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Message-ID: <f3ca5fb2-64c6-b525-0f16-5353f1f7eddb@digikod.net>
Date: Thu, 14 Jan 2021 19:59:57 +0100
From: Mickaël Salaün <mic@...ikod.net>
To: Jann Horn <jannh@...gle.com>
Cc: James Morris <jmorris@...ei.org>, "Serge E . Hallyn" <serge@...lyn.com>,
Al Viro <viro@...iv.linux.org.uk>, Andy Lutomirski <luto@...capital.net>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>, Arnd Bergmann
<arnd@...db.de>, Casey Schaufler <casey@...aufler-ca.com>,
Jeff Dike <jdike@...toit.com>, Jonathan Corbet <corbet@....net>,
Kees Cook <keescook@...omium.org>, Michael Kerrisk <mtk.manpages@...il.com>,
Richard Weinberger <richard@....at>, Shuah Khan <shuah@...nel.org>,
Vincent Dagonneau <vincent.dagonneau@....gouv.fr>,
Kernel Hardening <kernel-hardening@...ts.openwall.com>,
Linux API <linux-api@...r.kernel.org>,
linux-arch <linux-arch@...r.kernel.org>,
"open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
kernel list <linux-kernel@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK" <linux-kselftest@...r.kernel.org>,
linux-security-module <linux-security-module@...r.kernel.org>,
the arch/x86 maintainers <x86@...nel.org>,
Mickaël Salaün <mic@...ux.microsoft.com>
Subject: Re: [PATCH v26 11/12] samples/landlock: Add a sandbox manager example
On 14/01/2021 04:21, Jann Horn wrote:
> On Wed, Dec 9, 2020 at 8:29 PM Mickaël Salaün <mic@...ikod.net> wrote:
>> Add a basic sandbox tool to launch a command which can only access a
>> whitelist of file hierarchies in a read-only or read-write way.
>
> I have to admit that I didn't really look at this closely before
> because it's just sample code... but I guess I should. You can add
>
> Reviewed-by: Jann Horn <jannh@...gle.com>
>
> if you fix the following nits:
OK, I will!
>
> [...]
>> diff --git a/samples/Kconfig b/samples/Kconfig
> [...]
>> +config SAMPLE_LANDLOCK
>> + bool "Build Landlock sample code"
>> + depends on HEADERS_INSTALL
>> + help
>> + Build a simple Landlock sandbox manager able to launch a process
>> + restricted by a user-defined filesystem access control.
>
> nit: s/filesystem access control/filesystem access control policy/
>
> [...]
>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> [...]
>> +/*
>> + * Simple Landlock sandbox manager able to launch a process restricted by a
>> + * user-defined filesystem access control.
>
> nit: s/filesystem access control/filesystem access control policy/
>
> [...]
>> +int main(const int argc, char *const argv[], char *const *const envp)
>> +{
> [...]
>> + if (argc < 2) {
> [...]
>> + fprintf(stderr, "* %s: list of paths allowed to be used in a read-only way.\n",
>> + ENV_FS_RO_NAME);
>> + fprintf(stderr, "* %s: list of paths allowed to be used in a read-write way.\n",
>> + ENV_FS_RO_NAME);
>
> s/ENV_FS_RO_NAME/ENV_FS_RW_NAME/
>
>> + fprintf(stderr, "\nexample:\n"
>> + "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
>> + "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
>> + "%s bash -i\n",
>> + ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
>> + return 1;
>> + }
>> +
>> + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>> + if (ruleset_fd < 0) {
>> + perror("Failed to create a ruleset");
>> + switch (errno) {
>
> (Just as a note: In theory perror() can change the value of errno, as
> far as I know - so AFAIK you'd theoretically have to do something
> like:
>
> int errno_ = errno;
> perror("...");
> switch (errno_) {
> ...
> }
Indeed :)
>
> I'll almost certainly work fine as-is in practice though.)
>
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