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Commit 828716c2 authored by Jarkko Sakkinen's avatar Jarkko Sakkinen Committed by Casey Schaufler
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Smack: check permissions from user space (v2) 



Adds a new file into SmackFS called 'access'. Wanted
Smack permission is written into /smack/access.
After that result can be read from the opened file.
If access applies result contains 1 and otherwise
0. File access is protected from race conditions
by using simple_transaction_get()/set() API.

Fixes from the previous version:
- Removed smack.h changes, refactoring left-over
from previous version.
- Removed #include <linux/smack.h>, refactoring
left-over from previous version.

Signed-off-by: default avatarJarkko Sakkinen <jarkko.sakkinen@intel.com>
Signed-off-by: default avatarCasey Schaufler <cschaufler@cschaufler-intel.(none)>
parent 545a7260

security/smack/smackfs.c

+117 −63
Original line number Diff line number Diff line
@@ -44,6 +44,7 @@ enum smk_inos { 
	SMK_ONLYCAP	= 9,	/* the only "capable" label */

	SMK_LOGGING	= 10,	/* logging */

	SMK_LOAD_SELF	= 11,	/* task specific rules */

	SMK_ACCESSES	= 12,	/* access policy */

};



/*
@@ -176,71 +177,19 @@ static int smk_set_access(struct smack_rule *srp, struct list_head *rule_list, 
}



/**

 * smk_write_load_list - write() for any /smack/load

 * @file: file pointer, not actually used

 * @buf: where to get the data from

 * @count: bytes sent

 * @ppos: where to start - must be 0

 * @rule_list: the list of rules to write to

 * @rule_lock: lock for the rule list

 *

 * Get one smack access rule from above.

 * The format is exactly:

 *     char subject[SMK_LABELLEN]

 *     char object[SMK_LABELLEN]

 *     char access[SMK_ACCESSLEN]

 *

 * writes must be SMK_LABELLEN+SMK_LABELLEN+SMK_ACCESSLEN bytes.

 * smk_parse_rule - parse subject, object and access type

 * @data: string to be parsed whose size is SMK_LOADLEN

 * @rule: parsed entities are stored in here

 */

static ssize_t smk_write_load_list(struct file *file, const char __user *buf,

				size_t count, loff_t *ppos,

				struct list_head *rule_list,

				struct mutex *rule_lock)

static int smk_parse_rule(const char *data, struct smack_rule *rule)

{

	struct smack_rule *rule;

	char *data;

	int rc = -EINVAL;



	/*

	 * No partial writes.

	 * Enough data must be present.

	 */

	if (*ppos != 0)

		return -EINVAL;

	/*

	 * Minor hack for backward compatibility

	 */

	if (count < (SMK_OLOADLEN) || count > SMK_LOADLEN)

		return -EINVAL;



	data = kzalloc(SMK_LOADLEN, GFP_KERNEL);

	if (data == NULL)

		return -ENOMEM;



	if (copy_from_user(data, buf, count) != 0) {

		rc = -EFAULT;

		goto out;

	}



	/*

	 * More on the minor hack for backward compatibility

	 */

	if (count == (SMK_OLOADLEN))

		data[SMK_OLOADLEN] = '-';



	rule = kzalloc(sizeof(*rule), GFP_KERNEL);

	if (rule == NULL) {

		rc = -ENOMEM;

		goto out;

	}



	rule->smk_subject = smk_import(data, 0);

	if (rule->smk_subject == NULL)

		goto out_free_rule;

		return -1;



	rule->smk_object = smk_import(data + SMK_LABELLEN, 0);

	if (rule->smk_object == NULL)

		goto out_free_rule;

		return -1;



	rule->smk_access = 0;
@@ -252,7 +201,7 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf, 
		rule->smk_access |= MAY_READ;

		break;

	default:

		goto out_free_rule;

		return -1;

	}



	switch (data[SMK_LABELLEN + SMK_LABELLEN + 1]) {
@@ -263,7 +212,7 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf, 
		rule->smk_access |= MAY_WRITE;

		break;

	default:

		goto out_free_rule;

		return -1;

	}



	switch (data[SMK_LABELLEN + SMK_LABELLEN + 2]) {
@@ -274,7 +223,7 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf, 
		rule->smk_access |= MAY_EXEC;

		break;

	default:

		goto out_free_rule;

		return -1;

