+++ /dev/null
-/**
- * BSD Secure Levels LSM
- *
- * Maintainers:
- * Michael A. Halcrow <mike@halcrow.us>
- * Serge Hallyn <hallyn@cs.wm.edu>
- *
- * Copyright (c) 2001 WireX Communications, Inc <chris@wirex.com>
- * Copyright (c) 2001 Greg Kroah-Hartman <greg@kroah.com>
- * Copyright (c) 2002 International Business Machines <robb@austin.ibm.com>
- * Copyright (c) 2006 Davi E. M. Arnaut <davi.arnaut@gmail.com>
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- */
-
-#include <linux/err.h>
-#include <linux/module.h>
-#include <linux/moduleparam.h>
-#include <linux/kernel.h>
-#include <linux/init.h>
-#include <linux/security.h>
-#include <linux/netlink.h>
-#include <linux/fs.h>
-#include <linux/namei.h>
-#include <linux/mount.h>
-#include <linux/capability.h>
-#include <linux/time.h>
-#include <linux/proc_fs.h>
-#include <linux/kobject.h>
-#include <linux/crypto.h>
-#include <asm/scatterlist.h>
-#include <linux/scatterlist.h>
-#include <linux/gfp.h>
-#include <linux/sysfs.h>
-
-#define SHA1_DIGEST_SIZE 20
-
-/**
- * Module parameter that defines the initial secure level.
- *
- * When built as a module, it defaults to seclvl 1, which is the
- * behavior of BSD secure levels. Note that this default behavior
- * wrecks havoc on a machine when the seclvl module is compiled into
- * the kernel. In that case, we default to seclvl 0.
- */
-#ifdef CONFIG_SECURITY_SECLVL_MODULE
-static int initlvl = 1;
-#else
-static int initlvl;
-#endif
-module_param(initlvl, int, 0);
-MODULE_PARM_DESC(initlvl, "Initial secure level (defaults to 1)");
-
-/* Module parameter that defines the verbosity level */
-static int verbosity;
-module_param(verbosity, int, 0);
-MODULE_PARM_DESC(verbosity, "Initial verbosity level (0 or 1; defaults to "
- "0, which is Quiet)");
-
-/**
- * Optional password which can be passed in to bring seclvl to 0
- * (i.e., for halt/reboot). Defaults to NULL (the passwd attribute
- * file will not be registered in sysfs).
- *
- * This gets converted to its SHA1 hash when stored. It's probably
- * not a good idea to use this parameter when loading seclvl from a
- * script; use sha1_passwd instead.
- */
-
-#define MAX_PASSWD_SIZE 32
-static char passwd[MAX_PASSWD_SIZE];
-module_param_string(passwd, passwd, sizeof(passwd), 0);
-MODULE_PARM_DESC(passwd,
- "Plaintext of password that sets seclvl=0 when written to "
- "(sysfs mount point)/seclvl/passwd\n");
-
-/**
- * SHA1 hashed version of the optional password which can be passed in
- * to bring seclvl to 0 (i.e., for halt/reboot). Must be in
- * hexadecimal format (40 characters). Defaults to NULL (the passwd
- * attribute file will not be registered in sysfs).
- *
- * Use the sha1sum utility to generate the SHA1 hash of a password:
- *
- * echo -n "secret" | sha1sum
- */
-#define MAX_SHA1_PASSWD 41
-static char sha1_passwd[MAX_SHA1_PASSWD];
-module_param_string(sha1_passwd, sha1_passwd, sizeof(sha1_passwd), 0);
-MODULE_PARM_DESC(sha1_passwd,
- "SHA1 hash (40 hexadecimal characters) of password that "
- "sets seclvl=0 when plaintext password is written to "
- "(sysfs mount point)/seclvl/passwd\n");
-
-static int hideHash = 1;
-module_param(hideHash, int, 0);
-MODULE_PARM_DESC(hideHash, "When set to 0, reading seclvl/passwd from sysfs "
- "will return the SHA1-hashed value of the password that "
- "lowers the secure level to 0.\n");
-
-#define MY_NAME "seclvl"
-
-/**
- * This time-limits log writes to one per second.
- */
-#define seclvl_printk(verb, type, fmt, arg...) \
- do { \
- if (verbosity >= verb) { \
- static unsigned long _prior; \
- unsigned long _now = jiffies; \
- if ((_now - _prior) > HZ) { \
- printk(type "%s: %s: " fmt, \
- MY_NAME, __FUNCTION__ , \
- ## arg); \
- _prior = _now; \
- } \
- } \
- } while (0)
-
-/**
- * The actual security level. Ranges between -1 and 2 inclusive.
