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3318a386e4
While Linux doesn't honor setuid on scripts. However, it mistakenly behaves differently for file capabilities. This patch fixes that behavior by making sure that get_file_caps() begins with empty bprm->caps_*. That way when a script is loaded, its bprm->caps_* may be filled when binfmt_misc calls prepare_binprm(), but they will be cleared again when binfmt_elf calls prepare_binprm() next to read the interpreter's file capabilities. Signed-off-by: Serge Hallyn <serue@us.ibm.com> Acked-by: David Howells <dhowells@redhat.com> Acked-by: Andrew G. Morgan <morgan@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
713 lines
18 KiB
C
713 lines
18 KiB
C
/* Common capabilities, needed by capability.o and root_plug.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/module.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/security.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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int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
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{
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NETLINK_CB(skb).eff_cap = current->cap_effective;
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return 0;
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}
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int cap_netlink_recv(struct sk_buff *skb, int cap)
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{
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if (!cap_raised(NETLINK_CB(skb).eff_cap, cap))
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return -EPERM;
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return 0;
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}
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EXPORT_SYMBOL(cap_netlink_recv);
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/*
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* NOTE WELL: cap_capable() cannot be used like the kernel's capable()
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* function. That is, it has the reverse semantics: cap_capable()
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* returns 0 when a task has a capability, but the kernel's capable()
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* returns 1 for this case.
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*/
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int cap_capable (struct task_struct *tsk, int cap)
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{
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/* Derived from include/linux/sched.h:capable. */
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if (cap_raised(tsk->cap_effective, cap))
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return 0;
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return -EPERM;
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}
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int cap_settime(struct timespec *ts, 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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int cap_ptrace_may_access(struct task_struct *child, unsigned int mode)
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{
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/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
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if (cap_issubset(child->cap_permitted, current->cap_permitted))
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return 0;
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if (capable(CAP_SYS_PTRACE))
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return 0;
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return -EPERM;
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}
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int cap_ptrace_traceme(struct task_struct *parent)
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{
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/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
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if (cap_issubset(current->cap_permitted, parent->cap_permitted))
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return 0;
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if (has_capability(parent, CAP_SYS_PTRACE))
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return 0;
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return -EPERM;
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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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/* Derived from kernel/capability.c:sys_capget. */
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*effective = target->cap_effective;
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*inheritable = target->cap_inheritable;
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*permitted = target->cap_permitted;
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return 0;
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}
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#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
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static inline int cap_block_setpcap(struct task_struct *target)
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{
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/*
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* No support for remote process capability manipulation with
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* filesystem capability support.
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*/
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return (target != current);
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}
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static inline int cap_inh_is_capped(void)
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{
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/*
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* Return 1 if changes to the inheritable set are limited
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* to the old permitted set. That is, if the current task
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* does *not* possess the CAP_SETPCAP capability.
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*/
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return (cap_capable(current, CAP_SETPCAP) != 0);
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}
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static inline int cap_limit_ptraced_target(void) { return 1; }
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#else /* ie., ndef CONFIG_SECURITY_FILE_CAPABILITIES */
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static inline int cap_block_setpcap(struct task_struct *t) { return 0; }
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static inline int cap_inh_is_capped(void) { return 1; }
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static inline int cap_limit_ptraced_target(void)
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{
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return !capable(CAP_SETPCAP);
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}
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#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
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int cap_capset_check (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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if (cap_block_setpcap(target)) {
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return -EPERM;
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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(target->cap_inheritable,
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current->cap_permitted))) {
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/* incapable of using this inheritable set */
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return -EPERM;
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}
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if (!cap_issubset(*inheritable,
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cap_combine(target->cap_inheritable,
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current->cap_bset))) {
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/* no new pI capabilities outside bounding set */
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return -EPERM;
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}
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/* verify restrictions on target's new Permitted set */
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if (!cap_issubset (*permitted,
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cap_combine (target->cap_permitted,
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current->cap_permitted))) {
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return -EPERM;
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}
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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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}
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return 0;
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}
