Re: [PATCH] securityfs

serge
2005-07-04T16:01:50Z

Quoting Greg KH (greg@kroah.com):
> On Sun, Jul 03, 2005 at 02:53:17PM -0400, James Morris wrote:
> > On Sun, 3 Jul 2005, Tony Jones wrote:
> >
> > > There just isn't enough content to justify a stacker specific filesystem IMHO.
> >
> > It might be worth thinking about a more general securityfs as part of LSM,
> > to be used by stacker and LSM modules. SELinux could use this instead of
> > managing its own selinuxfs.
>
> Good idea. Here's a patch to do just that (compile tested only...)
>
> Comments?

Tested without a hitch.

In addition, the attached patch converts seclvl to use the securityfs.
Also tested without any problems. (Only meant as proof of concept:
Mike, you'll probably want to at least add the passwd_read_file
function back in, I assume?)

thanks,
-serge

--
seclvl.c | 226
+++++++++++++++++++++++++++------------------------------------
1 files changed, 99 insertions(+), 127 deletions(-)

Signed-off-by: Serge Hallyn <serue@us.ibm.com>

Index: linux-2.6.13-rc1/security/seclvl.c
===================================================================
--- linux-2.6.13-rc1.orig/security/seclvl.c 2005-07-02 21:49:34.000000000 -0500
+++ linux-2.6.13-rc1/security/seclvl.c 2005-07-04 07:58:15.000000000 -0500
@@ -119,69 +119,6 @@
} while (0)

/**
- * kobject stuff
- */
-
-struct subsystem seclvl_subsys;
-
-struct seclvl_obj {
- char *name;
- struct list_head slot_list;
- struct kobject kobj;
-};
-
-/**
- * There is a seclvl_attribute struct for each file in sysfs.
- *
- * In our case, we have one of these structs for "passwd" and another
- * for "seclvl".
- */
-struct seclvl_attribute {
- struct attribute attr;
- ssize_t(*show) (struct seclvl_obj *, char *);
- ssize_t(*store) (struct seclvl_obj *, const char *, size_t);
-};
-
-/**
- * When this function is called, one of the files in sysfs is being
- * written to. attribute->store is a function pointer to whatever the
- * struct seclvl_attribute store function pointer points to. It is
- * unique for "passwd" and "seclvl".
- */
-static ssize_t
-seclvl_attr_store(struct kobject *kobj,
- struct attribute *attr, const char *buf, size_t len)
-{
- struct seclvl_obj *obj = container_of(kobj, struct seclvl_obj, kobj);
- struct seclvl_attribute *attribute =
- container_of(attr, struct seclvl_attribute, attr);
- return attribute->store ? attribute->store(obj, buf, len) : -EIO;
-}
-
-static ssize_t
-seclvl_attr_show(struct kobject *kobj, struct attribute *attr, char *buf)
-{
- struct seclvl_obj *obj = container_of(kobj, struct seclvl_obj, kobj);
- struct seclvl_attribute *attribute =
- container_of(attr, struct seclvl_attribute, attr);
- return attribute->show ? attribute->show(obj, buf) : -EIO;
-}
-
-/**
- * Callback function pointers for show and store
- */
-static struct sysfs_ops seclvlfs_sysfs_ops = {
- .show = seclvl_attr_show,
- .store = seclvl_attr_store,
-};
-
-static struct kobj_type seclvl_ktype = {
- .sysfs_ops = &seclvlfs_sysfs_ops
-};
-
-decl_subsys(seclvl, &seclvl_ktype, NULL);
-
-/**
* The actual security level. Ranges between -1 and 2 inclusive.
*/
static int seclvl;
@@ -216,9 +153,15 @@
* Called whenever the user reads the sysfs handle to this kernel
* object
*/
-static ssize_t seclvl_read_file(struct seclvl_obj *obj, char *buff)
+#define TMPBUFLEN 12
+static ssize_t seclvl_read_file(struct file *filp, char __user *buf,
+ size_t count, loff_t *ppos)
{
- return snprintf(buff, PAGE_SIZE, "%d\n", seclvl);
+ char tmpbuf[TMPBUFLEN];
+ ssize_t length;
+
+ length = scnprintf(tmpbuf, TMPBUFLEN, "%d", seclvl);
+ return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
}

