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authorJustine Tunney <jtunney@gmail.com>2021-01-25 21:34:50 -0800
committerPeter Stephenson <p.stephenson@samsung.com>2021-02-16 09:16:20 +0000
commit326d9c203b3980c0f841bc62b06e37134c6e51ea (patch)
tree07854fc13213a27825758d55ac2cfc273ef4f4b5 /Doc
parent83cc7c6bf08762c3fdeb76a44e4086734ff1db13 (diff)
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Allow more scripts without #!
This change modifies the zsh binary safety check surrounding execve() so it can run shell scripts having concatenated binary content. We're using the same safety check as FreeBSD /bin/sh [1]. POSIX was recently revised to require this behavior: "The input file may be of any type, but the initial portion of the file intended to be parsed according to the shell grammar (XREF to XSH 2.10.2 Shell Grammar Rules) shall consist of characters and shall not contain the NUL character. The shell shall not enforce any line length limits." "Earlier versions of this standard required that input files to the shell be text files except that line lengths were unlimited. However, that was overly restrictive in relation to the fact that shells can parse a script without a trailing newline, and in relation to a common practice of concatenating a shell script ending with an 'exit' or 'exec $command' with a binary data payload to form a single-file self-extracting archive." [2] [3] One example use case of such scripts, is the Cosmopolitan C Library [4] which configuse the GNU Linker to output a polyglot shell+binary format that runs on Linux / Mac / Windows / FreeBSD / OpenBSD. [1] https://github.com/freebsd/freebsd-src/commit/9a1cd363318b7e9e70ef6af27d1675b371c16b1a [2] http://austingroupbugs.net/view.php?id=1250 [3] http://austingroupbugs.net/view.php?id=1226#c4394 [4] https://justine.lol/cosmopolitan/index.html
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