diff mbox series

[v5,15/15] samples/landlock: adds network demo

Message ID 20220516152038.39594-16-konstantin.meskhidze@huawei.com (mailing list archive)
State New
Headers show
Series Network support for Landlock | expand

Commit Message

Konstantin Meskhidze (A) May 16, 2022, 3:20 p.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 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(-)

--
2.25.1

Comments

Mickaël Salaün May 17, 2022, 9:19 a.m. UTC | #1
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@huawei.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
>
Konstantin Meskhidze (A) May 19, 2022, 1:33 p.m. UTC | #2
5/17/2022 12:19 PM, Mickaël Salaün пишет:
> 
> 
> 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@huawei.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.
> 
   Great. That makes sense. Cause anyway fs restrictions are major ones.
> 
>> +    }
>> +    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. ;)

   Yep. I will fix it. Thanks.
> 
>> +        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).
> 
  Ok. I will change it
> 
>> +            "%s=\"10000:12000\" "
> 
> Connect ports example should reference well-known ports such as "80:443".
> 
   Ditto.
>>               "%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?

   Oh. Sorry. My mistake. I will fix it as it was.
> 
> 
>>       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.
> 

  It was done just to reduce the number of checkpatch.pl warnings.
  If you want it to be formated in your way I will fix it.
> 
> 
>> -    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.

   Ok. No problems.
> 
>> +        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‽

   You are right. I will move this changes to another commit, related 
the kernel updates. I might have forgotten to rebase this change and 
left it in sandboxer patch. Thank you..
> 
> 
>>
>>   /* 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
>>
> .
Mickaël Salaün May 19, 2022, 3:09 p.m. UTC | #3
On 19/05/2022 15:33, Konstantin Meskhidze wrote:
> 
> 
> 5/17/2022 12:19 PM, Mickaël Salaün пишет:
>>
>>
>> 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@huawei.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.
>>>
>>> ---

[...]

>>>       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.
>>
> 
>   It was done just to reduce the number of checkpatch.pl warnings.
>   If you want it to be formated in your way I will fix it.

Yes please, checkpatch.pl helps to mantain kernel code but this is a 
user space code and I prefer to follow safe practices for this kind of 
checks.

[...]

>>> 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‽
> 
>    You are right. I will move this changes to another commit, related 
> the kernel updates. I might have forgotten to rebase this change and 
> left it in sandboxer patch. Thank you..

Indeed. Please check that every commit build (without warning) and that 
the related tests are OK.


>>
>>
>>>
>>>   /* 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
>>>
>> .
Konstantin Meskhidze (A) May 24, 2022, 8:41 a.m. UTC | #4
5/19/2022 6:09 PM, Mickaël Salaün пишет:
> 
> 
> On 19/05/2022 15:33, Konstantin Meskhidze wrote:
>>
>>
>> 5/17/2022 12:19 PM, Mickaël Salaün пишет:
>>>
>>>
>>> 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@huawei.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.
>>>>
>>>> ---
> 
> [...]
> 
>>>>       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.
>>>
>>
>>   It was done just to reduce the number of checkpatch.pl warnings.
>>   If you want it to be formated in your way I will fix it.
> 
> Yes please, checkpatch.pl helps to mantain kernel code but this is a 
> user space code and I prefer to follow safe practices for this kind of 
> checks.
> 
  Ok. I will keep you code here. Thanks.
> [...]
> 
>>>> 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‽
>>
>>    You are right. I will move this changes to another commit, related 
>> the kernel updates. I might have forgotten to rebase this change and 
>> left it in sandboxer patch. Thank you..
> 
> Indeed. Please check that every commit build (without warning) and that 
> the related tests are OK.

   Ok. I will. Thanks.
> 
> 
>>>
>>>
>>>>
>>>>   /* 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
>>>>
>>> .
> .
diff mbox series

Patch

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;
+	}
+	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);
+		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\" "
+			"%s=\"10000:12000\" "
 			"%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);
+
 	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(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))
+		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;

 /* 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[];
 		};
 	};
 };