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Subject[PATCH] Smack: onlycap limits on CAP_MAC_ADMIN
From: Casey Schaufler <casey@schaufler-ca.com>
Subject: [PATCH] Smack: onlycap limits on CAP_MAC_ADMIN

Smack is integrated with the POSIX capabilities scheme,
using the capabilities CAP_MAC_OVERRIDE and CAP_MAC_ADMIN to
determine if a process is allowed to ignore Smack checks or
change Smack related data respectively. Smack provides an
additional restriction that if an onlycap value is set
by writing to /smack/onlycap only tasks with that Smack
label are allowed to use CAP_MAC_OVERRIDE.

This change adds CAP_MAC_ADMIN as a capability that is affected
by the onlycap mechanism.

Targeted for git://git.gitorious.org/smack-next/kernel.git

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

---
security/smack/smack.h | 13 +++++++++++++
security/smack/smack_access.c | 9 ++-------
security/smack/smack_lsm.c | 17 +++++++++--------
security/smack/smackfs.c | 21 ++++++++++-----------
4 files changed, 34 insertions(+), 26 deletions(-)

diff --git a/security/smack/smack.h b/security/smack/smack.h
index 76feb31..99b3612 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -283,6 +283,19 @@ static inline char *smk_of_current(void)
}

/*
+ * Is the task privileged and allowed to be privileged
+ * by the onlycap rule.
+ */
+static inline int smack_privileged(int cap)
+{
+ if (!capable(cap))
+ return 0;
+ if (smack_onlycap == NULL || smack_onlycap == smk_of_current())
+ return 1;
+ return 0;
+}
+
+/*
* logging functions
*/
#define SMACK_AUDIT_DENIED 0x1
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 9f3705e..db14689 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -220,14 +220,9 @@ int smk_curacc(char *obj_label, u32 mode, struct smk_audit_info *a)
}

/*
- * Return if a specific label has been designated as the
- * only one that gets privilege and current does not
- * have that label.
+ * Allow for priviliged to override policy.
*/
- if (smack_onlycap != NULL && smack_onlycap != sp)
- goto out_audit;
-
- if (capable(CAP_MAC_OVERRIDE))
+ if (rc != 0 && smack_privileged(CAP_MAC_OVERRIDE))
rc = 0;

out_audit:
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 5a4d52c..99a457a 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -217,7 +217,7 @@ static int smack_syslog(int typefrom_file)
int rc = 0;
char *sp = smk_of_current();

- if (capable(CAP_MAC_OVERRIDE))
+ if (smack_privileged(CAP_MAC_OVERRIDE))
return 0;

if (sp != smack_known_floor.smk_known)
@@ -821,7 +821,7 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
strcmp(name, XATTR_NAME_SMACKIPOUT) == 0 ||
strcmp(name, XATTR_NAME_SMACKEXEC) == 0 ||
strcmp(name, XATTR_NAME_SMACKMMAP) == 0) {
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
rc = -EPERM;
/*
* check label validity here so import wont fail on
@@ -831,7 +831,7 @@ static int smack_inode_setxattr(struct dentry *dentry, const char *name,
smk_import(value, size) == NULL)
rc = -EINVAL;
} else if (strcmp(name, XATTR_NAME_SMACKTRANSMUTE) == 0) {
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
rc = -EPERM;
if (size != TRANS_TRUE_SIZE ||
strncmp(value, TRANS_TRUE, TRANS_TRUE_SIZE) != 0)
@@ -927,7 +927,7 @@ static int smack_inode_removexattr(struct dentry *dentry, const char *name)
strcmp(name, XATTR_NAME_SMACKEXEC) == 0 ||
strcmp(name, XATTR_NAME_SMACKTRANSMUTE) == 0 ||
strcmp(name, XATTR_NAME_SMACKMMAP)) {
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
rc = -EPERM;
} else
rc = cap_inode_removexattr(dentry, name);
@@ -1722,7 +1722,8 @@ static int smack_task_wait(struct task_struct *p)
* state into account in the decision as well as
* the smack value.
*/
- if (capable(CAP_MAC_OVERRIDE) || has_capability(p, CAP_MAC_OVERRIDE))
+ if (smack_privileged(CAP_MAC_OVERRIDE) ||
+ has_capability(p, CAP_MAC_OVERRIDE))
rc = 0;
/* we log only if we didn't get overriden */
out_log:
@@ -2723,7 +2724,7 @@ static int smack_setprocattr(struct task_struct *p, char *name,
if (p != current)
return -EPERM;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