/**
@@ -253,57 +196,58 @@
* object (seclvl/seclvl). It expects a single-digit number.
*/
static ssize_t
-seclvl_write_file(struct seclvl_obj *obj, const char *buff, size_t count)
+seclvl_write_file(struct file * file, const char __user * buf,
+ size_t count, loff_t *ppos)
{
- unsigned long val;
- if (count > 2 || (count == 2 && buff[1] != '\n')) {
- seclvl_printk(1, KERN_WARNING, "Invalid value passed to "
- "seclvl: [%s]\n", buff);
+ int val;
+ int err;
+ char *page;
+
+ if (count > 2)
return -EINVAL;
+ if (*ppos != 0)
+ return -EINVAL;
+
+ page = (char *) get_zeroed_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ if (copy_from_user(page, buf, count)) {
+ err = -EFAULT;
+ goto out;
+ }
+
+ if (sscanf(page, "%d", &val) != 1) {
+ err = -EINVAL;
+ goto out;
}
- val = buff[0] - 48;
+
if (seclvl_sanity(val)) {
seclvl_printk(1, KERN_WARNING, "Illegal secure level "
"requested: [%d]\n", (int)val);
- return -EPERM;
+ err = -EINVAL;
+ goto out;
}
+ err = count;
if (do_seclvl_advance(val)) {
seclvl_printk(0, KERN_ERR, "Failure advancing security level "
- "to %lu\n", val);
+ "to %d\n", val);
+ err = -EINVAL;
}
- return count;
+
+out:
+ free_page((unsigned long)page);
+ return err;
}

-/* Generate sysfs_attr_seclvl */
-static struct seclvl_attribute sysfs_attr_seclvl =
-__ATTR(seclvl, (S_IFREG | S_IRUGO | S_IWUSR), seclvl_read_file,
- seclvl_write_file);
+static struct file_operations seclvl_file_ops = {
+ .read = seclvl_read_file,
+ .write = seclvl_write_file,
+};

static unsigned char hashedPassword[SHA1_DIGEST_SIZE];

/**
- * Called whenever the user reads the sysfs passwd handle.
- */
-static ssize_t seclvl_read_passwd(struct seclvl_obj *obj, char *buff)
-{
- /* So just how good *is* your password? :-) */
- char tmp[3];
- int i = 0;
- buff[0] = '\0';
- if (hideHash) {
- /* Security through obscurity */
- return 0;
- }
- while (i < SHA1_DIGEST_SIZE) {
- snprintf(tmp, 3, "%02x", hashedPassword[i]);
- strncat(buff, tmp, 2);
- i++;
- }
- strcat(buff, "\n");
- return ((SHA1_DIGEST_SIZE * 2) + 1);
-}
-
-/**
* 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
@@ -347,12 +291,15 @@
* object. It hashes the password and compares the hashed results.
*/
static ssize_t
-seclvl_write_passwd(struct seclvl_obj *obj, const char *buff, size_t count)
+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;
int len;
+
if (!*passwd && !*sha1_passwd) {
seclvl_printk(0, KERN_ERR, "Attempt to password-unlock the "
"seclvl module, but neither a plain text "
@@ -363,13 +310,26 @@
"maintainer about this event.\n");
return -EINVAL;
}
- len = strlen(buff);
+
+ if (count < 0 || count >= PAGE_SIZE)
+ return -ENOMEM;
+ if (*ppos != 0) {
+ return -EINVAL;
+ }
+ page = (char *)get_zeroed_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+ len = -EFAULT;
+ if (copy_from_user(page, buf, count))
+ goto out;
+
+ len = strlen(page);
/* ``echo "secret" > seclvl/passwd'' includes a newline */
- if (buff[len - 1] == '\n') {
+ if (page[len - 1] == '\n') {
len--;
}
/* Hash the password, then compare the hashed values */
- if ((rc = plaintext_to_sha1(tmp, buff, len))) {
+ if ((rc = plaintext_to_sha1(tmp, page, len))) {
seclvl_printk(0, KERN_ERR, "Error hashing password: rc = "
"[%d]\n", rc);
return rc;
@@ -382,13 +342,16 @@
seclvl_printk(0, KERN_INFO,
"Password accepted; seclvl reduced to 0.\n");
seclvl = 0;
- return count;
+ len = count;
+
+out:
+ free_page((unsigned long)page);
+ return len;
}

