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Message-ID: <1d58533e-f6c4-29bb-800e-0638e9660051@huawei-partners.com>
Date: Thu, 3 Oct 2024 16:15:39 +0300
From: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
To: Günther Noack <gnoack@...gle.com>
CC: <mic@...ikod.net>, <willemdebruijn.kernel@...il.com>,
<gnoack3000@...il.com>, <linux-security-module@...r.kernel.org>,
<netdev@...r.kernel.org>, <netfilter-devel@...r.kernel.org>,
<yusongping@...wei.com>, <artem.kuzin@...wei.com>,
<konstantin.meskhidze@...wei.com>
Subject: Re: [RFC PATCH v3 18/19] samples/landlock: Support socket protocol
restrictions
On 10/1/2024 10:56 AM, Günther Noack wrote:
> On Wed, Sep 04, 2024 at 06:48:23PM +0800, Mikhail Ivanov wrote:
>> Add socket protocol control support in sandboxer demo. It's possible
>> to allow a sandboxer to create sockets with specified family and type
>> values. This is controlled with the new LL_SOCKET_CREATE environment
>> variable. Single token in this variable looks like this:
>> 'FAMILY.TYPE', where FAMILY and TYPE are integers corresponding to the
>> number of address family and socket type.
>>
>> Add parse_socket_protocol() method to parse socket family and type
>> strings into integers.
>>
>> Change LANDLOCK_ABI_LAST to 6.
>>
>> Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@...wei-partners.com>
>> ---
>> Changes since v2:
>> * Changes representation of socket protocol in LL_SOCKET_CREATE into
>> pair of integer values.
>> * Changes commit message.
>> * Minor fixes.
>>
>> Changes since v1:
>> * Refactors get_socket_protocol(). Rename it to parse_socket_protocol().
>> * Changes LANDLOCK_ABI_LAST to 6 since ioctl patchlist updated it to 5.
>> * Refactors commit message.
>> * Formats with clang-format.
>> * Minor changes.
>> ---
>> samples/landlock/sandboxer.c | 108 ++++++++++++++++++++++++++++++-----
>> 1 file changed, 95 insertions(+), 13 deletions(-)
>>
>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
>> index d4dba9e4ce89..1669095f9373 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>
>> @@ -55,8 +56,11 @@ 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_SOCKET_CREATE_NAME "LL_SOCKET_CREATE"
>> #define ENV_DELIMITER ":"
>>
>> +#define ENV_TOKEN_INTERNAL_DELIMITER "."
>> +
>> static int parse_path(char *env_path, const char ***const path_list)
>> {
>> int i, num_paths = 0;
>> @@ -209,6 +213,65 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
>> return ret;
>> }
>>
>> +static int populate_ruleset_socket(const char *const env_var,
>> + const int ruleset_fd,
>> + const __u64 allowed_access)
>> +{
>> + int ret = 1;
>> + char *env_protocol_name, *strprotocol, *strfamily, *strtype;
>> + unsigned long long family_ull, type_ull;
>> + struct landlock_socket_attr protocol = {
>> + .allowed_access = allowed_access,
>> + };
>> +
>> + env_protocol_name = getenv(env_var);
>> + if (!env_protocol_name)
>> + return 0;
>> + env_protocol_name = strdup(env_protocol_name);
>> + unsetenv(env_var);
>> +
>> + while ((strprotocol = strsep(&env_protocol_name, ENV_DELIMITER))) {
>> + strfamily = strsep(&strprotocol, ENV_TOKEN_INTERNAL_DELIMITER);
>> + strtype = strsep(&strprotocol, ENV_TOKEN_INTERNAL_DELIMITER);
>
> This works with strings such as "123:456:foobar", because you are using strsep()
> twice on strprotocol; this looks unintentional?
Thanks, strsep should be called only once.
