[PATCH] EDAC: mc numbers refactor 1-of-2
[linux-3.10.git] / security / seclvl.c
1 /**
2  * BSD Secure Levels LSM
3  *
4  * Maintainers:
5  *      Michael A. Halcrow <mike@halcrow.us>
6  *      Serge Hallyn <hallyn@cs.wm.edu>
7  *
8  * Copyright (c) 2001 WireX Communications, Inc <chris@wirex.com>
9  * Copyright (c) 2001 Greg Kroah-Hartman <greg@kroah.com>
10  * Copyright (c) 2002 International Business Machines <robb@austin.ibm.com>
11  * Copyright (c) 2006 Davi E. M. Arnaut <davi.arnaut@gmail.com>
12  *
13  *      This program is free software; you can redistribute it and/or modify
14  *      it under the terms of the GNU General Public License as published by
15  *      the Free Software Foundation; either version 2 of the License, or
16  *      (at your option) any later version.
17  */
18
19 #include <linux/config.h>
20 #include <linux/module.h>
21 #include <linux/moduleparam.h>
22 #include <linux/kernel.h>
23 #include <linux/init.h>
24 #include <linux/security.h>
25 #include <linux/netlink.h>
26 #include <linux/fs.h>
27 #include <linux/namei.h>
28 #include <linux/mount.h>
29 #include <linux/capability.h>
30 #include <linux/time.h>
31 #include <linux/proc_fs.h>
32 #include <linux/kobject.h>
33 #include <linux/crypto.h>
34 #include <asm/scatterlist.h>
35 #include <linux/scatterlist.h>
36 #include <linux/gfp.h>
37 #include <linux/sysfs.h>
38
39 #define SHA1_DIGEST_SIZE 20
40
41 /**
42  * Module parameter that defines the initial secure level.
43  *
44  * When built as a module, it defaults to seclvl 1, which is the
45  * behavior of BSD secure levels.  Note that this default behavior
46  * wrecks havoc on a machine when the seclvl module is compiled into
47  * the kernel.  In that case, we default to seclvl 0.
48  */
49 #ifdef CONFIG_SECURITY_SECLVL_MODULE
50 static int initlvl = 1;
51 #else
52 static int initlvl;
53 #endif
54 module_param(initlvl, int, 0);
55 MODULE_PARM_DESC(initlvl, "Initial secure level (defaults to 1)");
56
57 /* Module parameter that defines the verbosity level */
58 static int verbosity;
59 module_param(verbosity, int, 0);
60 MODULE_PARM_DESC(verbosity, "Initial verbosity level (0 or 1; defaults to "
61                  "0, which is Quiet)");
62
63 /**
64  * Optional password which can be passed in to bring seclvl to 0
65  * (i.e., for halt/reboot).  Defaults to NULL (the passwd attribute
66  * file will not be registered in sysfs).
67  *
68  * This gets converted to its SHA1 hash when stored.  It's probably
69  * not a good idea to use this parameter when loading seclvl from a
70  * script; use sha1_passwd instead.
71  */
72
73 #define MAX_PASSWD_SIZE 32
74 static char passwd[MAX_PASSWD_SIZE];
75 module_param_string(passwd, passwd, sizeof(passwd), 0);
76 MODULE_PARM_DESC(passwd,
77                  "Plaintext of password that sets seclvl=0 when written to "
78                  "(sysfs mount point)/seclvl/passwd\n");
79
80 /**
81  * SHA1 hashed version of the optional password which can be passed in
82  * to bring seclvl to 0 (i.e., for halt/reboot).  Must be in
83  * hexadecimal format (40 characters).  Defaults to NULL (the passwd
84  * attribute file will not be registered in sysfs).
