fix(config): strip ASCII control characters from env values before writing to .env

hermes_cli/config.py

@@ -6387,6 +6387,80 @@ def sanitize_env_file() -> int:
     return fixes
 
 
+
+
+def _strip_control_chars(key: str, value: str) -> str:
+    """Strip ASCII control characters (except TAB) from env values.
+
+    On Windows, pressing ESC during an ``input()`` prompt inserts a literal
+    ``\x1b`` character into the returned string.  When this value is persisted
+    to ``~/.hermes/.env`` it silently corrupts URL and API-key fields —
+    e.g. ``SEARXNG_URL=\x1b`` causes every ``web_search`` call to fail with
+    ``Invalid non-printable ASCII character in URL`` (issue #40840).
+
+    No legitimate env value contains control characters: API keys are
+    alphanumeric + punctuation; URLs require ``http://`` or ``https://``.
+    TAB (0x09) is preserved because some tools use it as a delimiter in
+    compound values.
+
+    Returns the cleaned value.  Prints a warning to stderr if any control
+    characters were removed.
+    """
+    if not isinstance(value, str) or not value:
+        return value
+
+    # Fast path: check if any C0 control chars (0x00-0x1F except TAB, plus DEL)
+    # are present before doing string replacement.
+    has_controls = False
+    for ch in value:
+        code = ord(ch)
+        if code <= 0x1F and code != 0x09:  # TAB = 0x09 is allowed
+            has_controls = True
+            break
+        if code == 0x7F:  # DEL
+            has_controls = True
+            break
+
+    if not has_controls:
+        return value
+
+    # Collect details for the warning message
+    bad_chars: list[str] = []
+    for i, ch in enumerate(value):
+        code = ord(ch)
+        if (code <= 0x1F and code != 0x09) or code == 0x7F:
+            char_name = {
+                0x00: "NUL", 0x01: "SOH", 0x02: "STX", 0x03: "ETX",
+                0x04: "EOT", 0x05: "ENQ", 0x06: "ACK", 0x07: "BEL",
+                0x08: "BS", 0x0A: "LF", 0x0B: "VT", 0x0C: "FF",
+                0x0D: "CR", 0x0E: "SO", 0x0F: "SI", 0x10: "DLE",
+                0x11: "DC1", 0x12: "DC2", 0x13: "DC3", 0x14: "DC4",
+                0x15: "NAK", 0x16: "SYN", 0x17: "ETB", 0x18: "CAN",
+                0x19: "EM", 0x1A: "SUB", 0x1B: "ESC", 0x1C: "FS",
+                0x1D: "GS", 0x1E: "RS", 0x1F: "US", 0x7F: "DEL",
+            }.get(code, f"0x{code:02X}")
+            bad_chars.append(f"  position {i}: {char_name} (\\x{code:02x})")
+
+    # Strip control characters
+    cleaned = "".join(
+        ch for ch in value
+        if not ((ord(ch) <= 0x1F and ord(ch) != 0x09) or ord(ch) == 0x7F)
+    )
+
+    print(
+        f"\n  Warning: {key} contains ASCII control characters that will break "
+        f"API requests or URL parsing.\n"
+        f"  This usually happens when ESC or another control key is pressed "
+        f"during input on Windows.\n"
+        f"\n"
+        + "\n".join(f"  {line}" for line in bad_chars[:5])
+        + ("\n  ... and more" if len(bad_chars) > 5 else "")
+        + f"\n\n  The control characters have been stripped automatically.\n"
+        f"  If the value looks wrong, please re-enter it.\n",
+        file=sys.stderr,
+    )
+    return cleaned
+
 def _check_non_ascii_credential(key: str, value: str) -> str:
     """Warn and strip non-ASCII characters from credential values.
 
@@ -6465,6 +6539,10 @@ def save_env_value(key: str, value: str):
         raise ValueError(f"Invalid environment variable name: {key!r}")
     _reject_denylisted_env_var(key)
     value = value.replace("\n", "").replace("\r", "")
+    # Strip ASCII control characters (ESC, BEL, etc.) that corrupt URLs/keys.
+    # On Windows, pressing ESC during input() inserts \x1b as the value
+    # (issue #40840). No legitimate env value contains control characters.
+    value = _strip_control_chars(key, value)
     # API keys / tokens must be ASCII — strip non-ASCII with a warning.
     value = _check_non_ascii_credential(key, value)
     ensure_hermes_home()