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void cap_capset_set (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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target->cap_effective = *effective;
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target->cap_inheritable = *inheritable;
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target->cap_permitted = *permitted;
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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->cap_post_exec_permitted);
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bprm->cap_effective = false;
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}
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#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
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int cap_inode_need_killpriv(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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int error;
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if (!inode->i_op || !inode->i_op->getxattr)
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return 0;
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error = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, NULL, 0);
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if (error <= 0)
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return 0;
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return 1;
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}
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int cap_inode_killpriv(struct dentry *dentry)
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{
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struct inode *inode = dentry->d_inode;
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if (!inode->i_op || !inode->i_op->removexattr)
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return 0;
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return inode->i_op->removexattr(dentry, XATTR_NAME_CAPS);
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}
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static inline int cap_from_disk(struct vfs_cap_data *caps,
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struct linux_binprm *bprm, unsigned size)
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{
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__u32 magic_etc;
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unsigned tocopy, i;
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int ret;
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if (size < sizeof(magic_etc))
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return -EINVAL;
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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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if (magic_etc & VFS_CAP_FLAGS_EFFECTIVE) {
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bprm->cap_effective = true;
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} else {
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bprm->cap_effective = false;
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}
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ret = 0;
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CAP_FOR_EACH_U32(i) {
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__u32 value_cpu;
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if (i >= tocopy) {
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/*
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* Legacy capability sets have no upper bits
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*/
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bprm->cap_post_exec_permitted.cap[i] = 0;
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continue;
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}
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/*
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* pP' = (X & fP) | (pI & fI)
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*/
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value_cpu = le32_to_cpu(caps->data[i].permitted);
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bprm->cap_post_exec_permitted.cap[i] =
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(current->cap_bset.cap[i] & value_cpu) |
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(current->cap_inheritable.cap[i] &
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le32_to_cpu(caps->data[i].inheritable));
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if (value_cpu & ~bprm->cap_post_exec_permitted.cap[i]) {
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/*
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* insufficient to execute correctly
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*/
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ret = -EPERM;
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}
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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 bprm->cap_effective ? ret : 0;
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}
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/* Locate any VFS capabilities: */
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static int get_file_caps(struct linux_binprm *bprm)
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{
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struct dentry *dentry;
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int rc = 0;
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struct vfs_cap_data vcaps;
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struct inode *inode;
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bprm_clear_caps(bprm);
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if (bprm->file->f_vfsmnt->mnt_flags & MNT_NOSUID)
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return 0;
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dentry = dget(bprm->file->f_dentry);
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inode = dentry->d_inode;
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if (!inode->i_op || !inode->i_op->getxattr)
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goto out;
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rc = inode->i_op->getxattr(dentry, XATTR_NAME_CAPS, &vcaps,
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XATTR_CAPS_SZ);
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if (rc == -ENODATA || rc == -EOPNOTSUPP) {
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/* no data, that's ok */
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rc = 0;
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goto out;
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}
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if (rc < 0)
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goto out;
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rc = cap_from_disk(&vcaps, bprm, rc);
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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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dput(dentry);
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if (rc)
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bprm_clear_caps(bprm);
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return rc;
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}
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#else
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int cap_inode_need_killpriv(struct dentry *dentry)
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{
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return 0;
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}
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int cap_inode_killpriv(struct dentry *dentry)
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{
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return 0;
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}
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static inline int get_file_caps(struct linux_binprm *bprm)
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{
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bprm_clear_caps(bprm);
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return 0;
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}
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#endif
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int cap_bprm_set_security (struct linux_binprm *bprm)
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{
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int ret;
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ret = get_file_caps(bprm);
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if (!issecure(SECURE_NOROOT)) {
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/*
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* To support inheritance of root-permissions and suid-root
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* executables under compatibility mode, we override the
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* capability sets for the file.
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*
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* If only the real uid is 0, we do not set the effective
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* bit.