85  *
86  * Use the sha1sum utility to generate the SHA1 hash of a password:
87  *
88  * echo -n "secret" | sha1sum
89  */
90 #define MAX_SHA1_PASSWD 41
91 static char sha1_passwd[MAX_SHA1_PASSWD];
92 module_param_string(sha1_passwd, sha1_passwd, sizeof(sha1_passwd), 0);
93 MODULE_PARM_DESC(sha1_passwd,
94                  "SHA1 hash (40 hexadecimal characters) of password that "
95                  "sets seclvl=0 when plaintext password is written to "
96                  "(sysfs mount point)/seclvl/passwd\n");
97
98 static int hideHash = 1;
99 module_param(hideHash, int, 0);
100 MODULE_PARM_DESC(hideHash, "When set to 0, reading seclvl/passwd from sysfs "
101                  "will return the SHA1-hashed value of the password that "
102                  "lowers the secure level to 0.\n");
103
104 #define MY_NAME "seclvl"
105
106 /**
107  * This time-limits log writes to one per second.
108  */
109 #define seclvl_printk(verb, type, fmt, arg...)                  \
110         do {                                                    \
111                 if (verbosity >= verb) {                        \
112                         static unsigned long _prior;            \
113                         unsigned long _now = jiffies;           \
114                         if ((_now - _prior) > HZ) {             \
115                                 printk(type "%s: %s: " fmt,     \
116                                         MY_NAME, __FUNCTION__ , \
117                                         ## arg);                \
118                                 _prior = _now;                  \
119                         }                                       \
120                 }                                               \
121         } while (0)
122
123 /**
124  * The actual security level.  Ranges between -1 and 2 inclusive.
125  */
126 static int seclvl;
127
128 /**
129  * flag to keep track of how we were registered
130  */
131 static int secondary;
132
133 /**
134  * Verifies that the requested secure level is valid, given the current
135  * secure level.
136  */
137 static int seclvl_sanity(int reqlvl)
138 {
139         if ((reqlvl < -1) || (reqlvl > 2)) {
140                 seclvl_printk(1, KERN_WARNING, "Attempt to set seclvl out of "
141                               "range: [%d]\n", reqlvl);
142                 return -EINVAL;
143         }
144         if ((seclvl == 0) && (reqlvl == -1))
145                 return 0;
146         if (reqlvl < seclvl) {
147                 seclvl_printk(1, KERN_WARNING, "Attempt to lower seclvl to "
148                               "[%d]\n", reqlvl);
149                 return -EPERM;
150         }
151         return 0;
152 }
153
154 /**
155  * security level advancement rules:
156  *   Valid levels are -1 through 2, inclusive.
157  *   From -1, stuck.  [ in case compiled into kernel ]
158  *   From 0 or above, can only increment.
159  */
160 static void do_seclvl_advance(void *data, u64 val)
161 {
162         int ret;
163         int newlvl = (int)val;
164
165         ret = seclvl_sanity(newlvl);
166         if (ret)
167                 return;
168
169         if (newlvl > 2) {
170                 seclvl_printk(1, KERN_WARNING, "Cannot advance to seclvl "
171                               "[%d]\n", newlvl);
172                 return;
173         }
174         if (seclvl == -1) {
175                 seclvl_printk(1, KERN_WARNING, "Not allowed to advance to "
176                               "seclvl [%d]\n", seclvl);
177                 return;
178         }
179         seclvl = newlvl;  /* would it be more "correct" to set *data? */
180         return;
181 }
182
183 static u64 seclvl_int_get(void *data)
184 {
185         return *(int *)data;
186 }
187
188 DEFINE_SIMPLE_ATTRIBUTE(seclvl_file_ops, seclvl_int_get, do_seclvl_advance, "%lld\n");
189
190 static unsigned char hashedPassword[SHA1_DIGEST_SIZE];
191
192 /**
193  * Converts a block of plaintext of into its SHA1 hashed value.
194  *
195  * It would be nice if crypto had a wrapper to do this for us linear
196  * people...
