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Date: Tue, 11 Mar 2014 17:07:05 +0100
From: Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
To: Casey Schaufler <casey@...aufler-ca.com>,
James Morris <james.l.morris@...cle.com>,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: r.krypa@...sung.com, t.swierczek@...sung.com,
Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
Subject: [PATCH 2/3] Smack: unify all ptrace accesses in the smack
The decision whether we can trace a process is made in the following
functions:
smack_ptrace_traceme()
smack_ptrace_access_check()
smack_bprm_set_creds() (in case the proces is traced)
This patch unifies all those decisions by introducing one function that
checks whether ptrace is allowed: smk_ptrace_rule_check().
This makes possible to actually trace with TRACEME where first the
TRACEME itself must be allowed and then exec() on a traced process.
Additional bugs fixed:
- The decision is made according to the mode parameter that is now correctly
translated from PTRACE_MODE_* to MAY_* instead of being treated 1:1.
PTRACE_MODE_READ requires MAY_READ.
PTRACE_MODE_ATTACH requires MAY_READWRITE.
- Add a smack audit log in case of exec() refused by bprm_set_creds().
- Honor the PTRACE_MODE_NOAUDIT flag and don't put smack audit info
in case this flag is set.
Signed-off-by: Lukasz Pawelczyk <l.pawelczyk@...tner.samsung.com>
Signed-off-by: Rafal Krypa <r.krypa@...sung.com>
---
security/smack/smack_lsm.c | 84 +++++++++++++++++++++++++++++++++++++++-------
1 file changed, 71 insertions(+), 13 deletions(-)
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 48d61f6..3da13fd 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -157,6 +157,54 @@ static int smk_copy_rules(struct list_head *nhead, struct list_head *ohead,
return rc;
}
+/**
+ * smk_ptrace_mode - helper function for converting PTRACE_MODE_* into MAY_*
+ * @mode - input mode in form of PTRACE_MODE_*
+ *
+ * Returns a converted MAY_* mode usable by smack rules
+ */
+static inline unsigned int smk_ptrace_mode(unsigned int mode)
+{
+ switch (mode) {
+ case PTRACE_MODE_READ:
+ return MAY_READ;
+ case PTRACE_MODE_ATTACH:
+ return MAY_READWRITE;
+ }
+
+ return 0;
+}
+
+/**
+ * smk_ptrace_rule_check - helper for ptrace access
+ * @tracer: tracer process
+ * @tracee_label: label of the process that's about to be traced
+ * @mode: ptrace attachment mode (PTRACE_MODE_*)
+ * @func: name of the function that called us, used for audit
+ *
+ * Returns 0 on access granted, -error on error
+ */
+static int smk_ptrace_rule_check(struct task_struct *tracer, char *tracee_label,
+ unsigned int mode, const char *func)
+{
+ int rc;
+ struct smk_audit_info ad, *saip = NULL;
+ struct task_smack *tsp;
+ struct smack_known *skp;
+
+ if ((mode & PTRACE_MODE_NOAUDIT) == 0) {
+ smk_ad_init(&ad, func, LSM_AUDIT_DATA_TASK);
+ smk_ad_setfield_u_tsk(&ad, tracer);
+ saip = &ad;
+ }
+
+ tsp = task_security(tracer);
+ skp = smk_of_task(tsp);
+
+ rc = smk_tskacc(tsp, tracee_label, smk_ptrace_mode(mode), saip);
+ return rc;
+}
+
/*
* LSM hooks.
* We he, that is fun!
@@ -165,16 +213,15 @@ static int smk_copy_rules(struct list_head *nhead, struct list_head *ohead,
/**
* smack_ptrace_access_check - Smack approval on PTRACE_ATTACH
* @ctp: child task pointer
- * @mode: ptrace attachment mode
+ * @mode: ptrace attachment mode (PTRACE_MODE_*)
*
* Returns 0 if access is OK, an error code otherwise
*
- * Do the capability checks, and require read and write.
+ * Do the capability checks.
*/
static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
{
int rc;
- struct smk_audit_info ad;
struct smack_known *skp;
rc = cap_ptrace_access_check(ctp, mode);
@@ -182,10 +229,8 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
return rc;
skp = smk_of_task(task_security(ctp));
- smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
- smk_ad_setfield_u_tsk(&ad, ctp);
- rc = smk_curacc(skp->smk_known, mode, &ad);
+ rc = smk_ptrace_rule_check(current, skp->smk_known, mode, __func__);
return rc;
}
@@ -195,12 +240,11 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
*
* Returns 0 if access is OK, an error code otherwise
*
- * Do the capability checks, and require read and write.
+ * Do the capability checks, and require PTRACE_MODE_ATTACH.
*/
static int smack_ptrace_traceme(struct task_struct *ptp)
{
int rc;
- struct smk_audit_info ad;
struct smack_known *skp;
rc = cap_ptrace_traceme(ptp);
@@ -208,10 +252,9 @@ static int smack_ptrace_traceme(struct task_struct *ptp)
return rc;
skp = smk_of_task(current_security());
- smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
- smk_ad_setfield_u_tsk(&ad, ptp);
- rc = smk_tskacc(ptp, skp->smk_known, MAY_READWRITE, &ad);
+ rc = smk_ptrace_rule_check(ptp, skp->smk_known,
+ PTRACE_MODE_ATTACH, __func__);
return rc;
}
@@ -453,7 +496,7 @@ static int smack_sb_statfs(struct dentry *dentry)
* smack_bprm_set_creds - set creds for exec
* @bprm: the exec information
*
- * Returns 0 if it gets a blob, -ENOMEM otherwise
+ * Returns 0 if it gets a blob, -EPERM if exec forbidden and -ENOMEM otherwise
*/
static int smack_bprm_set_creds(struct linux_binprm *bprm)
{
@@ -473,7 +516,22 @@ static int smack_bprm_set_creds(struct linux_binprm *bprm)
if (isp->smk_task == NULL || isp->smk_task == bsp->smk_task)
return 0;
- if (bprm->unsafe)
+ if (bprm->unsafe & (LSM_UNSAFE_PTRACE | LSM_UNSAFE_PTRACE_CAP)) {
+ struct task_struct *tracer;
+ rc = 0;
+
+ rcu_read_lock();
+ tracer = ptrace_parent(current);
+ if (likely(tracer != NULL))
+ rc = smk_ptrace_rule_check(tracer,
+ isp->smk_task->smk_known,
+ PTRACE_MODE_ATTACH,
+ __func__);
+ rcu_read_unlock();
+
+ if (rc != 0)
+ return rc;
+ } else if (bprm->unsafe)
return -EPERM;
bsp->smk_task = isp->smk_task;
--
1.8.5.3
--
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