[PATCH v2 1/1] NAX LSM: Add initial support support
THOBY Simon
Simon.THOBY at viveris.fr
Tue Aug 17 08:47:53 UTC 2021
Hi Igor,
First a side-note on the patch: you didn't send it to the same lists as the v1:
you only sent it to linux-integrity but not linux-security-module and you didn't
CC Mimi Zohar either. I added them in the loop (I guess it makes sense to submit a
LSM to the linux-security-module, and I assumed this was probably an
omission/manipulation error on you part).
On 8/16/21 8:45 PM, Igor Zhbanov wrote:
> NAX (No Anonymous Execution) is a Linux Security Module that extends DAC
> by making impossible to make anonymous and modified pages executable for
> privileged processes.
>
> The module intercepts anonymous executable pages created with mmap() and
> mprotect() system calls.
>
> This module will log violations (in non-quiet mode), and it can also
> block the action or kill the offending process, depending on the enabled
> settings.
Consider using imperative form here. Something like:
"Intercept anonymous executable pages created with the mmap() and
protect() system calls. Log any violation, and either block the action or
kill the offending process, depending on the enabled settings."
(Per Documentation/process/submitting-patches.rst:
«Describe your changes in imperative mood, e.g. "make xyzzy do frotz"
instead of "[This patch] makes xyzzy do frotz" or "[I] changed xyzzy
to do frotz", as if you are giving orders to the codebase to change
its behaviour.»)
>
> See Documentation/admin-guide/LSM/NAX.rst.
>
> Signed-off-by: Igor Zhbanov <izh1979 at gmail.com>
> ---
> Documentation/admin-guide/LSM/NAX.rst | 65 +++
> Documentation/admin-guide/LSM/index.rst | 1 +
> .../admin-guide/kernel-parameters.rst | 1 +
> .../admin-guide/kernel-parameters.txt | 23 +
> security/Kconfig | 11 +-
> security/Makefile | 2 +
> security/nax/Kconfig | 115 +++++
> security/nax/Makefile | 4 +
> security/nax/nax-lsm.c | 461 ++++++++++++++++++
> 9 files changed, 678 insertions(+), 5 deletions(-)
> create mode 100644 Documentation/admin-guide/LSM/NAX.rst
> create mode 100644 security/nax/Kconfig
> create mode 100644 security/nax/Makefile
> create mode 100644 security/nax/nax-lsm.c
>
> diff --git a/Documentation/admin-guide/LSM/NAX.rst b/Documentation/admin-guide/LSM/NAX.rst
> new file mode 100644
> index 000000000000..35c1fc89b970
> --- /dev/null
> +++ b/Documentation/admin-guide/LSM/NAX.rst
> @@ -0,0 +1,65 @@
> +=======
> +NAX LSM
> +=======
> +
> +:Author: Igor Zhbanov
> +
> +NAX (No Anonymous Execution) is a Linux Security Module that extends DAC
> +by making impossible to make anonymous and modified pages executable for
> +processes. The module intercepts anonymous executable pages created with
> +mmap() and mprotect() system calls.
> +
> +To select it at boot time, specify ``security=nax`` (though this will
> +disable any other LSM).
Maybe just write it as "To select it at boot time, add 'nax' to the 'security' kernel parameter"?
> +
> +The following sysctl parameters are available:
> +
> +* ``kernel.nax.check_all``:
> + - 0: Check all processes.
> + - 1: Check only privileged processes. The privileged process is a process
> + for which any of the following is true:
> + - ``uid == 0``
> + - ``euid == 0``
> + - ``suid == 0``
> + - ``cap_effective`` has any capability except for the ones allowed
> + in ``kernel.nax.allowed_caps``
> + - ``cap_permitted`` has any capability except for the ones allowed
> + in ``kernel.nax.allowed_caps``
> +
> + Checking of uid/euid/suid is important because a process may call seteuid(0)
> + to gain privileges (if SECURE_NO_SETUID_FIXUP secure bit is not set).
