1074 lines
31 KiB
C
1074 lines
31 KiB
C
/* Common capabilities, needed by capability.o.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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*/
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#include <linux/capability.h>
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#include <linux/audit.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/lsm_hooks.h>
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#include <linux/file.h>
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#include <linux/mm.h>
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#include <linux/mman.h>
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#include <linux/pagemap.h>
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#include <linux/swap.h>
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#include <linux/skbuff.h>
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#include <linux/netlink.h>
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#include <linux/ptrace.h>
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#include <linux/xattr.h>
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#include <linux/hugetlb.h>
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#include <linux/mount.h>
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#include <linux/sched.h>
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#include <linux/prctl.h>
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#include <linux/securebits.h>
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#include <linux/user_namespace.h>
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#include <linux/binfmts.h>
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#include <linux/personality.h>
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/*
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* If a non-root user executes a setuid-root binary in
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* !secure(SECURE_NOROOT) mode, then we raise capabilities.
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* However if fE is also set, then the intent is for only
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* the file capabilities to be applied, and the setuid-root
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* bit is left on either to change the uid (plausible) or
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* to get full privilege on a kernel without file capabilities
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* support. So in that case we do not raise capabilities.
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*
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* Warn if that happens, once per boot.
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*/
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static void warn_setuid_and_fcaps_mixed(const char *fname)
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{
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static int warned;
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if (!warned) {
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printk(KERN_INFO "warning: `%s' has both setuid-root and"
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" effective capabilities. Therefore not raising all"
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" capabilities.\n", fname);
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warned = 1;
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}
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}
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/**
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* cap_capable - Determine whether a task has a particular effective capability
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* @cred: The credentials to use
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* @ns: The user namespace in which we need the capability
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* @cap: The capability to check for
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* @audit: Whether to write an audit message or not
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*
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* Determine whether the nominated task has the specified capability amongst
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* its effective set, returning 0 if it does, -ve if it does not.
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*
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* NOTE WELL: cap_has_capability() cannot be used like the kernel's capable()
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* and has_capability() functions. That is, it has the reverse semantics:
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* cap_has_capability() returns 0 when a task has a capability, but the
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* kernel's capable() and has_capability() returns 1 for this case.
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*/
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int cap_capable(const struct cred *cred, struct user_namespace *targ_ns,
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int cap, int audit)
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{
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struct user_namespace *ns = targ_ns;
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/* See if cred has the capability in the target user namespace
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* by examining the target user namespace and all of the target
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* user namespace's parents.
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*/
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for (;;) {
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/* Do we have the necessary capabilities? */
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if (ns == cred->user_ns)
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return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
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/* Have we tried all of the parent namespaces? */
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if (ns == &init_user_ns)
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return -EPERM;
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/*
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* The owner of the user namespace in the parent of the
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* user namespace has all caps.
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*/
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if ((ns->parent == cred->user_ns) && uid_eq(ns->owner, cred->euid))
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return 0;
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/*
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* If you have a capability in a parent user ns, then you have
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* it over all children user namespaces as well.
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*/
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ns = ns->parent;
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}
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/* We never get here */
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}
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/**
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* cap_settime - Determine whether the current process may set the system clock
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* @ts: The time to set
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* @tz: The timezone to set
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*
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* Determine whether the current process may set the system clock and timezone
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* information, returning 0 if permission granted, -ve if denied.
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*/
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int cap_settime(const struct timespec64 *ts, const struct timezone *tz)
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{
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if (!capable(CAP_SYS_TIME))
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return -EPERM;
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return 0;
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}
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/**
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* cap_ptrace_access_check - Determine whether the current process may access
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* another
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* @child: The process to be accessed
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* @mode: The mode of attachment.
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*
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* If we are in the same or an ancestor user_ns and have all the target
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* task's capabilities, then ptrace access is allowed.
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* If we have the ptrace capability to the target user_ns, then ptrace
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* access is allowed.
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* Else denied.
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*
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* Determine whether a process may access another, returning 0 if permission
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* granted, -ve if denied.
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*/
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int cap_ptrace_access_check(struct task_struct *child, unsigned int mode)
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{
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int ret = 0;
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const struct cred *cred, *child_cred;
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const kernel_cap_t *caller_caps;
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rcu_read_lock();
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cred = current_cred();
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child_cred = __task_cred(child);
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if (mode & PTRACE_MODE_FSCREDS)
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caller_caps = &cred->cap_effective;
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else
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caller_caps = &cred->cap_permitted;
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if (cred->user_ns == child_cred->user_ns &&
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cap_issubset(child_cred->cap_permitted, *caller_caps))
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goto out;
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if (ns_capable(child_cred->user_ns, CAP_SYS_PTRACE))
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goto out;
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ret = -EPERM;
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out:
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rcu_read_unlock();
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return ret;
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}
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/**
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* cap_ptrace_traceme - Determine whether another process may trace the current
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* @parent: The task proposed to be the tracer
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*
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* If parent is in the same or an ancestor user_ns and has all current's
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* capabilities, then ptrace access is allowed.
