5/17/2022 11:51 AM, Mickaël Salaün пишет:

On 16/05/2022 17:20, Konstantin Meskhidze wrote:

quoted

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 <redacted>
---

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.

quoted

+    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.

quoted

+        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.

quoted

+    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.

quoted

+    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));
...

quoted

+    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.

quoted

      }
      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;
+       }

quoted

          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

.