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Discuss security considerations of racket/sandbox in Reference

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Scott Moore 2017-04-13 12:15:06 -04:00 committed by Vincent St-Amour
parent 3bc3fe9e26
commit 54bd21e65a
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pkgs/racket-doc/scribblings/reference/sandbox.scrbl
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@ -248,44 +248,30 @@ caller of the evaluation receives @|void-const|.
Finally, the fact that a sandboxed evaluator accept syntax objects
makes it usable as the value for @racket[current-eval], which means
that you can easily start a sandboxed read-eval-print-loop. For
example, here is a quick implementation of a networked REPL:
that you can easily start a sandboxed read-eval-print-loop:
@racketblock[
(define e (make-evaluator 'racket/base))
(let-values ([(i o) (tcp-accept (tcp-listen 9999))])
(parameterize ([current-input-port i]
[current-output-port o]
[current-error-port o]
[current-eval e])
(read-eval-print-loop)
(fprintf o "\nBye...\n")
(close-output-port o)))
(parameterize ([current-eval e])
(read-eval-print-loop))
]
Note that in this code it is only the REPL interactions that are going
over the network connection; using I/O operations inside the REPL will
Note that in this code only the REPL interactions will be printed to
the current output ports; using I/O operations inside the REPL will
still use the usual sandbox parameters (defaulting to no I/O). In
addition, the code works only from an existing toplevel REPL ---
specifically, @racket[read-eval-print-loop] reads a syntax value and
gives it the lexical context of the current namespace. Here is a
variation that uses the networked ports for user I/O, and works when
used from a module (by using a new namespace):
variation that also allows I/O over the current input and output
ports, and works when used from a module (by using a new namespace):
@racketblock[
(let-values ([(i o) (tcp-accept (tcp-listen 9999))])
(parameterize ([current-input-port i]
[current-output-port o]
[current-error-port o]
[sandbox-input i]
[sandbox-output o]
[sandbox-error-output o]
[current-namespace (make-empty-namespace)])
(parameterize ([current-eval
(make-evaluator 'racket/base)])
(read-eval-print-loop))
(fprintf o "\nBye...\n")
(close-output-port o)))
(parameterize ([sandbox-input current-input-port]
[sandbox-output current-output-port]
[sandbox-error-output current-error-port]
[current-namespace (make-empty-namespace)])
(parameterize ([current-eval (make-evaluator 'racket/base)])
(read-eval-print-loop)))
]
}
@ -300,6 +286,30 @@ is terminated. Once a sandbox raises such an exception, it will
continue to raise it on further evaluation attempts.
}
@; ----------------------------------------------------------------------
@section{Security Considerations}
Although the sandbox is designed to provide a safe environment for executing
Racket programs with restricted access to system resources, executing untrusted
programs in a sandbox still carries some risk. Because a malicious program can
exercise arbitrary functionality from the Racket runtime and installed collections,
an attacker who identifies a vulnerability in Racket or an installed collection
may be able to escape the sandbox.
To mitigate this risk, programs that use the sandbox should employ additional
precautions when possible. Suggested measures include:
@itemlist[
@item{Supplying a custom module language to @racket[make-evaluator] or
@racket[make-module-evaluator] that gives untrusted code access to only
the language constructs it absolutely requires.}
@item{If untrusted code needs access to installed collections, installing only
the collections required by your program.}
@item{Using operating-system-level security features to provide defense-in-depth
in case the process running the sandbox is compromised.}
@item{Making sure your Racket installation and installed packages are up-to-date
with the latest release.}
]
@; ----------------------------------------------------------------------