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* If parent has the ptrace capability to current's user_ns, then ptrace
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* access is allowed.
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* Else denied.
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*
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* Determine whether the nominated task is permitted to trace the current
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* process, returning 0 if permission is granted, -ve if denied.
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*/
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int cap_ptrace_traceme(struct task_struct *parent)
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{
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int ret = 0;
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const struct cred *cred, *child_cred;
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rcu_read_lock();
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cred = __task_cred(parent);
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child_cred = current_cred();
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if (cred->user_ns == child_cred->user_ns &&
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cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
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goto out;
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if (has_ns_capability(parent, child_cred->user_ns, CAP_SYS_PTRACE))
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goto out;
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ret = -EPERM;
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out:
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rcu_read_unlock();
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return ret;
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}
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/**
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* cap_capget - Retrieve a task's capability sets
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* @target: The task from which to retrieve the capability sets
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* @effective: The place to record the effective set
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* @inheritable: The place to record the inheritable set
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* @permitted: The place to record the permitted set
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*
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* This function retrieves the capabilities of the nominated task and returns
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* them to the caller.
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*/
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int cap_capget(struct task_struct *target, kernel_cap_t *effective,
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kernel_cap_t *inheritable, kernel_cap_t *permitted)
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{
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const struct cred *cred;
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/* Derived from kernel/capability.c:sys_capget. */
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rcu_read_lock();
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cred = __task_cred(target);
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*effective = cred->cap_effective;
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*inheritable = cred->cap_inheritable;
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*permitted = cred->cap_permitted;
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rcu_read_unlock();
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return 0;
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}
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/*
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* Determine whether the inheritable capabilities are limited to the old
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* permitted set. Returns 1 if they are limited, 0 if they are not.
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*/
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static inline int cap_inh_is_capped(void)
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{
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/* they are so limited unless the current task has the CAP_SETPCAP
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* capability
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*/
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if (cap_capable(current_cred(), current_cred()->user_ns,
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CAP_SETPCAP, SECURITY_CAP_AUDIT) == 0)
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return 0;
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return 1;
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}
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/**
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* cap_capset - Validate and apply proposed changes to current's capabilities
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* @new: The proposed new credentials; alterations should be made here
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* @old: The current task's current credentials
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* @effective: A pointer to the proposed new effective capabilities set
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* @inheritable: A pointer to the proposed new inheritable capabilities set
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* @permitted: A pointer to the proposed new permitted capabilities set
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*
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* This function validates and applies a proposed mass change to the current
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* process's capability sets. The changes are made to the proposed new
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* credentials, and assuming no error, will be committed by the caller of LSM.
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*/
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int cap_capset(struct cred *new,
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const struct cred *old,
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const kernel_cap_t *effective,
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const kernel_cap_t *inheritable,
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const kernel_cap_t *permitted)
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{
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if (cap_inh_is_capped() &&
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!cap_issubset(*inheritable,
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cap_combine(old->cap_inheritable,
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old->cap_permitted)))
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/* incapable of using this inheritable set */
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return -EPERM;
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if (!cap_issubset(*inheritable,
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cap_combine(old->cap_inheritable,
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old->cap_bset)))
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/* no new pI capabilities outside bounding set */
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return -EPERM;
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/* verify restrictions on target's new Permitted set */
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if (!cap_issubset(*permitted, old->cap_permitted))
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return -EPERM;
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/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
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if (!cap_issubset(*effective, *permitted))
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return -EPERM;
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new->cap_effective = *effective;
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new->cap_inheritable = *inheritable;
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new->cap_permitted = *permitted;
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/*
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* Mask off ambient bits that are no longer both permitted and
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* inheritable.
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*/
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new->cap_ambient = cap_intersect(new->cap_ambient,
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cap_intersect(*permitted,
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*inheritable));
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if (WARN_ON(!cap_ambient_invariant_ok(new)))
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return -EINVAL;
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return 0;
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}
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/**
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* cap_inode_need_killpriv - Determine if inode change affects privileges
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* @dentry: The inode/dentry in being changed with change marked ATTR_KILL_PRIV
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*
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* Determine if an inode having a change applied that's marked ATTR_KILL_PRIV
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* affects the security markings on that inode, and if it is, should
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* inode_killpriv() be invoked or the change rejected?
