From patchwork Tue Oct 29 17:14:59 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 11218339 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 255A413BD for ; Tue, 29 Oct 2019 17:21:00 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id 21DA32067D for ; Tue, 29 Oct 2019 17:20:58 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 21DA32067D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=digikod.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-17148-patchwork-kernel-hardening=patchwork.kernel.org@lists.openwall.com Received: (qmail 3570 invoked by uid 550); 29 Oct 2019 17:20:57 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 3538 invoked from network); 29 Oct 2019 17:20:57 -0000 From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: linux-kernel@vger.kernel.org Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Alexei Starovoitov , Andy Lutomirski , Casey Schaufler , Daniel Borkmann , David Drysdale , Florent Revest , James Morris , Jann Horn , John Johansen , Jonathan Corbet , Kees Cook , KP Singh , Michael Kerrisk , =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Paul Moore , Sargun Dhillon , "Serge E . Hallyn" , Shuah Khan , Stephen Smalley , Tejun Heo , Tetsuo Handa , Tycho Andersen , Will Drewry , bpf@vger.kernel.org, kernel-hardening@lists.openwall.com, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH bpf-next v11 1/7] bpf,landlock: Define an eBPF program type for Landlock hooks Date: Tue, 29 Oct 2019 18:14:59 +0100 Message-Id: <20191029171505.6650-2-mic@digikod.net> X-Mailer: git-send-email 2.24.0.rc1 In-Reply-To: <20191029171505.6650-1-mic@digikod.net> References: <20191029171505.6650-1-mic@digikod.net> MIME-Version: 1.0 X-Antivirus: Dr.Web (R) for Unix mail servers drweb plugin ver.6.0.2.8 X-Antivirus-Code: 0x100000 Add a new type of eBPF program used by Landlock hooks. The goal of this type of program is to accept or deny a requested access from userspace to a kernel object (e.g. process). This will be more useful with the next commit adding a new eBPF helper. This new BPF program type will be registered with the Landlock LSM initialization. Add an initial Landlock Kconfig and update the MAINTAINERS file. Signed-off-by: Mickaël Salaün Cc: Alexei Starovoitov Cc: Andy Lutomirski Cc: Daniel Borkmann Cc: James Morris Cc: Kees Cook Cc: Serge E. Hallyn Cc: Will Drewry --- Changes since v10: * replace file system program types with a (simpler) ptrace program type * add an eBPF task pointer type * split files Changes since v9: * handle inode put and map put, which fix unmount (reported by Al Viro) * replace subtype with expected_attach_type and expected_attach_triggers * check eBPF program return code Changes since v8: * Remove the chaining concept from the eBPF program contexts (chain and cookie). We need to keep these subtypes this way to be able to make them evolve, though. * remove bpf_landlock_put_extra() because there is no more a "previous" field to free (for now) Changes since v7: * cosmetic fixes * rename LANDLOCK_SUBTYPE_* to LANDLOCK_* * cleanup UAPI definitions and move them from bpf.h to landlock.h (suggested by Alexei Starovoitov) * disable Landlock by default (suggested by Alexei Starovoitov) * rename BPF_PROG_TYPE_LANDLOCK_{RULE,HOOK} * update the Kconfig * update the MAINTAINERS file * replace the IOCTL, LOCK and FCNTL events with FS_PICK, FS_WALK and FS_GET