197  */
198 static int
199 plaintext_to_sha1(unsigned char *hash, const char *plaintext, unsigned int len)
200 {
201         struct crypto_tfm *tfm;
202         struct scatterlist sg;
203         if (len > PAGE_SIZE) {
204                 seclvl_printk(0, KERN_ERR, "Plaintext password too large (%d "
205                               "characters).  Largest possible is %lu "
206                               "bytes.\n", len, PAGE_SIZE);
207                 return -EINVAL;
208         }
209         tfm = crypto_alloc_tfm("sha1", CRYPTO_TFM_REQ_MAY_SLEEP);
210         if (tfm == NULL) {
211                 seclvl_printk(0, KERN_ERR,
212                               "Failed to load transform for SHA1\n");
213                 return -EINVAL;
214         }
215         sg_init_one(&sg, (u8 *)plaintext, len);
216         crypto_digest_init(tfm);
217         crypto_digest_update(tfm, &sg, 1);
218         crypto_digest_final(tfm, hash);
219         crypto_free_tfm(tfm);
220         return 0;
221 }
222
223 /**
224  * Called whenever the user writes to the sysfs passwd handle to this kernel
225  * object.  It hashes the password and compares the hashed results.
226  */
227 static ssize_t
228 passwd_write_file(struct file * file, const char __user * buf,
229                                 size_t count, loff_t *ppos)
230 {
231         char *p;
232         int len;
233         unsigned char tmp[SHA1_DIGEST_SIZE];
234
235         if (!*passwd && !*sha1_passwd) {
236                 seclvl_printk(0, KERN_ERR, "Attempt to password-unlock the "
237                               "seclvl module, but neither a plain text "
238                               "password nor a SHA1 hashed password was "
239                               "passed in as a module parameter!  This is a "
240                               "bug, since it should not be possible to be in "
241                               "this part of the module; please tell a "
242                               "maintainer about this event.\n");
243                 return -EINVAL;
244         }
245
246         if (count >= PAGE_SIZE)
247                 return -EINVAL;
248         if (*ppos != 0)
249                 return -EINVAL;
250         p = kmalloc(count, GFP_KERNEL);
251         if (!p)
252                 return -ENOMEM;
253         len = -EFAULT;
254         if (copy_from_user(p, buf, count))
255                 goto out;
256         
257         len = count;
258         /* ``echo "secret" > seclvl/passwd'' includes a newline */
259         if (p[len - 1] == '\n')
260                 len--;
261         /* Hash the password, then compare the hashed values */
262         if ((len = plaintext_to_sha1(tmp, p, len))) {
263                 seclvl_printk(0, KERN_ERR, "Error hashing password: rc = "
264                               "[%d]\n", len);
265                 goto out;
266         }
267
268         len = -EPERM;
269         if (memcmp(hashedPassword, tmp, SHA1_DIGEST_SIZE))
270                 goto out;
271
272         seclvl_printk(0, KERN_INFO,
273                       "Password accepted; seclvl reduced to 0.\n");
274         seclvl = 0;
275         len = count;
276
277 out:
278         kfree (p);
279         return len;
280 }
281
282 static struct file_operations passwd_file_ops = {
283         .write = passwd_write_file,
284 };
285
286 /**
287  * Explicitely disallow ptrace'ing the init process.
288  */
289 static int seclvl_ptrace(struct task_struct *parent, struct task_struct *child)
290 {
291         if (seclvl >= 0 && child->pid == 1) {
292                 seclvl_printk(1, KERN_WARNING, "Attempt to ptrace "
293                               "the init process dissallowed in "
294                               "secure level %d\n", seclvl);
295                 return -EPERM;
296         }
297         return 0;
298 }
299
300 /**
301  * Capability checks for seclvl.  The majority of the policy
302  * enforcement for seclvl takes place here.