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*
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* Returns 0 if granted; +ve if granted, but inode_killpriv() is required; and
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* -ve to deny the change.
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*/
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int cap_inode_need_killpriv(struct dentry *dentry)
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{
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struct inode *inode = d_backing_inode(dentry);
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int error;
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error = __vfs_getxattr(dentry, inode, XATTR_NAME_CAPS, NULL, 0);
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return error > 0;
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}
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/**
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* cap_inode_killpriv - Erase the security markings on an inode
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* @dentry: The inode/dentry to alter
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*
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* Erase the privilege-enhancing security markings on an inode.
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*
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* Returns 0 if successful, -ve on error.
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*/
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int cap_inode_killpriv(struct dentry *dentry)
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{
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int error;
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error = __vfs_removexattr(dentry, XATTR_NAME_CAPS);
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if (error == -EOPNOTSUPP)
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error = 0;
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return error;
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}
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/*
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* Calculate the new process capability sets from the capability sets attached
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* to a file.
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*/
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static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
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struct linux_binprm *bprm,
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bool *effective,
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bool *has_cap)
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{
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struct cred *new = bprm->cred;
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unsigned i;
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int ret = 0;
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if (caps->magic_etc & VFS_CAP_FLAGS_EFFECTIVE)
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*effective = true;
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if (caps->magic_etc & VFS_CAP_REVISION_MASK)
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*has_cap = true;
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CAP_FOR_EACH_U32(i) {
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__u32 permitted = caps->permitted.cap[i];
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__u32 inheritable = caps->inheritable.cap[i];
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/*
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* pP' = (X & fP) | (pI & fI)
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* The addition of pA' is handled later.
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*/
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new->cap_permitted.cap[i] =
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(new->cap_bset.cap[i] & permitted) |
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(new->cap_inheritable.cap[i] & inheritable);
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if (permitted & ~new->cap_permitted.cap[i])
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/* insufficient to execute correctly */
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ret = -EPERM;
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}
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/*
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* For legacy apps, with no internal support for recognizing they
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* do not have enough capabilities, we return an error if they are
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* missing some "forced" (aka file-permitted) capabilities.
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*/
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return *effective ? ret : 0;
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}
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/*
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* Extract the on-exec-apply capability sets for an executable file.
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*/
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int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps)
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{
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struct inode *inode = d_backing_inode(dentry);
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__u32 magic_etc;
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unsigned tocopy, i;
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int size;
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struct vfs_cap_data caps;
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memset(cpu_caps, 0, sizeof(struct cpu_vfs_cap_data));
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if (!inode)
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return -ENODATA;
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size = __vfs_getxattr((struct dentry *)dentry, inode,
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XATTR_NAME_CAPS, &caps, XATTR_CAPS_SZ);
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if (size == -ENODATA || size == -EOPNOTSUPP)
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/* no data, that's ok */
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return -ENODATA;
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if (size < 0)
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return size;
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if (size < sizeof(magic_etc))
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return -EINVAL;
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cpu_caps->magic_etc = magic_etc = le32_to_cpu(caps.magic_etc);
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switch (magic_etc & VFS_CAP_REVISION_MASK) {
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case VFS_CAP_REVISION_1:
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if (size != XATTR_CAPS_SZ_1)
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return -EINVAL;
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tocopy = VFS_CAP_U32_1;
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break;
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case VFS_CAP_REVISION_2:
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if (size != XATTR_CAPS_SZ_2)
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return -EINVAL;
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tocopy = VFS_CAP_U32_2;
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break;
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default:
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return -EINVAL;
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}
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CAP_FOR_EACH_U32(i) {
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if (i >= tocopy)
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break;
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cpu_caps->permitted.cap[i] = le32_to_cpu(caps.data[i].permitted);
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cpu_caps->inheritable.cap[i] = le32_to_cpu(caps.data[i].inheritable);
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}
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cpu_caps->permitted.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
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cpu_caps->inheritable.cap[CAP_LAST_U32] &= CAP_LAST_U32_VALID_MASK;
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return 0;
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}
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/*
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* Attempt to get the on-exec apply capability sets for an executable file from
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* its xattrs and, if present, apply them to the proposed credentials being
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* constructed by execve().
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*/
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static int get_file_caps(struct linux_binprm *bprm, bool *effective, bool *has_cap)
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{
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int rc = 0;
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struct cpu_vfs_cap_data vcaps;
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cap_clear(bprm->cred->cap_permitted);
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if (!file_caps_enabled)
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return 0;
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if (!mnt_may_suid(bprm->file->f_path.mnt))
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return 0;
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/*
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* This check is redundant with mnt_may_suid() but is kept to make
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* explicit that capability bits are limited to s_user_ns and its
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* descendants.