> +
> +* ``kernel.nax.allowed_caps``:
> +
> + Hexadecimal number representing the set of capabilities a non-root
> + process can possess without being considered "privileged" by NAX LSM.
Maybe you could give a concrete example to help users understand what
this is supposed to look like in practice and how to compute it.
> +
> +* ``kernel.nax.mode``:
> +
> + - 0: Only log errors (when enabled by ``kernel.nax.quiet``) (default mode)
> + - 1: Forbid unsafe pages mappings (and log when enabled)
> + - 2: Kill the violating process (and log when enabled)
> +
> +* ``kernel.nax.quiet``:
> +
> + - 0: Log violations (default)
> + - 1: Be quiet
> +
> +* ``kernel.nax.locked``:
> +
> + - 0: Changing of the module's sysctl parameters is allowed
> + - 1: Further changing of the module's sysctl parameters is forbidden
> +
> + Setting this parameter to ``1`` after initial setup during the system boot
> + will prevent the module disabling at the later time.
> +
> +There are matching kernel command-line parameters (with the same values):
> +
> +- ``nax_allowed_caps``
> +- ``nax_check_all``
> +- ``nax_mode``
> +- ``nax_quiet``
> +- ``nax_locked``
> +
> +The ``nax_locked`` command-line parameter must be specified last to avoid
> +premature setting locking.
> diff --git a/Documentation/admin-guide/LSM/index.rst b/Documentation/admin-guide/LSM/index.rst
> index a6ba95fbaa9f..e9df7fc9a461 100644
> --- a/Documentation/admin-guide/LSM/index.rst
> +++ b/Documentation/admin-guide/LSM/index.rst
> @@ -42,6 +42,7 @@ subdirectories.
>
> apparmor
> LoadPin
> + NAX
> SELinux
> Smack
> tomoyo
> diff --git a/Documentation/admin-guide/kernel-parameters.rst b/Documentation/admin-guide/kernel-parameters.rst
> index 3996b54158bf..6d1a51612180 100644
> --- a/Documentation/admin-guide/kernel-parameters.rst
> +++ b/Documentation/admin-guide/kernel-parameters.rst
> @@ -131,6 +131,7 @@ parameter is applicable::
> MOUSE Appropriate mouse support is enabled.
> MSI Message Signaled Interrupts (PCI).
> MTD MTD (Memory Technology Device) support is enabled.
> + NAX NAX support is enabled.
> NET Appropriate network support is enabled.
> NUMA NUMA support is enabled.
> NFS Appropriate NFS support is enabled.
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 2991f6e692bd..a446d7bc05cc 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -3062,6 +3062,29 @@
>
> n2= [NET] SDL Inc. RISCom/N2 synchronous serial card
>
> + nax_allowed_caps= [NAX] Hexadecimal number representing the set of
> + capabilities a non-root process can possess without
> + being considered "privileged" by NAX LSM.
Same remark as above: maybe an example would be helpful.
> +
> + nax_check_all= [NAX] NAX LSM processes checking mode:
> + 0 - Check only privileged processes (default).
> + 1 - Check all processes.
> +
> + nax_locked= [NAX] NAX LSM settings' locking mode:
> + 0 - Changing NAX sysctl parameters is allowed.
> + 1 - Changing NAX sysctl parameters is forbidded until
"forbidden"
> + reboot.
> +
> + nax_mode= [NAX] NAX LSM violation reaction mode:
> + 0 - Only log errors (when not in quiet mode; default).
> + 1 - Forbid unsafe pages mappings (and log when
> + enabled).
> + 2 - Kill the violating process (and log when enabled).
> +
> + nax_quiet= [NAX] NAX LSM log verbosity:
> + 0 - Log messages to syslog.
> + 1 - Be quiet.
