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Commit c60b9066 authored by Casey Schaufler's avatar Casey Schaufler
Browse files

Smack: Signal delivery as an append operation 



Under a strict subject/object security policy delivering a
signal or delivering network IPC could be considered either
a write or an append operation. The original choice to make
both write operations leads to an issue where IPC delivery
is desired under policy, but delivery of signals is not.
This patch provides the option of making signal delivery
an append operation, allowing Smack rules that deny signal
delivery while allowing IPC. This was requested for Tizen.

Signed-off-by: default avatarCasey Schaufler <casey@schaufler-ca.com>
parent 63e24c49

security/smack/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -40,3 +40,15 @@ config SECURITY_SMACK_NETFILTER 
	  This enables security marking of network packets using

	  Smack labels.

	  If you are unsure how to answer this question, answer N.



config SECURITY_SMACK_APPEND_SIGNALS

	bool "Treat delivering signals as an append operation"

	depends on SECURITY_SMACK

	default n

	help

	  Sending a signal has been treated as a write operation to the

	  receiving process. If this option is selected, the delivery

	  will be an append operation instead. This makes it possible

	  to differentiate between delivering a network packet and

	  delivering a signal in the Smack rules.

	  If you are unsure how to answer this question, answer N.

security/smack/smack.h

+10 −0
Original line number Diff line number Diff line
@@ -256,6 +256,16 @@ enum { 
#define MAY_LOCK	0x00002000	/* Locks should be writes, but ... */

#define MAY_BRINGUP	0x00004000	/* Report use of this rule */



/*

 * The policy for delivering signals is configurable.

 * It is usually "write", but can be "append".

 */

#ifdef CONFIG_SECURITY_SMACK_APPEND_SIGNALS

#define MAY_DELIVER	MAY_APPEND	/* Signal delivery requires append */

#else

#define MAY_DELIVER	MAY_WRITE	/* Signal delivery requires write */

#endif



#define SMACK_BRINGUP_ALLOW		1	/* Allow bringup mode */

#define SMACK_UNCONFINED_SUBJECT	2	/* Allow unconfined label */

#define SMACK_UNCONFINED_OBJECT		3	/* Allow unconfined label */

security/smack/smack_lsm.c

+7 −7
Original line number Diff line number Diff line
@@ -1857,14 +1857,14 @@ static int smack_file_send_sigiotask(struct task_struct *tsk, 


	/* we don't log here as rc can be overriden */

	skp = file->f_security;

	rc = smk_access(skp, tkp, MAY_WRITE, NULL);

	rc = smk_bu_note("sigiotask", skp, tkp, MAY_WRITE, rc);

	rc = smk_access(skp, tkp, MAY_DELIVER, NULL);

	rc = smk_bu_note("sigiotask", skp, tkp, MAY_DELIVER, rc);

	if (rc != 0 && has_capability(tsk, CAP_MAC_OVERRIDE))

		rc = 0;



	smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);

	smk_ad_setfield_u_tsk(&ad, tsk);

	smack_log(skp->smk_known, tkp->smk_known, MAY_WRITE, rc, &ad);

	smack_log(skp->smk_known, tkp->smk_known, MAY_DELIVER, rc, &ad);

	return rc;

}
@@ -2265,8 +2265,8 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info, 
	 * can write the receiver.

	 */

	if (secid == 0) {

		rc = smk_curacc(tkp, MAY_WRITE, &ad);

		rc = smk_bu_task(p, MAY_WRITE, rc);

		rc = smk_curacc(tkp, MAY_DELIVER, &ad);

		rc = smk_bu_task(p, MAY_DELIVER, rc);

		return rc;

	}

	/*
@@ -2275,8 +2275,8 @@ static int smack_task_kill(struct task_struct *p, struct siginfo *info, 
	 * we can't take privilege into account.

	 */

	skp = smack_from_secid(secid);

	rc = smk_access(skp, tkp, MAY_WRITE, &ad);

	rc = smk_bu_note("USB signal", skp, tkp, MAY_WRITE, rc);

	rc = smk_access(skp, tkp, MAY_DELIVER, &ad);

	rc = smk_bu_note("USB signal", skp, tkp, MAY_DELIVER, rc);

	return rc;

}