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*/
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if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns))
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return 0;
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rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
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if (rc < 0) {
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if (rc == -EINVAL)
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printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
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__func__, rc, bprm->filename);
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else if (rc == -ENODATA)
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rc = 0;
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goto out;
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}
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rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
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if (rc == -EINVAL)
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printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
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__func__, rc, bprm->filename);
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out:
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if (rc)
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cap_clear(bprm->cred->cap_permitted);
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return rc;
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}
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/**
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* cap_bprm_set_creds - Set up the proposed credentials for execve().
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* @bprm: The execution parameters, including the proposed creds
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*
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* Set up the proposed credentials for a new execution context being
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* constructed by execve(). The proposed creds in @bprm->cred is altered,
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* which won't take effect immediately. Returns 0 if successful, -ve on error.
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*/
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int cap_bprm_set_creds(struct linux_binprm *bprm)
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{
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const struct cred *old = current_cred();
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struct cred *new = bprm->cred;
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bool effective, has_cap = false, is_setid;
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int ret;
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kuid_t root_uid;
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if (WARN_ON(!cap_ambient_invariant_ok(old)))
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return -EPERM;
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effective = false;
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ret = get_file_caps(bprm, &effective, &has_cap);
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if (ret < 0)
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return ret;
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root_uid = make_kuid(new->user_ns, 0);
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if (!issecure(SECURE_NOROOT)) {
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/*
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* If the legacy file capability is set, then don't set privs
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* for a setuid root binary run by a non-root user. Do set it
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* for a root user just to cause least surprise to an admin.
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*/
|
|
if (has_cap && !uid_eq(new->uid, root_uid) && uid_eq(new->euid, root_uid)) {
|
|
warn_setuid_and_fcaps_mixed(bprm->filename);
|
|
goto skip;
|
|
}
|
|
/*
|
|
* To support inheritance of root-permissions and suid-root
|
|
* executables under compatibility mode, we override the
|
|
* capability sets for the file.
|
|
*
|
|
* If only the real uid is 0, we do not set the effective bit.
|
|
*/
|
|
if (uid_eq(new->euid, root_uid) || uid_eq(new->uid, root_uid)) {
|
|
/* pP' = (cap_bset & ~0) | (pI & ~0) */
|
|
new->cap_permitted = cap_combine(old->cap_bset,
|
|
old->cap_inheritable);
|
|
}
|
|
if (uid_eq(new->euid, root_uid))
|
|
effective = true;
|
|
}
|
|
skip:
|
|
|
|
/* if we have fs caps, clear dangerous personality flags */
|
|
if (!cap_issubset(new->cap_permitted, old->cap_permitted))
|
|
bprm->per_clear |= PER_CLEAR_ON_SETID;
|
|
|
|
|
|
/* Don't let someone trace a set[ug]id/setpcap binary with the revised
|
|
* credentials unless they have the appropriate permit.
|
|
*
|
|
* In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
|
|
*/
|
|
is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
|
|
|
|
if ((is_setid ||
|
|
!cap_issubset(new->cap_permitted, old->cap_permitted)) &&
|
|
((bprm->unsafe & ~LSM_UNSAFE_PTRACE) ||
|
|
!ptracer_capable(current, new->user_ns))) {
|
|
/* downgrade; they get no more than they had, and maybe less */
|
|
if (!ns_capable(new->user_ns, CAP_SETUID) ||
|
|
(bprm->unsafe & LSM_UNSAFE_NO_NEW_PRIVS)) {
|
|
new->euid = new->uid;
|
|
new->egid = new->gid;
|
|
}
|
|
new->cap_permitted = cap_intersect(new->cap_permitted,
|
|
old->cap_permitted);
|
|
}
|
|
|
|
new->suid = new->fsuid = new->euid;
|
|
new->sgid = new->fsgid = new->egid;
|
|
|
|
/* File caps or setid cancels ambient. */
|
|
if (has_cap || is_setid)
|
|
cap_clear(new->cap_ambient);
|
|
|
|
/*
|
|
* Now that we've computed pA', update pP' to give:
|
|
* pP' = (X & fP) | (pI & fI) | pA'
|
|
*/
|
|
new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
|
|
|
|
/*
|
|
* Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
|
|
* this is the same as pE' = (fE ? pP' : 0) | pA'.
