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Message-ID: <20110617152912.GA21885@albatros>
Date: Fri, 17 Jun 2011 19:29:12 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org,
apparmor@...ts.ubuntu.com,
"selinux@...ho.nsa.gov Stephen Smalley" <sds@...ho.nsa.gov>,
James Morris <jmorris@...ei.org>,
Eric Paris <eparis@...isplace.org>,
John Johansen <john.johansen@...onical.com>,
kernel-hardening@...ts.openwall.com
Subject: [RFC v1] security: introduce ptrace_task_access_check()
Hi,
This patch introduces ptrace_task_access_check() to be able to check
whether a specific task (not current) is able to ptrace another task
(might be current). I need it to call "reversed" ptrace_may_access()
with swapped current and target task.
Specifically, I need it to filter taskstats and proc connector requests
for a restriction of getting other processes' information:
http://permalink.gmane.org/gmane.linux.kernel/1155354
Please help me to figure out how such patch should be divided to be
applied. I think about such scheme:
1) add generic security/* functions.
2-4) add ptrace_task_access_check() for SMACK, AppArmor and SELinux.
5) change ptrace_access_check() in security ops and all LSMs to
ptrace_task_access_check().
But I'd like to hear maintainers' oppinions not to put useless efforts.
Thanks,
---
include/linux/capability.h | 2 +
include/linux/security.h | 20 +++++++++++++++++-
kernel/capability.c | 24 ++++++++++++++++++++++
security/apparmor/lsm.c | 10 ++++----
security/capability.c | 2 +-
security/commoncap.c | 20 +++++++++++++++++++
security/security.c | 11 +++++++--
security/selinux/hooks.c | 13 +++++------
security/smack/smack.h | 1 +
security/smack/smack_access.c | 43 +++++++++++++++++++++++++++++++++++++++++
security/smack/smack_lsm.c | 9 ++++---
11 files changed, 133 insertions(+), 22 deletions(-)
diff --git a/include/linux/capability.h b/include/linux/capability.h
index c421123..cc0bcfe 100644
--- a/include/linux/capability.h
+++ b/include/linux/capability.h
@@ -544,7 +544,9 @@ extern bool has_ns_capability(struct task_struct *t,
struct user_namespace *ns, int cap);
extern bool has_capability_noaudit(struct task_struct *t, int cap);
extern bool capable(int cap);
+extern bool task_capable(struct task_struct *task, int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
+extern bool ns_task_capable(struct task_struct *t, struct user_namespace *ns, int cap);
extern bool task_ns_capable(struct task_struct *t, int cap);
extern bool nsown_capable(int cap);
diff --git a/include/linux/security.h b/include/linux/security.h
index 8ce59ef..88a2351 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -57,6 +57,8 @@ extern int cap_capable(struct task_struct *tsk, const struct cred *cred,
struct user_namespace *ns, int cap, int audit);
extern int cap_settime(const struct timespec *ts, const struct timezone *tz);
extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
+extern int cap_ptrace_task_access_check(struct task_struct *task, struct task_struct *child,
+ unsigned int mode);
extern int cap_ptrace_traceme(struct task_struct *parent);
extern int cap_capget(struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
extern int cap_capset(struct cred *new, const struct cred *old,
@@ -1375,7 +1377,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
struct security_operations {
char name[SECURITY_NAME_MAX + 1];
- int (*ptrace_access_check) (struct task_struct *child, unsigned int mode);
+ int (*ptrace_task_access_check) (struct task_struct *task,
+ struct task_struct *child,
+ unsigned int mode);
int (*ptrace_traceme) (struct task_struct *parent);
int (*capget) (struct task_struct *target,
kernel_cap_t *effective,
@@ -1667,6 +1671,10 @@ int security_capset(struct cred *new, const struct cred *old,
const kernel_cap_t *effective,
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
+int security_task_capable(struct task_struct *task,
+ struct user_namespace *ns,
+ const struct cred *cred,
+ int cap);
int security_capable(struct user_namespace *ns, const struct cred *cred,
int cap);
int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
@@ -1865,10 +1873,18 @@ static inline int security_capset(struct cred *new,
return cap_capset(new, old, effective, inheritable, permitted);
}
+static inline int security_task_capable(struct task_struct *task,
+ struct user_namespace *ns,
+ const struct cred *cred,
+ int cap)
+{
+ return cap_capable(task, cred, ns, cap, SECURITY_CAP_AUDIT);
+}
+
static inline int security_capable(struct user_namespace *ns,
const struct cred *cred, int cap)
{