> +
> netdev= [NET] Network devices parameters
> Format: <irq>,<io>,<mem_start>,<mem_end>,<name>
> Note that mem_start is often overloaded to mean
> diff --git a/security/Kconfig b/security/Kconfig
> index 0ced7fd33e4d..771419647ae1 100644
> --- a/security/Kconfig
> +++ b/security/Kconfig
> @@ -239,6 +239,7 @@ source "security/yama/Kconfig"
> source "security/safesetid/Kconfig"
> source "security/lockdown/Kconfig"
> source "security/landlock/Kconfig"
> +source "security/nax/Kconfig"
>
> source "security/integrity/Kconfig"
>
> @@ -278,11 +279,11 @@ endchoice
>
> config LSM
> string "Ordered list of enabled LSMs"
> - default "landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
> - default "landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
> - default "landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
> - default "landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
> - default "landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
> + default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,smack,selinux,tomoyo,apparmor,bpf" if DEFAULT_SECURITY_SMACK
> + default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,apparmor,selinux,smack,tomoyo,bpf" if DEFAULT_SECURITY_APPARMOR
> + default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,tomoyo,bpf" if DEFAULT_SECURITY_TOMOYO
> + default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,bpf" if DEFAULT_SECURITY_DAC
> + default "nax,landlock,lockdown,yama,loadpin,safesetid,integrity,selinux,smack,tomoyo,apparmor,bpf"
> help
> A comma-separated list of LSMs, in initialization order.
> Any LSMs left off this list will be ignored. This can be
> diff --git a/security/Makefile b/security/Makefile
> index 47e432900e24..5c261bbf4659 100644
> --- a/security/Makefile
> +++ b/security/Makefile
> @@ -14,6 +14,7 @@ subdir-$(CONFIG_SECURITY_SAFESETID) += safesetid
> subdir-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown
> subdir-$(CONFIG_BPF_LSM) += bpf
> subdir-$(CONFIG_SECURITY_LANDLOCK) += landlock
> +subdir-$(CONFIG_SECURITY_NAX) += nax
>
> # always enable default capabilities
> obj-y += commoncap.o
> @@ -34,6 +35,7 @@ obj-$(CONFIG_SECURITY_LOCKDOWN_LSM) += lockdown/
> obj-$(CONFIG_CGROUPS) += device_cgroup.o
> obj-$(CONFIG_BPF_LSM) += bpf/
> obj-$(CONFIG_SECURITY_LANDLOCK) += landlock/
> +obj-$(CONFIG_SECURITY_NAX) += nax/
>
> # Object integrity file lists
> subdir-$(CONFIG_INTEGRITY) += integrity
> diff --git a/security/nax/Kconfig b/security/nax/Kconfig
> new file mode 100644
> index 000000000000..a0d22f53a9c2
> --- /dev/null
> +++ b/security/nax/Kconfig
> @@ -0,0 +1,115 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config SECURITY_NAX
> + bool "NAX support"
> + depends on SECURITY
> + default n
> + help
> + This selects NAX (No Anonymous Execution), which extends DAC
> + support with additional system-wide security settings beyond
> + regular Linux discretionary access controls. Currently available
> + is restriction to make anonymous and modified pages executable.
The last sentence could probably be rephrased as "Currently, the only
available behavior is restricting the execution of anonymous and modified
pages".
> +
> + The module can restrict either privileged or all processes,
> + depending on the settings. It is possible to convigure action,
> + performed when the viloation is detected (log, log + block,
A couple of typos here: "configure" and "violation".
> + log + kill).
> +
> + Like capabilities, this security module stacks with other LSMs.
I'm not quite sure this information is needed, especially as I understand the
longterm goal is to have all LSMs support stacking. I think this notice
should only be added when LSM stacking is *not* supported by the considered
LSM.
> +
> + Further information can be found in
> + Documentation/admin-guide/LSM/NAX.rst.
> +
> + If you are unsure how to answer this question, answer N.
> +
> +choice
> + prompt "NAX violation action mode"
> + default SECURITY_NAX_MODE_LOG
> + depends on SECURITY_NAX
> + help
> + Select the NAX violation action mode.
