[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>

1 files changed, 113 insertions, 97 deletions

diff --git a/security/seclvl.c b/security/seclvl.c
index 8529ea6f7aa8..441beaf1bbc1 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 @@ static unsigned char hashedPassword[SHA1_DIGEST_SIZE];
  * 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 @@ static ssize_t
 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 @@ passwd_write_file(struct file * file, const char __user * buf,
                 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;
-        }
-        for (i = 0; i < SHA1_DIGEST_SIZE; i++) {
-                if (hashedPassword[i] != tmp[i])
-                        return -EPERM;
+                              "[%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:
-        free_page((unsigned long)page);
+        kfree (p);
         return len;
 }
 
@@ -295,13 +288,11 @@ static struct file_operations passwd_file_ops = {
  */
 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_ptrace(struct task_struct *parent, struct task_struct *child)
  */
 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 int seclvl_inode_setattr(struct dentry *dentry, struct iattr *iattr)
 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 void seclvl_file_free_security(struct file *filp)
  */
 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 struct security_operations seclvl_ops = {
 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 @@ static int processPassword(void)
                                       "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 @@ static int processPassword(void)
                         sha1_passwd[i + 2] = tmp;
                 }
         }
-        return 0;
+        return rc;
 }
 
 /**
@@ -552,28 +542,46 @@ struct dentry *dir_ino, *seclvl_ino, *passwd_ino;
 
 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_delf:
+        securityfs_remove(seclvl_ino);
 
 out_deldir:
         securityfs_remove(dir_ino);
-out_delf:
+
+        return rc;
+}
+
+static void seclvlfs_unregister(void)
+{
         securityfs_remove(seclvl_ino);
 
-        return -EFAULT;
+        if (*passwd || *sha1_passwd)
+                securityfs_remove(passwd_ino);
+
+        securityfs_remove(dir_ino);
 }
 
 /**
@@ -582,6 +590,8 @@ out_delf:
 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 @@ static int __init seclvl_init(void)
                               "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 @@ static int __init seclvl_init(void)
                         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 int __init seclvl_init(void)
  */
 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);