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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: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Signed-off-by: Casey Schaufler <cschaufler@cschaufler-intel.(none)>
This commit is contained in:
Jarkko Sakkinen 2011-09-08 10:12:01 +03:00 committed by Casey Schaufler
parent 545a726034
commit 828716c28f
1 changed files with 117 additions and 63 deletions
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180
security/smack/smackfs.c
View File

@ -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 */
};
/*
@ -175,6 +176,81 @@ static int smk_set_access(struct smack_rule *srp, struct list_head *rule_list,
return found;
}
/**
* 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 int smk_parse_rule(const char *data, struct smack_rule *rule)
{
rule->smk_subject = smk_import(data, 0);
if (rule->smk_subject == NULL)
return -1;
rule->smk_object = smk_import(data + SMK_LABELLEN, 0);
if (rule->smk_object == NULL)
return -1;
rule->smk_access = 0;
switch (data[SMK_LABELLEN + SMK_LABELLEN]) {
case '-':
break;
case 'r':
case 'R':
rule->smk_access |= MAY_READ;
break;
default:
return -1;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 1]) {
case '-':
break;
case 'w':
case 'W':
rule->smk_access |= MAY_WRITE;
break;
default:
return -1;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 2]) {
case '-':
break;
case 'x':
case 'X':
rule->smk_access |= MAY_EXEC;
break;
default:
return -1;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 3]) {
case '-':
break;
case 'a':
case 'A':
rule->smk_access |= MAY_APPEND;
break;
default:
return -1;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 4]) {
case '-':
break;
case 't':
case 'T':
rule->smk_access |= MAY_TRANSMUTE;
break;
default:
return -1;
}
return 0;
}
/**
* smk_write_load_list - write() for any /smack/load
* @file: file pointer, not actually used
@ -234,71 +310,9 @@ static ssize_t smk_write_load_list(struct file *file, const char __user *buf,
goto out;
}
rule->smk_subject = smk_import(data, 0);
if (rule->smk_subject == NULL)
if (smk_parse_rule(data, rule))
goto out_free_rule;
rule->smk_object = smk_import(data + SMK_LABELLEN, 0);
if (rule->smk_object == NULL)
goto out_free_rule;
rule->smk_access = 0;
switch (data[SMK_LABELLEN + SMK_LABELLEN]) {
case '-':
break;
case 'r':
case 'R':
rule->smk_access |= MAY_READ;
break;
default:
goto out_free_rule;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 1]) {
case '-':
break;
case 'w':
case 'W':
rule->smk_access |= MAY_WRITE;
break;
default:
goto out_free_rule;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 2]) {
case '-':
break;
case 'x':
case 'X':
rule->smk_access |= MAY_EXEC;
break;
default:
goto out_free_rule;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 3]) {
case '-':
break;
case 'a':
case 'A':
rule->smk_access |= MAY_APPEND;
break;
default:
goto out_free_rule;
}
switch (data[SMK_LABELLEN + SMK_LABELLEN + 4]) {
case '-':
break;
case 't':
case 'T':
rule->smk_access |= MAY_TRANSMUTE;
break;
default:
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 */
{""}
};