hook types * add the ability to chain programs with an eBPF program file descriptor (i.e. the "previous" field in a Landlock subtype) and keep a state with a "cookie" value available from the context * add a "triggers" subtype bitfield to match specific actions (e.g. append, chdir, read...) Changes since v6: * add 3 more sub-events: IOCTL, LOCK, FCNTL https://lkml.kernel.org/r/2fbc99a6-f190-f335-bd14-04bdeed35571@digikod.net * rename LANDLOCK_VERSION to LANDLOCK_ABI to better reflect its purpose, and move it from landlock.h to common.h * rename BPF_PROG_TYPE_LANDLOCK to BPF_PROG_TYPE_LANDLOCK_RULE: an eBPF program could be used for something else than a rule * simplify struct landlock_context by removing the arch and syscall_nr fields * remove all eBPF map functions call, remove ABILITY_WRITE * refactor bpf_landlock_func_proto() (suggested by Kees Cook) * constify pointers * fix doc inclusion Changes since v5: * rename file hooks.c to init.c * fix spelling Changes since v4: * merge a minimal (not enabled) LSM code and Kconfig in this commit Changes since v3: * split commit * revamp the landlock_context: * add arch, syscall_nr and syscall_cmd (ioctl, fcntl…) to be able to cross-check action with the event type * replace args array with dedicated fields to ease the addition of new fields --- MAINTAINERS | 8 ++++ include/linux/bpf.h | 1 + include/linux/bpf_types.h | 3 ++ include/uapi/linux/bpf.h | 2 + include/uapi/linux/landlock.h | 39 ++++++++++++++++ kernel/bpf/syscall.c | 9 ++++ kernel/bpf/verifier.c | 7 +++ security/Kconfig | 1 + security/Makefile | 2 + security/landlock/Kconfig | 19 ++++++++ security/landlock/Makefile | 4 ++ security/landlock/bpf_ptrace.c | 30 ++++++++++++ security/landlock/bpf_ptrace.h | 17 +++++++ security/landlock/bpf_verify.c | 83 ++++++++++++++++++++++++++++++++++ security/landlock/common.h | 30 ++++++++++++ 15 files changed, 255 insertions(+) create mode 100644 include/uapi/linux/landlock.h create mode 100644 security/landlock/Kconfig create mode 100644 security/landlock/Makefile create mode 100644 security/landlock/bpf_ptrace.c create mode 100644 security/landlock/bpf_ptrace.h create mode 100644 security/landlock/bpf_verify.c create mode 100644 security/landlock/common.h diff --git a/MAINTAINERS b/MAINTAINERS index 7fc074632eac..4cabb85ea52d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9146,6 +9146,14 @@ F: net/core/skmsg.c F: net/core/sock_map.c F: net/ipv4/tcp_bpf.c +LANDLOCK SECURITY MODULE +M: Mickaël Salaün +S: Supported +F: include/uapi/linux/landlock.h +F: security/landlock/ +K: landlock +K: LANDLOCK + LANTIQ / INTEL Ethernet drivers M: Hauke Mehrtens L: netdev@vger.kernel.org diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 171be30fe0ae..819a3e207438 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -291,6 +291,7 @@ enum bpf_reg_type { PTR_TO_TP_BUFFER, /* reg points to a writable raw tp's buffer */ PTR_TO_XDP_SOCK, /* reg points to struct xdp_sock */ PTR_TO_BTF_ID, /* reg points to kernel struct */ + PTR_TO_TASK, /* reg points to struct task_struct */ }; /* The information passed from prog-specific *_is_valid_access diff --git a/include/linux/bpf_types.h b/include/linux/bpf_types.h index 36a9c2325176..bddabc961a3b 100644 --- a/include/linux/bpf_types.h +++ b/include/linux/bpf_types.h @@ -38,6 +38,9 @@ BPF_PROG_TYPE(BPF_PROG_TYPE_LIRC_MODE2, lirc_mode2) #ifdef CONFIG_INET