fix(egress): close GOOGLE_API_KEY coverage gap + config/mappings write TOCTOU

Two correctness gaps surfaced in the review thread (texasich) that
survived the prior rounds:

- GOOGLE_API_KEY was warn-only while GEMINI_API_KEY was fail-closed,
  despite both authenticating the same generativelanguage LLM endpoint
  (auth.py treats them as interchangeable). An operator with only
  GOOGLE_API_KEY set + fail_on_uncovered_providers got false coverage.
  Added it to _LLM_SPECIFIC_NON_BEARER_PROVIDERS.
- write_proxy_config / write_mappings chmod'd AFTER os.replace, leaving
  the token-bearing files briefly world-readable under a slack umask
  (the 0o700 state dir mitigates but same-uid race remained). chmod the
  temp file BEFORE the atomic replace, matching the CA-key write path.

Tests: assert GOOGLE_API_KEY in blocked tier; assert proxy.yaml +
mappings.json land at 0o600.

agent/proxy_sources/iron_proxy.py

@@ -187,6 +187,13 @@ _LLM_SPECIFIC_NON_BEARER_PROVIDERS: Tuple[str, ...] = (
     "ANTHROPIC_API_KEY",
     "AZURE_OPENAI_API_KEY",
     "GEMINI_API_KEY",
+    # GOOGLE_API_KEY is an interchangeable alias for GEMINI_API_KEY in
+    # Hermes (auth.py keys Google on both; the native Gemini adapter
+    # accepts either) and authenticates the same generativelanguage
+    # LLM endpoint.  It belongs in the fail-closed tier too — otherwise
+    # an operator with only GOOGLE_API_KEY set who enables
+    # fail_on_uncovered_providers gets a false sense of coverage.
+    "GOOGLE_API_KEY",
 )
 
 
@@ -1155,8 +1162,13 @@ def write_proxy_config(config: Dict) -> Path:
     tmp_path = state / ".proxy.yaml.tmp"
     with open(tmp_path, "w", encoding="utf-8") as f:
         yaml.safe_dump(config, f, default_flow_style=False, sort_keys=False)
+    # Tighten perms on the temp file BEFORE the atomic replace so the
+    # final path is never briefly world-readable under a slack umask
+    # (the config embeds proxy token values).  chmod-after-replace would
+    # leave a TOCTOU window; the 0o700 state dir mitigates but same-uid
+    # processes could still race.
+    os.chmod(tmp_path, stat.S_IRUSR | stat.S_IWUSR)
     os.replace(tmp_path, out)
-    os.chmod(out, stat.S_IRUSR | stat.S_IWUSR)
     return out
 
 
@@ -1184,8 +1196,11 @@ def write_mappings(mappings: List[TokenMapping]) -> Path:
     tmp_path = state / ".mappings.json.tmp"
     with open(tmp_path, "w", encoding="utf-8") as f:
         json.dump(payload, f, indent=2)
+    # chmod before the atomic replace — see write_proxy_config.  The
+    # mappings file holds proxy token values, so close the TOCTOU window
+    # rather than chmod-ing after the file is already at its final path.
+    os.chmod(tmp_path, stat.S_IRUSR | stat.S_IWUSR)
     os.replace(tmp_path, out)
-    os.chmod(out, stat.S_IRUSR | stat.S_IWUSR)
     return out
 
 

tests/test_iron_proxy.py

@@ -392,6 +392,16 @@ def test_write_proxy_config_serializes_yaml(hermes_home, tmp_path):
     text = out.read_text(encoding="utf-8")
     assert "tunnel_listen" in text
     assert f"ca_cert: {ca_crt}" in text
+    # The rendered config embeds proxy token values — it must land at
+    # 0o600, and (TOCTOU) must never be transiently world-readable
+    # between the atomic replace and the chmod.  We chmod the temp file
+    # before the replace, so the final file is 0o600 from first byte.
+    import os as _os
+    mode = _os.stat(out).st_mode & 0o777
+    assert mode == 0o600, f"proxy.yaml perms {oct(mode)}, expected 0o600"
+    mappings_out = ip.write_mappings([_sample_mapping()])
+    mmode = _os.stat(mappings_out).st_mode & 0o777
+    assert mmode == 0o600, f"mappings.json perms {oct(mmode)}, expected 0o600"
 
 
 # ---------------------------------------------------------------------------
@@ -1360,6 +1370,7 @@ def test_blocked_providers_subset_of_uncovered(hermes_home, monkeypatch):
     monkeypatch.setenv("AWS_ACCESS_KEY_ID", "AKIA-test")
     monkeypatch.setenv("GOOGLE_APPLICATION_CREDENTIALS", "/etc/gcp.json")
     monkeypatch.setenv("GEMINI_API_KEY", "g-test")
+    monkeypatch.setenv("GOOGLE_API_KEY", "g-test-alias")
 
     uncovered = set(ip.discover_uncovered_providers())
     blocked = set(ip.discover_blocked_providers())
@@ -1376,6 +1387,10 @@ def test_blocked_providers_subset_of_uncovered(hermes_home, monkeypatch):
     # LLM-specific providers ARE blocked.
     assert "ANTHROPIC_API_KEY" in blocked
     assert "GEMINI_API_KEY" in blocked
+    # GOOGLE_API_KEY is an alias for GEMINI_API_KEY (same generativelanguage
+    # LLM endpoint) — it must be in the fail-closed tier, not warn-only,
+    # or fail_on_uncovered_providers gives false coverage.
+    assert "GOOGLE_API_KEY" in blocked
 
 
 # ---------------------------------------------------------------------------