- */
-static int seclvl;
-
-/**
- * flag to keep track of how we were registered
- */
-static int secondary;
-
-/**
- * Verifies that the requested secure level is valid, given the current
- * secure level.
- */
-static int seclvl_sanity(int reqlvl)
-{
- if ((reqlvl < -1) || (reqlvl > 2)) {
- seclvl_printk(1, KERN_WARNING, "Attempt to set seclvl out of "
- "range: [%d]\n", reqlvl);
- return -EINVAL;
- }
- if ((seclvl == 0) && (reqlvl == -1))
- return 0;
- if (reqlvl < seclvl) {
- seclvl_printk(1, KERN_WARNING, "Attempt to lower seclvl to "
- "[%d]\n", reqlvl);
- return -EPERM;
- }
- return 0;
-}
-
-/**
- * security level advancement rules:
- * Valid levels are -1 through 2, inclusive.
- * From -1, stuck. [ in case compiled into kernel ]
- * From 0 or above, can only increment.
- */
-static void do_seclvl_advance(void *data, u64 val)
-{
- int ret;
- int newlvl = (int)val;
-
- ret = seclvl_sanity(newlvl);
- if (ret)
- return;
-
- if (newlvl > 2) {
- seclvl_printk(1, KERN_WARNING, "Cannot advance to seclvl "
- "[%d]\n", newlvl);
- return;
- }
- if (seclvl == -1) {
- seclvl_printk(1, KERN_WARNING, "Not allowed to advance to "
- "seclvl [%d]\n", seclvl);
- return;
- }
- seclvl = newlvl; /* would it be more "correct" to set *data? */
- return;
-}
-
-static u64 seclvl_int_get(void *data)
-{
- return *(int *)data;
-}
-
-DEFINE_SIMPLE_ATTRIBUTE(seclvl_file_ops, seclvl_int_get, do_seclvl_advance, "%lld\n");
-
-static unsigned char hashedPassword[SHA1_DIGEST_SIZE];
-
-/**
- * Converts a block of plaintext of into its SHA1 hashed value.
- *
- * It would be nice if crypto had a wrapper to do this for us linear
- * people...
- */
-static int
-plaintext_to_sha1(unsigned char *hash, const char *plaintext, unsigned int len)
-{
- struct hash_desc desc;
- struct scatterlist sg;
- int err;
-
- if (len > PAGE_SIZE) {
- seclvl_printk(0, KERN_ERR, "Plaintext password too large (%d "
- "characters). Largest possible is %lu "
- "bytes.\n", len, PAGE_SIZE);
- return -EINVAL;
- }
- desc.tfm = crypto_alloc_hash("sha1", 0, CRYPTO_ALG_ASYNC);
- if (IS_ERR(desc.tfm)) {
- seclvl_printk(0, KERN_ERR,
- "Failed to load transform for SHA1\n");
- return -EINVAL;
- }
- sg_init_one(&sg, (u8 *)plaintext, len);
- desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
- err = crypto_hash_digest(&desc, &sg, len, hash);
- crypto_free_hash(desc.tfm);
- return err;
-}
-
-/**
- * Called whenever the user writes to the sysfs passwd handle to this kernel
- * object. It hashes the password and compares the hashed results.
- */
-static ssize_t
-passwd_write_file(struct file * file, const char __user * buf,
- size_t count, loff_t *ppos)
-{
- char *p;
- int len;
- unsigned char tmp[SHA1_DIGEST_SIZE];
-
- if (!*passwd && !*sha1_passwd) {
- seclvl_printk(0, KERN_ERR, "Attempt to password-unlock the "
- "seclvl module, but neither a plain text "
- "password nor a SHA1 hashed password was "
- "passed in as a module parameter! This is a "
- "bug, since it should not be possible to be in "
- "this part of the module; please tell a "
- "maintainer about this event.\n");
- return -EINVAL;
- }
-
- if (count >= PAGE_SIZE)
- return -EINVAL;
- if (*ppos != 0)
- return -EINVAL;
- p = kmalloc(count, GFP_KERNEL);
- if (!p)
- return -ENOMEM;
- len = -EFAULT;
- if (copy_from_user(p, buf, count))
- goto out;
-
- len = count;
- /* ``echo "secret" > seclvl/passwd'' includes a newline */
- if (p[len - 1] == '\n')
- len--;
- /* Hash the password, then compare the hashed values */
- if ((len = plaintext_to_sha1(tmp, p, len))) {
- seclvl_printk(0, KERN_ERR, "Error hashing password: rc = "
- "[%d]\n", len);
- goto out;
- }
-
- len = -EPERM;
- if (memcmp(hashedPassword, tmp, SHA1_DIGEST_SIZE))
- goto out;
-
- seclvl_printk(0, KERN_INFO,
- "Password accepted; seclvl reduced to 0.\n");
- seclvl = 0;
- len = count;
-
-out:
- kfree (p);
- return len;
-}
-
-static struct file_operations passwd_file_ops = {
- .write = passwd_write_file,
-};
-
-/**
- * Explicitely disallow ptrace'ing the init process.