> +
> + In the default permissive mode the violations are only logged
> + (if logging is not suppressed). In the enforcing mode the violations
> + are prohibited. And in the kill mode the process is terminated.
> +
> + The value can be overridden at boot time with the kernel command-line
> + parameter "nax_mode=" (0, 1, 2) or "kernel.nax.mode=" (0, 1, 2)
> + sysctl parameter (if the settings are not locked).
> +
> + config SECURITY_NAX_MODE_LOG
> + bool "Permissive mode"
> + help
> + In this mode violations are only logged (if logging is not
> + suppressed by the "kernel.nax.quiet" parameter). The
> + violating system call will not be prohibited.
> + config SECURITY_NAX_MODE_ENFORCING
> + bool "Enforcing mode"
> + help
> + In this mode violations are prohibited and logged (if
> + logging is not suppressed by the "kernel.nax.quiet"
> + parameter). The violating system call will return -EACCES
> + error.
> + config SECURITY_NAX_MODE_KILL
> + bool "Kill mode"
> + help
> + In this mode the violating process is terminated on the
> + first violation system call. The violation event is logged
> + (if logging is not suppressed by the "kernel.nax.quiet"
> + parameter).
> +endchoice
> +
> +config SECURITY_NAX_MODE
> + int
> + depends on SECURITY_NAX
> + default 0 if SECURITY_NAX_MODE_LOG
> + default 1 if SECURITY_NAX_MODE_ENFORCING
> + default 2 if SECURITY_NAX_MODE_KILL
> +
> +config SECURITY_NAX_CHECK_ALL
> + bool "Check all processes"
> + depends on SECURITY_NAX
> + help
> + If selected, NAX will check all processes. If not selected, NAX
> + will check only privileged processes (which is determined either
> + by having zero uid, euid, suid or fsuid; or by possessing
> + capabilities outside of allowed set).
> +
> + The value can also be overridden at boot time with the kernel
> + command-line parameter "nax_check_all=" (0, 1) or
> + "kernel.nax_check_all=" (0, 1) sysctl parameter (if the settings
> + are not locked).
> +
> +config SECURITY_NAX_ALLOWED_CAPS
> + hex "Process capabilities ignored by NAX"
> + default 0x0
> + range 0x0 0xffffffffffff
> + depends on SECURITY_NAX
> + help
> + Hexadecimal number representing the set of capabilities
> + a non-root process can possess without being considered
> + "privileged" by NAX LSM.
> +
> + The value can be overridden at boot time with the command-line
> + parameter "nax_allowed_caps=" or "kernel.nax.allowed_caps=" sysctl
> + parameter (if the settings are not locked).
> +
> +config SECURITY_NAX_QUIET
> + bool "Silence NAX messages"
> + depends on SECURITY_NAX
> + help
> + If selected, NAX will not print violations.
> +
> + The value can be overridden at boot with the command-line
> + parameter "nax_quiet=" (0, 1) or "kernel.nax_quiet=" (0, 1) sysctl
> + parameter (if the settings are not locked).
> +
> +config SECURITY_NAX_LOCKED
> + bool "Lock NAX settings"
> + depends on SECURITY_NAX
> + help
> + If selected, it will not be possible to change any NAX LSM
> + settings via sysctl or the kernel command line.
Maybe the imperative form here too would be clearer:
"Prevent any update to the settings of the NAX LSM. This applies to both sysctl writes and the
kernel command line."
> +
> + If not selected, it can be enabled at boot time with the kernel
> + command-line parameter "nax_locked=1" or "kernel.nax_locked=1"
> + sysctl parameter (if the settings are not locked).
> diff --git a/security/nax/Makefile b/security/nax/Makefile
> new file mode 100644
> index 000000000000..9c3372210c77
> --- /dev/null
> +++ b/security/nax/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_SECURITY_NAX) := nax.o
> +
> +nax-y := nax-lsm.o
> diff --git a/security/nax/nax-lsm.c b/security/nax/nax-lsm.c
> new file mode 100644
> index 000000000000..b8cd7b528ba2
> --- /dev/null
> +++ b/security/nax/nax-lsm.c
> @@ -0,0 +1,461 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2016-2021 Open Mobile Platform LLC.
