CrowdControl.Backend.Shell (crowd_control v0.2.0)

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Shell quoting shared by every backend that crosses an sh -c boundary.

This exists as one module, used by every backend, on purpose. Backend.Local interpolates env values into a sourced env file; Backend.Docker interpolates prompts into a printf ... >> fifo exec. Both carry attacker-influenced input across the same boundary, and a second, subtly different escaper is precisely how one of them ends up wrong. test/crowd_control/security_test.exs is the oracle for this function.

Summary

Functions

escape(value)

Wrap value in single quotes, rendering every byte inside it inert to sh.

Functions

escape(value)

@spec escape(term()) :: String.t()

Wrap value in single quotes, rendering every byte inside it inert to sh.

Single-quoting is total in POSIX shell — no escape sequence, variable, or substitution is interpreted inside '...'. The only byte that needs handling is ' itself, which closes the quote; the standard '\'' idiom closes, emits a literal quote, and reopens.

iex> CrowdControl.Backend.Shell.escape("plain")
"'plain'"

iex> CrowdControl.Backend.Shell.escape("it's")
"'it'\\''s'"

iex> CrowdControl.Backend.Shell.escape("$(rm -rf /)")
"'$(rm -rf /)'"