- */
-static int seclvl_ptrace(struct task_struct *parent, struct task_struct *child)
-{
- if (seclvl >= 0 && child->pid == 1) {
- seclvl_printk(1, KERN_WARNING, "Attempt to ptrace "
- "the init process dissallowed in "
- "secure level %d\n", seclvl);
- return -EPERM;
- }
- return 0;
-}
-
-/**
- * Capability checks for seclvl. The majority of the policy
- * enforcement for seclvl takes place here.
- */
-static int seclvl_capable(struct task_struct *tsk, int cap)
-{
- int rc = 0;
-
- /* init can do anything it wants */
- if (tsk->pid == 1)
- return 0;
-
- if (seclvl > 0) {
- rc = -EPERM;
-
- if (cap == CAP_LINUX_IMMUTABLE)
- seclvl_printk(1, KERN_WARNING, "Attempt to modify "
- "the IMMUTABLE and/or APPEND extended "
- "attribute on a file with the IMMUTABLE "
- "and/or APPEND extended attribute set "
- "denied in seclvl [%d]\n", seclvl);
- else if (cap == CAP_SYS_RAWIO)
- seclvl_printk(1, KERN_WARNING, "Attempt to perform "
- "raw I/O while in secure level [%d] "
- "denied\n", seclvl);
- else if (cap == CAP_NET_ADMIN)
- seclvl_printk(1, KERN_WARNING, "Attempt to perform "
- "network administrative task while "
- "in secure level [%d] denied\n", seclvl);
- else if (cap == CAP_SETUID)
- seclvl_printk(1, KERN_WARNING, "Attempt to setuid "
- "while in secure level [%d] denied\n",
- seclvl);
- else if (cap == CAP_SETGID)
- seclvl_printk(1, KERN_WARNING, "Attempt to setgid "
- "while in secure level [%d] denied\n",
- seclvl);
- else if (cap == CAP_SYS_MODULE)
- seclvl_printk(1, KERN_WARNING, "Attempt to perform "
- "a module operation while in secure "
- "level [%d] denied\n", seclvl);
- else
- rc = 0;
- }
-
- if (!rc) {
- if (!(cap_is_fs_cap(cap) ? tsk->fsuid == 0 : tsk->euid == 0))
- rc = -EPERM;
- }
-
- if (rc)
- seclvl_printk(1, KERN_WARNING, "Capability denied\n");
-
- return rc;
-}
-
-/**
- * Disallow reversing the clock in seclvl > 1
- */
-static int seclvl_settime(struct timespec *tv, struct timezone *tz)
-{
- if (tv && seclvl > 1) {
- struct timespec now;
- now = current_kernel_time();
- if (tv->tv_sec < now.tv_sec ||
- (tv->tv_sec == now.tv_sec && tv->tv_nsec < now.tv_nsec)) {
- seclvl_printk(1, KERN_WARNING, "Attempt to decrement "
- "time in secure level %d denied: "
- "current->pid = [%d], "
- "current->group_leader->pid = [%d]\n",
- seclvl, current->pid,
- current->group_leader->pid);
- return -EPERM;
- } /* if attempt to decrement time */
- } /* if seclvl > 1 */
- return 0;
-}
-
-/* claim the blockdev to exclude mounters, release on file close */
-static int seclvl_bd_claim(struct inode *inode)
-{
- int holder;
- struct block_device *bdev = NULL;
- dev_t dev = inode->i_rdev;
- bdev = open_by_devnum(dev, FMODE_WRITE);
- if (bdev) {
- if (bd_claim(bdev, &holder)) {
- blkdev_put(bdev);
- return -EPERM;
- }
- /* claimed, mark it to release on close */
- inode->i_security = current;
- }
- return 0;
-}
-
-/* release the blockdev if you claimed it */
-static void seclvl_bd_release(struct inode *inode)
-{
- if (inode && S_ISBLK(inode->i_mode) && inode->i_security == current) {
- struct block_device *bdev = inode->i_bdev;
- if (bdev) {
- bd_release(bdev);
- blkdev_put(bdev);
- inode->i_security = NULL;
- }
- }
-}
-
-/**
- * Security for writes to block devices is regulated by this seclvl
- * function. Deny all writes to block devices in seclvl 2. In
- * seclvl 1, we only deny writes to *mounted* block devices.