hermes_cli/tools_config.py

@@ -3081,6 +3081,24 @@ def _configure_provider(
                 value = _prompt(f"    {var.get('prompt', var['key'])}", password=True)
 
             if value:
+                # Validate URL-type env vars start with http:// or https://.
+                # Catches corrupted values from terminal control characters
+                # (e.g. ESC \x1b on Windows, issue #40840) and obvious
+                # user mistakes like missing the scheme.
+                _lower_key = var["key"].lower()
+                if _lower_key.endswith("_url") or _lower_key.endswith("_host") or _lower_key.endswith("_endpoint"):
+                    if not value.startswith(("http://", "https://")):
+                        _print_warning(
+                            f"    '{value}' doesn't look like a valid URL — "
+                            f"it should start with http:// or https://"
+                        )
+                        _retry = _prompt(f"    {var.get('prompt', var['key'])} (must start with http:// or https://)", password=True)
+                        if _retry and _retry.startswith(("http://", "https://")):
+                            value = _retry
+                        else:
+                            _print_warning("    Skipped — invalid URL")
+                            all_configured = False
+                            continue
                 save_env_value(var["key"], value)
                 _print_success("    Saved")
             else:

tests/hermes_cli/test_control_char_stripping.py

@@ -0,0 +1,162 @@
+"""Tests for ASCII control character stripping in save_env_value.
+
+Covers the fix for issue #40840 — on Windows, pressing ESC during an
+``input()`` prompt inserts a literal ``\\x1b`` character into the returned
+string. When this value is persisted to ``~/.hermes/.env`` it silently
+corrupts URL and API-key fields (e.g. ``SEARXNG_URL=\\x1b`` causes every
+``web_search`` call to fail permanently).
+
+The fix adds ``_strip_control_chars()`` in the ``save_env_value`` path
+to strip all C0 control characters (0x00–0x1F except TAB) and DEL (0x7F)
+from env values before they are written to disk.
+"""
+
+import os
+import tempfile
+from pathlib import Path
+from unittest.mock import patch
+
+import pytest
+
+
+class TestStripControlChars:
+    """Tests for hermes_cli.config._strip_control_chars()."""
+
+    def test_clean_value_unchanged(self):
+        from hermes_cli.config import _strip_control_chars
+
+        assert _strip_control_chars("TEST_KEY", "https://example.com") == "https://example.com"
+
+    def test_clean_api_key_unchanged(self):
+        from hermes_cli.config import _strip_control_chars
+
+        key = "sk-proj-" + "a" * 48
+        assert _strip_control_chars("OPENAI_API_KEY", key) == key
+
+    def test_empty_value_unchanged(self):
+        from hermes_cli.config import _strip_control_chars
+
+        assert _strip_control_chars("TEST_KEY", "") == ""
+
+    def test_none_value_unchanged(self):
+        from hermes_cli.config import _strip_control_chars
+
+        assert _strip_control_chars("TEST_KEY", None) is None
+
+    def test_strips_bare_esc_character(self, capsys):
+        """The exact scenario from issue #40840: bare ESC as entire value."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("SEARXNG_URL", "\x1b")
+        assert result == ""
+        captured = capsys.readouterr()
+        assert "ESC" in captured.err
+        assert "control characters" in captured.err
+
+    def test_strips_esc_embedded_in_url(self, capsys):
+        """ESC accidentally inserted into a URL value."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("SEARXNG_URL", "http://\x1blocalhost:8080")
+        assert result == "http://localhost:8080"
+        captured = capsys.readouterr()
+        assert "ESC" in captured.err
+
+    def test_strips_bell_character(self, capsys):
+        """BEL (0x07) is another common terminal control character."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("API_KEY", "sk-\x07test")
+        assert result == "sk-test"
+        captured = capsys.readouterr()
+        assert "BEL" in captured.err
+
+    def test_strips_del_character(self, capsys):
+        """DEL (0x7F) is also stripped."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("API_KEY", "sk-test\x7f")
+        assert result == "sk-test"
+        captured = capsys.readouterr()
+        assert "DEL" in captured.err
+
+    def test_preserves_tab_character(self):
+        """TAB (0x09) is preserved — some tools use it as a delimiter."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("COMPOUND_VALUE", "val1\tval2")