>
>
>> +
>> + if (!strtype) {
>> + fprintf(stderr,
>> + "Failed to extract socket protocol with "
>> + "unspecified type value\n");
>> + goto out_free_name;
>> + }
>> +
>> + if (str2num(strfamily, &family_ull)) {
>> + fprintf(stderr,
>> + "Failed to convert \"%s\" into a number\n",
>> + strfamily);
>> + goto out_free_name;
>> + }
>> + if (str2num(strtype, &type_ull)) {
>> + fprintf(stderr,
>> + "Failed to convert \"%s\" into a number\n",
>> + strtype);
>> + goto out_free_name;
>> + }
>> + protocol.family = (int)family_ull;
>> + protocol.type = (int)type_ull;
>> +
>> + if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_SOCKET,
>> + &protocol, 0)) {
>> + fprintf(stderr,
>> + "Failed to update the ruleset with "
>> + "family \"%s\" and type \"%s\": %s\n",
>> + strfamily, strtype, strerror(errno));
>> + goto out_free_name;
>> + }
>> + }
>> + ret = 0;
>> +
>> +out_free_name:
>> + free(env_protocol_name);
>> + return ret;
>> +}
>> +
>> /* clang-format off */
>>
>> #define ACCESS_FS_ROUGHLY_READ ( \
>> @@ -233,14 +296,14 @@ 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)
>> {
>> const char *cmd_path;
>> char *const *cmd_argv;
>> int ruleset_fd, abi;
>> - char *env_port_name;
>> + char *env_optional_name;
>> __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,
>> access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;
>>
>> @@ -248,18 +311,19 @@ 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,
>> + .handled_access_socket = LANDLOCK_ACCESS_SOCKET_CREATE,
>> };
>>
>> 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_SOCKET_CREATE_NAME, argv[0]);
>> fprintf(stderr,
>> "Execute a command in a restricted environment.\n\n");
>> fprintf(stderr,
>> - "Environment variables containing paths and ports "
>> + "Environment variables containing paths, ports and protocols "
>> "each separated by a colon:\n");
>> fprintf(stderr,
>> "* %s: list of paths allowed to be used in a read-only way.\n",
>> @@ -268,7 +332,7 @@ 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\n",
>> ENV_FS_RW_NAME);
>> fprintf(stderr,
>> - "Environment variables containing ports are optional "
>> + "Environment variables containing ports or protocols are optional "
>> "and could be skipped.\n");
>> fprintf(stderr,
>> "* %s: list of ports allowed to bind (server).\n",
>> @@ -276,15 +340,19 @@ 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 socket protocols allowed to be created.\n",
>> + ENV_SOCKET_CREATE_NAME);
>
> Might be worth listing some example values for this parameter, e.g. for TCP/IP
> and UDP/IP? This is also needed to make it clear that these can't be given by
> name, but only by number.
Ofc, it would be really useful for the user (since not everyone keeps
the adress family table in their head :)).
>
>
>> 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=\"10.2:1.1\" "
>> "%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_SOCKET_CREATE_NAME, argv[0]);
>> fprintf(stderr,
>> "This sandboxer can use Landlock features "
>> "up to ABI version %d.\n",
>> @@ -351,7 +419,11 @@ 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;
>> -
>> + __attribute__((fallthrough));
>> + case 5:
>> + /* Removes socket support for ABI < 6 */
>> + ruleset_attr.handled_access_socket &=
>> + ~LANDLOCK_ACCESS_SOCKET_CREATE;
>> fprintf(stderr,
>> "Hint: You should update the running kernel "
>> "to leverage Landlock features "
>> @@ -371,18 +443,23 @@ int main(const int argc, char *const argv[], char *const *const envp)
>> access_fs_rw &= ruleset_attr.handled_access_fs;
>>
>> /* Removes bind access attribute if not supported by a user. */
>> - env_port_name = getenv(ENV_TCP_BIND_NAME);
>> - if (!env_port_name) {
>> + env_optional_name = getenv(ENV_TCP_BIND_NAME);
>> + if (!env_optional_name) {
>> ruleset_attr.handled_access_net &=
>> ~LANDLOCK_ACCESS_NET_BIND_TCP;
>> }
>> /* Removes connect access attribute if not supported by a user. */
>> - env_port_name = getenv(ENV_TCP_CONNECT_NAME);
>> - if (!env_port_name) {
>> + env_optional_name = getenv(ENV_TCP_CONNECT_NAME);
>> + if (!env_optional_name) {
>> ruleset_attr.handled_access_net &=
>> ~LANDLOCK_ACCESS_NET_CONNECT_TCP;
>> }
>> -
>> + /* Removes socket create access attribute if not supported by a user. */
>
> Phrasing nit: I would say "requested by a user"?
>
> (And maybe also in the two cases above)
Yeap, I'll fix this each case.
>
>
>> + env_optional_name = getenv(ENV_SOCKET_CREATE_NAME);
>> + if (!env_optional_name) {
>> + ruleset_attr.handled_access_socket &=
>> + ~LANDLOCK_ACCESS_SOCKET_CREATE;
>> + }
>> ruleset_fd =
>> landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
>> if (ruleset_fd < 0) {
>> @@ -406,6 +483,11 @@ int main(const int argc, char *const argv[], char *const *const envp)
>> goto err_close_ruleset;
>> }
>>
>> + if (populate_ruleset_socket(ENV_SOCKET_CREATE_NAME, ruleset_fd,
>> + LANDLOCK_ACCESS_SOCKET_CREATE)) {
>> + goto err_close_ruleset;
>> + }
>> +
>> if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
>> perror("Failed to restrict privileges");
>> goto err_close_ruleset;
>> --
>> 2.34.1
>>
>
> As I also said on the Documentation patch, please remember to double check the
> places where the ABI number is mentioned, after rebasing on Tahera's "scoped"
> patches.
Ofc, thanks for the reminder!
>
> —Günther
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