BPF_PROG_TYPE(BPF_PROG_TYPE_SK_REUSEPORT, sk_reuseport) #endif +#ifdef CONFIG_SECURITY_LANDLOCK +BPF_PROG_TYPE(BPF_PROG_TYPE_LANDLOCK_HOOK, landlock) +#endif BPF_MAP_TYPE(BPF_MAP_TYPE_ARRAY, array_map_ops) BPF_MAP_TYPE(BPF_MAP_TYPE_PERCPU_ARRAY, percpu_array_map_ops) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 4af8b0819a32..6e4147790f96 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -173,6 +173,7 @@ enum bpf_prog_type { BPF_PROG_TYPE_CGROUP_SYSCTL, BPF_PROG_TYPE_RAW_TRACEPOINT_WRITABLE, BPF_PROG_TYPE_CGROUP_SOCKOPT, + BPF_PROG_TYPE_LANDLOCK_HOOK, }; enum bpf_attach_type { @@ -199,6 +200,7 @@ enum bpf_attach_type { BPF_CGROUP_UDP6_RECVMSG, BPF_CGROUP_GETSOCKOPT, BPF_CGROUP_SETSOCKOPT, + BPF_LANDLOCK_PTRACE, __MAX_BPF_ATTACH_TYPE }; diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h new file mode 100644 index 000000000000..3ffe3cbdbad6 --- /dev/null +++ b/include/uapi/linux/landlock.h @@ -0,0 +1,39 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +/* + * Landlock - UAPI headers + * + * Copyright © 2017-2019 Mickaël Salaün + * Copyright © 2018-2019 ANSSI + */ + +#ifndef _UAPI__LINUX_LANDLOCK_H__ +#define _UAPI__LINUX_LANDLOCK_H__ + +#include + +/** + * DOC: landlock_ret + * + * The return value of a landlock program is a bitmask that can allow or deny + * the action for which the program is run. + * + * In the future, this could be used to trigger an audit event as well. + * + * - %LANDLOCK_RET_ALLOW + * - %LANDLOCK_RET_DENY + */ +#define LANDLOCK_RET_ALLOW 0 +#define LANDLOCK_RET_DENY 1 + +/** + * struct landlock_context_ptrace - context accessible to BPF_LANDLOCK_PTRACE + * + * @tracer: pointer to the task requesting to debug @tracee + * @tracee: pointer to the task being debugged + */ +struct landlock_context_ptrace { + __u64 tracer; + __u64 tracee; +}; + +#endif /* _UAPI__LINUX_LANDLOCK_H__ */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index ff5225759553..5159e582a0d8 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -1621,6 +1621,15 @@ bpf_prog_load_check_attach(enum bpf_prog_type prog_type, default: return -EINVAL; } +#ifdef CONFIG_SECURITY_LANDLOCK + case BPF_PROG_TYPE_LANDLOCK_HOOK: + switch (expected_attach_type) { + case BPF_LANDLOCK_PTRACE: + return 0; + default: + return -EINVAL; + } +#endif default: return 0; } diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c59778c0fc4d..ebf1991906b7 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -421,6 +421,7 @@ static const char * const reg_type_str[] = { [PTR_TO_TP_BUFFER] = "tp_buffer", [PTR_TO_XDP_SOCK] = "xdp_sock", [PTR_TO_BTF_ID] = "ptr_", + [PTR_TO_TASK] = "task", }; static char slot_type_char[] = { @@ -1878,6 +1879,7 @@ static bool is_spillable_regtype(enum bpf_reg_type type) case PTR_TO_TCP_SOCK: case PTR_TO_TCP_SOCK_OR_NULL: case PTR_TO_XDP_SOCK: + case PTR_TO_TASK: return true; default: return false; @@ -2600,6 +2602,9 @@ static int check_ptr_alignment(struct bpf_verifier_env *env, case PTR_TO_XDP_SOCK: pointer_desc = "xdp_sock "; break; + case PTR_TO_TASK: + pointer_desc = "task "; + break; default: break; } @@ -4527,6 +4532,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, case PTR_TO_TCP_SOCK: case PTR_TO_TCP_SOCK_OR_NULL: case PTR_TO_XDP_SOCK: + case PTR_TO_TASK: verbose(env, "R%d pointer arithmetic on %s prohibited\n", dst, reg_type_str[ptr_reg->type]); return -EACCES; @@ -6278,6 +6284,7 @@ static int