> + *
> + * Written by: Igor Zhbanov <i.zhbanov at omp.ru, izh1979 at gmail.com>
> + *
> + * NAX (No Anonymous Execution) Linux Security Module
> + * This module prevents execution of the code in anonymous or modified pages.
> + * For more details, see Documentation/admin-guide/LSM/NAX.rst and
> + * Documentation/admin-guide/kernel-parameters.rst
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2, as
> + * published by the Free Software Foundation.
> + */
> +
> +#define pr_fmt(fmt) "NAX: " fmt
> +
> +#include <linux/capability.h>
> +#include <linux/cred.h>
> +#include <linux/ctype.h>
> +#include <linux/lsm_hooks.h>
> +#include <linux/mman.h>
> +#include <linux/rcupdate.h>
> +#include <linux/sched.h>
> +#include <linux/securebits.h>
> +#include <linux/security.h>
> +#include <linux/sysctl.h>
> +#include <linux/uidgid.h>
> +
> +#define NAX_MODE_PERMISSIVE 0 /* Log only */
> +#define NAX_MODE_ENFORCING 1 /* Enforce and log */
> +#define NAX_MODE_KILL 2 /* Kill process and log */
> +
> +static int mode = CONFIG_SECURITY_NAX_MODE,
> + quiet = IS_ENABLED(CONFIG_SECURITY_NAX_QUIET),
> + locked = IS_ENABLED(CONFIG_SECURITY_NAX_LOCKED),
> + check_all = IS_ENABLED(CONFIG_SECURITY_NAX_CHECK_ALL);
> +
> +#define ALLOWED_CAPS_HEX_LEN (_KERNEL_CAPABILITY_U32S * 8)
> +
> +static char allowed_caps_hex[ALLOWED_CAPS_HEX_LEN + 1];
> +static kernel_cap_t __rcu *allowed_caps;
> +
> +static bool
> +is_interesting_process(void)
> +{
> + bool ret = false;
> + const struct cred *cred;
> + kuid_t root_uid;
> + kernel_cap_t *caps;
> +
> + if (check_all)
> + return true;
> +
> + cred = current_cred();
> + root_uid = make_kuid(cred->user_ns, 0);
> +
> + rcu_read_lock();
> + caps = rcu_dereference(allowed_caps);
> + /*
> + * We count a process as interesting if it any of its uid/euid/suid
> + * is zero (because it may call seteuid(0) to gain privileges) or
> + * it has any not allowed capability (even in a user namespace)
> + */
> + if ((!issecure(SECURE_NO_SETUID_FIXUP) &&
> + (uid_eq(cred->uid, root_uid) ||
> + uid_eq(cred->euid, root_uid) ||
> + uid_eq(cred->suid, root_uid))) ||
> + (!cap_issubset(cred->cap_effective, *caps)) ||
> + (!cap_issubset(cred->cap_permitted, *caps)))
> + ret = true;
> +
> + rcu_read_unlock();
> + return ret;
> +}
> +
> +static void
> +log_warn(const char *reason)
> +{
> + if (quiet)
> + return;
> +
> + pr_warn_ratelimited("%s: pid=%d, uid=%u, comm=\"%s\"\n",
> + reason, current->pid,
> + from_kuid(&init_user_ns, current_cred()->uid),
> + current->comm);
> +}
> +
> +static void
> +kill_current_task(void)
> +{
> + pr_warn("Killing pid=%d, uid=%u, comm=\"%s\"\n",
> + current->pid, from_kuid(&init_user_ns, current_cred()->uid),
> + current->comm);
> + force_sig(SIGKILL);
> +}
> +
> +static int
> +nax_mmap_file(struct file *file, unsigned long reqprot,
> + unsigned long prot, unsigned long flags)
> +{
> + int ret = 0;
> +
> + if (mode == NAX_MODE_PERMISSIVE && quiet)
> + return 0; /* Skip further checks in this case */