- */
-static int
-seclvl_inode_permission(struct inode *inode, int mask, struct nameidata *nd)
-{
- if (current->pid != 1 && S_ISBLK(inode->i_mode) && (mask & MAY_WRITE)) {
- switch (seclvl) {
- case 2:
- seclvl_printk(1, KERN_WARNING, "Write to block device "
- "denied in secure level [%d]\n", seclvl);
- return -EPERM;
- case 1:
- if (seclvl_bd_claim(inode)) {
- seclvl_printk(1, KERN_WARNING,
- "Write to mounted block device "
- "denied in secure level [%d]\n",
- seclvl);
- return -EPERM;
- }
- }
- }
- return 0;
-}
-
-/**
- * The SUID and SGID bits cannot be set in seclvl >= 1
- */
-static int seclvl_inode_setattr(struct dentry *dentry, struct iattr *iattr)
-{
- if (seclvl > 0) {
- if (iattr->ia_valid & ATTR_MODE)
- if (iattr->ia_mode & S_ISUID ||
- iattr->ia_mode & S_ISGID) {
- seclvl_printk(1, KERN_WARNING, "Attempt to "
- "modify SUID or SGID bit "
- "denied in seclvl [%d]\n",
- seclvl);
- return -EPERM;
- }
- }
- return 0;
-}
-
-/* release busied block devices */
-static void seclvl_file_free_security(struct file *filp)
-{
- struct dentry *dentry = filp->f_dentry;
-
- if (dentry)
- seclvl_bd_release(dentry->d_inode);
-}
-
-/**
- * Cannot unmount in secure level 2
- */
-static int seclvl_umount(struct vfsmount *mnt, int flags)
-{
- if (current->pid != 1 && seclvl == 2) {
- seclvl_printk(1, KERN_WARNING, "Attempt to unmount in secure "
- "level %d\n", seclvl);
- return -EPERM;
- }
- return 0;
-}
-
-static struct security_operations seclvl_ops = {
- .ptrace = seclvl_ptrace,
- .capable = seclvl_capable,
- .inode_permission = seclvl_inode_permission,
- .inode_setattr = seclvl_inode_setattr,
- .file_free_security = seclvl_file_free_security,
- .settime = seclvl_settime,
- .sb_umount = seclvl_umount,
-};
-
-/**
- * Process the password-related module parameters
- */
-static int processPassword(void)
-{
- int rc = 0;
- if (*passwd) {
- char *p;
-
- if (*sha1_passwd) {
- seclvl_printk(0, KERN_ERR, "Error: Both "
- "passwd and sha1_passwd "
- "were set, but they are mutually "
- "exclusive.\n");
- return -EINVAL;
- }
-
- p = kstrdup(passwd, GFP_KERNEL);
- if (p == NULL)
- return -ENOMEM;
-
- if ((rc = plaintext_to_sha1(hashedPassword, p, strlen(p))))
- seclvl_printk(0, KERN_ERR, "Error: SHA1 support not "
- "in kernel\n");
-
- kfree (p);
- /* All static data goes to the BSS, which zero's the
- * plaintext password out for us. */
- } else if (*sha1_passwd) { // Base 16
- int i;
- i = strlen(sha1_passwd);
- if (i != (SHA1_DIGEST_SIZE * 2)) {
- seclvl_printk(0, KERN_ERR, "Received [%d] bytes; "
- "expected [%d] for the hexadecimal "
- "representation of the SHA1 hash of "
- "the password.\n",
- i, (SHA1_DIGEST_SIZE * 2));
- return -EINVAL;
- }
- while ((i -= 2) + 2) {
- unsigned char tmp;
- tmp = sha1_passwd[i + 2];
- sha1_passwd[i + 2] = '\0';
- hashedPassword[i / 2] = (unsigned char)
- simple_strtol(&sha1_passwd[i], NULL, 16);
- sha1_passwd[i + 2] = tmp;
- }
- }
- return rc;
-}
-
-/**
- * securityfs registrations
- */
-struct dentry *dir_ino, *seclvl_ino, *passwd_ino;
-
-static int seclvlfs_register(void)
