From: "Mickaël Salaün" <mic@digikod.net>
To: linux-kernel@vger.kernel.org
Cc: "Mickaël Salaün" <mic@digikod.net>,
"Alexei Starovoitov" <ast@kernel.org>,
"Andy Lutomirski" <luto@amacapital.net>,
"Arnd Bergmann" <arnd@arndb.de>,
"Casey Schaufler" <casey@schaufler-ca.com>,
"Daniel Borkmann" <daniel@iogearbox.net>,
"Daniel Mack" <daniel@zonque.org>,
"David Drysdale" <drysdale@google.com>,
"David S . Miller" <davem@davemloft.net>,
"Elena Reshetova" <elena.reshetova@intel.com>,
"Eric W . Biederman" <ebiederm@xmission.com>,
"James Morris" <james.l.morris@oracle.com>,
"Kees Cook" <keescook@chromium.org>,
"Paul Moore" <pmoore@redhat.com>,
"Sargun Dhillon" <sargun@sargun.me>,
"Serge E . Hallyn" <serge@hallyn.com>,
"Tejun Heo" <tj@kernel.org>, "Will Drewry" <wad@chromium.org>,
kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org,
linux-security-module@vger.kernel.org, netdev@vger.kernel.org,
cgroups@vger.kernel.org
Subject: [kernel-hardening] [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context
Date: Wed, 14 Sep 2016 09:24:14 +0200 [thread overview]
Message-ID: <20160914072415.26021-22-mic@digikod.net> (raw)
In-Reply-To: <20160914072415.26021-1-mic@digikod.net>
This is a proof of concept to expose optional values that could depend
of the process access rights.
There is two dedicated flags: LANDLOCK_FLAG_ACCESS_SKB_READ and
LANDLOCK_FLAG_ACCESS_SKB_WRITE. Each of them can be activated to access
eBPF functions manipulating a skb in a read or write way.
Signed-off-by: Mickaël Salaün <mic@digikod.net>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David S. Miller <davem@davemloft.net>
Cc: Kees Cook <keescook@chromium.org>
Cc: Sargun Dhillon <sargun@sargun.me>
---
include/linux/bpf.h | 2 ++
include/uapi/linux/bpf.h | 7 ++++++-
kernel/bpf/verifier.c | 6 ++++++
security/landlock/lsm.c | 26 ++++++++++++++++++++++++++
4 files changed, 40 insertions(+), 1 deletion(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f7325c17f720..218973777612 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -88,6 +88,7 @@ enum bpf_arg_type {
ARG_PTR_TO_STRUCT_FILE, /* pointer to struct file */
ARG_CONST_PTR_TO_LANDLOCK_HANDLE_FS, /* pointer to Landlock FS handle */
+ ARG_PTR_TO_STRUCT_SKB, /* pointer to struct skb */
};
/* type of values returned from helper functions */
@@ -150,6 +151,7 @@ enum bpf_reg_type {
/* Landlock */
PTR_TO_STRUCT_FILE,
CONST_PTR_TO_LANDLOCK_HANDLE_FS,
+ PTR_TO_STRUCT_SKB,
};
struct bpf_prog;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 8cfc2de2ab76..7d9e56952ed9 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -586,7 +586,9 @@ enum landlock_hook_id {
/* context of function access flags */
#define LANDLOCK_FLAG_ACCESS_UPDATE (1 << 0)
#define LANDLOCK_FLAG_ACCESS_DEBUG (1 << 1)
-#define _LANDLOCK_FLAG_ACCESS_MASK ((1ULL << 2) - 1)
+#define LANDLOCK_FLAG_ACCESS_SKB_READ (1 << 2)
+#define LANDLOCK_FLAG_ACCESS_SKB_WRITE (1 << 3)
+#define _LANDLOCK_FLAG_ACCESS_MASK ((1ULL << 4) - 1)
/* Handle check flags */
#define LANDLOCK_FLAG_FS_DENTRY (1 << 0)
@@ -619,12 +621,15 @@ struct landlock_handle {
* @args: LSM hook arguments, see include/linux/lsm_hooks.h for there
* description and the LANDLOCK_HOOK* definitions from
* security/landlock/lsm.c for their types.
+ * @opt_skb: optional skb pointer, accessible with the
+ * LANDLOCK_FLAG_ACCESS_SKB_* flags for network-related hooks.