check_return_code(struct bpf_verifier_env *env) case BPF_PROG_TYPE_CGROUP_DEVICE: case BPF_PROG_TYPE_CGROUP_SYSCTL: case BPF_PROG_TYPE_CGROUP_SOCKOPT: + case BPF_PROG_TYPE_LANDLOCK_HOOK: break; default: return 0; diff --git a/security/Kconfig b/security/Kconfig index 2a1a2d396228..9d9981394fb0 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -238,6 +238,7 @@ source "security/loadpin/Kconfig" source "security/yama/Kconfig" source "security/safesetid/Kconfig" source "security/lockdown/Kconfig" +source "security/landlock/Kconfig" source "security/integrity/Kconfig" diff --git a/security/Makefile b/security/Makefile index be1dd9d2cb2f..60b7f6f2fd30 100644 --- a/security/Makefile +++ b/security/Makefile @@ -12,6 +12,7 @@ subdir-$(CONFIG_SECURITY_YAMA) += yama subdir-$(CONFIG_SECURITY_LOADPIN) += loadpin subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown +subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock # always enable default capabilities obj-y += commoncap.o @@ -29,6 +30,7 @@ obj-$(CONFIG_SECURITY_YAMA) += yama/ obj-$(CONFIG_SECURITY_LOADPIN) += loadpin/ obj-$(CONFIG_SECURITY_SAFESETID) += safesetid/ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/ +obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/ obj-$(CONFIG_CGROUP_DEVICE) += device_cgroup.o # Object integrity file lists diff --git a/security/landlock/Kconfig b/security/landlock/Kconfig new file mode 100644 index 000000000000..44921bd72380 --- /dev/null +++ b/security/landlock/Kconfig @@ -0,0 +1,19 @@ +config SECURITY_LANDLOCK + bool "Landlock support" + depends on SECURITY + depends on BPF_SYSCALL + depends on SECCOMP_FILTER + default n + help + This selects Landlock, a programmatic access control. It enables to + restrict processes on the fly (i.e. create a sandbox) or log some + actions. The security policy is a set of eBPF programs, dedicated to + allow or deny a list of actions on specific kernel objects (e.g. + process). + + You need to enable seccomp filter to apply a security policy to a + process hierarchy (e.g. application with built-in sandboxing). + + See Documentation/security/landlock/ for further information. + + If you are unsure how to answer this question, answer N. diff --git a/security/landlock/Makefile b/security/landlock/Makefile new file mode 100644 index 000000000000..682b798c6b76 --- /dev/null +++ b/security/landlock/Makefile @@ -0,0 +1,4 @@ +obj-$(CONFIG_SECURITY_LANDLOCK) := landlock.o + +landlock-y := \ + bpf_verify.o bpf_ptrace.o diff --git a/security/landlock/bpf_ptrace.c b/security/landlock/bpf_ptrace.c new file mode 100644 index 000000000000..2ec73078ad01 --- /dev/null +++ b/security/landlock/bpf_ptrace.c @@ -0,0 +1,30 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Landlock LSM - eBPF ptrace + * + * Copyright © 2017-2019 Mickaël Salaün + * Copyright © 2019 ANSSI + */ + +#include +#include + +#include "bpf_ptrace.h" + +bool landlock_is_valid_access_ptrace(int off, enum bpf_access_type type, + enum bpf_reg_type *reg_type, int *max_size) +{ + if (type != BPF_READ) + return false; + + switch (off) { + case offsetof(struct landlock_context_ptrace, tracer): + /* fall through */ + case offsetof(struct landlock_context_ptrace, tracee): + *reg_type = PTR_TO_TASK; + *max_size = sizeof(u64); + return true; + default: + return false; + } +} diff --git a/security/landlock/bpf_ptrace.h b/security/landlock/bpf_ptrace.h new