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Smack: allow multiple labels in onlycap 

Smack onlycap allows limiting of CAP_MAC_ADMIN and CAP_MAC_OVERRIDE to
processes running with the configured label. But having single privileged
label is not enough in some real use cases. On a complex system like Tizen,
there maybe few programs that need to configure Smack policy in run-time
and running them all with a single label is not always practical.
This patch extends onlycap feature for multiple labels. They are configured
in the same smackfs "onlycap" interface, separated by spaces.

Signed-off-by: Rafal Krypa <r.krypa@samsung.com>
hifive-unleashed-5.1
Rafal Krypa 2015-06-02 11:23:48 +02:00 committed by Casey Schaufler
parent 01fa8474fb
commit c0d77c8844
4 changed files with 163 additions and 72 deletions
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6
Documentation/security/Smack.txt
View File

@ -206,11 +206,11 @@ netlabel
label. The format accepted on write is:
"%d.%d.%d.%d label" or "%d.%d.%d.%d/%d label".
onlycap
This contains the label processes must have for CAP_MAC_ADMIN
This contains labels processes must have for CAP_MAC_ADMIN
and CAP_MAC_OVERRIDE to be effective. If this file is empty
these capabilities are effective at for processes with any
label. The value is set by writing the desired label to the
file or cleared by writing "-" to the file.
label. The values are set by writing the desired labels, separated
by spaces, to the file or cleared by writing "-" to the file.
ptrace
This is used to define the current ptrace policy
0 - default: this is the policy that relies on Smack access rules.

25
security/smack/smack.h
View File

@ -138,6 +138,11 @@ struct smk_port_label {
struct smack_known *smk_out; /* outgoing label */
};
struct smack_onlycap {
struct list_head list;
struct smack_known *smk_label;
};
/*
* Mount options
*/
@ -249,6 +254,7 @@ int smk_netlbl_mls(int, char *, struct netlbl_lsm_secattr *, int);
struct smack_known *smk_import_entry(const char *, int);
void smk_insert_entry(struct smack_known *skp);
struct smack_known *smk_find_entry(const char *);
int smack_privileged(int cap);
/*
* Shared data.
@ -257,7 +263,6 @@ extern int smack_enabled;
extern int smack_cipso_direct;
extern int smack_cipso_mapped;
extern struct smack_known *smack_net_ambient;
extern struct smack_known *smack_onlycap;
extern struct smack_known *smack_syslog_label;
#ifdef CONFIG_SECURITY_SMACK_BRINGUP
extern struct smack_known *smack_unconfined;
@ -276,6 +281,9 @@ extern struct mutex smack_known_lock;
extern struct list_head smack_known_list;
extern struct list_head smk_netlbladdr_list;
extern struct mutex smack_onlycap_lock;
extern struct list_head smack_onlycap_list;
#define SMACK_HASH_SLOTS 16
extern struct hlist_head smack_known_hash[SMACK_HASH_SLOTS];
@ -331,21 +339,6 @@ static inline struct smack_known *smk_of_current(void)
return smk_of_task(current_security());
}
/*
* Is the task privileged and allowed to be privileged
* by the onlycap rule.
*/
static inline int smack_privileged(int cap)
{
struct smack_known *skp = smk_of_current();
if (!capable(cap))
return 0;
if (smack_onlycap == NULL || smack_onlycap == skp)
return 1;
return 0;
}
/*
* logging functions
*/

41
security/smack/smack_access.c
View File

@ -617,3 +617,44 @@ struct smack_known *smack_from_secid(const u32 secid)
rcu_read_unlock();
return &smack_known_invalid;
}
/*
* Unless a process is running with one of these labels
* even having CAP_MAC_OVERRIDE isn't enough to grant
* privilege to violate MAC policy. If no labels are
* designated (the empty list case) capabilities apply to
* everyone.
*/
LIST_HEAD(smack_onlycap_list);
DEFINE_MUTEX(smack_onlycap_lock);
/*
* Is the task privileged and allowed to be privileged
* by the onlycap rule.
*
* Returns 1 if the task is allowed to be privileged, 0 if it's not.
*/
int smack_privileged(int cap)
{
struct smack_known *skp = smk_of_current();
struct smack_onlycap *sop;
if (!capable(cap))
return 0;
rcu_read_lock();
if (list_empty(&smack_onlycap_list)) {
rcu_read_unlock();
return 1;
}
list_for_each_entry_rcu(sop, &smack_onlycap_list, list) {
if (sop->smk_label == skp) {
rcu_read_unlock();
return 1;
}
}
rcu_read_unlock();
return 0;
}

