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[PATCH] seclvl securityfs
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Once again, the simple_attr in libfs was actually sufficient - I'd
thought the __attribute__(format(printk(1,2))) was more mysterious than
it really is.

At last, here is the full patch to make seclvl use securityfs.

Signed-off-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Chris Wright <chrisw@osdl.org>
--

 seclvl.c |  228 +++++++++++++++++++--------------------------------------------
 1 files changed, 70 insertions(+), 158 deletions(-)

Index: linux-2.6.13-rc1/security/seclvl.c
===================================================================
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serue@us.ibm.com authored and Chris Wright committed Jul 9, 2005
1 parent b67dbf9 commit 5a73c30
Showing 1 changed file with 70 additions and 158 deletions.
228 changes: 70 additions & 158 deletions security/seclvl.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -118,69 +118,6 @@ MODULE_PARM_DESC(hideHash, "When set to 0, reading seclvl/passwd from sysfs "
} \
} 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.
*/
Expand Down Expand Up @@ -212,97 +149,44 @@ static int seclvl_sanity(int reqlvl)
return 0;
}

/**
* Called whenever the user reads the sysfs handle to this kernel
* object
*/
static ssize_t seclvl_read_file(struct seclvl_obj *obj, char *buff)
{
return snprintf(buff, PAGE_SIZE, "%d\n", seclvl);
}

/**
* 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 int do_seclvl_advance(int newlvl)
static void do_seclvl_advance(void *data, u64 val)
{
if (newlvl <= seclvl) {
seclvl_printk(1, KERN_WARNING, "Cannot advance to seclvl "
"[%d]\n", newlvl);
return -EINVAL;
}
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 -EINVAL;
return;
}
if (seclvl == -1) {
seclvl_printk(1, KERN_WARNING, "Not allowed to advance to "
"seclvl [%d]\n", seclvl);
return -EPERM;
return;
}
seclvl = newlvl;
return 0;
seclvl = newlvl; /* would it be more "correct" to set *data? */
return;
}

/**
* Called whenever the user writes to the sysfs handle to this kernel
* 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)
static u64 seclvl_int_get(void *data)
{
unsigned long val;
if (count > 2 || (count == 2 && buff[1] != '\n')) {
seclvl_printk(1, KERN_WARNING, "Invalid value passed to "
"seclvl: [%s]\n", buff);
return -EINVAL;
}
val = buff[0] - 48;
if (seclvl_sanity(val)) {
seclvl_printk(1, KERN_WARNING, "Illegal secure level "
"requested: [%d]\n", (int)val);
return -EPERM;
}
if (do_seclvl_advance(val)) {
seclvl_printk(0, KERN_ERR, "Failure advancing security level "
"to %lu\n", val);
}
return count;
return *(int *)data;
}

/* 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);
DEFINE_SIMPLE_ATTRIBUTE(seclvl_file_ops, seclvl_int_get, do_seclvl_advance, "%lld\n");

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.
*
Expand Down Expand Up @@ -347,12 +231,15 @@ plaintext_to_sha1(unsigned char *hash, const char *plaintext, int len)
* 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 "
Expand All @@ -363,13 +250,26 @@ seclvl_write_passwd(struct seclvl_obj *obj, const char *buff, size_t count)
"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;
Expand All @@ -382,13 +282,16 @@ seclvl_write_passwd(struct seclvl_obj *obj, const char *buff, size_t count)
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.
Expand Down Expand Up @@ -647,22 +550,34 @@ static int processPassword(void)
}

/**
* 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, &seclvl, &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;
}

/**
Expand All @@ -677,8 +592,6 @@ static int __init seclvl_init(void)
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);
Expand Down Expand Up @@ -706,7 +619,7 @@ static int __init seclvl_init(void)
} /* 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;
}
Expand All @@ -724,12 +637,11 @@ static int __init seclvl_init(void)
*/
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)) {
Expand Down

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