-/* Generate sysfs_attr_passwd */
-static struct seclvl_attribute sysfs_attr_passwd =
-__ATTR(passwd, (S_IFREG | S_IRUGO | S_IWUSR), seclvl_read_passwd,
- seclvl_write_passwd);
+static struct file_operations passwd_file_ops = {
+ .write = passwd_write_file,
+};

/**
* Explicitely disallow ptrace'ing the init process.
@@ -647,22 +610,34 @@
}

/**
- * Sysfs registrations
+ * securityfs registrations
*/
-static int doSysfsRegistrations(void)
+struct dentry *dir_ino, *seclvl_ino, *passwd_ino;
+
+static int seclvlfs_register(void)
{
- int rc = 0;
- if ((rc = subsystem_register(&seclvl_subsys))) {
- seclvl_printk(0, KERN_WARNING,
- "Error [%d] registering seclvl subsystem\n", rc);
- return rc;
- }
- sysfs_create_file(&seclvl_subsys.kset.kobj, &sysfs_attr_seclvl.attr);
+ dir_ino = securityfs_create_dir("seclvl", NULL);
+ if (!dir_ino)
+ return -EFAULT;
+
+ seclvl_ino = securityfs_create_file("seclvl", S_IRUGO | S_IWUSR,
+ dir_ino, NULL, &seclvl_file_ops);
+ if (!seclvl_ino)
+ goto out_deldir;
if (*passwd || *sha1_passwd) {
- sysfs_create_file(&seclvl_subsys.kset.kobj,
- &sysfs_attr_passwd.attr);
+ passwd_ino = securityfs_create_file("passwd", S_IRUGO | S_IWUSR,
+ dir_ino, NULL, &passwd_file_ops);
+ if (!passwd_ino)
+ goto out_delf;
}
return 0;
+
+out_deldir:
+ securityfs_remove(dir_ino);
+out_delf:
+ securityfs_remove(seclvl_ino);
+
+ return -EFAULT;
}

/**
@@ -677,8 +652,6 @@
rc = -EINVAL;
goto exit;
}
- sysfs_attr_seclvl.attr.owner = THIS_MODULE;
- sysfs_attr_passwd.attr.owner = THIS_MODULE;
if (initlvl < -1 || initlvl > 2) {
seclvl_printk(0, KERN_ERR, "Error: bad initial securelevel "
"[%d].\n", initlvl);
@@ -706,7 +679,7 @@
} /* if primary module registered */
secondary = 1;
} /* if we registered ourselves with the security framework */
- if ((rc = doSysfsRegistrations())) {
+ if ((rc = seclvlfs_register())) {
seclvl_printk(0, KERN_ERR, "Error registering with sysfs\n");
goto exit;
}
@@ -724,12 +697,11 @@
*/
static void __exit seclvl_exit(void)
{
- sysfs_remove_file(&seclvl_subsys.kset.kobj, &sysfs_attr_seclvl.attr);
+ securityfs_remove(seclvl_ino);
if (*passwd || *sha1_passwd) {
- sysfs_remove_file(&seclvl_subsys.kset.kobj,
- &sysfs_attr_passwd.attr);
+ securityfs_remove(passwd_ino);
}
- subsystem_unregister(&seclvl_subsys);
+ securityfs_remove(dir_ino);
if (secondary == 1) {
mod_unreg_security(MY_NAME, &seclvl_ops);
} else if (unregister_security(&seclvl_ops)) {