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https://github.com/torvalds/linux
synced 2024-09-06 18:01:05 +00:00
![Eric W. Biederman](/assets/img/avatar_default.png)
This represents a change in strategy of how to handle user namespaces. Instead of tagging everything explicitly with a user namespace and bulking up all of the comparisons of uids and gids in the kernel, all uids and gids in use will have a mapping to a flat kuid and kgid spaces respectively. This allows much more of the existing logic to be preserved and in general allows for faster code. In this new and improved world we allow someone to utiliize capabilities over an inode if the inodes owner mapps into the capabilities holders user namespace and the user has capabilities in their user namespace. Which is simple and efficient. Moving the fs uid comparisons to be comparisons in a flat kuid space follows in later patches, something that is only significant if you are using user namespaces. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
441 lines
12 KiB
C
441 lines
12 KiB
C
/*
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* linux/kernel/capability.c
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*
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* Copyright (C) 1997 Andrew Main <zefram@fysh.org>
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*
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* Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
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* 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
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*/
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#include <linux/audit.h>
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#include <linux/capability.h>
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#include <linux/mm.h>
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#include <linux/export.h>
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#include <linux/security.h>
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#include <linux/syscalls.h>
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#include <linux/pid_namespace.h>
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#include <linux/user_namespace.h>
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#include <asm/uaccess.h>
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/*
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* Leveraged for setting/resetting capabilities
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*/
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const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
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EXPORT_SYMBOL(__cap_empty_set);
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int file_caps_enabled = 1;
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static int __init file_caps_disable(char *str)
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{
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file_caps_enabled = 0;
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return 1;
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}
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__setup("no_file_caps", file_caps_disable);
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/*
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* More recent versions of libcap are available from:
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*
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* http://www.kernel.org/pub/linux/libs/security/linux-privs/
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*/
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static void warn_legacy_capability_use(void)
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{
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static int warned;
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if (!warned) {
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char name[sizeof(current->comm)];
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printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
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" (legacy support in use)\n",
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get_task_comm(name, current));
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warned = 1;
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}
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}
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/*
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* Version 2 capabilities worked fine, but the linux/capability.h file
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* that accompanied their introduction encouraged their use without
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* the necessary user-space source code changes. As such, we have
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* created a version 3 with equivalent functionality to version 2, but
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* with a header change to protect legacy source code from using
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* version 2 when it wanted to use version 1. If your system has code
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* that trips the following warning, it is using version 2 specific
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* capabilities and may be doing so insecurely.
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*
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* The remedy is to either upgrade your version of libcap (to 2.10+,
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* if the application is linked against it), or recompile your
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* application with modern kernel headers and this warning will go
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* away.
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*/
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static void warn_deprecated_v2(void)
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{
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static int warned;
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if (!warned) {
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char name[sizeof(current->comm)];
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printk(KERN_INFO "warning: `%s' uses deprecated v2"
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" capabilities in a way that may be insecure.\n",
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get_task_comm(name, current));
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warned = 1;
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}
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}
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/*
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* Version check. Return the number of u32s in each capability flag
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* array, or a negative value on error.
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*/
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static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
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{
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__u32 version;
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if (get_user(version, &header->version))
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return -EFAULT;
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switch (version) {
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case _LINUX_CAPABILITY_VERSION_1:
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warn_legacy_capability_use();
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*tocopy = _LINUX_CAPABILITY_U32S_1;
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break;
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case _LINUX_CAPABILITY_VERSION_2:
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warn_deprecated_v2();
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/*
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* fall through - v3 is otherwise equivalent to v2.
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*/
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case _LINUX_CAPABILITY_VERSION_3:
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*tocopy = _LINUX_CAPABILITY_U32S_3;
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break;
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default:
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if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
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return -EFAULT;
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return -EINVAL;
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}
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return 0;
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}
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/*
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* The only thing that can change the capabilities of the current
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* process is the current process. As such, we can't be in this code
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* at the same time as we are in the process of setting capabilities
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* in this process. The net result is that we can limit our use of
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* locks to when we are reading the caps of another process.
