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SubjectRe: [PATCH v26 11/12] samples/landlock: Add a sandbox manager example
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On 14/01/2021 04:21, Jann Horn wrote:
> On Wed, Dec 9, 2020 at 8:29 PM Mickaël Salaün <mic@digikod.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@google.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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