diff mbox series

[v6,17/17] samples/landlock: adds network demo

Message ID 20220621082313.3330667-18-konstantin.meskhidze@huawei.com (mailing list archive)
State Not Applicable
Headers show
Series Network support for Landlock | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch, async

Commit Message

Konstantin Meskhidze (A) June 21, 2022, 8:23 a.m. UTC 
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@huawei.com>
---

Changes since v5:
* Makes network ports sandboxing optional.
* Fixes some logic errors.
* Formats code with clang-format-14.

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.
* Refactors main() to support network sandboxing.

---
 samples/landlock/sandboxer.c | 118 +++++++++++++++++++++++++++++++----
 1 file changed, 107 insertions(+), 11 deletions(-)

--
2.25.1

Comments

Mickaël Salaün July 27, 2022, 8:26 p.m. UTC | #1 
On 21/06/2022 10:23, 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@huawei.com>
> ---
> 
> Changes since v5:
> * Makes network ports sandboxing optional.
> * Fixes some logic errors.
> * Formats code with clang-format-14.
> 
> 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.
> * Refactors main() to support network sandboxing.
> 
> ---
>   samples/landlock/sandboxer.c | 118 +++++++++++++++++++++++++++++++----
>   1 file changed, 107 insertions(+), 11 deletions(-)
> 
> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
> index 3e404e51ec64..0606c676fded 100644
> --- a/samples/landlock/sandboxer.c
> +++ b/samples/landlock/sandboxer.c


[...]

> @@ -232,16 +308,36 @@ int main(const int argc, char *const argv[], char *const *const envp)
>   		access_fs_rw &= ~ACCESS_ABI_2;

We need to check the ABI to make this sample work without a kernel 
supporting Landlock network access rights, and error out if the user 
explicitely asked for it anyway (with the environement variable).


>   	}
> 
> +	/* Adds optionally network bind() support. */
> +	env_port_name = getenv(ENV_TCP_BIND_NAME);
> +	if (env_port_name) {
> +		access_net_tcp |= LANDLOCK_ACCESS_NET_BIND_TCP;
> +	}
> +	/* Adds optionally network connect() support. */
> +	env_port_name = getenv(ENV_TCP_CONNECT_NAME);
> +	if (env_port_name) {
> +		access_net_tcp |= LANDLOCK_ACCESS_NET_CONNECT_TCP;
> +	}
> +	ruleset_attr.handled_access_net = access_net_tcp;
> +
>   	ruleset_fd =
>   		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>   	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;
> +	}
> +	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)) {
>   		goto err_close_ruleset;
>   	}
> -	if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
> +	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)) {
> --
> 2.25.1
>
Konstantin Meskhidze (A) July 28, 2022, 9:21 a.m. UTC | #2 
7/27/2022 11:26 PM, Mickaël Salaün пишет:
> 
> On 21/06/2022 10:23, 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@huawei.com>
>> ---
>> 
>> Changes since v5:
>> * Makes network ports sandboxing optional.
>> * Fixes some logic errors.
>> * Formats code with clang-format-14.
>> 
>> 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.
>> * Refactors main() to support network sandboxing.
>> 
>> ---
>>   samples/landlock/sandboxer.c | 118 +++++++++++++++++++++++++++++++----
>>   1 file changed, 107 insertions(+), 11 deletions(-)
>> 
>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
>> index 3e404e51ec64..0606c676fded 100644
>> --- a/samples/landlock/sandboxer.c
>> +++ b/samples/landlock/sandboxer.c
> 
> 
> [...]
> 
>> @@ -232,16 +308,36 @@ int main(const int argc, char *const argv[], char *const *const envp)
>>   		access_fs_rw &= ~ACCESS_ABI_2;
> 
> We need to check the ABI to make this sample work without a kernel
> supporting Landlock network access rights, and error out if the user
> explicitely asked for it anyway (with the environement variable).
> 
   Good point. Thanks for that.
   I will check it.
> 
>>   	}
>> 
>> +	/* Adds optionally network bind() support. */
>> +	env_port_name = getenv(ENV_TCP_BIND_NAME);
>> +	if (env_port_name) {
>> +		access_net_tcp |= LANDLOCK_ACCESS_NET_BIND_TCP;
>> +	}
>> +	/* Adds optionally network connect() support. */
>> +	env_port_name = getenv(ENV_TCP_CONNECT_NAME);
>> +	if (env_port_name) {
>> +		access_net_tcp |= LANDLOCK_ACCESS_NET_CONNECT_TCP;
>> +	}
>> +	ruleset_attr.handled_access_net = access_net_tcp;
>> +
>>   	ruleset_fd =
>>   		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>>   	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;
>> +	}
>> +	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)) {
>>   		goto err_close_ruleset;
>>   	}
>> -	if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
>> +	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)) {
>> --
>> 2.25.1
>> 
> .
diff mbox series

Patch

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 3e404e51ec64..0606c676fded 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 ( \
@@ -80,8 +96,8 @@  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,
-			    const __u64 allowed_access)
+static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,
+			       const __u64 allowed_access)
 {
 	int num_paths, i, ret = 1;
 	char *env_path_name;
@@ -142,6 +158,48 @@  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) {
+		ret = 0;
+		goto out_free_name;
+	}
+	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 ( \
@@ -172,32 +230,50 @@  int main(const int argc, char *const argv[], char *const *const envp)
 	const char *cmd_path;
 	char *const *cmd_argv;
 	int ruleset_fd, abi;
+	char *env_port_name;
 	__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 = 0;
 	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);
 		fprintf(stderr,
-			"* %s: list of paths allowed to be used in a read-write way.\n",
+			"* %s: list of paths allowed to be used in a read-write way.\n\n",
 			ENV_FS_RW_NAME);
+		fprintf(stderr,
+			"Environment variables containing ports are optional "
+			"and could be skipped.\n");
+		fprintf(stderr,
+			"* %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);
 		fprintf(stderr,
 			"\nexample:\n"
 			"%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "
 			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
+			"%s=\"9418\" "
+			"%s=\"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;
 	}

@@ -232,16 +308,36 @@  int main(const int argc, char *const argv[], char *const *const envp)
 		access_fs_rw &= ~ACCESS_ABI_2;
 	}

+	/* Adds optionally network bind() support. */
+	env_port_name = getenv(ENV_TCP_BIND_NAME);
+	if (env_port_name) {
+		access_net_tcp |= LANDLOCK_ACCESS_NET_BIND_TCP;
+	}
+	/* Adds optionally network connect() support. */
+	env_port_name = getenv(ENV_TCP_CONNECT_NAME);
+	if (env_port_name) {
+		access_net_tcp |= LANDLOCK_ACCESS_NET_CONNECT_TCP;
+	}
+	ruleset_attr.handled_access_net = access_net_tcp;
+
 	ruleset_fd =
 		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
 	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;
+	}
+	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)) {
 		goto err_close_ruleset;
 	}
-	if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {
+	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)) {