5/17/2022 11:51 AM, Mickaël Salaün пишет:
On 16/05/2022 17:20, Konstantin Meskhidze wrote:
Support of socket_bind() and socket_connect() hooks.
Its possible to restrict binding and connecting of TCP
types of sockets to particular ports. Its just basic idea
how Landlock could support network confinement.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---
Changes since v3:
* Split commit.
* Add SECURITY_NETWORK in config.
* Add IS_ENABLED(CONFIG_INET) if a kernel has no INET configuration.
* Add hook_socket_bind and hook_socket_connect hooks.
Changes since v4:
* Factors out CONFIG_INET into make file.
* Refactoring check_socket_access().
* Adds helper get_port().
* Adds CONFIG_IPV6 in get_port(), hook_socket_bind/connect
functions to support AF_INET6 family.
* Adds AF_UNSPEC family support in hook_socket_bind/connect
functions.
* Refactoring add_rule_net_service() and landlock_add_rule
syscall to support network rule inserting.
* Refactoring init_layer_masks() to support network rules.
---
security/landlock/Kconfig | 1 +
security/landlock/Makefile | 2 +
security/landlock/net.c | 159 +++++++++++++++++++++++++++++++++++
security/landlock/net.h | 25 ++++++
security/landlock/ruleset.c | 15 +++-
security/landlock/setup.c | 2 +
security/landlock/syscalls.c | 63 ++++++++++++--
7 files changed, 261 insertions(+), 6 deletions(-)
create mode 100644 security/landlock/net.c
create mode 100644 security/landlock/net.h
diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig
index 8e33c4e8ffb8..10c099097533 100644
--- a/security/landlock/Kconfig
+++ b/security/landlock/Kconfig
@@ -3,6 +3,7 @@
config SECURITY_LANDLOCK
bool "Landlock support"
depends on SECURITY && !ARCH_EPHEMERAL_INODES
+ select SECURITY_NETWORK
select SECURITY_PATH
help
Landlock is a sandboxing mechanism that enables processes to
restrict
diff --git a/security/landlock/Makefile b/security/landlock/Makefile
index 7bbd2f413b3e..53d3c92ae22e 100644
--- a/security/landlock/Makefile
+++ b/security/landlock/Makefile
@@ -2,3 +2,5 @@ obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o
landlock-y := setup.o syscalls.o object.o ruleset.o \
cred.o ptrace.o fs.o
+
+landlock-$(CONFIG_INET) += net.o
\ No newline at end of file
diff --git a/security/landlock/net.c b/security/landlock/net.c
new file mode 100644
index 000000000000..9302e5891991
--- /dev/null
+++ b/security/landlock/net.c
@@ -0,0 +1,159 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Network management and hooks
+ *
+ * Copyright (C) 2022 Huawei Tech. Co., Ltd.
+ */
+
+#include <linux/in.h>
+#include <linux/net.h>
+#include <linux/socket.h>
+#include <net/ipv6.h>
+
+#include "cred.h"
+#include "limits.h"
+#include "net.h"
+
+int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
+ u16 port, u32 access_rights)
+{
+ int err;
+
+ /* Transforms relative access rights to absolute ones. */
+ access_rights |= LANDLOCK_MASK_ACCESS_NET &
+ ~landlock_get_net_access_mask(ruleset, 0);
+
+ BUILD_BUG_ON(sizeof(port) > sizeof(uintptr_t));
+ mutex_lock(&ruleset->lock);
+ err = landlock_insert_rule(ruleset, NULL, port,
+ access_rights, LANDLOCK_RULE_NET_SERVICE);
+ mutex_unlock(&ruleset->lock);
+
+ return err;
+}
+
+static int check_socket_access(const struct landlock_ruleset *const
domain,
+ u16 port, access_mask_t access_request)
+{
+ bool allowed = false;
+ layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
+ const struct landlock_rule *rule;
+ access_mask_t handled_access;
+
+ if (WARN_ON_ONCE(!domain))
+ return 0;
+ if (WARN_ON_ONCE(domain->num_layers < 1))
+ return -EACCES;
+
+ rule = landlock_find_rule(domain, port,
+ LANDLOCK_RULE_NET_SERVICE);
+
+ handled_access = init_layer_masks(domain, access_request,
+ &layer_masks, sizeof(layer_masks),
+ LANDLOCK_RULE_NET_SERVICE);
+ allowed = unmask_layers(rule, handled_access,
+ &layer_masks, ARRAY_SIZE(layer_masks));
+
+ return allowed ? 0 : -EACCES;
+}
+
+static u16 get_port(const struct sockaddr *const address)
+{
+ /* Gets port value in host byte order. */
+ switch (address->sa_family) {
+ case AF_UNSPEC:
Are you sure about that?