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*/
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static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
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kernel_cap_t *pIp, kernel_cap_t *pPp)
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{
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int ret;
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if (pid && (pid != task_pid_vnr(current))) {
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struct task_struct *target;
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rcu_read_lock();
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target = find_task_by_vpid(pid);
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if (!target)
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ret = -ESRCH;
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else
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ret = security_capget(target, pEp, pIp, pPp);
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rcu_read_unlock();
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} else
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ret = security_capget(current, pEp, pIp, pPp);
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return ret;
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}
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/**
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* sys_capget - get the capabilities of a given process.
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* @header: pointer to struct that contains capability version and
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* target pid data
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* @dataptr: pointer to struct that contains the effective, permitted,
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* and inheritable capabilities that are returned
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*
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* Returns 0 on success and < 0 on error.
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*/
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SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
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{
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int ret = 0;
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pid_t pid;
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unsigned tocopy;
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kernel_cap_t pE, pI, pP;
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ret = cap_validate_magic(header, &tocopy);
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if ((dataptr == NULL) || (ret != 0))
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return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
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if (get_user(pid, &header->pid))
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return -EFAULT;
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if (pid < 0)
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return -EINVAL;
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ret = cap_get_target_pid(pid, &pE, &pI, &pP);
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if (!ret) {
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struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
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unsigned i;
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for (i = 0; i < tocopy; i++) {
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kdata[i].effective = pE.cap[i];
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kdata[i].permitted = pP.cap[i];
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kdata[i].inheritable = pI.cap[i];
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}
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/*
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* Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
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* we silently drop the upper capabilities here. This
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* has the effect of making older libcap
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* implementations implicitly drop upper capability
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* bits when they perform a: capget/modify/capset
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* sequence.
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*
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* This behavior is considered fail-safe
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* behavior. Upgrading the application to a newer
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* version of libcap will enable access to the newer
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* capabilities.
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*
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* An alternative would be to return an error here
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* (-ERANGE), but that causes legacy applications to
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* unexpectidly fail; the capget/modify/capset aborts
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* before modification is attempted and the application
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* fails.
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*/
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if (copy_to_user(dataptr, kdata, tocopy
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* sizeof(struct __user_cap_data_struct))) {
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return -EFAULT;
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}
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}
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return ret;
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}
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/**
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* sys_capset - set capabilities for a process or (*) a group of processes
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* @header: pointer to struct that contains capability version and
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* target pid data
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* @data: pointer to struct that contains the effective, permitted,
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* and inheritable capabilities
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*
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* Set capabilities for the current process only. The ability to any other
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* process(es) has been deprecated and removed.
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*
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* The restrictions on setting capabilities are specified as:
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*
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* I: any raised capabilities must be a subset of the old permitted
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* P: any raised capabilities must be a subset of the old permitted
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* E: must be set to a subset of new permitted
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*
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* Returns 0 on success and < 0 on error.
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*/
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SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
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{
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struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
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unsigned i, tocopy, copybytes;
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kernel_cap_t inheritable, permitted, effective;
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struct cred *new;
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int ret;
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pid_t pid;
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ret = cap_validate_magic(header, &tocopy);
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if (ret != 0)
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return ret;
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if (get_user(pid, &header->pid))
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return -EFAULT;
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/* may only affect current now */
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if (pid != 0 && pid != task_pid_vnr(current))
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return -EPERM;
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copybytes = tocopy * sizeof(struct __user_cap_data_struct);
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if (copybytes > sizeof(kdata))
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return -EFAULT;
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if (copy_from_user(&kdata, data, copybytes))
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return -EFAULT;
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for (i = 0; i < tocopy; i++) {
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effective.cap[i] = kdata[i].effective;
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permitted.cap[i] = kdata[i].permitted;
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inheritable.cap[i] = kdata[i].inheritable;
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}
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while (i < _KERNEL_CAPABILITY_U32S) {
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effective.cap[i] = 0;
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permitted.cap[i] = 0;
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inheritable.cap[i] = 0;
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i++;
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}
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new = prepare_creds();
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if (!new)
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return -ENOMEM;
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ret = security_capset(new, current_cred(),
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&effective, &inheritable, &permitted);
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if (ret < 0)
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goto error;
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audit_log_capset(pid, new, current_cred());
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return commit_creds(new);
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error:
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abort_creds(new);
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return ret;
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}
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/**
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* has_ns_capability - Does a task have a capability in a specific user ns
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* @t: The task in question
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* @ns: target user namespace
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* @cap: The capability to be tested for
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*
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* Return true if the specified task has the given superior capability
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* currently in effect to the specified user namespace, false if not.
