On 14/01/2021 04:21, Jann Horn wrote:

On Wed, Dec 9, 2020 at 8:29 PM Mickaël Salaün [off-list ref] wrote:

quoted

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!

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quoted

diff --git a/samples/Kconfig b/samples/Kconfig

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quoted

+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/

[...]

quoted

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c

[...]

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+/*
+ * 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/

[...]

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+int main(const int argc, char *const argv[], char *const *const envp)
+{

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+       if (argc < 2) {

[...]

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+               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/

quoted

+               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.)