*/
struct landlock_data {
__u32 hook; /* enum landlock_hook_id */
__u16 origin; /* LANDLOCK_FLAG_ORIGIN_* */
__u16 cookie; /* seccomp RET_LANDLOCK */
__u64 args[6];
+ __u64 opt_skb;
};
#endif /* _UAPI__LINUX_BPF_H__ */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8d7b18574f5a..a95154c1a60f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -247,6 +247,7 @@ static const char * const reg_type_str[] = {
[PTR_TO_PACKET_END] = "pkt_end",
[PTR_TO_STRUCT_FILE] = "struct_file",
[CONST_PTR_TO_LANDLOCK_HANDLE_FS] = "landlock_handle_fs",
+ [PTR_TO_STRUCT_SKB] = "struct_skb",
};
static void print_verifier_state(struct verifier_state *state)
@@ -559,6 +560,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type)
case CONST_PTR_TO_MAP:
case PTR_TO_STRUCT_FILE:
case CONST_PTR_TO_LANDLOCK_HANDLE_FS:
+ case PTR_TO_STRUCT_SKB:
return true;
default:
return false;
@@ -984,6 +986,10 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
expected_type = CONST_PTR_TO_LANDLOCK_HANDLE_FS;
if (type != expected_type)
goto err_type;
+ } else if (arg_type == ARG_PTR_TO_STRUCT_SKB) {
+ expected_type = PTR_TO_STRUCT_SKB;
+ if (type != expected_type)
+ goto err_type;
} else if (arg_type == ARG_PTR_TO_STACK ||
arg_type == ARG_PTR_TO_RAW_STACK) {
expected_type = PTR_TO_STACK;
diff --git a/security/landlock/lsm.c b/security/landlock/lsm.c
index 56c45abe979c..8b0e6f0eb6b7 100644
--- a/security/landlock/lsm.c
+++ b/security/landlock/lsm.c
@@ -281,6 +281,7 @@ static bool __is_valid_access(int off, int size, enum bpf_access_type type,
break;
case offsetof(struct landlock_data, args[0]) ...
offsetof(struct landlock_data, args[5]):
+ case offsetof(struct landlock_data, opt_skb):
expected_size = sizeof(__u64);
break;
default:
@@ -299,6 +300,13 @@ static bool __is_valid_access(int off, int size, enum bpf_access_type type,
if (*reg_type == NOT_INIT)
return false;
break;
+ case offsetof(struct landlock_data, opt_skb):
+ if (!(prog_subtype->landlock_hook.access &
+ (LANDLOCK_FLAG_ACCESS_SKB_READ |
+ LANDLOCK_FLAG_ACCESS_SKB_WRITE)))
+ return false;
+ *reg_type = PTR_TO_STRUCT_SKB;
+ break;
}
return true;
@@ -401,6 +409,24 @@ static inline bool bpf_landlock_is_valid_subtype(
if (prog_subtype->landlock_hook.access & LANDLOCK_FLAG_ACCESS_DEBUG &&
!capable(CAP_SYS_ADMIN))
return false;
+ /*
+ * Capability checks must be enforced for every landlocked process.
+ * To support user namespaces/capabilities, we must then check the
+ * namespaces of a task before putting it in a landlocked cgroup.
+ * This could be implemented in the future.
+ */
+ if (prog_subtype->landlock_hook.access & LANDLOCK_FLAG_ACCESS_SKB_READ &&
+ !capable(CAP_NET_ADMIN))
+ return false;
+ /*
+ * It is interesting to differentiate read and write access to be able
+ * to securely delegate some work to unprivileged (and potentially
+ * compromised/untrusted) processes. This different type of access can
+ * be checked for function calls or context accesses.