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*/
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if (bprm->e_uid == 0 || current->uid == 0) {
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/* pP' = (cap_bset & ~0) | (pI & ~0) */
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bprm->cap_post_exec_permitted = cap_combine(
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current->cap_bset, current->cap_inheritable
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);
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bprm->cap_effective = (bprm->e_uid == 0);
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ret = 0;
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}
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}
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return ret;
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}
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void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
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{
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if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
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!cap_issubset(bprm->cap_post_exec_permitted,
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current->cap_permitted)) {
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set_dumpable(current->mm, suid_dumpable);
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current->pdeath_signal = 0;
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if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
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if (!capable(CAP_SETUID)) {
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bprm->e_uid = current->uid;
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bprm->e_gid = current->gid;
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}
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if (cap_limit_ptraced_target()) {
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bprm->cap_post_exec_permitted = cap_intersect(
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bprm->cap_post_exec_permitted,
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current->cap_permitted);
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}
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}
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}
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current->suid = current->euid = current->fsuid = bprm->e_uid;
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current->sgid = current->egid = current->fsgid = bprm->e_gid;
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/* For init, we want to retain the capabilities set
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* in the init_task struct. Thus we skip the usual
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* capability rules */
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if (!is_global_init(current)) {
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current->cap_permitted = bprm->cap_post_exec_permitted;
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if (bprm->cap_effective)
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current->cap_effective = bprm->cap_post_exec_permitted;
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else
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cap_clear(current->cap_effective);
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}
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/* AUD: Audit candidate if current->cap_effective is set */
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current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
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}
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int cap_bprm_secureexec (struct linux_binprm *bprm)
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{
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if (current->uid != 0) {
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if (bprm->cap_effective)
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return 1;
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if (!cap_isclear(bprm->cap_post_exec_permitted))
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return 1;
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}
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return (current->euid != current->uid ||
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current->egid != current->gid);
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}
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int cap_inode_setxattr(struct dentry *dentry, const char *name,
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const void *value, size_t size, int flags)
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{
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if (!strcmp(name, XATTR_NAME_CAPS)) {
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if (!capable(CAP_SETFCAP))
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return -EPERM;
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return 0;
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} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
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sizeof(XATTR_SECURITY_PREFIX) - 1) &&
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!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return 0;
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}
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int cap_inode_removexattr(struct dentry *dentry, const char *name)
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{
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if (!strcmp(name, XATTR_NAME_CAPS)) {
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if (!capable(CAP_SETFCAP))
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return -EPERM;
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return 0;
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} else if (!strncmp(name, XATTR_SECURITY_PREFIX,
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sizeof(XATTR_SECURITY_PREFIX) - 1) &&
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!capable(CAP_SYS_ADMIN))
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return -EPERM;
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return 0;
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}
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/* moved from kernel/sys.c. */
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/*
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* cap_emulate_setxuid() fixes the effective / permitted capabilities of
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* a process after a call to setuid, setreuid, or setresuid.
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*
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* 1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
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* {r,e,s}uid != 0, the permitted and effective capabilities are
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* cleared.
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*
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* 2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
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* capabilities of the process are cleared.
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*
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* 3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
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* capabilities are set to the permitted capabilities.
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*
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* fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should
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* never happen.
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*
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* -astor
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*
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* cevans - New behaviour, Oct '99
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* A process may, via prctl(), elect to keep its capabilities when it
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* calls setuid() and switches away from uid==0. Both permitted and
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* effective sets will be retained.
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* Without this change, it was impossible for a daemon to drop only some
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* of its privilege. The call to setuid(!=0) would drop all privileges!
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* Keeping uid 0 is not an option because uid 0 owns too many vital
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* files..
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* Thanks to Olaf Kirch and Peter Benie for spotting this.
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*/
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static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
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int old_suid)
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{
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if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
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(current->uid != 0 && current->euid != 0 && current->suid != 0) &&
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!issecure(SECURE_KEEP_CAPS)) {
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cap_clear (current->cap_permitted);
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cap_clear (current->cap_effective);
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}
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if (old_euid == 0 && current->euid != 0) {
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cap_clear (current->cap_effective);
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}
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if (old_euid != 0 && current->euid == 0) {
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current->cap_effective = current->cap_permitted;
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}
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}
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int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
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int flags)
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{
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switch (flags) {
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case LSM_SETID_RE:
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case LSM_SETID_ID:
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case LSM_SETID_RES:
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/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
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if (!issecure (SECURE_NO_SETUID_FIXUP)) {
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cap_emulate_setxuid (old_ruid, old_euid, old_suid);
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}
|
|
break;
|
|
case LSM_SETID_FS:
|
|
{
|
|
uid_t old_fsuid = old_ruid;
|
|
|
|
/* Copied from kernel/sys.c:setfsuid. */
|
|
|
|
/*
|
|
* 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)) {
|
|
if (old_fsuid == 0 && current->fsuid != 0) {
|
|
current->cap_effective =
|
|
cap_drop_fs_set(
|
|
current->cap_effective);
|
|
}
|
|
if (old_fsuid != 0 && current->fsuid == 0) {
|
|
current->cap_effective =
|
|
cap_raise_fs_set(
|
|
current->cap_effective,
|
|
current->cap_permitted);
|
|
}
|
|
}
|
|
break;
|
|
}
|
|
default:
|
|
return -EINVAL;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
/*
|
|
* 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)
|
|
{
|
|
if (!cap_issubset(p->cap_permitted, current->cap_permitted) &&
|
|
!capable(CAP_SYS_NICE))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_task_setscheduler (struct task_struct *p, int policy,
|
|
struct sched_param *lp)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
int cap_task_setioprio (struct task_struct *p, int ioprio)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
int cap_task_setnice (struct task_struct *p, int nice)
|
|
{
|
|
return cap_safe_nice(p);
|
|
}
|
|
|
|
/*
|
|
* called from kernel/sys.c for prctl(PR_CABSET_DROP)
|
|
* done without task_capability_lock() because it introduces
|
|
* no new races - i.e. only another task doing capget() on
|
|
* this task could get inconsistent info. There can be no
|
|
* racing writer bc a task can only change its own caps.