- return cap_capable(current, cred, ns, cap, SECURITY_CAP_AUDIT);
+ return security_task_capable(current, ns, cred, cap);
}
static inline int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, int cap)
diff --git a/kernel/capability.c b/kernel/capability.c
index 283c529..6a2d636 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -356,6 +356,30 @@ bool capable(int cap)
}
EXPORT_SYMBOL(capable);
+bool task_capable(struct task_struct *task, int cap)
+{
+ return ns_task_capable(task, &init_user_ns, cap);
+}
+EXPORT_SYMBOL(capable);
+
+bool ns_task_capable(struct task_struct *task, struct user_namespace *ns, int cap)
+{
+ if (unlikely(!cap_valid(cap))) {
+ printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
+ BUG();
+ }
+
+ rcu_read_lock();
+ if (security_task_capable(task, ns, __task_cred(task), cap) == 0) {
+ rcu_read_unlock();
+ current->flags |= PF_SUPERPRIV;
+ return true;
+ }
+ rcu_read_unlock();
+ return false;
+}
+EXPORT_SYMBOL(ns_task_capable);
+
/**
* ns_capable - Determine if the current task has a superior capability in effect
* @ns: The usernamespace we want the capability in
diff --git a/security/apparmor/lsm.c b/security/apparmor/lsm.c
index ec1bcec..707f087 100644
--- a/security/apparmor/lsm.c
+++ b/security/apparmor/lsm.c
@@ -93,14 +93,14 @@ static void apparmor_cred_transfer(struct cred *new, const struct cred *old)
aa_dup_task_context(new_cxt, old_cxt);
}
-static int apparmor_ptrace_access_check(struct task_struct *child,
- unsigned int mode)
+static int apparmor_ptrace_task_access_check(struct task_struct *task,
+ struct task_struct *child, unsigned int mode)
{
- int error = cap_ptrace_access_check(child, mode);
+ int error = cap_ptrace_task_access_check(task, child, mode);
if (error)
return error;
- return aa_ptrace(current, child, mode);
+ return aa_ptrace(task, child, mode);
}
static int apparmor_ptrace_traceme(struct task_struct *parent)
@@ -624,7 +624,7 @@ static int apparmor_task_setrlimit(struct task_struct *task,
static struct security_operations apparmor_ops = {
.name = "apparmor",
- .ptrace_access_check = apparmor_ptrace_access_check,
+ .ptrace_task_access_check = apparmor_ptrace_task_access_check,
.ptrace_traceme = apparmor_ptrace_traceme,
.capget = apparmor_capget,
.capable = apparmor_capable,
diff --git a/security/capability.c b/security/capability.c
index bbb5115..1bdbe44 100644
--- a/security/capability.c
+++ b/security/capability.c
@@ -874,7 +874,7 @@ static void cap_audit_rule_free(void *lsmrule)
void __init security_fixup_ops(struct security_operations *ops)
{
- set_to_cap_if_null(ops, ptrace_access_check);
+ set_to_cap_if_null(ops, ptrace_task_access_check);
set_to_cap_if_null(ops, ptrace_traceme);
set_to_cap_if_null(ops, capget);
set_to_cap_if_null(ops, capset);
diff --git a/security/commoncap.c b/security/commoncap.c
index a93b3b7..aa76791 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -155,6 +155,26 @@ out:
return ret;
}
+int cap_ptrace_task_access_check(struct task_struct *task, struct task_struct *child,
+ unsigned int mode)
+{
+ int ret = 0;
+ const struct cred *cred, *child_cred;
+
+ rcu_read_lock();
+ cred = __task_cred(task);
+ child_cred = __task_cred(child);
+ if (cred->user->user_ns == child_cred->user->user_ns &&
+ cap_issubset(child_cred->cap_permitted, cred->cap_permitted))
+ goto out;
+ if (ns_task_capable(task, child_cred->user->user_ns, CAP_SYS_PTRACE))
+ goto out;
+ ret = -EPERM;
+out:
+ rcu_read_unlock();
+ return ret;
+}
+
/**
* cap_ptrace_traceme - Determine whether another process may trace the current
* @parent: The task proposed to be the tracer
diff --git a/security/security.c b/security/security.c
index 4ba6d4c..d51330b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -129,7 +129,7 @@ int __init register_security(struct security_operations *ops)
int security_ptrace_access_check(struct task_struct *child, unsigned int mode)
{
- return security_ops->ptrace_access_check(child, mode);
+ return security_ops->ptrace_task_access_check(current, child, mode);
}
int security_ptrace_traceme(struct task_struct *parent)
@@ -154,11 +154,16 @@ int security_capset(struct cred *new, const struct cred *old,
effective, inheritable, permitted);
}
+int security_task_capable(struct task_struct *task, struct user_namespace *ns,
+ const struct cred *cred, int cap)
+{
+ return security_ops->capable(task, cred, ns, cap, SECURITY_CAP_AUDIT);
+}
+
int security_capable(struct user_namespace *ns, const struct cred *cred,
int cap)
{
- return security_ops->capable(current, cred, ns, cap,
- SECURITY_CAP_AUDIT);
+ return security_task_capable(current, ns, cred, cap);