file mode 100644 index 000000000000..85edce37b70a --- /dev/null +++ b/security/landlock/bpf_ptrace.h @@ -0,0 +1,17 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock LSM - eBPF ptrace headers + * + * Copyright © 2017-2019 Mickaël Salaün + * Copyright © 2019 ANSSI + */ + +#ifndef _SECURITY_LANDLOCK_BPF_PTRACE_H +#define _SECURITY_LANDLOCK_BPF_PTRACE_H + +#include + +bool landlock_is_valid_access_ptrace(int off, enum bpf_access_type type, + enum bpf_reg_type *reg_type, int *max_size); + +#endif /* _SECURITY_LANDLOCK_BPF_PTRACE_H */ diff --git a/security/landlock/bpf_verify.c b/security/landlock/bpf_verify.c new file mode 100644 index 000000000000..6ed921588178 --- /dev/null +++ b/security/landlock/bpf_verify.c @@ -0,0 +1,83 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Landlock LSM - eBPF program verifications + * + * Copyright © 2016-2019 Mickaël Salaün + * Copyright © 2018-2019 ANSSI + */ + +#include +#include + +#include "common.h" +#include "bpf_ptrace.h" + +static bool bpf_landlock_is_valid_access(int off, int size, + enum bpf_access_type type, const struct bpf_prog *prog, + struct bpf_insn_access_aux *info) +{ + enum bpf_reg_type reg_type = NOT_INIT; + int max_size = 0; + + if (WARN_ON(!prog->expected_attach_type)) + return false; + + if (off < 0) + return false; + if (size <= 0 || size > sizeof(__u64)) + return false; + + /* set register type and max size */ + switch (get_hook_type(prog)) { + case LANDLOCK_HOOK_PTRACE: + if (!landlock_is_valid_access_ptrace(off, type, ®_type, + &max_size)) + return false; + break; + } + + /* check memory range access */ + switch (reg_type) { + case NOT_INIT: + return false; + case SCALAR_VALUE: + /* allow partial raw value */ + if (size > max_size) + return false; + info->ctx_field_size = max_size; + break; + default: + /* deny partial pointer */ + if (size != max_size) + return false; + } + + info->reg_type = reg_type; + return true; +} + +static const struct bpf_func_proto *bpf_landlock_func_proto( + enum bpf_func_id func_id, + const struct bpf_prog *prog) +{ + if (WARN_ON(!prog->expected_attach_type)) + return NULL; + + switch (func_id) { + case BPF_FUNC_map_lookup_elem: + return &bpf_map_lookup_elem_proto; + case BPF_FUNC_map_update_elem: + return &bpf_map_update_elem_proto; + case BPF_FUNC_map_delete_elem: + return &bpf_map_delete_elem_proto; + default: + return NULL; + } +} + +const struct bpf_verifier_ops landlock_verifier_ops = { + .get_func_proto = bpf_landlock_func_proto, + .is_valid_access = bpf_landlock_is_valid_access, +}; + +const struct bpf_prog_ops landlock_prog_ops = {}; diff --git a/security/landlock/common.h b/security/landlock/common.h new file mode 100644 index 000000000000..0234c4bc4acd --- /dev/null +++ b/security/landlock/common.h @@ -0,0 +1,30 @@ +/* SPDX-License-Identifier: GPL-2.0-only */ +/* + * Landlock LSM - private headers + * + * Copyright © 2016-2019 Mickaël Salaün + * Copyright © 2018-2019 ANSSI + */ + +#ifndef _SECURITY_LANDLOCK_COMMON_H +#define _SECURITY_LANDLOCK_COMMON_H + +#include +#include + +enum landlock_hook_type { + LANDLOCK_HOOK_PTRACE = 1, +}; + +static inline enum landlock_hook_type get_hook_type(const struct bpf_prog *prog) +{ + switch (prog->expected_attach_type) { + case BPF_LANDLOCK_PTRACE: + return LANDLOCK_HOOK_PTRACE; + default: + WARN_ON(1); + return BPF_LANDLOCK_PTRACE; + } +} + +#endif /* _SECURITY_LANDLOCK_COMMON_H */