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Subject[PATCH ghak90 V8 16/16] audit: add capcontid to set contid outside init_user_ns
Date
Provide a mechanism similar to CAP_AUDIT_CONTROL to explicitly give a
process in a non-init user namespace the capability to set audit
container identifiers.

Provide /proc/$PID/audit_capcontid interface to capcontid.
Valid values are: 1==enabled, 0==disabled

Report this action in message type AUDIT_SET_CAPCONTID 1022 with fields
opid= capcontid= old-capcontid=

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
---
fs/proc/base.c | 55 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/audit.h | 14 ++++++++++++
include/uapi/linux/audit.h | 1 +
kernel/audit.c | 35 +++++++++++++++++++++++++++++
4 files changed, 105 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 26091800180c..283ef8e006e7 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1360,6 +1360,59 @@ static ssize_t proc_contid_write(struct file *file, const char __user *buf,
.write = proc_contid_write,
.llseek = generic_file_llseek,
};
+
+static ssize_t proc_capcontid_read(struct file *file, char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode *inode = file_inode(file);
+ struct task_struct *task = get_proc_task(inode);
+ ssize_t length;
+ char tmpbuf[TMPBUFLEN];
+
+ if (!task)
+ return -ESRCH;
+ /* if we don't have caps, reject */
+ if (!capable(CAP_AUDIT_CONTROL) && !audit_get_capcontid(current))
+ return -EPERM;
+ length = scnprintf(tmpbuf, TMPBUFLEN, "%u", audit_get_capcontid(task));
+ put_task_struct(task);
+ return simple_read_from_buffer(buf, count, ppos, tmpbuf, length);
+}
+
+static ssize_t proc_capcontid_write(struct file *file, const char __user *buf,
+ size_t count, loff_t *ppos)
+{
+ struct inode *inode = file_inode(file);
+ u32 capcontid;
+ int rv;
+ struct task_struct *task = get_proc_task(inode);
+
+ if (!task)
+ return -ESRCH;
+ if (*ppos != 0) {
+ /* No partial writes. */
+ put_task_struct(task);
+ return -EINVAL;
+ }
+
+ rv = kstrtou32_from_user(buf, count, 10, &capcontid);
+ if (rv < 0) {
+ put_task_struct(task);
+ return rv;
+ }
+
+ rv = audit_set_capcontid(task, capcontid);
+ put_task_struct(task);
+ if (rv < 0)
+ return rv;
+ return count;
+}
+
+static const struct file_operations proc_capcontid_operations = {
+ .read = proc_capcontid_read,
+ .write = proc_capcontid_write,
+ .llseek = generic_file_llseek,
+};
#endif

#ifdef CONFIG_FAULT_INJECTION
@@ -3121,6 +3174,7 @@ static int proc_stack_depth(struct seq_file *m, struct pid_namespace *ns,
REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
REG("sessionid", S_IRUGO, proc_sessionid_operations),
REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
+ REG("audit_capcontainerid", S_IWUSR|S_IRUSR|S_IRUSR, proc_capcontid_operations),
#endif
#ifdef CONFIG_FAULT_INJECTION
REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
@@ -3522,6 +3576,7 @@ static int proc_tid_comm_permission(struct inode *inode, int mask)
REG("loginuid", S_IWUSR|S_IRUGO, proc_loginuid_operations),
REG("sessionid", S_IRUGO, proc_sessionid_operations),
REG("audit_containerid", S_IWUSR|S_IRUSR, proc_contid_operations),
+ REG("audit_capcontainerid", S_IWUSR|S_IRUSR|S_IRUSR, proc_capcontid_operations),
#endif
#ifdef CONFIG_FAULT_INJECTION
REG("make-it-fail", S_IRUGO|S_IWUSR, proc_fault_inject_operations),
diff --git a/include/linux/audit.h b/include/linux/audit.h
index 28b9c7cd86a6..62c453306c2a 100644
--- a/include/linux/audit.h
+++ b/include/linux/audit.h
@@ -116,6 +116,7 @@ struct audit_task_info {
kuid_t loginuid;
unsigned int sessionid;
struct audit_contobj *cont;
+ u32 capcontid;
#ifdef CONFIG_AUDITSYSCALL
struct audit_context *ctx;
#endif
@@ -224,6 +225,14 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
return tsk->audit->sessionid;
}

+static inline u32 audit_get_capcontid(struct task_struct *tsk)
+{
+ if (!tsk->audit)
+ return 0;
+ return tsk->audit->capcontid;
+}
+
+extern int audit_set_capcontid(struct task_struct *tsk, u32 enable);
extern int audit_set_contid(struct task_struct *tsk, u64 contid);

static inline u64 audit_get_contid(struct task_struct *tsk)
@@ -305,6 +314,11 @@ static inline unsigned int audit_get_sessionid(struct task_struct *tsk)
return AUDIT_SID_UNSET;
}

+static inline u32 audit_get_capcontid(struct task_struct *tsk)
+{
+ return 0;
+}
+
static inline u64 audit_get_contid(struct task_struct *tsk)
{
return AUDIT_CID_UNSET;
diff --git a/include/uapi/linux/audit.h b/include/uapi/linux/audit.h
index 2844d78cd7af..01251e6dcec0 100644
--- a/include/uapi/linux/audit.h
+++ b/include/uapi/linux/audit.h
@@ -73,6 +73,7 @@
#define AUDIT_GET_FEATURE 1019 /* Get which features are enabled */
#define AUDIT_CONTAINER_OP 1020 /* Define the container id and info */
#define AUDIT_SIGNAL_INFO2 1021 /* Get info auditd signal sender */
+#define AUDIT_SET_CAPCONTID 1022 /* Set cap_contid of a task */

#define AUDIT_FIRST_USER_MSG 1100 /* Userspace messages mostly uninteresting to kernel */
#define AUDIT_USER_AVC 1107 /* We filter this differently */
diff --git a/kernel/audit.c b/kernel/audit.c
index 1287f0b63757..1c22dd084ae8 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -2698,6 +2698,41 @@ static bool audit_contid_isowner(struct task_struct *tsk)
return false;
}

+int audit_set_capcontid(struct task_struct *task, u32 enable)
+{
+ u32 oldcapcontid;
+ int rc = 0;
+ struct audit_buffer *ab;
+
+ if (!task->audit)
+ return -ENOPROTOOPT;
+ oldcapcontid = audit_get_capcontid(task);
+ /* if task is not descendant, block */
+ if (task == current)
+ rc = -EBADSLT;
+ else if (!task_is_descendant(current, task))
+ rc = -EXDEV;
+ else if (current_user_ns() == &init_user_ns) {
+ if (!capable(CAP_AUDIT_CONTROL) && !audit_get_capcontid(current))
+ rc = -EPERM;
+ }
+ if (!rc)
+ task->audit->capcontid = enable;
+
+ if (!audit_enabled)
+ return rc;
+
+ ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_SET_CAPCONTID);
+ if (!ab)
+ return rc;
+
+ audit_log_format(ab,
+ "opid=%d capcontid=%u old-capcontid=%u",
+ task_tgid_nr(task), enable, oldcapcontid);
+ audit_log_end(ab);
+ return rc;
+}
+
/*
* audit_set_contid - set current task's audit contid
* @task: target task
--
1.8.3.1
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