> +
> + if (!(prot & PROT_EXEC)) /* Not executable memory */
> + return 0;
> +
> + if (!is_interesting_process())
> + return 0; /* Not interesting processes can do anything */
> +
> + if (!file) { /* Anonymous executable memory */
> + log_warn("MMAP_ANON_EXEC");
> + ret = -EACCES;
> + } else if (prot & PROT_WRITE) { /* Mapping file RWX */
> + log_warn("MMAP_FILE_WRITE_EXEC");
> + ret = -EACCES;
> + }
> +
> + if (ret && mode == NAX_MODE_KILL)
> + kill_current_task();
> +
> + return (mode != NAX_MODE_PERMISSIVE) ? ret : 0;
> +}
> +
> +static int
> +nax_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
> + unsigned long prot)
> +{
> + int ret = 0;
> +
> + if (mode == NAX_MODE_PERMISSIVE && quiet)
> + return 0; /* Skip further checks in this case */
> +
> + if (!(prot & PROT_EXEC)) /* Not executable memory */
> + return 0;
> +
> + if (!is_interesting_process())
> + return 0; /* Not interesting processes can do anything */
> +
> + if (!(vma->vm_flags & VM_EXEC)) {
> + if (vma->vm_start >= vma->vm_mm->start_brk &&
> + vma->vm_end <= vma->vm_mm->brk) {
> + log_warn("MPROTECT_EXEC_HEAP");
> + ret = -EACCES;
> + } else if (!vma->vm_file &&
> + ((vma->vm_start <= vma->vm_mm->start_stack &&
> + vma->vm_end >= vma->vm_mm->start_stack) ||
> + vma_is_stack_for_current(vma))) {
> + log_warn("MPROTECT_EXEC_STACK");
> + ret = -EACCES;
> + } else if (vma->vm_file && vma->anon_vma) {
> + /*
> + * We are making executable a file mapping that has
> + * had some COW done. Since pages might have been
> + * written, check ability to execute the possibly
> + * modified content. This typically should only
> + * occur for text relocations.
> + */
> + log_warn("MPROTECT_EXEC_MODIFIED");
> + ret = -EACCES;
> + }
> + }
> +
> + if (!vma->vm_file) { /* Anonymous executable memory */
> + log_warn("MPROTECT_ANON_EXEC");
> + ret = -EACCES;
> + } else if (prot & PROT_WRITE) { /* Remapping file as RWX */
> + log_warn("MPROTECT_FILE_WRITE_EXEC");
> + ret = -EACCES;
> + }
Maybe this if/else clause should be wrapped in an "if (!ret) {}" block.
Because I currently fear there are cases where this would log two errors
for the same file, like MPROTECT_EXEC_HEAP and then MPROTECT_ANON_EXEC.
> +
> + if (ret && mode == NAX_MODE_KILL)
> + kill_current_task();
> +
> + return (mode != NAX_MODE_PERMISSIVE) ? ret : 0;
> +}
> +
> +static struct security_hook_list nax_hooks[] __lsm_ro_after_init = {
> + LSM_HOOK_INIT(mmap_file, nax_mmap_file),
> + LSM_HOOK_INIT(file_mprotect, nax_file_mprotect),
> +};
> +
> +static void
> +update_allowed_caps(kernel_cap_t *caps)
> +{
> + *caps = cap_intersect(*caps, CAP_FULL_SET); /* Drop unsupported */
> + rcu_assign_pointer(allowed_caps, caps);
> + synchronize_rcu();
I'm happy to see this work to fix possible concurrency issues, and it seems perfectly
fine in this regard for me.
One remaining issue is that I think this leaks memory: we keep on kmalloc()-ing
memory in parse_and_set_caps and we never kfree it.