|
|
*/
|
|
if (effective)
|
|
new->cap_effective = new->cap_permitted;
|
|
else
|
|
new->cap_effective = new->cap_ambient;
|
|
|
|
if (WARN_ON(!cap_ambient_invariant_ok(new)))
|
|
return -EPERM;
|
|
|
|
/*
|
|
* Audit candidate if current->cap_effective is set
|
|
*
|
|
* We do not bother to audit if 3 things are true:
|
|
* 1) cap_effective has all caps
|
|
* 2) we are root
|
|
* 3) root is supposed to have all caps (SECURE_NOROOT)
|
|
* Since this is just a normal root execing a process.
|
|
*
|
|
* Number 1 above might fail if you don't have a full bset, but I think
|
|
* that is interesting information to audit.
|
|
*/
|
|
if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
|
|
if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
|
|
!uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
|
|
issecure(SECURE_NOROOT)) {
|
|
ret = audit_log_bprm_fcaps(bprm, new, old);
|
|
if (ret < 0)
|
|
return ret;
|
|
}
|
|
}
|
|
|
|
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
|
|
|
|
if (WARN_ON(!cap_ambient_invariant_ok(new)))
|
|
return -EPERM;
|
|
|
|
/* Check for privilege-elevated exec. */
|
|
bprm->cap_elevated = 0;
|
|
if (is_setid) {
|
|
bprm->cap_elevated = 1;
|
|
} else if (!uid_eq(new->uid, root_uid)) {
|
|
if (effective ||
|
|
!cap_issubset(new->cap_permitted, new->cap_ambient))
|
|
bprm->cap_elevated = 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_inode_setxattr - Determine whether an xattr may be altered
|
|
* @dentry: The inode/dentry being altered
|
|
* @name: The name of the xattr to be changed
|
|
* @value: The value that the xattr will be changed to
|
|
* @size: The size of value
|
|
* @flags: The replacement flag
|
|
*
|
|
* Determine whether an xattr may be altered or set on an inode, returning 0 if
|
|
* permission is granted, -ve if denied.
|
|
*
|
|
* This is used to make sure security xattrs don't get updated or set by those
|
|
* who aren't privileged to do so.
|
|
*/
|
|
int cap_inode_setxattr(struct dentry *dentry, const char *name,
|
|
const void *value, size_t size, int flags)
|
|
{
|
|
if (!strcmp(name, XATTR_NAME_CAPS)) {
|
|
if (!capable(CAP_SETFCAP))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_inode_removexattr - Determine whether an xattr may be removed
|
|
* @dentry: The inode/dentry being altered
|
|
* @name: The name of the xattr to be changed
|
|
*
|
|
* Determine whether an xattr may be removed from an inode, returning 0 if
|
|
* permission is granted, -ve if denied.
|
|
*
|
|
* This is used to make sure security xattrs don't get removed by those who
|
|
* aren't privileged to remove them.
|
|
*/
|
|
int cap_inode_removexattr(struct dentry *dentry, const char *name)
|
|
{
|
|
if (!strcmp(name, XATTR_NAME_CAPS)) {
|
|
if (!capable(CAP_SETFCAP))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
if (!strncmp(name, XATTR_SECURITY_PREFIX,
|
|
sizeof(XATTR_SECURITY_PREFIX) - 1) &&
|
|
!capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* cap_emulate_setxuid() fixes the effective / permitted capabilities of
|
|
* a process after a call to setuid, setreuid, or setresuid.
|
|
*
|
|
* 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
|
|
* {r,e,s}uid != 0, the permitted and effective capabilities are
|
|
* cleared.
|
|
*
|
|
* 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
|
|
* capabilities of the process are cleared.
|
|
*
|
|
* 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
|
|
* capabilities are set to the permitted capabilities.
|
|
*
|
|
* fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
|
|
* never happen.
|
|
*
|
|
* -astor
|
|
*
|
|
* cevans - New behaviour, Oct '99
|
|
* A process may, via prctl(), elect to keep its capabilities when it
|
|
* calls setuid() and switches away from uid==0. Both permitted and
|
|
* effective sets will be retained.
|
|
* Without this change, it was impossible for a daemon to drop only some
|
|
* of its privilege. The call to setuid(!=0) would drop all privileges!
|
|
* Keeping uid 0 is not an option because uid 0 owns too many vital
|
|
* files..
|
|
* Thanks to Olaf Kirch and Peter Benie for spotting this.
|
|
*/
|
|
static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
|
|
{
|
|
kuid_t root_uid = make_kuid(old->user_ns, 0);
|
|
|
|
if ((uid_eq(old->uid, root_uid) ||
|
|
uid_eq(old->euid, root_uid) ||
|
|
uid_eq(old->suid, root_uid)) &&
|
|
(!uid_eq(new->uid, root_uid) &&
|
|
!uid_eq(new->euid, root_uid) &&
|
|
!uid_eq(new->suid, root_uid))) {
|
|
if (!issecure(SECURE_KEEP_CAPS)) {
|
|
cap_clear(new->cap_permitted);
|
|
cap_clear(new->cap_effective);
|
|
}
|
|
|
|
/*
|
|
* Pre-ambient programs expect setresuid to nonroot followed
|
|
* by exec to drop capabilities. We should make sure that
|
|
* this remains the case.
