[PATCH] Bug fixes and cleanup for the BSD Secure Levels LSM
This patch address several issues in the current BSD Secure Levels code:
o plaintext_to_sha1: Missing check for a NULL return from __get_free_page
o passwd_write_file: A page is leaked if the password is wrong.
o fix securityfs registration order
o seclvl_init is a mess and can't properly tolerate failures, failure
path is upside down (deldif and delf should be switched)
Cleanups:
o plaintext_to_sha1: Use buffers passed in
o passwd_write_file: Use kmalloc() instead of get_zeroed_page()
o passwd_write_file: hashedPassword comparison is just memcmp
o s/ENOSYS/EINVAL/
o misc
(akpm: after some discussion it appears that the BSD secure levels feature
should be scheduled for removal. But for now, let's fix these problems up).
Signed-off-by: Davi Arnaut <davi.arnaut@gmail.com>
Cc: Michael Halcrow <mhalcrow@us.ibm.com>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: Stephen Smalley <sds@epoch.ncsc.mil>
Cc: James Morris <jmorris@namei.org>
Cc: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/security/seclvl.c b/security/seclvl.c
index 8529ea6..441beaf 100644
--- a/security/seclvl.c
+++ b/security/seclvl.c
@@ -8,6 +8,7 @@
* 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
@@ -31,6 +32,7 @@
#include <linux/kobject.h>
#include <linux/crypto.h>
#include <asm/scatterlist.h>
+#include <linux/scatterlist.h>
#include <linux/gfp.h>
#include <linux/sysfs.h>
@@ -194,35 +196,27 @@
* people...
*/
static int
-plaintext_to_sha1(unsigned char *hash, const char *plaintext, int len)
+plaintext_to_sha1(unsigned char *hash, const char *plaintext, unsigned int len)
{
- char *pgVirtAddr;
struct crypto_tfm *tfm;
- struct scatterlist sg[1];
+ struct scatterlist sg;
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 -ENOMEM;
+ return -EINVAL;
}
tfm = crypto_alloc_tfm("sha1", CRYPTO_TFM_REQ_MAY_SLEEP);
if (tfm == NULL) {
seclvl_printk(0, KERN_ERR,
"Failed to load transform for SHA1\n");
- return -ENOSYS;
+ return -EINVAL;
}
- // Just get a new page; don't play around with page boundaries
- // and scatterlists.
- pgVirtAddr = (char *)__get_free_page(GFP_KERNEL);
- sg[0].page = virt_to_page(pgVirtAddr);
- sg[0].offset = 0;
- sg[0].length = len;
- strncpy(pgVirtAddr, plaintext, len);
+ sg_init_one(&sg, (u8 *)plaintext, len);
crypto_digest_init(tfm);
- crypto_digest_update(tfm, sg, 1);
+ crypto_digest_update(tfm, &sg, 1);
crypto_digest_final(tfm, hash);
crypto_free_tfm(tfm);
- free_page((unsigned long)pgVirtAddr);
return 0;
}
@@ -234,11 +228,9 @@
passwd_write_file(struct file * file, const char __user * buf,
size_t count, loff_t *ppos)
{
- int i;
- unsigned char tmp[SHA1_DIGEST_SIZE];
- char *page;
- int rc;
+ char *p;
int len;
+ unsigned char tmp[SHA1_DIGEST_SIZE];
if (!*passwd && !*sha1_passwd) {
seclvl_printk(0, KERN_ERR, "Attempt to password-unlock the "
@@ -251,38 +243,39 @@
return -EINVAL;
}
- if (count < 0 || count >= PAGE_SIZE)
+ if (count >= PAGE_SIZE)
return -EINVAL;
if (*ppos != 0)
return -EINVAL;
- page = (char *)get_zeroed_page(GFP_KERNEL);
- if (!page)
+ p = kmalloc(count, GFP_KERNEL);
+ if (!p)
return -ENOMEM;
len = -EFAULT;
- if (copy_from_user(page, buf, count))
+ if (copy_from_user(p, buf, count))
goto out;
- len = strlen(page);
+ len = count;
/* ``echo "secret" > seclvl/passwd'' includes a newline */
- if (page[len - 1] == '\n')
+ if (p[len - 1] == '\n')
len--;
/* Hash the password, then compare the hashed values */
- if ((rc = plaintext_to_sha1(tmp, page, len))) {
+ if ((len = plaintext_to_sha1(tmp, p, len))) {
seclvl_printk(0, KERN_ERR, "Error hashing password: rc = "
- "[%d]\n", rc);
- return rc;
+ "[%d]\n", len);
+ goto out;
}
- for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
- if (hashedPassword[i] != tmp[i])
- return -EPERM;
- }
+
+ 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:
- free_page((unsigned long)page);
+ kfree (p);
return len;
}
@@ -295,13 +288,11 @@
*/
static int seclvl_ptrace(struct task_struct *parent, struct task_struct *child)
{
- if (seclvl >= 0) {
- if (child->pid == 1) {
- seclvl_printk(1, KERN_WARNING, "Attempt to ptrace "
- "the init process dissallowed in "
- "secure level %d\n", seclvl);
- return -EPERM;
- }
+ 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;
}
@@ -312,55 +303,54 @@
*/
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;
- switch (seclvl) {
- case 2:
- /* fall through */
- case 1:
- if (cap == CAP_LINUX_IMMUTABLE) {
+ 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);
- return -EPERM;
- } else if (cap == CAP_SYS_RAWIO) { // Somewhat broad...