I'm terrible at RCU, but I think something like that could work:
+ kernel_cap_t *old = rcu_access_pointer(allowed_caps);
+ *caps = cap_intersect(*caps, CAP_FULL_SET); /* Drop unsupported */
+ rcu_assign_pointer(allowed_caps, caps);
+ synchronize_rcu();
+ kfree(old);
> +}
> +
> +static int
> +set_default_allowed_caps(void)
> +{
> + size_t i;
> + kernel_cap_t *caps;
> +
> + caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> + if (!caps)
> + return -ENOMEM;
> +
> + CAP_FOR_EACH_U32(i)
> + caps->cap[i] = (CONFIG_CONFIG_SECURITY_NAX_ALLOWED_CAPS >> (i * 8)) &
> + 0xff;
> +
> + update_allowed_caps(caps);
> + return 0;
> +}
> +
> +static int
> +parse_and_set_caps(char *str)
> +{
> + size_t len, i;
> + kernel_cap_t *caps;
> +
> + /* len is guaranteed not to exceed ALLOWED_CAPS_HEX_LEN */
> + len = strlen(str);
> + for (i = 0; i < len; i++)
> + if (!isxdigit(str[i]))
> + return -EINVAL;
> +
> + caps = kmalloc(sizeof(*caps), GFP_KERNEL);
> + if (!caps)
> + return -ENOMEM;
> +
> + CAP_FOR_EACH_U32(i) {
> + unsigned long l;
> +
> + if (kstrtoul(str + (len >= 8 ? len - 8 : 0), 16, &l))
> + return -EINVAL;
> +
> + caps->cap[i] = l;
> + if (len < 8)
> + break;
> +
> + len -= 8;
> + str[len] = '\0';
> + }
> +
> + update_allowed_caps(caps);
> + return 0;
> +}
> +
> +#ifdef CONFIG_SYSCTL
> +
> +static int
> +nax_dointvec_minmax(struct ctl_table *table, int write,
> + void *buffer, size_t *lenp, loff_t *ppos)
> +{
> + if (write && (!capable(CAP_SYS_ADMIN) || locked))
> + return -EPERM;
> +
> + return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
> +}
> +
> +static int
> +nax_dostring(struct ctl_table *table, int write, void *buffer,
> + size_t *lenp, loff_t *ppos)
> +{
> + int ret;
> +
> + if (write) { /* A user is setting the allowed capabilities */
> + int error;
> + char *buf = (char *)buffer;
> + size_t len = *lenp;
> +
> + if (!capable(CAP_SYS_ADMIN) || locked)
> + return -EPERM;
> +
> + /* Do not allow trailing garbage or excessive length */
> + if (len == ALLOWED_CAPS_HEX_LEN + 1) {
> + if (buf[--len] != '\n')
> + return -EINVAL;
> + } else if (len > ALLOWED_CAPS_HEX_LEN || len <= 0) {
> + return -EINVAL;
> + }
> +
> + error = proc_dostring(table, write, buffer, lenp, ppos);
> + if (error)
> + return error;
> +
> + ret = parse_and_set_caps(allowed_caps_hex);
> + } else { /* A user is getting the allowed capabilities */
> + unsigned int i;
> + kernel_cap_t *caps;
> +
> + rcu_read_lock();
> + caps = rcu_dereference(allowed_caps);
> + CAP_FOR_EACH_U32(i)
> + snprintf(allowed_caps_hex + i * 8, 9, "%08x",
> + caps->cap[CAP_LAST_U32 - i]);
> +
> + rcu_read_unlock();
> + ret = proc_dostring(table, write, buffer, lenp, ppos);
> + }
> +
> + return ret;
> +}
> +
> +struct ctl_path nax_sysctl_path[] = {
> + { .procname = "kernel" },
> + { .procname = "nax" },
> + { }
> +};
> +
> +static int max_mode = NAX_MODE_KILL;
> +
> +static struct ctl_table nax_sysctl_table[] = {
> + {
> + .procname = "allowed_caps",
> + .data = allowed_caps_hex,
> + .maxlen = ALLOWED_CAPS_HEX_LEN + 1,
> + .mode = 0644,
> + .proc_handler = nax_dostring,