|
|
*/
|
|
cap_clear(new->cap_ambient);
|
|
}
|
|
if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
|
|
cap_clear(new->cap_effective);
|
|
if (!uid_eq(old->euid, root_uid) && uid_eq(new->euid, root_uid))
|
|
new->cap_effective = new->cap_permitted;
|
|
}
|
|
|
|
/**
|
|
* cap_task_fix_setuid - Fix up the results of setuid() call
|
|
* @new: The proposed credentials
|
|
* @old: The current task's current credentials
|
|
* @flags: Indications of what has changed
|
|
*
|
|
* Fix up the results of setuid() call before the credential changes are
|
|
* actually applied, returning 0 to grant the changes, -ve to deny them.
|
|
*/
|
|
int cap_task_fix_setuid(struct cred *new, const struct cred *old, int flags)
|
|
{
|
|
switch (flags) {
|
|
case LSM_SETID_RE:
|
|
case LSM_SETID_ID:
|
|
case LSM_SETID_RES:
|
|
/* juggle the capabilities to follow [RES]UID changes unless
|
|
* otherwise suppressed */
|
|
if (!issecure(SECURE_NO_SETUID_FIXUP))
|
|
cap_emulate_setxuid(new, old);
|
|
break;
|
|
|
|
case LSM_SETID_FS:
|
|
/* juggle the capabilties to follow FSUID changes, unless
|
|
* otherwise suppressed
|
|
*
|
|
* FIXME - is fsuser used for all CAP_FS_MASK capabilities?
|
|
* if not, we might be a bit too harsh here.
|
|
*/
|
|
if (!issecure(SECURE_NO_SETUID_FIXUP)) {
|
|
kuid_t root_uid = make_kuid(old->user_ns, 0);
|
|
if (uid_eq(old->fsuid, root_uid) && !uid_eq(new->fsuid, root_uid))
|
|
new->cap_effective =
|
|
cap_drop_fs_set(new->cap_effective);
|
|
|
|
if (!uid_eq(old->fsuid, root_uid) && uid_eq(new->fsuid, root_uid))
|
|
new->cap_effective =
|
|
cap_raise_fs_set(new->cap_effective,
|
|
new->cap_permitted);
|
|
}
|
|
break;
|
|
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Rationale: code calling task_setscheduler, task_setioprio, and
|
|
* task_setnice, assumes that
|
|
* . if capable(cap_sys_nice), then those actions should be allowed
|
|
* . if not capable(cap_sys_nice), but acting on your own processes,
|
|
* then those actions should be allowed
|
|
* This is insufficient now since you can call code without suid, but
|
|
* yet with increased caps.
|
|
* So we check for increased caps on the target process.
|
|
*/
|
|
static int cap_safe_nice(struct task_struct *p)
|
|
{
|
|
int is_subset, ret = 0;
|
|
|
|
rcu_read_lock();
|
|
is_subset = cap_issubset(__task_cred(p)->cap_permitted,
|
|
current_cred()->cap_permitted);
|
|
if (!is_subset && !ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
|
|
ret = -EPERM;
|
|
rcu_read_unlock();
|
|
|
|
return ret;
|
|
}
|
|
|
|
/**
|
|
* cap_task_setscheduler - Detemine if scheduler policy change is permitted
|
|
* @p: The task to affect
|
|
*
|
|
* Detemine if the requested scheduler policy change is permitted for the
|
|
* specified task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setscheduler(struct task_struct *p)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/**
|
|
* cap_task_ioprio - Detemine if I/O priority change is permitted
|
|
* @p: The task to affect
|
|
* @ioprio: The I/O priority to set
|
|
*
|
|
* Detemine if the requested I/O priority change is permitted for the specified
|
|
* task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setioprio(struct task_struct *p, int ioprio)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/**
|
|
* cap_task_ioprio - Detemine if task priority change is permitted
|
|
* @p: The task to affect
|
|
* @nice: The nice value to set
|
|
*
|
|
* Detemine if the requested task priority change is permitted for the
|
|
* specified task, returning 0 if permission is granted, -ve if denied.
|
|
*/
|
|
int cap_task_setnice(struct task_struct *p, int nice)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/*
|
|
* Implement PR_CAPBSET_DROP. Attempt to remove the specified capability from
|
|
* the current task's bounding set. Returns 0 on success, -ve on error.
