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

[Mickaël Salaün]

On Thu, Mar 07, 2024 at 04:15:31PM +0100, Günther Noack wrote:
> 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."

Good catch. I integrated your suggestion. Thanks.

> 
> >   *
> >   * 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>
>