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Smack: unify all ptrace accesses in the smack

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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@partner.samsung.com>
Signed-off-by: Rafal Krypa <r.krypa@samsung.com>
This commit is contained in:
Lukasz Pawelczyk 2014-03-11 17:07:05 +01:00 committed by Casey Schaufler
parent 959e6c7f1e
commit 5663884caa
1 changed files with 71 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

84
security/smack/smack_lsm.c
View File

@ -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;
}
@ -455,7 +498,7 @@ 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)
{
@ -475,7 +518,22 @@ 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;