346 lines
9.4 KiB
C
346 lines
9.4 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/config.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/smp_lock.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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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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EXPORT_SYMBOL(cap_netlink_send);
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int cap_netlink_recv(struct sk_buff *skb)
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{
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if (!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
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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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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 (struct task_struct *parent, struct task_struct *child)
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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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!capable(CAP_SYS_PTRACE))
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return -EPERM;
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return 0;
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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 = cap_t (target->cap_effective);
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*inheritable = cap_t (target->cap_inheritable);
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*permitted = cap_t (target->cap_permitted);
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return 0;
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}
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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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/* Derived from kernel/capability.c:sys_capset. */
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/* verify restrictions on target's new Inheritable set */
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if (!cap_issubset (*inheritable,
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cap_combine (target->cap_inheritable,
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current->cap_permitted))) {
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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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int cap_bprm_set_security (struct linux_binprm *bprm)
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{
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/* Copied from fs/exec.c:prepare_binprm. */
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/* We don't have VFS support for capabilities yet */
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cap_clear (bprm->cap_inheritable);
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cap_clear (bprm->cap_permitted);
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cap_clear (bprm->cap_effective);
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/* To support inheritance of root-permissions and suid-root
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* executables under compatibility mode, we raise all three
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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 only raise the inheritable
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* and permitted sets of the executable file.
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*/
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if (!issecure (SECURE_NOROOT)) {
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if (bprm->e_uid == 0 || current->uid == 0) {
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cap_set_full (bprm->cap_inheritable);
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cap_set_full (bprm->cap_permitted);
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}
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if (bprm->e_uid == 0)
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cap_set_full (bprm->cap_effective);
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}
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return 0;
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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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/* Derived from fs/exec.c:compute_creds. */
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kernel_cap_t new_permitted, working;
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new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
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working = cap_intersect (bprm->cap_inheritable,
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current->cap_inheritable);
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new_permitted = cap_combine (new_permitted, working);
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if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
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!cap_issubset (new_permitted, current->cap_permitted)) {
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current->mm->dumpable = suid_dumpable;
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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 (!capable (CAP_SETPCAP)) {
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new_permitted = cap_intersect (new_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 (current->pid != 1) {
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current->cap_permitted = new_permitted;
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current->cap_effective =
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cap_intersect (new_permitted, bprm->cap_effective);
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}
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/* AUD: Audit candidate if current->cap_effective is set */
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current->keep_capabilities = 0;
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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/when this module is enhanced to incorporate capability
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bits on files, the test below should be extended to also perform a
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test between the old and new capability sets. For now,
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it simply preserves the legacy decision algorithm used by
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the old userland. */
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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, char *name, void *value,
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size_t size, int flags)
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{
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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, char *name)
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{
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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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!current->keep_capabilities) {
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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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}
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break;
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case LSM_SETID_FS:
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{
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uid_t old_fsuid = old_ruid;
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/* Copied from kernel/sys.c:setfsuid. */
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/*
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* FIXME - is fsuser used for all CAP_FS_MASK capabilities?
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* if not, we might be a bit too harsh here.
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*/
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if (!issecure (SECURE_NO_SETUID_FIXUP)) {
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if (old_fsuid == 0 && current->fsuid != 0) {
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cap_t (current->cap_effective) &=
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~CAP_FS_MASK;
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}
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if (old_fsuid != 0 && current->fsuid == 0) {
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cap_t (current->cap_effective) |=
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(cap_t (current->cap_permitted) &
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CAP_FS_MASK);
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}
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}
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break;
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}
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default:
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return -EINVAL;
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}
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return 0;
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}
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void cap_task_reparent_to_init (struct task_struct *p)
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{
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p->cap_effective = CAP_INIT_EFF_SET;
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p->cap_inheritable = CAP_INIT_INH_SET;
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p->cap_permitted = CAP_FULL_SET;
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p->keep_capabilities = 0;
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return;
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}
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int cap_syslog (int type)
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{
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if ((type != 3 && type != 10) && !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_vm_enough_memory(long pages)
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{
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int cap_sys_admin = 0;
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if (cap_capable(current, CAP_SYS_ADMIN) == 0)
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cap_sys_admin = 1;
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return __vm_enough_memory(pages, cap_sys_admin);
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}
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EXPORT_SYMBOL(cap_capable);
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EXPORT_SYMBOL(cap_settime);
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EXPORT_SYMBOL(cap_ptrace);
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EXPORT_SYMBOL(cap_capget);
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EXPORT_SYMBOL(cap_capset_check);
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EXPORT_SYMBOL(cap_capset_set);
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EXPORT_SYMBOL(cap_bprm_set_security);
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EXPORT_SYMBOL(cap_bprm_apply_creds);
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EXPORT_SYMBOL(cap_bprm_secureexec);
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EXPORT_SYMBOL(cap_inode_setxattr);
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EXPORT_SYMBOL(cap_inode_removexattr);
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EXPORT_SYMBOL(cap_task_post_setuid);
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EXPORT_SYMBOL(cap_task_reparent_to_init);
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EXPORT_SYMBOL(cap_syslog);
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EXPORT_SYMBOL(cap_vm_enough_memory);
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MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
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MODULE_LICENSE("GPL");
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