Please write a test for this case.
I checked the logic in Selinux LSM in a bind() hook and AF_UNSPEC
family is treated as AF_INET (only for INADDR_ANY address) but we can
discuss it.
+ case AF_INET:
+ {
You don't need these braces (except if it is required by checkpatch.pl).
I got compilation error without braces:
...
error: a label can only be part of a statement and a declaration is not
a statement
67 | const struct sockaddr_in *const sockaddr =
...
so I added braces.
+ const struct sockaddr_in *const sockaddr =
+ (struct sockaddr_in *)address;
+ return ntohs(sockaddr->sin_port);
+ }
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+ {
+ const struct sockaddr_in6 *const sockaddr_ip6 =
+ (struct sockaddr_in6 *)address;
+ return ntohs(sockaddr_ip6->sin6_port);
+ }
+#endif
+ }
You missed some part of my patch… We should not get the port for a
protocol we don't know, hence the WARN_ON_ONCE.
Sorry. I manually updated the code and missed that. I will fix it.
+ return 0;
+}
+
+static int hook_socket_bind(struct socket *sock, struct sockaddr
*address,
+ int addrlen)
+{
+ const struct landlock_ruleset *const dom =
+ landlock_get_current_domain();
+
+ if (!dom)
+ return 0;
+
+ /* Check if it's a TCP socket */
+ if (sock->type != SOCK_STREAM)
+ return 0;
+
+ /* Get port value in host byte order */
I moved/removed this in my patch against v4 for a reason. Please, ask if
you don't understand or if you don't agree with something I said.
Sorry. I updated your changed manually and missed that.
Will be fixed.
+ switch (address->sa_family) {
+ case AF_UNSPEC:
Is this correct?
Actually I did'not find any issue with bind() using AF_UNSPEC family.
(instead of connect() one and we came to an agreement that it must be
banned). So I checked athoner LSMs like Selinux and found out that
it treats bind() hook with AF_UNSPEC family as with AF_INET one.
But Selinux allows AF_UNSPEC family only for INADDR_ANY address and
I cant understand the reason now. So I let AF_UNSPEC family bind()
hook for any address, but we can discuss it. What do you think?
Please write a test for this case.
I have one. Please check it in connect_afunspec_with_restictions
test:
...
/* Enforces the ruleset. */
enforce_ruleset(_metadata, ruleset_fd_1);
/* Creates a server socket 1 */
sockfd = create_socket(_metadata, false, false);
ASSERT_LE(0, sockfd);
/* Binds the socket 1 to address with port[0] with AF_UNSPEC
family */
self->addr4[0].sin_family = AF_UNSPEC;
ASSERT_EQ(0, bind(sockfd, (struct sockaddr *)&self->addr4[0],
sizeof(self->addr4[0])));
/* Makes connection to socket with port[0] */
ASSERT_EQ(0, connect(sockfd, (struct sockaddr *)&self->addr4[0],
sizeof(self->addr4[0])));
const int ruleset_fd_2 =
landlock_create_ruleset(&ruleset_attr_2,
sizeof(ruleset_attr_2), 0);
ASSERT_LE(0, ruleset_fd_2);
/* Allows connect and bind operations to the port[0] socket */
ASSERT_EQ(0, landlock_add_rule(ruleset_fd_2,
LANDLOCK_RULE_NET_SERVICE,
&net_service_2, 0));
...
+ case AF_INET:
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+#endif
+ return check_socket_access(dom, get_port(address),
+ LANDLOCK_ACCESS_NET_BIND_TCP);
+ default:
+ return 0;
+ }
+}
+
+static int hook_socket_connect(struct socket *sock, struct sockaddr
*address,
+ int addrlen)
+{
+ const struct landlock_ruleset *const dom =
+ landlock_get_current_domain();
+
+ if (!dom)
+ return 0;
+
+ /* Check if it's a TCP socket */
+ if (sock->type != SOCK_STREAM)
+ return 0;
+
+ /* Get port value in host byte order */
+ switch (address->sa_family) {
+ case AF_INET:
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
+#endif
+ return check_socket_access(dom, get_port(address),
+ LANDLOCK_ACCESS_NET_CONNECT_TCP);
+ case AF_UNSPEC:
+ {
+ u16 i;
+ /*
+ * If just in a layer a mask supports connect access,
+ * the socket_connect() hook with AF_UNSPEC family flag
+ * must be banned. This prevents from disconnecting already
+ * connected sockets.