303  */
304 static int seclvl_capable(struct task_struct *tsk, int cap)
305 {
306         int rc = 0;
307
308         /* init can do anything it wants */
309         if (tsk->pid == 1)
310                 return 0;
311
312         if (seclvl > 0) {
313                 rc = -EPERM;
314
315                 if (cap == CAP_LINUX_IMMUTABLE)
316                         seclvl_printk(1, KERN_WARNING, "Attempt to modify "
317                                       "the IMMUTABLE and/or APPEND extended "
318                                       "attribute on a file with the IMMUTABLE "
319                                       "and/or APPEND extended attribute set "
320                                       "denied in seclvl [%d]\n", seclvl);
321                 else if (cap == CAP_SYS_RAWIO)
322                         seclvl_printk(1, KERN_WARNING, "Attempt to perform "
323                                       "raw I/O while in secure level [%d] "
324                                       "denied\n", seclvl);
325                 else if (cap == CAP_NET_ADMIN)
326                         seclvl_printk(1, KERN_WARNING, "Attempt to perform "
327                                       "network administrative task while "
328                                       "in secure level [%d] denied\n", seclvl);
329                 else if (cap == CAP_SETUID)
330                         seclvl_printk(1, KERN_WARNING, "Attempt to setuid "
331                                       "while in secure level [%d] denied\n",
332                                       seclvl);
333                 else if (cap == CAP_SETGID)
334                         seclvl_printk(1, KERN_WARNING, "Attempt to setgid "
335                                       "while in secure level [%d] denied\n",
336                                       seclvl);
337                 else if (cap == CAP_SYS_MODULE)
338                         seclvl_printk(1, KERN_WARNING, "Attempt to perform "
339                                       "a module operation while in secure "
340                                       "level [%d] denied\n", seclvl);
341                 else
342                         rc = 0;
343         }
344
345         if (!rc) {
346                 if (!(cap_is_fs_cap(cap) ? tsk->fsuid == 0 : tsk->euid == 0))
347                         rc = -EPERM;
348         }
349
350         if (rc)
351                 seclvl_printk(1, KERN_WARNING, "Capability denied\n");
352
353         return rc;
354 }
355
356 /**
357  * Disallow reversing the clock in seclvl > 1
358  */
359 static int seclvl_settime(struct timespec *tv, struct timezone *tz)
360 {
361         if (tv && seclvl > 1) {
362                 struct timespec now;
363                 now = current_kernel_time();
364                 if (tv->tv_sec < now.tv_sec ||
365                     (tv->tv_sec == now.tv_sec && tv->tv_nsec < now.tv_nsec)) {
366                         seclvl_printk(1, KERN_WARNING, "Attempt to decrement "
367                                       "time in secure level %d denied: "
368                                       "current->pid = [%d], "
369                                       "current->group_leader->pid = [%d]\n",
370                                       seclvl, current->pid,
371                                       current->group_leader->pid);
372                         return -EPERM;
373                 }               /* if attempt to decrement time */
374         }                       /* if seclvl > 1 */
375         return 0;
376 }
377
378 /* claim the blockdev to exclude mounters, release on file close */
379 static int seclvl_bd_claim(struct inode *inode)
380 {
381         int holder;
382         struct block_device *bdev = NULL;
383         dev_t dev = inode->i_rdev;
384         bdev = open_by_devnum(dev, FMODE_WRITE);
385         if (bdev) {
386                 if (bd_claim(bdev, &holder)) {
387                         blkdev_put(bdev);
388                         return -EPERM;
389                 }
390                 /* claimed, mark it to release on close */
391                 inode->i_security = current;
392         }
393         return 0;
394 }
395
396 /* release the blockdev if you claimed it */
397 static void seclvl_bd_release(struct inode *inode)
398 {
399         if (inode && S_ISBLK(inode->i_mode) && inode->i_security == current) {
400                 struct block_device *bdev = inode->i_bdev;
401                 if (bdev) {
402                         bd_release(bdev);
403                         blkdev_put(bdev);
404                         inode->i_security = NULL;
405                 }
406         }
407 }
408
409 /**
410  * Security for writes to block devices is regulated by this seclvl
411  * function.  Deny all writes to block devices in seclvl 2.  In
412  * seclvl 1, we only deny writes to *mounted* block devices.
