Subject: Re: [PATCH v7 3/4] samples/landlock: Support abstract unix socket restriction

From: Mickaël Salaün <[email-masked]>
Date: Thu, 25 Jul 2024 16:18:57 +0200

On Wed, Jul 17, 2024 at 10:15:21PM -0600, Tahera Fahimi wrote:
> - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED"
>   environment variable. "LL_SCOPED" gets value "a" to restrict abstract
>   unix sockets.
> - Change to LANDLOCK_ABI_LAST to 6.
> 
> Signed-off-by: Tahera Fahimi <[email-masked]>
> ---
>  samples/landlock/sandboxer.c | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index e8223c3e781a..d280616585d4 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c
> @@ -14,6 +14,7 @@
>  #include <fcntl.h>
>  #include <linux/landlock.h>
>  #include <linux/prctl.h>
> +#include <linux/socket.h>
>  #include <stddef.h>
>  #include <stdio.h>
>  #include <stdlib.h>
> @@ -55,6 +56,7 @@ static inline int landlock_restrict_self(const int ruleset_fd,
>  #define ENV_FS_RW_NAME "LL_FS_RW"
>  #define ENV_TCP_BIND_NAME "LL_TCP_BIND"
>  #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
> +#define ENV_SCOPED_NAME "LL_SCOPED"
>  #define ENV_DELIMITER ":"
>  
>  static int parse_path(char *env_path, const char ***const path_list)
> @@ -208,7 +210,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
>  
>  /* clang-format on */
>  
> -#define LANDLOCK_ABI_LAST 5
> +#define LANDLOCK_ABI_LAST 6
>  
>  int main(const int argc, char *const argv[], char *const *const envp)
>  {
> @@ -216,6 +218,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  	char *const *cmd_argv;
>  	int ruleset_fd, abi;
>  	char *env_port_name;
> +	char *env_scoped_name;
>  	__u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
>  	      access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
>  
> @@ -223,14 +226,15 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  		.handled_access_fs = access_fs_rw,
>  		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
>  				      LANDLOCK_ACCESS_NET_CONNECT_TCP,
> +		.scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET,
>  	};
>  
>  	if (argc < 2) {
>  		fprintf(stderr,
> -			"usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s "
> +			"usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s "
>  			"<cmd> [args]...\n\n",
>  			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
> -			ENV_TCP_CONNECT_NAME, argv[0]);
> +			ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
>  		fprintf(stderr,
>  			"Execute a command in a restricted environment.\n\n");
>  		fprintf(stderr,
> @@ -251,15 +255,18 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  		fprintf(stderr,
>  			"* %s: list of ports allowed to connect (client).\n",
>  			ENV_TCP_CONNECT_NAME);
> +		fprintf(stderr, "* %s: list of allowed restriction on IPCs.\n",

"allowed restrictions" or "restrictions"?

> +			ENV_SCOPED_NAME);
>  		fprintf(stderr,
>  			"\nexample:\n"
>  			"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
>  			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
>  			"%s=\"9418\" "
>  			"%s=\"80:443\" "
> +			"%s=\"a\" "
>  			"%s bash -i\n\n",
>  			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
> -			ENV_TCP_CONNECT_NAME, argv[0]);
> +			ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
>  		fprintf(stderr,
>  			"This sandboxer can use Landlock features "
>  			"up to ABI version %d.\n",
> @@ -326,7 +333,10 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  	case 4:
>  		/* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */
>  		ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV;
> -

No need to remove this line.

> +		__attribute__((fallthrough));
> +	case 5:
> +		/* Removes IPC scoping mechanism for ABI < 6 */
> +		ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;

There is an inconsistency here, please take a look at previous similar
changes.

>  		fprintf(stderr,
>  			"Hint: You should update the running kernel "
>  			"to leverage Landlock features "
> @@ -357,7 +367,10 @@ int main(const int argc, char *const argv[], char *const *const envp)
>  		ruleset_attr.handled_access_net &=
>  			~LANDLOCK_ACCESS_NET_CONNECT_TCP;
>  	}
> -
> +	/* Removes IPC scoping attribute if not supported by a user. */
> +	env_scoped_name = getenv(ENV_SCOPED_NAME);
> +	if (!env_scoped_name)
> +		ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET;
>  	ruleset_fd =
>  		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>  	if (ruleset_fd < 0) {
> -- 
> 2.34.1
> 
>