[PATCH] samples/landlock: Don't error out if a file path cannot be opened

[Günther Noack]

On Thu, Mar 07, 2024 at 03:38:49PM +0100, Mickaël Salaün wrote:
> Instead of creating a hard error and aborting the sandbox creation,
> accept file path not usable in the LL_FS_RO and LL_FS_RW environment
> variables but only print a warning.  This makes it easier to test, for
> instance with LL_FS_RO="${PATH}:/usr/lib:/lib"
> 
> Print that we are going to execute the command in the sandbox before
> doing so.
> 
> Rename "launch" to "execute".
> 
> Cc: Günther Noack <gnoack at google.com>
> Signed-off-by: Mickaël Salaün <mic at digikod.net>
> ---
>  samples/landlock/sandboxer.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index d7323e5526be..22e8c35103ce 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c
> @@ -1,6 +1,6 @@
>  // SPDX-License-Identifier: BSD-3-Clause
>  /*
> - * Simple Landlock sandbox manager able to launch a process restricted by a
> + * Simple Landlock sandbox manager able to execute a process restricted by a
>   * user-defined filesystem access control policy.

Slightly out of scope, but I think it should be "...restricted by user-defined
file system and network access control policies."

>   *
>   * Copyright © 2017-2020 Mickaël Salaün <mic at digikod.net>
> @@ -121,9 +121,11 @@ static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
>  		if (path_beneath.parent_fd < 0) {
>  			fprintf(stderr, "Failed to open \"%s\": %s\n",
>  				path_list[i], strerror(errno));
> -			goto out_free_name;
> +			continue;
>  		}
>  		if (fstat(path_beneath.parent_fd, &statbuf)) {
> +			fprintf(stderr, "Failed to stat \"%s\": %s\n",
> +				path_list[i], strerror(errno));
>  			close(path_beneath.parent_fd);
>  			goto out_free_name;
>  		}
> @@ -229,7 +231,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
>  			ENV_TCP_CONNECT_NAME, argv[0]);
>  		fprintf(stderr,
> -			"Launch a command in a restricted environment.\n\n");
> +			"Execute a command in a restricted environment.\n\n");
>  		fprintf(stderr,
>  			"Environment variables containing paths and ports "
>  			"each separated by a colon:\n");
> @@ -250,7 +252,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  			ENV_TCP_CONNECT_NAME);
>  		fprintf(stderr,
>  			"\nexample:\n"
> -			"%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
> +			"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
>  			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
>  			"%s=\"9418\" "
>  			"%s=\"80:443\" "
> @@ -390,6 +392,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  
>  	cmd_path = argv[1];
>  	cmd_argv = argv + 1;
> +	fprintf(stderr, "Executing the sandboxed command...\n");
>  	execvpe(cmd_path, cmd_argv, envp);
>  	fprintf(stderr, "Failed to execute \"%s\": %s\n", cmd_path,
>  		strerror(errno));
> -- 
> 2.44.0
> 

Reviewed-by: Günther Noack <gnoack at google.com>