|
|
*/
|
|
static long cap_prctl_drop(unsigned long cap)
|
|
{
|
|
if (!capable(CAP_SETPCAP))
|
|
return -EPERM;
|
|
if (!cap_valid(cap))
|
|
return -EINVAL;
|
|
cap_lower(current->cap_bset, cap);
|
|
return 0;
|
|
}
|
|
|
|
#else
|
|
int cap_task_setscheduler (struct task_struct *p, int policy,
|
|
struct sched_param *lp)
|
|
{
|
|
return 0;
|
|
}
|
|
int cap_task_setioprio (struct task_struct *p, int ioprio)
|
|
{
|
|
return 0;
|
|
}
|
|
int cap_task_setnice (struct task_struct *p, int nice)
|
|
{
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
|
|
unsigned long arg4, unsigned long arg5, long *rc_p)
|
|
{
|
|
long error = 0;
|
|
|
|
switch (option) {
|
|
case PR_CAPBSET_READ:
|
|
if (!cap_valid(arg2))
|
|
error = -EINVAL;
|
|
else
|
|
error = !!cap_raised(current->cap_bset, arg2);
|
|
break;
|
|
#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
|
|
case PR_CAPBSET_DROP:
|
|
error = cap_prctl_drop(arg2);
|
|
break;
|
|
|
|
/*
|
|
* 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 ((((current->securebits & SECURE_ALL_LOCKS) >> 1)
|
|
& (current->securebits ^ arg2)) /*[1]*/
|
|
|| ((current->securebits & SECURE_ALL_LOCKS
|
|
& ~arg2)) /*[2]*/
|
|
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
|
|
|| (cap_capable(current, CAP_SETPCAP) != 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")
|
|
*/
|
|
error = -EPERM; /* cannot change a locked bit */
|
|
} else {
|
|
current->securebits = arg2;
|
|
}
|
|
break;
|
|
case PR_GET_SECUREBITS:
|
|
error = current->securebits;
|
|
break;
|
|
|
|
#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
|
|
|
|
case PR_GET_KEEPCAPS:
|
|
if (issecure(SECURE_KEEP_CAPS))
|
|
error = 1;
|
|
break;
|
|
case PR_SET_KEEPCAPS:
|
|
if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
|
|
error = -EINVAL;
|
|
else if (issecure(SECURE_KEEP_CAPS_LOCKED))
|
|
error = -EPERM;
|
|
else if (arg2)
|
|
current->securebits |= issecure_mask(SECURE_KEEP_CAPS);
|
|
else
|
|
current->securebits &=
|
|
~issecure_mask(SECURE_KEEP_CAPS);
|
|
break;
|
|
|
|
default:
|
|
/* No functionality available - continue with default */
|
|
return 0;
|
|
}
|
|
|
|
/* Functionality provided */
|
|
*rc_p = error;
|
|
return 1;
|
|
}
|
|
|
|
void cap_task_reparent_to_init (struct task_struct *p)
|
|
{
|
|
cap_set_init_eff(p->cap_effective);
|
|
cap_clear(p->cap_inheritable);
|
|
cap_set_full(p->cap_permitted);
|
|
p->securebits = SECUREBITS_DEFAULT;
|
|
return;
|
|
}
|
|
|
|
int cap_syslog (int type)
|
|
{
|
|
if ((type != 3 && type != 10) && !capable(CAP_SYS_ADMIN))
|
|
return -EPERM;
|
|
return 0;
|
|
}
|
|
|
|
int cap_vm_enough_memory(struct mm_struct *mm, long pages)
|
|
{
|
|
int cap_sys_admin = 0;
|
|
|
|
if (cap_capable(current, CAP_SYS_ADMIN) == 0)
|
|
cap_sys_admin = 1;
|
|
return __vm_enough_memory(mm, pages, cap_sys_admin);
|
|
}
|
|
|