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 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 index 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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