413  */
414 static int
415 seclvl_inode_permission(struct inode *inode, int mask, struct nameidata *nd)
416 {
417         if (current->pid != 1 && S_ISBLK(inode->i_mode) && (mask & MAY_WRITE)) {
418                 switch (seclvl) {
419                 case 2:
420                         seclvl_printk(1, KERN_WARNING, "Write to block device "
421                                       "denied in secure level [%d]\n", seclvl);
422                         return -EPERM;
423                 case 1:
424                         if (seclvl_bd_claim(inode)) {
425                                 seclvl_printk(1, KERN_WARNING,
426                                               "Write to mounted block device "
427                                               "denied in secure level [%d]\n",
428                                               seclvl);
429                                 return -EPERM;
430                         }
431                 }
432         }
433         return 0;
434 }
435
436 /**
437  * The SUID and SGID bits cannot be set in seclvl >= 1
438  */
439 static int seclvl_inode_setattr(struct dentry *dentry, struct iattr *iattr)
440 {
441         if (seclvl > 0) {
442                 if (iattr->ia_valid & ATTR_MODE)
443                         if (iattr->ia_mode & S_ISUID ||
444                             iattr->ia_mode & S_ISGID) {
445                                 seclvl_printk(1, KERN_WARNING, "Attempt to "
446                                               "modify SUID or SGID bit "
447                                               "denied in seclvl [%d]\n",
448                                               seclvl);
449                                 return -EPERM;
450                         }
451         }
452         return 0;
453 }
454
455 /* release busied block devices */
456 static void seclvl_file_free_security(struct file *filp)
457 {
458         struct dentry *dentry = filp->f_dentry;
459
460         if (dentry)
461                 seclvl_bd_release(dentry->d_inode);
462 }
463
464 /**
465  * Cannot unmount in secure level 2
466  */
467 static int seclvl_umount(struct vfsmount *mnt, int flags)
468 {
469         if (current->pid != 1 && seclvl == 2) {
470                 seclvl_printk(1, KERN_WARNING, "Attempt to unmount in secure "
471                               "level %d\n", seclvl);
472                 return -EPERM;
473         }
474         return 0;
475 }
476
477 static struct security_operations seclvl_ops = {
478         .ptrace = seclvl_ptrace,
479         .capable = seclvl_capable,
480         .inode_permission = seclvl_inode_permission,
481         .inode_setattr = seclvl_inode_setattr,
482         .file_free_security = seclvl_file_free_security,
483         .settime = seclvl_settime,
484         .sb_umount = seclvl_umount,
485 };
486
487 /**
488  * Process the password-related module parameters
489  */
490 static int processPassword(void)
491 {
492         int rc = 0;
493         if (*passwd) {
494                 char *p;
495
496                 if (*sha1_passwd) {
497                         seclvl_printk(0, KERN_ERR, "Error: Both "
498                                       "passwd and sha1_passwd "
499                                       "were set, but they are mutually "
500                                       "exclusive.\n");
501                         return -EINVAL;
502                 }
503
504                 p = kstrdup(passwd, GFP_KERNEL);
505                 if (p == NULL)
506                         return -ENOMEM;
507
508                 if ((rc = plaintext_to_sha1(hashedPassword, p, strlen(p))))
509                         seclvl_printk(0, KERN_ERR, "Error: SHA1 support not "
510                                       "in kernel\n");
511
512                 kfree (p);
513                 /* All static data goes to the BSS, which zero's the
514                  * plaintext password out for us. */
515         } else if (*sha1_passwd) {      // Base 16
516                 int i;
517                 i = strlen(sha1_passwd);
518                 if (i != (SHA1_DIGEST_SIZE * 2)) {
519                         seclvl_printk(0, KERN_ERR, "Received [%d] bytes; "
520                                       "expected [%d] for the hexadecimal "
521                                       "representation of the SHA1 hash of "
522                                       "the password.\n",
523                                       i, (SHA1_DIGEST_SIZE * 2));
524                         return -EINVAL;
525                 }
526                 while ((i -= 2) + 2) {
527                         unsigned char tmp;
528                         tmp = sha1_passwd[i + 2];
529                         sha1_passwd[i + 2] = '\0';
530                         hashedPassword[i / 2] = (unsigned char)
531                             simple_strtol(&sha1_passwd[i], NULL, 16);
532                         sha1_passwd[i + 2] = tmp;
533                 }
534         }
535         return rc;
536 }
537
538 /**
539  * securityfs registrations
540  */
541 struct dentry *dir_ino, *seclvl_ino, *passwd_ino;
542
543 static int seclvlfs_register(void)
544 {
545         int rc = 0;
546
547         dir_ino = securityfs_create_dir("seclvl", NULL);
548
549         if (IS_ERR(dir_ino))
550                 return PTR_ERR(dir_ino);
551
552         seclvl_ino = securityfs_create_file("seclvl", S_IRUGO | S_IWUSR,
553                                 dir_ino, &seclvl, &seclvl_file_ops);
554         if (IS_ERR(seclvl_ino)) {
555                 rc = PTR_ERR(seclvl_ino);
556                 goto out_deldir;
557         }
558         if (*passwd || *sha1_passwd) {
559                 passwd_ino = securityfs_create_file("passwd", S_IRUGO | S_IWUSR,
560                                 dir_ino, NULL, &passwd_file_ops);
561                 if (IS_ERR(passwd_ino)) {
562                         rc = PTR_ERR(passwd_ino);
563                         goto out_delf;
564                 }
565         }
566         return rc;
567
568 out_delf:
569         securityfs_remove(seclvl_ino);
570
571 out_deldir:
572         securityfs_remove(dir_ino);
573
574         return rc;
575 }
576
577 static void seclvlfs_unregister(void)
578 {
579         securityfs_remove(seclvl_ino);
580
581         if (*passwd || *sha1_passwd)
582                 securityfs_remove(passwd_ino);
583
584         securityfs_remove(dir_ino);
585 }
586
587 /**
588  * Initialize the seclvl module.
