On 21/04/2023 11:39, Konstantin Meskhidze (A) wrote:
4/16/2023 7:11 PM, Mickaël Salaün пишет:
On 23/03/2023 09:52, Konstantin Meskhidze wrote:
This commit adds network rules support in the ruleset management
helpers and the landlock_create_ruleset syscall.
Refactor user space API to support network actions. Add new network
access flags, network rule and network attributes. Increment Landlock
ABI version. Expand access_masks_t to u32 to be sure network access
rights can be stored. Implement socket_bind() and socket_connect()
LSM hooks, which enable to restrict TCP socket binding and connection
"which enables to"
Got it.
to specific ports.
Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx>
---
[...]
+static u16 get_port(const struct sockaddr *const address)
+{
+ /* Gets port value in host byte order. */
+ switch (address->sa_family) {
+ case AF_UNSPEC:
+ case AF_INET: {
+ 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
+ }
+ WARN_ON_ONCE(1);
+ return 0;
+}
+
+static int check_socket_access(struct socket *sock, struct sockaddr *address, int addrlen, u16 port,
+ access_mask_t access_request)
+{
+ int ret;
+ bool allowed = false;
+ layer_mask_t layer_masks[LANDLOCK_NUM_ACCESS_NET] = {};
+ const struct landlock_rule *rule;
+ access_mask_t handled_access;
+ const struct landlock_id id = {
+ .key.data = port,
+ .type = LANDLOCK_KEY_NET_PORT,
+ };
+ const struct landlock_ruleset *const domain = get_current_net_domain();
+
+ if (WARN_ON_ONCE(!domain))
+ return 0;
+ if (WARN_ON_ONCE(domain->num_layers < 1))
+ return -EACCES;
+ /* Check if it's a TCP socket. */
+ if (sock->type != SOCK_STREAM)
+ return 0;
+
+ ret = check_addrlen(address, addrlen);
+ if (ret)
+ return ret;
As explained above, this should be replaced with:
if (addrlen < offsetofend(struct sockaddr, sa_family))
return -EINVAL;
Ok.
+
+ switch (address->sa_family) {
This below block should be moved after the generic switch statement
(i.e. once port is checked).
Do you mean checking address family after a port has been checked??
These specific AF_UNSPEC checks should be in an `if (address->sa_family
== AF_UNSPEC)` block after the generic AF_UNSPEC, AF_INET, and AF_INET6
checks in the address->sa_family switch/case, because the checks and
errors order must be consistent whatever the sa_family. The AF_UNSPEC
checks are really an exception to the AF_INET ones, and should then come
after.
This may look like this:
switch (address->sa_family) {
case AF_UNSPEC:
case AF_INET:
port = ...;
break;
#if IS_ENABLED(CONFIG_IPV6)
case AF_INET6:
port = ...;
break;
#endif
default:
return 0;
}
/* Specific AF_UNSPEC handling. */
if (address->sa_family == AF_UNSPEC) {
...
if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
return 0;
...
}
id.key.data = (__force uintptr_t)port;
BUILD_BUG_ON(sizeof(port) > sizeof(id.key.data));
rule = landlock_find_rule(domain, id);
handled_access = landlock_init_layer_masks(
domain, access_request, &layer_masks,
LANDLOCK_KEY_NET_PORT);
if (landlock_unmask_layers(rule, handled_access,
&layer_masks,
ARRAY_SIZE(layer_masks)))
return 0;
return -EACCES;
+ case AF_UNSPEC:
+ /*
+ * Connecting to an address with AF_UNSPEC dissolves the TCP
+ * association, which have the same effect as closing the
+ * connection while retaining the socket object (i.e., the file
+ * descriptor). As for dropping privileges, closing
+ * connections is always allowed.
+ */
+ if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
+ return 0;
+
+ /*
+ * For compatibility reason, accept AF_UNSPEC for bind
+ * accesses (mapped to AF_INET) only if the address is
+ * INADDR_ANY (cf. __inet_bind). Checking the address is
+ * required to not wrongfully return -EACCES instead of
+ * -EAFNOSUPPORT.
+ */
+ if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
+ const struct sockaddr_in *const sockaddr =
+ (struct sockaddr_in *)address;
+
+ if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
+ return -EAFNOSUPPORT;
+ }
+
+ fallthrough;
case AF_UNSPEC:
+ case AF_INET:
if (addrlen < sizeof(struct sockaddr_in))
return -EINVAL;
port = ((struct sockaddr_in *)address)->sin_port;
break;
+#if IS_ENABLED(CONFIG_IPV6)
+ case AF_INET6:
if (addrlen < SIN6_LEN_RFC2133)
return -EINVAL;
port = ((struct sockaddr_in6 *)address)->sin6_port;
break;
+#endif
/* Allows unhandled protocols. */
default:
return 0;
}
if (address->sa_family == AF_UNSPEC) {
// Add here the above AF_UNSPEC checks to be consistent with the
EINVAL/EAFNOSUPPORT return ordering.
}
id.key.data = (__force uintprt_t)port;
BUID_BUG_ON(...);
Will be refactored. Thanks.