	}



	switch (data[SMK_LABELLEN + SMK_LABELLEN + 3]) {
@@ -285,7 +234,7 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf, 
		rule->smk_access |= MAY_APPEND;

		break;

	default:

		goto out_free_rule;

		return -1;

	}



	switch (data[SMK_LABELLEN + SMK_LABELLEN + 4]) {
@@ -296,9 +245,74 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf, 
		rule->smk_access |= MAY_TRANSMUTE;

		break;

	default:

		goto out_free_rule;

		return -1;

	}



	return 0;

}



/**

 * smk_write_load_list - write() for any /smack/load

 * @file: file pointer, not actually used

 * @buf: where to get the data from

 * @count: bytes sent

 * @ppos: where to start - must be 0

 * @rule_list: the list of rules to write to

 * @rule_lock: lock for the rule list

 *

 * Get one smack access rule from above.

 * The format is exactly:

 *     char subject[SMK_LABELLEN]

 *     char object[SMK_LABELLEN]

 *     char access[SMK_ACCESSLEN]

 *

 * writes must be SMK_LABELLEN+SMK_LABELLEN+SMK_ACCESSLEN bytes.

 */

static ssize_t smk_write_load_list(struct file *file, const char __user *buf,

				size_t count, loff_t *ppos,

				struct list_head *rule_list,

				struct mutex *rule_lock)

{

	struct smack_rule *rule;

	char *data;

	int rc = -EINVAL;



	/*

	 * No partial writes.

	 * Enough data must be present.

	 */

	if (*ppos != 0)

		return -EINVAL;

	/*

	 * Minor hack for backward compatibility

	 */

	if (count < (SMK_OLOADLEN) || count > SMK_LOADLEN)

		return -EINVAL;



	data = kzalloc(SMK_LOADLEN, GFP_KERNEL);

	if (data == NULL)

		return -ENOMEM;



	if (copy_from_user(data, buf, count) != 0) {

		rc = -EFAULT;

		goto out;

	}



	/*

	 * More on the minor hack for backward compatibility

	 */

	if (count == (SMK_OLOADLEN))

		data[SMK_OLOADLEN] = '-';



	rule = kzalloc(sizeof(*rule), GFP_KERNEL);

	if (rule == NULL) {

		rc = -ENOMEM;

		goto out;

	}



	if (smk_parse_rule(data, rule))

		goto out_free_rule;



	rc = count;

	/*

	 * smk_set_access returns true if there was already a rule
@@ -1425,6 +1439,44 @@ static const struct file_operations smk_load_self_ops = { 
	.write		= smk_write_load_self,

	.release        = seq_release,

};



/**

 * smk_write_access - handle access check transaction

 * @file: file pointer

 * @buf: data from user space

 * @count: bytes sent

 * @ppos: where to start - must be 0

 */

static ssize_t smk_write_access(struct file *file, const char __user *buf,

				size_t count, loff_t *ppos)

{

	struct smack_rule rule;

	char *data;



	if (!capable(CAP_MAC_ADMIN))

		return -EPERM;



	data = simple_transaction_get(file, buf, count);

	if (IS_ERR(data))

		return PTR_ERR(data);



	if (count < SMK_LOADLEN || smk_parse_rule(data, &rule))

		return -EINVAL;



	data[0] = smk_access(rule.smk_subject, rule.smk_object,

			     rule.smk_access, NULL) == 0;



	simple_transaction_set(file, 1);

	return SMK_LOADLEN;

}



static const struct file_operations smk_access_ops = {

	.write		= smk_write_access,

	.read		= simple_transaction_read,

	.release	= simple_transaction_release,

	.llseek		= generic_file_llseek,

};



/**

 * smk_fill_super - fill the /smackfs superblock

 * @sb: the empty superblock
@@ -1459,6 +1511,8 @@ static int smk_fill_super(struct super_block *sb, void *data, int silent) 
			"logging", &smk_logging_ops, S_IRUGO|S_IWUSR},

		[SMK_LOAD_SELF] = {

			"load-self", &smk_load_self_ops, S_IRUGO|S_IWUGO},

		[SMK_ACCESSES] = {

			"access", &smk_access_ops, S_IRUGO|S_IWUSR},

		/* last one */

			{""}

	};