+ 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);
- return -EPERM;
- } else if (cap == CAP_NET_ADMIN) {
+ 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);
- return -EPERM;
- } else if (cap == CAP_SETUID) {
+ else if (cap == CAP_SETUID)
seclvl_printk(1, KERN_WARNING, "Attempt to setuid "
"while in secure level [%d] denied\n",
seclvl);
- return -EPERM;
- } else if (cap == CAP_SETGID) {
+ 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) {
+ 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);
- return -EPERM;
- }
- break;
- default:
- break;
+ else
+ rc = 0;
}
- /* from dummy.c */
- if (cap_is_fs_cap(cap) ? tsk->fsuid == 0 : tsk->euid == 0)
- return 0; /* capability granted */
- seclvl_printk(1, KERN_WARNING, "Capability denied\n");
- return -EPERM; /* capability denied */
+
+ 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;
}
/**
@@ -466,12 +456,9 @@
static void seclvl_file_free_security(struct file *filp)
{
struct dentry *dentry = filp->f_dentry;
- struct inode *inode = NULL;
- if (dentry) {
- inode = dentry->d_inode;
- seclvl_bd_release(inode);
- }
+ if (dentry)
+ seclvl_bd_release(dentry->d_inode);
}
/**
@@ -479,9 +466,7 @@
*/
static int seclvl_umount(struct vfsmount *mnt, int flags)
{
- if (current->pid == 1)
- return 0;
- if (seclvl == 2) {
+ if (current->pid != 1 && seclvl == 2) {
seclvl_printk(1, KERN_WARNING, "Attempt to unmount in secure "
"level %d\n", seclvl);
return -EPERM;
@@ -505,8 +490,9 @@
static int processPassword(void)
{
int rc = 0;
- hashedPassword[0] = '\0';
if (*passwd) {
+ char *p;
+
if (*sha1_passwd) {
seclvl_printk(0, KERN_ERR, "Error: Both "
"passwd and sha1_passwd "
@@ -514,12 +500,16 @@
"exclusive.\n");
return -EINVAL;
}
- if ((rc = plaintext_to_sha1(hashedPassword, passwd,
- strlen(passwd)))) {
+
+ 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");
- return rc;
- }
+
+ kfree (p);
/* All static data goes to the BSS, which zero's the
* plaintext password out for us. */
} else if (*sha1_passwd) { // Base 16
@@ -542,7 +532,7 @@
sha1_passwd[i + 2] = tmp;
}
}
- return 0;
+ return rc;
}
/**
@@ -552,28 +542,46 @@
static int seclvlfs_register(void)
{
+ int rc = 0;
+
dir_ino = securityfs_create_dir("seclvl", NULL);
- if (!dir_ino)
- return -EFAULT;
+
+ 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 (!seclvl_ino)
+ 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 (!passwd_ino)
+ if (IS_ERR(passwd_ino)) {
+ rc = PTR_ERR(passwd_ino);
goto out_delf;
+ }
}
- return 0;
+ return rc;
-out_deldir:
- securityfs_remove(dir_ino);
out_delf:
securityfs_remove(seclvl_ino);
- return -EFAULT;
+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);
}
/**
@@ -582,6 +590,8 @@
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);
@@ -600,6 +610,11 @@
"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,
@@ -611,20 +626,24 @@
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 */
- if ((rc = seclvlfs_register())) {
- seclvl_printk(0, KERN_ERR, "Error registering with sysfs\n");
- goto exit;
- }
+
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) {
+ if (rc)
printk(KERN_ERR "seclvl: Error during initialization: rc = "
"[%d]\n", rc);
- }
return rc;
}
@@ -633,17 +652,14 @@
*/
static void __exit seclvl_exit(void)
{
- securityfs_remove(seclvl_ino);
- if (*passwd || *sha1_passwd)
- securityfs_remove(passwd_ino);
- securityfs_remove(dir_ino);
- if (secondary == 1) {
+ seclvlfs_unregister();
+
+ if (secondary)
mod_unreg_security(MY_NAME, &seclvl_ops);
- } else if (unregister_security(&seclvl_ops)) {
+ else if (unregister_security(&seclvl_ops))
seclvl_printk(0, KERN_INFO,
"seclvl: Failure unregistering with the "
"kernel\n");
- }
}
module_init(seclvl_init);