163
security/smack/smackfs.c
View File

@ -87,16 +87,6 @@ int smack_cipso_direct = SMACK_CIPSO_DIRECT_DEFAULT;
*/
int smack_cipso_mapped = SMACK_CIPSO_MAPPED_DEFAULT;
/*
* Unless a process is running with this label even
* having CAP_MAC_OVERRIDE isn't enough to grant
* privilege to violate MAC policy. If no label is
* designated (the NULL case) capabilities apply to
* everyone. It is expected that the hat (^) label
* will be used if any label is used.
*/
struct smack_known *smack_onlycap;
#ifdef CONFIG_SECURITY_SMACK_BRINGUP
/*
* Allow one label to be unconfined. This is for
@ -1636,34 +1626,79 @@ static const struct file_operations smk_ambient_ops = {
.llseek = default_llseek,
};
/**
* smk_read_onlycap - read() for smackfs/onlycap
* @filp: file pointer, not actually used
* @buf: where to put the result
* @cn: maximum to send along
* @ppos: where to start
*
* Returns number of bytes read or error code, as appropriate
/*
* Seq_file operations for /smack/onlycap
*/
static ssize_t smk_read_onlycap(struct file *filp, char __user *buf,
size_t cn, loff_t *ppos)
static void *onlycap_seq_start(struct seq_file *s, loff_t *pos)
{
char *smack = "";
ssize_t rc = -EINVAL;
int asize;
return smk_seq_start(s, pos, &smack_onlycap_list);
}
if (*ppos != 0)
return 0;
static void *onlycap_seq_next(struct seq_file *s, void *v, loff_t *pos)
{
return smk_seq_next(s, v, pos, &smack_onlycap_list);
}
if (smack_onlycap != NULL)
smack = smack_onlycap->smk_known;
static int onlycap_seq_show(struct seq_file *s, void *v)
{
struct list_head *list = v;
struct smack_onlycap *sop =
list_entry_rcu(list, struct smack_onlycap, list);
asize = strlen(smack) + 1;
seq_puts(s, sop->smk_label->smk_known);
seq_putc(s, ' ');
if (cn >= asize)
rc = simple_read_from_buffer(buf, cn, ppos, smack, asize);
return 0;
}
return rc;
static const struct seq_operations onlycap_seq_ops = {
.start = onlycap_seq_start,
.next = onlycap_seq_next,
.show = onlycap_seq_show,
.stop = smk_seq_stop,
};
static int smk_open_onlycap(struct inode *inode, struct file *file)
{
return seq_open(file, &onlycap_seq_ops);
}
/**
* smk_list_swap_rcu - swap public list with a private one in RCU-safe way
* The caller must hold appropriate mutex to prevent concurrent modifications
* to the public list.
* Private list is assumed to be not accessible to other threads yet.
*
* @public: public list
* @private: private list
*/
static void smk_list_swap_rcu(struct list_head *public,
struct list_head *private)
{
struct list_head *first, *last;
if (list_empty(public)) {
list_splice_init_rcu(private, public, synchronize_rcu);
} else {
/* Remember public list before replacing it */
first = public->next;
last = public->prev;
/* Publish private list in place of public in RCU-safe way */
private->prev->next = public;
private->next->prev = public;
rcu_assign_pointer(public->next, private->next);
public->prev = private->prev;
synchronize_rcu();
/* When all readers are done with the old public list,
* attach it in place of private */
private->next = first;
private->prev = last;
first->prev = private;
last->next = private;
}
}
/**
@ -1679,29 +1714,48 @@ static ssize_t smk_write_onlycap(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
char *data;
struct smack_known *skp = smk_of_task(current->cred->security);
char *data_parse;
char *tok;
struct smack_known *skp;
struct smack_onlycap *sop;
struct smack_onlycap *sop2;
LIST_HEAD(list_tmp);
int rc = count;
if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
/*
* This can be done using smk_access() but is done
* explicitly for clarity. The smk_access() implementation
* would use smk_access(smack_onlycap, MAY_WRITE)
*/
if (smack_onlycap != NULL && smack_onlycap != skp)
return -EPERM;
data = kzalloc(count + 1, GFP_KERNEL);
if (data == NULL)
return -ENOMEM;
if (copy_from_user(data, buf, count) != 0) {
rc = -EFAULT;
goto freeout;
kfree(data);
return -EFAULT;
}
data_parse = data;
while ((tok = strsep(&data_parse, " ")) != NULL) {
if (!*tok)
continue;
skp = smk_import_entry(tok, 0);
if (IS_ERR(skp)) {
rc = PTR_ERR(skp);
break;
}
sop = kzalloc(sizeof(*sop), GFP_KERNEL);
if (sop == NULL) {
rc = -ENOMEM;
break;
}
sop->smk_label = skp;
list_add_rcu(&sop->list, &list_tmp);
}
kfree(data);
/*
* Clear the smack_onlycap on invalid label errors. This means
* that we can pass a null string to unset the onlycap value.
@ -1710,26 +1764,29 @@ static ssize_t smk_write_onlycap(struct file *file, const char __user *buf,
* so "-usecapabilities" will also work.
*
* But do so only on invalid label, not on system errors.
* The invalid label must be first to count as clearing attempt.
*/
skp = smk_import_entry(data, count);
if (PTR_ERR(skp) == -EINVAL)
skp = NULL;
else if (IS_ERR(skp)) {
rc = PTR_ERR(skp);
goto freeout;
if (rc == -EINVAL && list_empty(&list_tmp))
rc = count;
if (rc >= 0) {
mutex_lock(&smack_onlycap_lock);
smk_list_swap_rcu(&smack_onlycap_list, &list_tmp);
mutex_unlock(&smack_onlycap_lock);
}
smack_onlycap = skp;
list_for_each_entry_safe(sop, sop2, &list_tmp, list)
kfree(sop);
freeout:
kfree(data);
return rc;
}
static const struct file_operations smk_onlycap_ops = {
.read = smk_read_onlycap,
.open = smk_open_onlycap,
.read = seq_read,
.write = smk_write_onlycap,
.llseek = default_llseek,
.llseek = seq_lseek,
.release = seq_release,
};
#ifdef CONFIG_SECURITY_SMACK_BRINGUP