if (value == NULL || size == 0 || size >= SMK_LONGLABEL)
@@ -2786,7 +2787,7 @@ static int smack_unix_stream_connect(struct sock *sock,
smk_ad_setfield_u_net_sk(&ad, other);
#endif

- if (!capable(CAP_MAC_OVERRIDE))
+ if (!smack_privileged(CAP_MAC_OVERRIDE))
rc = smk_access(ssp->smk_out, osp->smk_in, MAY_WRITE, &ad);

/*
@@ -2822,7 +2823,7 @@ static int smack_unix_may_send(struct socket *sock, struct socket *other)
smk_ad_setfield_u_net_sk(&ad, other->sk);
#endif

- if (!capable(CAP_MAC_OVERRIDE))
+ if (!smack_privileged(CAP_MAC_OVERRIDE))
rc = smk_access(ssp->smk_out, osp->smk_in, MAY_WRITE, &ad);

return rc;
diff --git a/security/smack/smackfs.c b/security/smack/smackfs.c
index 3686db7..2152965 100644
--- a/security/smack/smackfs.c
+++ b/security/smack/smackfs.c
@@ -595,13 +595,12 @@ static int smk_open_load(struct inode *inode, struct file *file)
static ssize_t smk_write_load(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
-
/*
* Must have privilege.
* No partial writes.
* Enough data must be present.
*/
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

return smk_write_rules_list(file, buf, count, ppos, NULL, NULL,
@@ -787,7 +786,7 @@ static ssize_t smk_set_cipso(struct file *file, const char __user *buf,
* No partial writes.
* Enough data must be present.
*/
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
if (*ppos != 0)
return -EINVAL;
@@ -1090,7 +1089,7 @@ static ssize_t smk_write_netlbladdr(struct file *file, const char __user *buf,
* "<addr/mask, as a.b.c.d/e><space><label>"
* "<addr, as a.b.c.d><space><label>"
*/
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;
if (*ppos != 0)
return -EINVAL;
@@ -1267,7 +1266,7 @@ static ssize_t smk_write_doi(struct file *file, const char __user *buf,
char temp[80];
int i;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

if (count >= sizeof(temp) || count == 0)
@@ -1334,7 +1333,7 @@ static ssize_t smk_write_direct(struct file *file, const char __user *buf,
char temp[80];
int i;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

if (count >= sizeof(temp) || count == 0)
@@ -1412,7 +1411,7 @@ static ssize_t smk_write_mapped(struct file *file, const char __user *buf,
char temp[80];
int i;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

if (count >= sizeof(temp) || count == 0)
@@ -1503,7 +1502,7 @@ static ssize_t smk_write_ambient(struct file *file, const char __user *buf,
char *data;
int rc = count;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

data = kzalloc(count + 1, GFP_KERNEL);
@@ -1586,7 +1585,7 @@ static ssize_t smk_write_onlycap(struct file *file, const char __user *buf,
char *sp = smk_of_task(current->cred->security);
int rc = count;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

/*
@@ -1664,7 +1663,7 @@ static ssize_t smk_write_logging(struct file *file, const char __user *buf,
char temp[32];
int i;

- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

if (count >= sizeof(temp) || count == 0)
@@ -1885,7 +1884,7 @@ static ssize_t smk_write_load2(struct file *file, const char __user *buf,
/*
* Must have privilege.
*/
- if (!capable(CAP_MAC_ADMIN))
+ if (!smack_privileged(CAP_MAC_ADMIN))
return -EPERM;

return smk_write_rules_list(file, buf, count, ppos, NULL, NULL,




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