| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <179ac2ee-37ff-92da-c381-c2c716725045@digikod.net>
Date: Tue, 17 May 2022 11:19:41 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
Cc: willemdebruijn.kernel@...il.com,
linux-security-module@...r.kernel.org, netdev@...r.kernel.org,
netfilter-devel@...r.kernel.org, yusongping@...wei.com,
anton.sirazetdinov@...wei.com
Subject: Re: [PATCH v5 15/15] samples/landlock: adds network demo
On 16/05/2022 17:20, Konstantin Meskhidze wrote:
> This commit adds network demo. It's possible to
> allow a sandoxer to bind/connect to a list of
> particular ports restricting networks actions to
> the rest of ports.
>
> Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@...wei.com>
> ---
>
> Changes since v4:
> * Adds ENV_TCP_BIND_NAME "LL_TCP_BIND" and
> ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" variables
> to insert TCP ports.
> * Renames populate_ruleset() to populate_ruleset_fs().
> * Adds populate_ruleset_net() and parse_port_num() helpers.
> * Refactoring main() to support network sandboxing.
>
> ---
> samples/landlock/sandboxer.c | 105 +++++++++++++++++++++++++++++++----
> security/landlock/ruleset.h | 4 +-
> 2 files changed, 95 insertions(+), 14 deletions(-)
>
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index 3e404e51ec64..4006c42eec1c 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c
> @@ -51,6 +51,8 @@ static inline int landlock_restrict_self(const int ruleset_fd,
>
> #define ENV_FS_RO_NAME "LL_FS_RO"
> #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_PATH_TOKEN ":"
>
> static int parse_path(char *env_path, const char ***const path_list)
> @@ -71,6 +73,20 @@ static int parse_path(char *env_path, const char ***const path_list)
> return num_paths;
> }
>
> +static int parse_port_num(char *env_port)
> +{
> + int i, num_ports = 0;
> +
> + if (env_port) {
> + num_ports++;
> + for (i = 0; env_port[i]; i++) {
> + if (env_port[i] == ENV_PATH_TOKEN[0])
> + num_ports++;
> + }
> + }
> + return num_ports;
> +}
> +
> /* clang-format off */
>
> #define ACCESS_FILE ( \
> @@ -80,7 +96,7 @@ static int parse_path(char *env_path, const char ***const path_list)
>
> /* clang-format on */
>
> -static int populate_ruleset(const char *const env_var, const int ruleset_fd,
> +static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
> const __u64 allowed_access)
> {
> int num_paths, i, ret = 1;
> @@ -142,6 +158,49 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd,
> return ret;
> }
>
> +static int populate_ruleset_net(const char *const env_var,
> + const int ruleset_fd,
> + const __u64 allowed_access)
> +{
> + int num_ports, i, ret = 1;
> + char *env_port_name;
> + struct landlock_net_service_attr net_service = {
> + .allowed_access = 0,
> + .port = 0,
> + };
> +
> + env_port_name = getenv(env_var);
> + if (!env_port_name) {
> + /* Prevents users to forget a setting. */
> + fprintf(stderr, "Missing environment variable %s\n", env_var);
> + return 1;
I think network ports should be optional to be able to test without that
(and not break compatibility). You can pass &ruleset_attr as argument to
update it accordingly:
- without environment variable: no network restriction;
- with empty environment variable: all connect (or bind) denied;
- otherwise: only allow the listed ports.