+ */
+ for (i = 0; i < dom->num_layers; i++) {
+ if (landlock_get_net_access_mask(dom, i) &
+ LANDLOCK_ACCESS_NET_CONNECT_TCP)
+ return -EACCES;
+ }
+ }
+ }
+ return 0;
+}
+
+static struct security_hook_list landlock_hooks[] __lsm_ro_after_init
= {
+ LSM_HOOK_INIT(socket_bind, hook_socket_bind),
+ LSM_HOOK_INIT(socket_connect, hook_socket_connect),
+};
+
+__init void landlock_add_net_hooks(void)
+{
+ security_add_hooks(landlock_hooks, ARRAY_SIZE(landlock_hooks),
+ LANDLOCK_NAME);
+}
diff --git a/security/landlock/net.h b/security/landlock/net.h
new file mode 100644
index 000000000000..da5ce8fa04cc
--- /dev/null
+++ b/security/landlock/net.h
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Landlock LSM - Network management and hooks
+ *
+ * Copyright (C) 2022 Huawei Tech. Co., Ltd.
+ */
+
+#ifndef _SECURITY_LANDLOCK_NET_H
+#define _SECURITY_LANDLOCK_NET_H
+
+#include "common.h"
+#include "ruleset.h"
+#include "setup.h"
+
+#if IS_ENABLED(CONFIG_INET)
+__init void landlock_add_net_hooks(void);
+
+int landlock_append_net_rule(struct landlock_ruleset *const ruleset,
+ u16 port, u32 access_hierarchy);
+#else /* IS_ENABLED(CONFIG_INET) */
+static inline void landlock_add_net_hooks(void)
+{}
+#endif /* IS_ENABLED(CONFIG_INET) */
+
+#endif /* _SECURITY_LANDLOCK_NET_H */
diff --git a/security/landlock/ruleset.c b/security/landlock/ruleset.c
index ea9ecb3f471a..317cf98890f6 100644
--- a/security/landlock/ruleset.c
+++ b/security/landlock/ruleset.c
@@ -671,7 +671,7 @@ access_mask_t get_handled_accesses(
}
break;
default:
- break;
+ return 0;
Why?
You are right - this is useless code, cause anyway 0 is retured in
default rule_type. Will be fixed.
}
return access_dom;
}
@@ -763,6 +763,19 @@ access_mask_t init_layer_masks(const struct
landlock_ruleset *const domain,
}
}
break;
+ case LANDLOCK_RULE_NET_SERVICE:
+ for_each_set_bit(access_bit, &access_req,
+ LANDLOCK_NUM_ACCESS_NET) {
+ if (landlock_get_net_access_mask(domain,
+ layer_level) &
+ BIT_ULL(access_bit)) {
+ (*layer_masks)[access_bit] |=
+ BIT_ULL(layer_level);
+ handled_accesses |=
+ BIT_ULL(access_bit);
+ }
+ }
+ break;
default:
return 0;
}
diff --git a/security/landlock/setup.c b/security/landlock/setup.c
index f8e8e980454c..8059dc0b47d3 100644
--- a/security/landlock/setup.c
+++ b/security/landlock/setup.c
@@ -14,6 +14,7 @@
#include "fs.h"
#include "ptrace.h"
#include "setup.h"
+#include "net.h"
bool landlock_initialized __lsm_ro_after_init = false;
@@ -28,6 +29,7 @@ static int __init landlock_init(void)
landlock_add_cred_hooks();
landlock_add_ptrace_hooks();
landlock_add_fs_hooks();
+ landlock_add_net_hooks();
landlock_initialized = true;
pr_info("Up and running.\n");
return 0;
diff --git a/security/landlock/syscalls.c b/security/landlock/syscalls.c
index 812541f4e155..9454c6361011 100644
--- a/security/landlock/syscalls.c
+++ b/security/landlock/syscalls.c
@@ -29,6 +29,7 @@
#include "cred.h"
#include "fs.h"
#include "limits.h"
+#include "net.h"
#include "ruleset.h"
#include "setup.h"
@@ -74,7 +75,8 @@ static void build_check_abi(void)
{
struct landlock_ruleset_attr ruleset_attr;
struct landlock_path_beneath_attr path_beneath_attr;
- size_t ruleset_size, path_beneath_size;
+ struct landlock_net_service_attr net_service_attr;
+ size_t ruleset_size, path_beneath_size, net_service_size;
/*
* For each user space ABI structures, first checks that there
is no
@@ -90,6 +92,11 @@ static void build_check_abi(void)
path_beneath_size += sizeof(path_beneath_attr.parent_fd);
BUILD_BUG_ON(sizeof(path_beneath_attr) != path_beneath_size);
BUILD_BUG_ON(sizeof(path_beneath_attr) != 12);
+
+ net_service_size = sizeof(net_service_attr.allowed_access);
+ net_service_size += sizeof(net_service_attr.port);
+ BUILD_BUG_ON(sizeof(net_service_attr) != net_service_size);
+ BUILD_BUG_ON(sizeof(net_service_attr) != 10);
}
/* Ruleset handling */
@@ -299,9 +306,9 @@ static int add_rule_path_beneath(struct
landlock_ruleset *const ruleset,
* Informs about useless rule: empty allowed_access (i.e. deny
rules)
* are ignored in path walks.