}
int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 20219ef..ee963d1 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1804,23 +1804,22 @@ static inline u32 open_file_to_av(struct file *file)
}
/* Hook functions begin here. */
-
-static int selinux_ptrace_access_check(struct task_struct *child,
- unsigned int mode)
+static int selinux_ptrace_task_access_check(struct task_struct *task,
+ struct task_struct *child, unsigned int mode)
{
int rc;
- rc = cap_ptrace_access_check(child, mode);
+ rc = cap_ptrace_task_access_check(task, child, mode);
if (rc)
return rc;
if (mode == PTRACE_MODE_READ) {
- u32 sid = current_sid();
+ u32 sid = task_sid(task);
u32 csid = task_sid(child);
return avc_has_perm(sid, csid, SECCLASS_FILE, FILE__READ, NULL);
}
- return current_has_perm(child, PROCESS__PTRACE);
+ return task_has_perm(task, child, PROCESS__PTRACE);
}
static int selinux_ptrace_traceme(struct task_struct *parent)
@@ -5457,7 +5456,7 @@ static int selinux_key_getsecurity(struct key *key, char **_buffer)
static struct security_operations selinux_ops = {
.name = "selinux",
- .ptrace_access_check = selinux_ptrace_access_check,
+ .ptrace_task_access_check = selinux_ptrace_task_access_check,
.ptrace_traceme = selinux_ptrace_traceme,
.capget = selinux_capget,
.capset = selinux_capset,
diff --git a/security/smack/smack.h b/security/smack/smack.h
index 2b6c6a5..4d9fb0f 100644
--- a/security/smack/smack.h
+++ b/security/smack/smack.h
@@ -199,6 +199,7 @@ struct inode_smack *new_inode_smack(char *);
*/
int smk_access_entry(char *, char *, struct list_head *);
int smk_access(char *, char *, int, struct smk_audit_info *);
+int smk_taskacc(struct task_struct *, char *, u32, struct smk_audit_info *);
int smk_curacc(char *, u32, struct smk_audit_info *);
int smack_to_cipso(const char *, struct smack_cipso *);
void smack_from_cipso(u32, char *, char *);
diff --git a/security/smack/smack_access.c b/security/smack/smack_access.c
index 9637e10..f6582a7 100644
--- a/security/smack/smack_access.c
+++ b/security/smack/smack_access.c
@@ -200,6 +200,49 @@ out_audit:
return rc;
}
+int smk_taskacc(struct task_struct *task, char *obj_label, u32 mode, struct smk_audit_info *a)
+{
+ struct task_smack *tsp = task_cred_xxx(task, security);
+ char *subject_label = smk_of_task(tsp);
+ int may;
+ int rc;
+
+ /*
+ * Check the global rule list
+ */
+ rc = smk_access(subject_label, obj_label, mode, NULL);
+ if (rc == 0) {
+ /*
+ * If there is an entry in the task's rule list
+ * it can further restrict access.
+ */
+ may = smk_access_entry(subject_label, obj_label, &tsp->smk_rules);
+ if (may < 0)
+ goto out_audit;
+ if ((mode & may) == mode)
+ goto out_audit;
+ rc = -EACCES;
+ }
+
+ /*
+ * Return if a specific label has been designated as the
+ * only one that gets privilege and current does not
+ * have that label.
+ */
+ if (smack_onlycap != NULL && smack_onlycap != subject_label)
+ goto out_audit;
+
+ if (task_capable(task, CAP_MAC_OVERRIDE))
+ rc = 0;
+
+out_audit:
+#ifdef CONFIG_AUDIT
+ if (a)
+ smack_log(subject_label, obj_label, mode, rc, a);
+#endif
+ return rc;
+}
+
/**
* smk_curacc - determine if current has a specific access to an object
* @obj_label: a pointer to the object's Smack label
diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
index 9831a39..d168974 100644
--- a/security/smack/smack_lsm.c
+++ b/security/smack/smack_lsm.c
@@ -149,13 +149,14 @@ static int smk_copy_rules(struct list_head *nhead, struct list_head *ohead,
*
* Do the capability checks, and require read and write.
*/
-static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
+static int smack_ptrace_task_access_check(struct task_struct *task,
+ struct task_struct *ctp, unsigned int mode)
{
int rc;
struct smk_audit_info ad;
char *tsp;
- rc = cap_ptrace_access_check(ctp, mode);
+ rc = cap_ptrace_task_access_check(task, ctp, mode);
if (rc != 0)
return rc;
@@ -163,7 +164,7 @@ static int smack_ptrace_access_check(struct task_struct *ctp, unsigned int mode)
smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_TASK);
smk_ad_setfield_u_tsk(&ad, ctp);
- rc = smk_curacc(tsp, MAY_READWRITE, &ad);
+ rc = smk_taskacc(task, tsp, MAY_READWRITE, &ad);
return rc;
}
@@ -3395,7 +3396,7 @@ static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
struct security_operations smack_ops = {
.name = "smack",
- .ptrace_access_check = smack_ptrace_access_check,
+ .ptrace_task_access_check = smack_ptrace_task_access_check,
.ptrace_traceme = smack_ptrace_traceme,
.syslog = smack_syslog,
---
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