> + }
> + env_port_name = strdup(env_port_name);
> + unsetenv(env_var);
> + num_ports = parse_port_num(env_port_name);
> +
> + if (num_ports == 1 && (strtok(env_port_name, ENV_PATH_TOKEN) == NULL)) {
> + ret = 0;
> + goto out_free_name;
> + }
> +
> + for (i = 0; i < num_ports; i++) {
> + net_service.allowed_access = allowed_access;
> + net_service.port = atoi(strsep(&env_port_name, ENV_PATH_TOKEN));
> + if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_SERVICE,
> + &net_service, 0)) {
> + fprintf(stderr, "Failed to update the ruleset with port \"%d\": %s\n",
> + net_service.port, strerror(errno));
> + goto out_free_name;
> + }
> + }
> + ret = 0;
> +
> +out_free_name:
> + free(env_port_name);
> + return ret;
> +}
> +
> /* clang-format off */
>
> #define ACCESS_FS_ROUGHLY_READ ( \
> @@ -173,19 +232,24 @@ int main(const int argc, char *const argv[], char *const *const envp)
> char *const *cmd_argv;
> int ruleset_fd, abi;
> __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
> - access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
> + access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE,
> + access_net_tcp = LANDLOCK_ACCESS_NET_BIND_TCP |
> + LANDLOCK_ACCESS_NET_CONNECT_TCP;
> struct landlock_ruleset_attr ruleset_attr = {
> .handled_access_fs = access_fs_rw,
> + .handled_access_net = access_net_tcp,
> };
>
> if (argc < 2) {
> fprintf(stderr,
> - "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",
> - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
> + "usage: %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]);
> fprintf(stderr,
> "Launch a command in a restricted environment.\n\n");
> - fprintf(stderr, "Environment variables containing paths, "
> - "each separated by a colon:\n");
> + fprintf(stderr,
> + "Environment variables containing paths and ports "
> + "each separated by a colon:\n");
> fprintf(stderr,
> "* %s: list of paths allowed to be used in a read-only way.\n",
> ENV_FS_RO_NAME);
> @@ -193,11 +257,19 @@ int main(const int argc, char *const argv[], char *const *const envp)
> "* %s: list of paths allowed to be used in a read-write way.\n",
> ENV_FS_RW_NAME);
> fprintf(stderr,
> - "\nexample:\n"
> + "* %s: list of ports allowed to bind (server).\n",
> + ENV_TCP_BIND_NAME);
> + fprintf(stderr,
> + "* %s: list of ports allowed to connect (client).\n",
> + ENV_TCP_CONNECT_NAME);
This is good and will be better with clang-format. ;)
> + fprintf(stderr, "\nexample:\n"
> "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
> "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
> + "%s=\"15000:16000\" "
Bind ports example should reference unprivileged ports such as "9418"
(git, not well-known but OK).
> + "%s=\"10000:12000\" "
Connect ports example should reference well-known ports such as "80:443".
> "%s bash -i\n",
> - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);
> + ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
> + ENV_TCP_CONNECT_NAME, argv[0]);
> return 1;
> }
>
> @@ -234,16 +306,25 @@ int main(const int argc, char *const argv[], char *const *const envp)
>
> ruleset_fd =
> landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
> +
Why?
> if (ruleset_fd < 0) {
> perror("Failed to create a ruleset");
> return 1;
> }
> - if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {
> + if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro))
> goto err_close_ruleset;
> - }
Why? I know that checkpatch.pl prints a warning for that but I
delibirately chooe to use curly braces even for "if" statements with one
line because it is safer. This code may be copied/pasted and I'd like
others to avoid introducing goto-fail-like issues.
> - if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
> +
> + if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw))
> goto err_close_ruleset;
> - }
> +
> + if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd,
> + LANDLOCK_ACCESS_NET_BIND_TCP))
So please use curly braces here too.
> + goto err_close_ruleset;
> +
> + if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd,
> + LANDLOCK_ACCESS_NET_CONNECT_TCP))
> + goto err_close_ruleset;
> +
> if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
> perror("Failed to restrict privileges");
> goto err_close_ruleset;
> diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h
> index 916b30b31c06..e1ff40f238a6 100644
> --- a/security/landlock/ruleset.h
> +++ b/security/landlock/ruleset.h
> @@ -19,7 +19,7 @@
> #include "limits.h"
> #include "object.h"
>
> -typedef u16 access_mask_t;
> +typedef u32 access_mask_t;
What‽
>
> /* Makes sure all filesystem access rights can be stored. */
> static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS);
> @@ -157,7 +157,7 @@ struct landlock_ruleset {
> * layers are set once and never changed for the
> * lifetime of the ruleset.
> */
> - u32 access_masks[];
> + access_mask_t access_masks[];
> };
> };
> };
> --
> 2.25.1
>
Powered by blists - more mailing lists