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*
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* Note that this does not set PF_SUPERPRIV on the task.
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*/
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bool has_ns_capability(struct task_struct *t,
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struct user_namespace *ns, int cap)
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{
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int ret;
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rcu_read_lock();
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ret = security_capable(__task_cred(t), ns, cap);
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rcu_read_unlock();
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return (ret == 0);
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}
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/**
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* has_capability - Does a task have a capability in init_user_ns
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* @t: The task in question
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* @cap: The capability to be tested for
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*
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* Return true if the specified task has the given superior capability
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* currently in effect to the initial user namespace, false if not.
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*
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* Note that this does not set PF_SUPERPRIV on the task.
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*/
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bool has_capability(struct task_struct *t, int cap)
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{
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return has_ns_capability(t, &init_user_ns, cap);
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}
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/**
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* has_ns_capability_noaudit - Does a task have a capability (unaudited)
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* in a specific user ns.
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* @t: The task in question
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* @ns: target user namespace
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* @cap: The capability to be tested for
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*
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* Return true if the specified task has the given superior capability
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* currently in effect to the specified user namespace, false if not.
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* Do not write an audit message for the check.
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*
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* Note that this does not set PF_SUPERPRIV on the task.
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*/
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bool has_ns_capability_noaudit(struct task_struct *t,
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struct user_namespace *ns, int cap)
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{
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int ret;
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rcu_read_lock();
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ret = security_capable_noaudit(__task_cred(t), ns, cap);
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rcu_read_unlock();
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return (ret == 0);
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}
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/**
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* has_capability_noaudit - Does a task have a capability (unaudited) in the
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* initial user ns
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* @t: The task in question
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* @cap: The capability to be tested for
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*
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* Return true if the specified task has the given superior capability
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* currently in effect to init_user_ns, false if not. Don't write an
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* audit message for the check.
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*
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* Note that this does not set PF_SUPERPRIV on the task.
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*/
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bool has_capability_noaudit(struct task_struct *t, int cap)
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{
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return has_ns_capability_noaudit(t, &init_user_ns, cap);
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}
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/**
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* ns_capable - Determine if the current task has a superior capability in effect
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* @ns: The usernamespace we want the capability in
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* @cap: The capability to be tested for
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*
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* Return true if the current task has the given superior capability currently
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* available for use, false if not.
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*
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* This sets PF_SUPERPRIV on the task if the capability is available on the
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* assumption that it's about to be used.
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*/
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bool ns_capable(struct user_namespace *ns, int cap)
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{
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if (unlikely(!cap_valid(cap))) {
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printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
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BUG();
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}
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if (security_capable(current_cred(), ns, cap) == 0) {
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current->flags |= PF_SUPERPRIV;
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return true;
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}
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return false;
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}
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EXPORT_SYMBOL(ns_capable);
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/**
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* capable - Determine if the current task has a superior capability in effect
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* @cap: The capability to be tested for
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*
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* Return true if the current task has the given superior capability currently
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* available for use, false if not.
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*
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* This sets PF_SUPERPRIV on the task if the capability is available on the
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* assumption that it's about to be used.
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*/
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bool capable(int cap)
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{
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return ns_capable(&init_user_ns, cap);
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}
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EXPORT_SYMBOL(capable);
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/**
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* nsown_capable - Check superior capability to one's own user_ns
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* @cap: The capability in question
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*
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* Return true if the current task has the given superior capability
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* targeted at its own user namespace.
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*/
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bool nsown_capable(int cap)
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{
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return ns_capable(current_user_ns(), cap);
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}
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/**
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* inode_capable - Check superior capability over inode
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* @inode: The inode in question
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* @cap: The capability in question
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*
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* Return true if the current task has the given superior capability
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* targeted at it's own user namespace and that the given inode is owned
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* by the current user namespace or a child namespace.
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*
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* Currently inodes can only be owned by the initial user namespace.
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*
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*/
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bool inode_capable(const struct inode *inode, int cap)
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{
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struct user_namespace *ns = current_user_ns();
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return ns_capable(ns, cap) && (ns == &init_user_ns);
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}
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