Adds the only #17873 category not covered by the in-flight PRs #17962
(briandevans, reverse shell + download-execute) and #7993 (SHL0MS,
credential reads + curl/wget exfiltration): sudo invocations that an
LLM-driven agent can drive without TTY interaction.
The agent has no TTY, so the sudo forms that succeed without human
involvement are those reading the password from stdin (`-S` / `--stdin`)
or via an askpass helper (`-A` / `--askpass`). The shell-launch (`-s`)
and list-privileges (`-a`) flags are also gated since they are
privilege-relevant invocations the agent can chain after acquiring the
password (e.g. read SUDO_PASSWORD from .env -> sudo -S -s -> root shell).
Plain `sudo cmd` (no flag) is TTY-bound and excluded.
Two patterns:
1. Direct flag: `\bsudo\b[^;|&\n]*?\s+(?:-s\b|--stdin\b|-a\b|--askpass\b)`
The lazy `[^;|&\n]*?` consumes flag-arguments without spanning
command separators, so `sudo -u root -S whoami` matches (a textbook
offensive form that a strict `(?:\s+-[^\s]+)*` "leading flags only"
pattern would have missed because `root` is a flag-value not a flag).
2. Combined short flags: `\bsudo\b[^;|&\n]*?\s+-[a-z]*[sa][a-z]*\b`
Catches packed forms like `sudo -nS id` where multiple flags share
a single `-X` token.
`_normalize_command_for_detection` lowercases input before pattern
matching (tools/approval.py:340), so case variants of S/s and A/a
collapse — both letter-pairs are gated since each is a privilege-
relevant invocation.
Tests: 21 new cases in TestDetectSudoStdin (12 positive covering all
flag-order permutations including herestring source and printf-piped
forms; 9 negative including TTY-bound `sudo whoami`, interactive
`sudo -i`, env-var reference `$SUDO_USER`, doc lookup `man sudo`,
package install, and the `pseudosudo` word-boundary edge case).
Empirical coverage: 11/11 attacks matched, 0/10 false positives.
Refs: #17873 category 4. Adjacent: #17962 (reverse shell + download-
execute), #7993 (credential reads + curl/wget exfiltration).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
