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f1ef09fde1
Pull namespace updates from Eric Biederman: "There is a lot here. A lot of these changes result in subtle user visible differences in kernel behavior. I don't expect anything will care but I will revert/fix things immediately if any regressions show up. From Seth Forshee there is a continuation of the work to make the vfs ready for unpriviled mounts. We had thought the previous changes prevented the creation of files outside of s_user_ns of a filesystem, but it turns we missed the O_CREAT path. Ooops. Pavel Tikhomirov and Oleg Nesterov worked together to fix a long standing bug in the implemenation of PR_SET_CHILD_SUBREAPER where only children that are forked after the prctl are considered and not children forked before the prctl. The only known user of this prctl systemd forks all children after the prctl. So no userspace regressions will occur. Holding earlier forked children to the same rules as later forked children creates a semantic that is sane enough to allow checkpoing of processes that use this feature. There is a long delayed change by Nikolay Borisov to limit inotify instances inside a user namespace. Michael Kerrisk extends the API for files used to maniuplate namespaces with two new trivial ioctls to allow discovery of the hierachy and properties of namespaces. Konstantin Khlebnikov with the help of Al Viro adds code that when a network namespace exits purges it's sysctl entries from the dcache. As in some circumstances this could use a lot of memory. Vivek Goyal fixed a bug with stacked filesystems where the permissions on the wrong inode were being checked. I continue previous work on ptracing across exec. Allowing a file to be setuid across exec while being ptraced if the tracer has enough credentials in the user namespace, and if the process has CAP_SETUID in it's own namespace. Proc files for setuid or otherwise undumpable executables are now owned by the root in the user namespace of their mm. Allowing debugging of setuid applications in containers to work better. A bug I introduced with permission checking and automount is now fixed. The big change is to mark the mounts that the kernel initiates as a result of an automount. This allows the permission checks in sget to be safely suppressed for this kind of mount. As the permission check happened when the original filesystem was mounted. Finally a special case in the mount namespace is removed preventing unbounded chains in the mount hash table, and making the semantics simpler which benefits CRIU. The vfs fix along with related work in ima and evm I believe makes us ready to finish developing and merge fully unprivileged mounts of the fuse filesystem. The cleanups of the mount namespace makes discussing how to fix the worst case complexity of umount. The stacked filesystem fixes pave the way for adding multiple mappings for the filesystem uids so that efficient and safer containers can be implemented" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: proc/sysctl: Don't grab i_lock under sysctl_lock. vfs: Use upper filesystem inode in bprm_fill_uid() proc/sysctl: prune stale dentries during unregistering mnt: Tuck mounts under others instead of creating shadow/side mounts. prctl: propagate has_child_subreaper flag to every descendant introduce the walk_process_tree() helper nsfs: Add an ioctl() to return owner UID of a userns fs: Better permission checking for submounts exit: fix the setns() && PR_SET_CHILD_SUBREAPER interaction vfs: open() with O_CREAT should not create inodes with unknown ids nsfs: Add an ioctl() to return the namespace type proc: Better ownership of files for non-dumpable tasks in user namespaces exec: Remove LSM_UNSAFE_PTRACE_CAP exec: Test the ptracer's saved cred to see if the tracee can gain caps exec: Don't reset euid and egid when the tracee has CAP_SETUID inotify: Convert to using per-namespace limits
1102 lines
32 KiB
C
1102 lines
32 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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* Clear proposed capability sets for execve().
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*/
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static inline void bprm_clear_caps(struct linux_binprm *bprm)
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{
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cap_clear(bprm->cred->cap_permitted);
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bprm->cap_effective = false;
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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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bprm_clear_caps(bprm);
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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;
|
|
|
|
/*
|
|
* This check is redundant with mnt_may_suid() but is kept to make
|
|
* explicit that capability bits are limited to s_user_ns and its
|
|
* descendants.
|
|
*/
|
|
if (!current_in_userns(bprm->file->f_path.mnt->mnt_sb->s_user_ns))
|
|
return 0;
|
|
|
|
rc = get_vfs_caps_from_disk(bprm->file->f_path.dentry, &vcaps);
|
|
if (rc < 0) {
|
|
if (rc == -EINVAL)
|
|
printk(KERN_NOTICE "%s: get_vfs_caps_from_disk returned %d for %s\n",
|
|
__func__, rc, bprm->filename);
|
|
else if (rc == -ENODATA)
|
|
rc = 0;
|
|
goto out;
|
|
}
|
|
|
|
rc = bprm_caps_from_vfs_caps(&vcaps, bprm, effective, has_cap);
|
|
if (rc == -EINVAL)
|
|
printk(KERN_NOTICE "%s: cap_from_disk returned %d for %s\n",
|
|
__func__, rc, bprm->filename);
|
|
|
|
out:
|
|
if (rc)
|
|
bprm_clear_caps(bprm);
|
|
|
|
return rc;
|
|
}
|
|
|
|
/**
|
|
* cap_bprm_set_creds - Set up the proposed credentials for execve().
|
|
* @bprm: The execution parameters, including the proposed creds
|
|
*
|
|
* Set up the proposed credentials for a new execution context being
|
|
* constructed by execve(). The proposed creds in @bprm->cred is altered,
|
|
* which won't take effect immediately. Returns 0 if successful, -ve on error.
|
|
*/
|
|
int cap_bprm_set_creds(struct linux_binprm *bprm)
|
|
{
|
|
const struct cred *old = current_cred();
|
|
struct cred *new = bprm->cred;
|
|
bool effective, has_cap = false, is_setid;
|
|
int ret;
|
|
kuid_t root_uid;
|
|
|
|
if (WARN_ON(!cap_ambient_invariant_ok(old)))
|
|
return -EPERM;
|
|
|
|
effective = false;
|
|
ret = get_file_caps(bprm, &effective, &has_cap);
|
|
if (ret < 0)
|
|
return ret;
|
|
|
|
root_uid = make_kuid(new->user_ns, 0);
|
|
|
|
if (!issecure(SECURE_NOROOT)) {
|
|
/*
|
|
* If the legacy file capability is set, then don't set privs
|
|
* for a setuid root binary run by a non-root user. Do set it
|
|
* for a root user just to cause least surprise to an admin.
|
|
*/
|
|
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;
|
|
|
|
bprm->cap_effective = effective;
|
|
|
|
/*
|
|
* 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;
|
|
|
|
return 0;
|
|
}
|
|
|
|
/**
|
|
* cap_bprm_secureexec - Determine whether a secure execution is required
|
|
* @bprm: The execution parameters
|
|
*
|
|
* Determine whether a secure execution is required, return 1 if it is, and 0
|
|
* if it is not.
|
|
*
|
|
* The credentials have been committed by this point, and so are no longer
|
|
* available through @bprm->cred.
|
|
*/
|
|
int cap_bprm_secureexec(struct linux_binprm *bprm)
|
|
{
|
|
const struct cred *cred = current_cred();
|
|
kuid_t root_uid = make_kuid(cred->user_ns, 0);
|
|
|
|
if (!uid_eq(cred->uid, root_uid)) {
|
|
if (bprm->cap_effective)
|
|
return 1;
|
|
if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
|
|
return 1;
|
|
}
|
|
|
|
return (!uid_eq(cred->euid, cred->uid) ||
|
|
!gid_eq(cred->egid, cred->gid));
|
|
}
|
|
|
|
/**
|
|
* 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_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(bprm_secureexec, cap_bprm_secureexec),
|
|
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 */
|