configure.ac: check for sandbox-shell's FEATURE_SH_STANDALONE

See also: https://bugs.archlinux.org/task/73998. Busybox's
FEATURE_SH_STANDALONE feature causes other busybox applets to
leak into the sandbox, where system() calls will start preferring
them over tools in $PATH. On arch, this even includes `ar`.

Let's check for this evil feature and disallow using this as a
sandbox shell.
This commit is contained in:
Yorick 2022-05-24 16:26:40 +02:00
parent 4f98bc29ff
commit cbf60bec6f
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@ -294,6 +294,17 @@ esac
AC_ARG_WITH(sandbox-shell, AS_HELP_STRING([--with-sandbox-shell=PATH],[path of a statically-linked shell to use as /bin/sh in sandboxes]),
sandbox_shell=$withval)
AC_SUBST(sandbox_shell)
if ! test -z ${sandbox_shell+x}; then
AC_MSG_CHECKING([whether sandbox-shell has the standalone feature])
# busybox shell sometimes allows executing other busybox applets,
# even if they are not in the path, breaking our sandbox
if PATH= $sandbox_shell -c "busybox" 2>&1 | grep -qv "not found"; then
AC_MSG_RESULT(enabled)
AC_MSG_ERROR([Please disable busybox FEATURE_SH_STANDALONE])
else
AC_MSG_RESULT(disabled)
fi
fi
# Expand all variables in config.status.
test "$prefix" = NONE && prefix=$ac_default_prefix