+ */
+ if (prog_subtype->landlock_hook.access & LANDLOCK_FLAG_ACCESS_SKB_WRITE &&
+ !capable(CAP_NET_ADMIN))
+ return false;
return true;
}
--
2.9.3
next prev parent reply other threads:[~2016-09-14 7:24 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-14 7:23 [kernel-hardening] [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 01/22] landlock: Add Kconfig Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 02/22] bpf: Move u64_to_ptr() to BPF headers and inline it Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 03/22] bpf,landlock: Add a new arraymap type to deal with (Landlock) handles Mickaël Salaün
2016-09-14 18:51 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 23:22 ` Mickaël Salaün
2016-09-14 23:28 ` Alexei Starovoitov
2016-09-15 21:51 ` Mickaël Salaün
2016-10-03 23:53 ` Kees Cook
2016-10-05 22:02 ` Mickaël Salaün
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 04/22] bpf: Set register type according to is_valid_access() Mickaël Salaün
2016-10-19 14:54 ` [kernel-hardening] " Thomas Graf
2016-10-19 15:10 ` Daniel Borkmann
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 05/22] bpf,landlock: Add eBPF program subtype and is_valid_subtype() verifier Mickaël Salaün
2016-10-19 15:01 ` [kernel-hardening] " Thomas Graf
2016-09-14 7:23 ` [kernel-hardening] [RFC v3 06/22] landlock: Add LSM hooks Mickaël Salaün
2016-10-19 15:19 ` [kernel-hardening] " Thomas Graf
2016-10-19 22:42 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 07/22] landlock: Handle file comparisons Mickaël Salaün
2016-09-14 19:07 ` [kernel-hardening] " Jann Horn
2016-09-14 22:39 ` Mickaël Salaün
2016-09-14 21:06 ` Alexei Starovoitov
2016-09-14 23:02 ` Mickaël Salaün
2016-09-14 23:24 ` Alexei Starovoitov
2016-09-15 21:25 ` Mickaël Salaün
2016-09-20 0:12 ` [kernel-hardening] lsm naming dilemma. " Alexei Starovoitov
2016-09-20 1:10 ` [kernel-hardening] " Sargun Dhillon
2016-09-20 16:58 ` Mickaël Salaün
2016-10-03 23:30 ` [kernel-hardening] " Kees Cook
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 08/22] seccomp: Fix documentation for struct seccomp_filter Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 09/22] seccomp: Move struct seccomp_filter in seccomp.h Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 10/22] seccomp: Split put_seccomp_filter() with put_seccomp() Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 11/22] seccomp,landlock: Handle Landlock hooks per process hierarchy Mickaël Salaün
2016-09-14 18:43 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:34 ` Mickaël Salaün
2016-10-03 23:52 ` Kees Cook
2016-10-05 21:05 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 12/22] bpf: Cosmetic change for bpf_prog_attach() Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 13/22] bpf/cgroup: Replace struct bpf_prog with union bpf_object Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 14/22] bpf/cgroup: Make cgroup_bpf_update() return an error code Mickaël Salaün
2016-09-14 21:16 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 15/22] bpf/cgroup: Move capability check Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 16/22] bpf/cgroup,landlock: Handle Landlock hooks per cgroup Mickaël Salaün
2016-10-03 23:43 ` [kernel-hardening] " Kees Cook
2016-10-05 20:58 ` Mickaël Salaün
2016-10-05 21:25 ` Kees Cook
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 17/22] cgroup: Add access check for cgroup_get_from_fd() Mickaël Salaün
2016-09-14 22:06 ` [kernel-hardening] " Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 18/22] cgroup,landlock: Add CGRP_NO_NEW_PRIVS to handle unprivileged hooks Mickaël Salaün
2016-09-14 18:27 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:11 ` Mickaël Salaün
2016-09-15 1:25 ` Andy Lutomirski
2016-09-15 2:19 ` Alexei Starovoitov
2016-09-15 2:27 ` Andy Lutomirski
2016-09-15 4:00 ` Alexei Starovoitov
2016-09-15 4:08 ` Andy Lutomirski
2016-09-15 4:31 ` Alexei Starovoitov
2016-09-15 4:38 ` Andy Lutomirski
2016-09-15 4:48 ` Alexei Starovoitov
2016-09-15 19:41 ` Mickaël Salaün
2016-09-20 4:37 ` Sargun Dhillon
2016-09-20 17:02 ` Mickaël Salaün
2016-09-15 19:35 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 19/22] landlock: Add interrupted origin Mickaël Salaün
2016-09-14 18:29 ` [kernel-hardening] " Andy Lutomirski
2016-09-14 22:14 ` Mickaël Salaün
2016-09-15 1:19 ` Andy Lutomirski
2016-10-03 23:46 ` Kees Cook
2016-10-05 21:01 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 20/22] landlock: Add update and debug access flags Mickaël Salaün
2016-09-14 7:24 ` Mickaël Salaün [this message]
2016-09-14 21:20 ` [kernel-hardening] Re: [RFC v3 21/22] bpf,landlock: Add optional skb pointer in the Landlock context Alexei Starovoitov
2016-09-14 22:46 ` Mickaël Salaün
2016-09-14 7:24 ` [kernel-hardening] [RFC v3 22/22] samples/landlock: Add sandbox example Mickaël Salaün
2016-09-14 21:24 ` [kernel-hardening] " Alexei Starovoitov
2016-09-14 14:36 ` [kernel-hardening] RE: [RFC v3 00/22] Landlock LSM: Unprivileged sandboxing David Laight
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