589  */
590 static int __init seclvl_init(void)
591 {
592         int rc = 0;
593         static char once;
594
595         if (verbosity < 0 || verbosity > 1) {
596                 printk(KERN_ERR "Error: bad verbosity [%d]; only 0 or 1 "
597                        "are valid values\n", verbosity);
598                 rc = -EINVAL;
599                 goto exit;
600         }
601         if (initlvl < -1 || initlvl > 2) {
602                 seclvl_printk(0, KERN_ERR, "Error: bad initial securelevel "
603                               "[%d].\n", initlvl);
604                 rc = -EINVAL;
605                 goto exit;
606         }
607         seclvl = initlvl;
608         if ((rc = processPassword())) {
609                 seclvl_printk(0, KERN_ERR, "Error processing the password "
610                               "module parameter(s): rc = [%d]\n", rc);
611                 goto exit;
612         }
613
614         if ((rc = seclvlfs_register())) {
615                 seclvl_printk(0, KERN_ERR, "Error registering with sysfs\n");
616                 goto exit;
617         }
618         /* register ourselves with the security framework */
619         if (register_security(&seclvl_ops)) {
620                 seclvl_printk(0, KERN_ERR,
621                               "seclvl: Failure registering with the "
622                               "kernel.\n");
623                 /* try registering with primary module */
624                 rc = mod_reg_security(MY_NAME, &seclvl_ops);
625                 if (rc) {
626                         seclvl_printk(0, KERN_ERR, "seclvl: Failure "
627                                       "registering with primary security "
628                                       "module.\n");
629                         seclvlfs_unregister();
630                         goto exit;
631                 }               /* if primary module registered */
632                 secondary = 1;
633         }                       /* if we registered ourselves with the security framework */
634
635         seclvl_printk(0, KERN_INFO, "seclvl: Successfully initialized.\n");
636
637         if (once) {
638                 once = 1;
639                 seclvl_printk(0, KERN_INFO, "seclvl is going away. It has been "
640                                 "buggy for ages. Also, be warned that "
641                                 "Securelevels are useless.");
642         }
643  exit:
644         if (rc)
645                 printk(KERN_ERR "seclvl: Error during initialization: rc = "
646                        "[%d]\n", rc);
647         return rc;
648 }
649
650 /**
651  * Remove the seclvl module.
652  */
653 static void __exit seclvl_exit(void)
654 {
655         seclvlfs_unregister();
656
657         if (secondary)
658                 mod_unreg_security(MY_NAME, &seclvl_ops);
659         else if (unregister_security(&seclvl_ops))
660                 seclvl_printk(0, KERN_INFO,
661                               "seclvl: Failure unregistering with the "
662                               "kernel\n");
663 }
664
665 module_init(seclvl_init);
666 module_exit(seclvl_exit);
667
668 MODULE_AUTHOR("Michael A. Halcrow <mike@halcrow.us>");
669 MODULE_DESCRIPTION("LSM implementation of the BSD Secure Levels");
670 MODULE_LICENSE("GPL");