert "does not pin or verify" not in err
 
 
 def test_install_agent_warns_for_package_installer(monkeypatch, capsys):
@@ -160,8 +175,8 @@ def test_hermes_install_hint_is_windows_native_on_windows(monkeypatch):
     # Scriptblock form so `-SkipSetup` reaches the installer and the interactive
     # setup wizard is skipped during the unattended `unsloth start hermes` run.
     assert start._hermes_install_hint() == (
-        "& ([scriptblock]::Create((irm https://hermes-agent.nousresearch.com/install.ps1)))"
-        " -SkipSetup"
+        f"& ([scriptblock]::Create((irm {start._HERMES_INSTALL_BASE}/install.ps1)))"
+        f" -SkipSetup -Commit {start._HERMES_INSTALL_COMMIT}"
     )
 
 
@@ -170,11 +185,20 @@ def test_hermes_install_hint_is_bash_on_posix(monkeypatch):
 
     # `bash -s -- --skip-setup` forwards the skip flag to the piped installer.
     assert start._hermes_install_hint() == (
-        "curl -fsSL https://raw.githubusercontent.com/NousResearch/hermes-agent"
-        "/main/scripts/install.sh | bash -s -- --skip-setup"
+        f"curl -fsSL {start._HERMES_INSTALL_BASE}/install.sh | bash -s --"
+        f" --skip-setup --commit {start._HERMES_INSTALL_COMMIT}"
     )
 
 
+def test_hermes_install_hints_pin_script_and_checkout_to_full_commit():
+    commit = start._HERMES_INSTALL_COMMIT
+    assert re.fullmatch(r"[0-9a-f]{40}", commit)
+    for hint in (start._HERMES_WINDOWS_INSTALL_HINT, start._HERMES_POSIX_INSTALL_HINT):
+        assert hint.count(commit) == 2
+        assert "/main/" not in hint
+        assert "hermes-agent.nousresearch.com" not in hint
+
+
 def test_refresh_windows_path_noop_off_windows(monkeypatch):
     monkeypatch.setattr(start.os, "name", "posix")
     before = os.environ.get("PATH", "")