*/
- if (!path_beneath_attr.allowed_access) {
+ if (!path_beneath_attr.allowed_access)
Why?
Unnecessary braces for single statement blocks.
I got a warning by scripts/checkpatch.pl:
WARNING: braces {} are not necessary for single statement blocks
#309: FILE: security/landlock/syscalls.c:309:
+ if (!path_beneath_attr.allowed_access) {
+ return -ENOMSG;
+ }
return -ENOMSG;
- }
+
/*
* Checks that allowed_access matches the @ruleset constraints
* (ruleset->access_masks[0] is automatically upgraded to 64-bits).
@@ -323,13 +330,54 @@ static int add_rule_path_beneath(struct
landlock_ruleset *const ruleset,
return err;
}
+static int add_rule_net_service(struct landlock_ruleset *ruleset,
+ const void *const rule_attr)
+{
+#if IS_ENABLED(CONFIG_INET)
+ struct landlock_net_service_attr net_service_attr;
+ int res;
+ u32 mask;
+
+ /* Copies raw user space buffer, only one type for now. */
+ res = copy_from_user(&net_service_attr, rule_attr,
+ sizeof(net_service_attr));
+ if (res)
+ return -EFAULT;
+
+ /*
+ * Informs about useless rule: empty allowed_access (i.e. deny
rules)
+ * are ignored by network actions
+ */
+ if (!net_service_attr.allowed_access)
+ return -ENOMSG;
+
+ /*
+ * Checks that allowed_access matches the @ruleset constraints
+ * (ruleset->access_masks[0] is automatically upgraded to 64-bits).
+ */
+ mask = landlock_get_net_access_mask(ruleset, 0);
+ if ((net_service_attr.allowed_access | mask) != mask)
+ return -EINVAL;
+
+ /* Denies inserting a rule with port 0 */
+ if (net_service_attr.port == 0)
+ return -EINVAL;
+
+ /* Imports the new rule. */
+ return landlock_append_net_rule(ruleset, net_service_attr.port,
+ net_service_attr.allowed_access);
+#else /* IS_ENABLED(CONFIG_INET) */
+ return -EAFNOSUPPORT;
+#endif /* IS_ENABLED(CONFIG_INET) */
+}
+
/**
* sys_landlock_add_rule - Add a new rule to a ruleset
*
* @ruleset_fd: File descriptor tied to the ruleset that should be
extended
* with the new rule.
- * @rule_type: Identify the structure type pointed to by @rule_attr
(only
- * LANDLOCK_RULE_PATH_BENEATH for now).
+ * @rule_type: Identify the structure type pointed to by @rule_attr:
+ * LANDLOCK_RULE_PATH_BENEATH or LANDLOCK_RULE_NET_SERVICE.
* @rule_attr: Pointer to a rule (only of type &struct
* landlock_path_beneath_attr for now).
* @flags: Must be 0.
@@ -340,6 +388,8 @@ static int add_rule_path_beneath(struct
landlock_ruleset *const ruleset,
* Possible returned errors are:
*
* - EOPNOTSUPP: Landlock is supported by the kernel but disabled at
boot time;
+ * - EAFNOSUPPORT: @rule_type is LANDLOCK_RULE_NET_SERVICE but TCP/IP
is not
+ * supported by the running kernel;
* - EINVAL: @flags is not 0, or inconsistent access in the rule (i.e.
* &landlock_path_beneath_attr.allowed_access is not a subset of
the rule's
* accesses);
@@ -375,6 +425,9 @@ SYSCALL_DEFINE4(landlock_add_rule,
case LANDLOCK_RULE_PATH_BENEATH:
err = add_rule_path_beneath(ruleset, rule_attr);
break;
+ case LANDLOCK_RULE_NET_SERVICE:
+ err = add_rule_net_service(ruleset, rule_attr);
+ break;
default:
err = -EINVAL;
break;
--
2.25.1
.