|
|
*/
|
|
static int cap_prctl_drop(unsigned long cap)
|
|
{
|
|
struct cred *new;
|
|
|
|
if (!ns_capable(current_user_ns(), CAP_SETPCAP))
|
|
return -EPERM;
|
|
if (!cap_valid(cap))
|
|
return -EINVAL;
|
|
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
cap_lower(new->cap_bset, cap);
|
|
return commit_creds(new);
|
|
}
|
|
|
|
/**
|
|
* cap_task_prctl - Implement process control functions for this security module
|
|
* @option: The process control function requested
|
|
* @arg2, @arg3, @arg4, @arg5: The argument data for this function
|
|
*
|
|
* Allow process control functions (sys_prctl()) to alter capabilities; may
|
|
* also deny access to other functions not otherwise implemented here.
|
|
*
|
|
* Returns 0 or +ve on success, -ENOSYS if this function is not implemented
|
|
* here, other -ve on error. If -ENOSYS is returned, sys_prctl() and other LSM
|
|
* modules will consider performing the function.
|
|
*/
|
|
int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
|
|
unsigned long arg4, unsigned long arg5)
|
|
{
|
|
const struct cred *old = current_cred();
|
|
struct cred *new;
|
|
|
|
switch (option) {
|
|
case PR_CAPBSET_READ:
|
|
if (!cap_valid(arg2))
|
|
return -EINVAL;
|
|
return !!cap_raised(old->cap_bset, arg2);
|
|
|
|
case PR_CAPBSET_DROP:
|
|
return cap_prctl_drop(arg2);
|
|
|
|
/*
|
|
* The next four prctl's remain to assist with transitioning a
|
|
* system from legacy UID=0 based privilege (when filesystem
|
|
* capabilities are not in use) to a system using filesystem
|
|
* capabilities only - as the POSIX.1e draft intended.
|
|
*
|
|
* Note:
|
|
*
|
|
* PR_SET_SECUREBITS =
|
|
* issecure_mask(SECURE_KEEP_CAPS_LOCKED)
|
|
* | issecure_mask(SECURE_NOROOT)
|
|
* | issecure_mask(SECURE_NOROOT_LOCKED)
|
|
* | issecure_mask(SECURE_NO_SETUID_FIXUP)
|
|
* | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
|
|
*
|
|
* will ensure that the current process and all of its
|
|
* children will be locked into a pure
|
|
* capability-based-privilege environment.
|
|
*/
|
|
case PR_SET_SECUREBITS:
|
|
if ((((old->securebits & SECURE_ALL_LOCKS) >> 1)
|
|
& (old->securebits ^ arg2)) /*[1]*/
|
|
|| ((old->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
|
|
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
|
|
|| (cap_capable(current_cred(),
|
|
current_cred()->user_ns, CAP_SETPCAP,
|
|
SECURITY_CAP_AUDIT) != 0) /*[4]*/
|
|
/*
|
|
* [1] no changing of bits that are locked
|
|
* [2] no unlocking of locks
|
|
* [3] no setting of unsupported bits
|
|
* [4] doing anything requires privilege (go read about
|
|
* the "sendmail capabilities bug")
|
|
*/
|
|
)
|
|
/* cannot change a locked bit */
|
|
return -EPERM;
|
|
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
new->securebits = arg2;
|
|
return commit_creds(new);
|
|
|
|
case PR_GET_SECUREBITS:
|
|
return old->securebits;
|
|
|
|
case PR_GET_KEEPCAPS:
|
|
return !!issecure(SECURE_KEEP_CAPS);
|
|
|
|
case PR_SET_KEEPCAPS:
|
|
if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
|
|
return -EINVAL;
|
|
if (issecure(SECURE_KEEP_CAPS_LOCKED))
|
|
return -EPERM;
|
|
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
if (arg2)
|
|
new->securebits |= issecure_mask(SECURE_KEEP_CAPS);
|
|
else
|
|
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
|
|
return commit_creds(new);
|
|
|
|
case PR_CAP_AMBIENT:
|
|
if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
|
|
if (arg3 | arg4 | arg5)
|
|
return -EINVAL;
|
|
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
cap_clear(new->cap_ambient);
|
|
return commit_creds(new);
|
|
}
|
|
|
|
if (((!cap_valid(arg3)) | arg4 | arg5))
|
|
return -EINVAL;
|
|
|
|
if (arg2 == PR_CAP_AMBIENT_IS_SET) {
|
|
return !!cap_raised(current_cred()->cap_ambient, arg3);
|
|
} else if (arg2 != PR_CAP_AMBIENT_RAISE &&
|
|
arg2 != PR_CAP_AMBIENT_LOWER) {
|
|
return -EINVAL;
|
|
} else {
|
|
if (arg2 == PR_CAP_AMBIENT_RAISE &&
|
|
(!cap_raised(current_cred()->cap_permitted, arg3) ||
|
|
!cap_raised(current_cred()->cap_inheritable,
|
|
arg3) ||
|
|
issecure(SECURE_NO_CAP_AMBIENT_RAISE)))
|
|
return -EPERM;
|
|
|
|
new = prepare_creds();
|
|
if (!new)
|
|
return -ENOMEM;
|
|
if (arg2 == PR_CAP_AMBIENT_RAISE)
|
|
cap_raise(new->cap_ambient, arg3);
|
|
else
|
|
cap_lower(new->cap_ambient, arg3);
|
|
return commit_creds(new);
|
|
}
|
|
|
|
default:
|
|
/* No functionality available - continue with default */
|
|
return -ENOSYS;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* cap_vm_enough_memory - Determine whether a new virtual mapping is permitted
|
|
* @mm: The VM space in which the new mapping is to be made
|
|
* @pages: The size of the mapping
|
|
*
|
|
* Determine whether the allocation of a new virtual mapping by the current
|
|
* task is permitted, returning 1 if permission is granted, 0 if not.
