Re: [PATCH] Smack: onlycap limits on CAP_MAC_ADMIN

[Casey Schaufler]

On 6/5/2012 3:28 PM, Casey Schaufler wrote:
> From: Casey Schaufler <casey@xxxxxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxxxxx>

Applied to git://git.gitorious.org/smack-next/kernel.git

>
> ---
>  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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