> + }, {
> + .procname = "check_all",
> + .data = &check_all,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = nax_dointvec_minmax,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = SYSCTL_ONE,
> + }, {
> + .procname = "locked",
> + .data = &locked,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = nax_dointvec_minmax,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = SYSCTL_ONE,
> + }, {
> + .procname = "mode",
> + .data = &mode,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = nax_dointvec_minmax,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = &max_mode,
> + }, {
> + .procname = "quiet",
> + .data = &quiet,
> + .maxlen = sizeof(int),
> + .mode = 0644,
> + .proc_handler = nax_dointvec_minmax,
> + .extra1 = SYSCTL_ZERO,
> + .extra2 = SYSCTL_ONE,
> + },
> + { }
> +};
> +
> +static void __init
> +nax_init_sysctl(void)
> +{
> + if (!register_sysctl_paths(nax_sysctl_path, nax_sysctl_table))
> + panic("NAX: sysctl registration failed.\n");
> +}
> +
> +#else /* !CONFIG_SYSCTL */
> +
> +static inline void
> +nax_init_sysctl(void)
> +{
> +
> +}
> +
> +#endif /* !CONFIG_SYSCTL */
> +
> +static int __init setup_allowed_caps(char *str)
> +{
> + if (locked)
> + return 1;
> +
> + /* Do not allow trailing garbage or excessive length */
> + if (strlen(str) > ALLOWED_CAPS_HEX_LEN) {
> + pr_err("Invalid 'nax_allowed_caps' parameter value (%s)\n",
> + str);
> + return 1;
> + }
> +
> + strscpy(allowed_caps_hex, str, sizeof(allowed_caps_hex));
> + if (parse_and_set_caps(allowed_caps_hex))
> + pr_err("Invalid 'nax_allowed_caps' parameter value (%s)\n",
> + str);
> +
> + return 1;
> +}
> +__setup("nax_allowed_caps=", setup_allowed_caps);
> +
> +static int __init setup_check_all(char *str)
> +{
> + unsigned long val;
> +
> + if (!locked && !kstrtoul(str, 0, &val))
> + check_all = val ? 1 : 0;
> +
> + return 1;
> +}
> +__setup("nax_quiet=", setup_check_all);
> +
> +static int __init setup_locked(char *str)
> +{
> + unsigned long val;
> +
> + if (!locked && !kstrtoul(str, 0, &val))
> + locked = val ? 1 : 0;
> +
> + return 1;
> +}
> +__setup("nax_locked=", setup_locked);
> +
> +static int __init setup_mode(char *str)
> +{
> + unsigned long val;
> +
> + if (!locked && !kstrtoul(str, 0, &val)) {
> + if (val > max_mode) {
> + pr_err("Invalid 'nax_mode' parameter value (%s)\n",
> + str);
> + val = max_mode;
> + }
> +
> + mode = val;
> + }
> +
> + return 1;
> +}
> +__setup("nax_mode=", setup_mode);
> +
> +static int __init setup_quiet(char *str)
> +{
> + unsigned long val;
> +
> + if (!locked && !kstrtoul(str, 0, &val))
> + quiet = val ? 1 : 0;
> +
> + return 1;
> +}
> +__setup("nax_quiet=", setup_quiet);
> +
> +static __init int
> +nax_init(void)
> +{
> + int rc;
> +
> + pr_info("Starting.\n");
> + rc = set_default_allowed_caps();
> + if (rc < 0)
> + return rc;
> +
> + security_add_hooks(nax_hooks, ARRAY_SIZE(nax_hooks), "nax");
> + nax_init_sysctl();
> +
> + return 0;
> +}
> +
> +DEFINE_LSM(nax) = {
> + .name = "nax",
> + .init = nax_init,
> +};
>
Thanks,
Simon
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