|
|
*/
|
|
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
|
|
{
|
|
int cap_sys_admin = 0;
|
|
|
|
if (cap_capable(current_cred(), &init_user_ns, CAP_SYS_ADMIN,
|
|
SECURITY_CAP_NOAUDIT) == 0)
|
|
cap_sys_admin = 1;
|
|
return cap_sys_admin;
|
|
}
|
|
|
|
/*
|
|
* cap_mmap_addr - check if able to map given addr
|
|
* @addr: address attempting to be mapped
|
|
*
|
|
* If the process is attempting to map memory below dac_mmap_min_addr they need
|
|
* CAP_SYS_RAWIO. The other parameters to this function are unused by the
|
|
* capability security module. Returns 0 if this mapping should be allowed
|
|
* -EPERM if not.
|
|
*/
|
|
int cap_mmap_addr(unsigned long addr)
|
|
{
|
|
int ret = 0;
|
|
|
|
if (addr < dac_mmap_min_addr) {
|
|
ret = cap_capable(current_cred(), &init_user_ns, CAP_SYS_RAWIO,
|
|
SECURITY_CAP_AUDIT);
|
|
/* set PF_SUPERPRIV if it turns out we allow the low mmap */
|
|
if (ret == 0)
|
|
current->flags |= PF_SUPERPRIV;
|
|
}
|
|
return ret;
|
|
}
|
|
|
|
int cap_mmap_file(struct file *file, unsigned long reqprot,
|
|
unsigned long prot, unsigned long flags)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SECURITY
|
|
|
|
struct security_hook_list capability_hooks[] __lsm_ro_after_init = {
|
|
LSM_HOOK_INIT(capable, cap_capable),
|
|
LSM_HOOK_INIT(settime, cap_settime),
|
|
LSM_HOOK_INIT(ptrace_access_check, cap_ptrace_access_check),
|
|
LSM_HOOK_INIT(ptrace_traceme, cap_ptrace_traceme),
|
|
LSM_HOOK_INIT(capget, cap_capget),
|
|
LSM_HOOK_INIT(capset, cap_capset),
|
|
LSM_HOOK_INIT(bprm_set_creds, cap_bprm_set_creds),
|
|
LSM_HOOK_INIT(inode_need_killpriv, cap_inode_need_killpriv),
|
|
LSM_HOOK_INIT(inode_killpriv, cap_inode_killpriv),
|
|
LSM_HOOK_INIT(mmap_addr, cap_mmap_addr),
|
|
LSM_HOOK_INIT(mmap_file, cap_mmap_file),
|
|
LSM_HOOK_INIT(task_fix_setuid, cap_task_fix_setuid),
|
|
LSM_HOOK_INIT(task_prctl, cap_task_prctl),
|
|
LSM_HOOK_INIT(task_setscheduler, cap_task_setscheduler),
|
|
LSM_HOOK_INIT(task_setioprio, cap_task_setioprio),
|
|
LSM_HOOK_INIT(task_setnice, cap_task_setnice),
|
|
LSM_HOOK_INIT(vm_enough_memory, cap_vm_enough_memory),
|
|
};
|
|
|
|
void __init capability_add_hooks(void)
|
|
{
|
|
security_add_hooks(capability_hooks, ARRAY_SIZE(capability_hooks),
|
|
"capability");
|
|
}
|
|
|
|
#endif /* CONFIG_SECURITY */
|