-{
- int rc = 0;
-
- dir_ino = securityfs_create_dir("seclvl", NULL);
-
- if (IS_ERR(dir_ino))
- return PTR_ERR(dir_ino);
-
- seclvl_ino = securityfs_create_file("seclvl", S_IRUGO | S_IWUSR,
- dir_ino, &seclvl, &seclvl_file_ops);
- if (IS_ERR(seclvl_ino)) {
- rc = PTR_ERR(seclvl_ino);
- goto out_deldir;
- }
- if (*passwd || *sha1_passwd) {
- passwd_ino = securityfs_create_file("passwd", S_IRUGO | S_IWUSR,
- dir_ino, NULL, &passwd_file_ops);
- if (IS_ERR(passwd_ino)) {
- rc = PTR_ERR(passwd_ino);
- goto out_delf;
- }
- }
- return rc;
-
-out_delf:
- securityfs_remove(seclvl_ino);
-
-out_deldir:
- securityfs_remove(dir_ino);
-
- return rc;
-}
-
-static void seclvlfs_unregister(void)
-{
- securityfs_remove(seclvl_ino);
-
- if (*passwd || *sha1_passwd)
- securityfs_remove(passwd_ino);
-
- securityfs_remove(dir_ino);
-}
-
-/**
- * Initialize the seclvl module.
- */
-static int __init seclvl_init(void)
-{
- int rc = 0;
- static char once;
-
- if (verbosity < 0 || verbosity > 1) {
- printk(KERN_ERR "Error: bad verbosity [%d]; only 0 or 1 "
- "are valid values\n", verbosity);
- rc = -EINVAL;
- goto exit;
- }
- if (initlvl < -1 || initlvl > 2) {
- seclvl_printk(0, KERN_ERR, "Error: bad initial securelevel "
- "[%d].\n", initlvl);
- rc = -EINVAL;
- goto exit;
- }
- seclvl = initlvl;
- if ((rc = processPassword())) {
- seclvl_printk(0, KERN_ERR, "Error processing the password "
- "module parameter(s): rc = [%d]\n", rc);
- goto exit;
- }
-
- if ((rc = seclvlfs_register())) {
- seclvl_printk(0, KERN_ERR, "Error registering with sysfs\n");
- goto exit;
- }
- /* register ourselves with the security framework */
- if (register_security(&seclvl_ops)) {
- seclvl_printk(0, KERN_ERR,
- "seclvl: Failure registering with the "
- "kernel.\n");
- /* try registering with primary module */
- rc = mod_reg_security(MY_NAME, &seclvl_ops);
- if (rc) {
- seclvl_printk(0, KERN_ERR, "seclvl: Failure "
- "registering with primary security "
- "module.\n");
- seclvlfs_unregister();
- goto exit;
- } /* if primary module registered */
- secondary = 1;
- } /* if we registered ourselves with the security framework */
-
- seclvl_printk(0, KERN_INFO, "seclvl: Successfully initialized.\n");
-
- if (once) {
- once = 1;
- seclvl_printk(0, KERN_INFO, "seclvl is going away. It has been "
- "buggy for ages. Also, be warned that "
- "Securelevels are useless.");
- }
- exit:
- if (rc)
- printk(KERN_ERR "seclvl: Error during initialization: rc = "
- "[%d]\n", rc);
- return rc;
-}
-
-/**
- * Remove the seclvl module.
- */
-static void __exit seclvl_exit(void)
-{
- seclvlfs_unregister();
-
- if (secondary)
- mod_unreg_security(MY_NAME, &seclvl_ops);
- else if (unregister_security(&seclvl_ops))
- seclvl_printk(0, KERN_INFO,
- "seclvl: Failure unregistering with the "
- "kernel\n");
-}
-
-module_init(seclvl_init);
-module_exit(seclvl_exit);
-
-MODULE_AUTHOR("Michael A. Halcrow <mike@halcrow.us>");
-MODULE_DESCRIPTION("LSM implementation of the BSD Secure Levels");
-MODULE_LICENSE("GPL");
projects / linux-2.6 / commitdiff