+        assert result == "val1\tval2"
+
+    def test_strips_multiple_control_chars(self, capsys):
+        """Multiple different control characters are all stripped."""
+        from hermes_cli.config import _strip_control_chars
+
+        result = _strip_control_chars("SEARXNG_URL", "\x1b\x07http://localhost\x00")
+        assert result == "http://localhost"
+        captured = capsys.readouterr()
+        assert "ESC" in captured.err
+        assert "BEL" in captured.err or "NUL" in captured.err
+
+    def test_no_warning_for_clean_value(self, capsys):
+        from hermes_cli.config import _strip_control_chars
+
+        _strip_control_chars("API_KEY", "sk-clean-key-123")
+        assert capsys.readouterr().err == ""
+
+
+class TestSaveEnvValueControlChars:
+    """Integration test: save_env_value strips control chars before writing."""
+
+    def test_save_env_value_strips_esc(self, monkeypatch, capsys, tmp_path):
+        """Verify that save_env_value strips ESC before writing to .env."""
+        from hermes_cli.config import save_env_value, get_env_path
+
+        env_path = tmp_path / ".env"
+        monkeypatch.setattr("hermes_cli.config.get_env_path", lambda: env_path)
+        monkeypatch.setattr("hermes_cli.config.ensure_hermes_home", lambda: None)
+        # Prevent _secure_file from running (needs real path)
+        monkeypatch.setattr("hermes_cli.config._secure_file", lambda p: None)
+        # Prevent os.environ side effects from polluting test environment
+        monkeypatch.delenv("SEARXNG_URL", raising=False)
+
+        save_env_value("SEARXNG_URL", "\x1b")
+
+        # The value written to .env should be empty (ESC stripped)
+        if env_path.exists():
+            content = env_path.read_text(encoding="utf-8")
+            assert "\x1b" not in content
+            # After stripping ESC, the value is empty string
+            assert "SEARXNG_URL=" in content
+
+    def test_save_env_value_strips_esc_in_url(self, monkeypatch, capsys, tmp_path):
+        """Verify that save_env_value strips ESC from a URL value."""
+        from hermes_cli.config import save_env_value, get_env_path
+
+        env_path = tmp_path / ".env"
+        monkeypatch.setattr("hermes_cli.config.get_env_path", lambda: env_path)
+        monkeypatch.setattr("hermes_cli.config.ensure_hermes_home", lambda: None)
+        monkeypatch.setattr("hermes_cli.config._secure_file", lambda p: None)
+        monkeypatch.delenv("SEARXNG_URL", raising=False)
+
+        save_env_value("SEARXNG_URL", "http://\x1blocalhost:8080")
+
+        if env_path.exists():
+            content = env_path.read_text(encoding="utf-8")
+            assert "\x1b" not in content
+            assert "SEARXNG_URL=http://localhost:8080" in content
+
+    def test_save_env_value_clean_url_unchanged(self, monkeypatch, tmp_path):
+        """A clean URL should pass through unchanged."""
+        from hermes_cli.config import save_env_value, get_env_path
+
+        env_path = tmp_path / ".env"
+        monkeypatch.setattr("hermes_cli.config.get_env_path", lambda: env_path)
+        monkeypatch.setattr("hermes_cli.config.ensure_hermes_home", lambda: None)
+        monkeypatch.setattr("hermes_cli.config._secure_file", lambda p: None)
+        monkeypatch.delenv("SEARXNG_URL", raising=False)
+
+        save_env_value("SEARXNG_URL", "http://localhost:8080")
+
+        if env_path.exists():
+            content = env_path.read_text(encoding="utf-8")
+            assert "SEARXNG_URL=http://localhost:8080" in content

tests/hermes_cli/test_non_ascii_credential.py

@@ -115,11 +115,11 @@ def test_warning_fires_only_once_per_key(self, monkeypatch, capsys):
         assert "GEMINI_API_KEY" in first
         assert second == ""  # no repeat warning
 
-    def test_ascii_control_chars_not_stripped(self, monkeypatch, capsys):
-        """ASCII control bytes (e.g. ESC 0x1B from terminal paste) are NOT non-ASCII.
-
-        This is intentional — they're valid ASCII for HTTP headers even if the
-        provider rejects them. Documents the scope of the sanitizer.
+    def test_ascii_control_chars_not_stripped_by_non_ascii_sanitizer(self, monkeypatch, capsys):
+        """ASCII control bytes (e.g. ESC 0x1B) are NOT non-ASCII, so the
+        non-ASCII sanitizer (env_loader._sanitize_loaded_credentials) does
+        not strip them. They ARE now stripped by ``save_env_value`` via
+        ``_strip_control_chars`` — see test_control_char_stripping.py.
         """
         from hermes_cli.env_loader import _sanitize_loaded_credentials, _WARNED_KEYS