[PATCH] BSD Secure Levels LSM: add time hooks

I have received positive feedback from various individuals who have applied my
BSD Secure Levels LSM patch, and so at this point I am submitting it to you
with a request to merge it in.  Nothing has changed in this patch since when I
last posted it to the LKML, so I am not re-sending it there.

This first patch adds hooks to catch attempts to set the system clock back.
Signed-off-by: Michael A. Halcrow <mahalcro@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/mips/kernel/sysirix.c

@@ -619,8 +619,14 @@ asmlinkage int irix_getgid(struct pt_regs *regs)
 
 asmlinkage int irix_stime(int value)
 {
-	if (!capable(CAP_SYS_TIME))
-		return -EPERM;
+	int err;
+	struct timespec tv;
+
+	tv.tv_sec = value;
+	tv.tv_nsec = 0;
+	err = security_settime(&tv, NULL);
+	if (err)
+		return err;
 
 	write_seqlock_irq(&xtime_lock);
 	xtime.tv_sec = value;

arch/ppc64/kernel/time.c

@@ -49,6 +49,7 @@
 #include <linux/init.h>
 #include <linux/profile.h>
 #include <linux/cpu.h>
+#include <linux/security.h>
 
 #include <asm/segment.h>
 #include <asm/io.h>
@@ -434,9 +435,7 @@ long ppc64_sys32_stime(int __user * tptr)
 {
 	int value;
 	struct timespec myTimeval;
-
-	if (!capable(CAP_SYS_TIME))
-		return -EPERM;
+	int err;
 
 	if (get_user(value, tptr))
 		return -EFAULT;
@@ -444,6 +443,10 @@ long ppc64_sys32_stime(int __user * tptr)
 	myTimeval.tv_sec = value;
 	myTimeval.tv_nsec = 0;
 
+	err = security_settime(&myTimeval, NULL);
+	if (err)
+		return err;
+
 	do_settimeofday(&myTimeval);
 
 	return 0;
@@ -459,9 +462,7 @@ long ppc64_sys_stime(long __user * tptr)
 {
 	long value;
 	struct timespec myTimeval;
-
-	if (!capable(CAP_SYS_TIME))
-		return -EPERM;
+	int err;
 
 	if (get_user(value, tptr))
 		return -EFAULT;
@@ -469,6 +470,10 @@ long ppc64_sys_stime(long __user * tptr)
 	myTimeval.tv_sec = value;
 	myTimeval.tv_nsec = 0;
 
+	err = security_settime(&myTimeval, NULL);
+	if (err)
+		return err;
+
 	do_settimeofday(&myTimeval);
 
 	return 0;

include/linux/security.h

@@ -40,6 +40,7 @@ struct ctl_table;
  * as the default capabilities functions
  */
 extern int cap_capable (struct task_struct *tsk, int cap);
+extern int cap_settime (struct timespec *ts, struct timezone *tz);
 extern int cap_ptrace (struct task_struct *parent, struct task_struct *child);
 extern int cap_capget (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
 extern int cap_capset_check (struct task_struct *target, kernel_cap_t *effective, kernel_cap_t *inheritable, kernel_cap_t *permitted);
@@ -1001,6 +1002,12 @@ struct swap_info_struct;
  *	See the syslog(2) manual page for an explanation of the @type values.  
  *	@type contains the type of action.
  *	Return 0 if permission is granted.
+ * @settime:
+ *	Check permission to change the system time.
+ *	struct timespec and timezone are defined in include/linux/time.h
+ *	@ts contains new time
+ *	@tz contains new timezone
+ *	Return 0 if permission is granted.
  * @vm_enough_memory:
  *	Check permissions for allocating a new virtual mapping.
  *      @pages contains the number of pages.
@@ -1036,6 +1043,7 @@ struct security_operations {
 	int (*quotactl) (int cmds, int type, int id, struct super_block * sb);
 	int (*quota_on) (struct file * f);
 	int (*syslog) (int type);
+	int (*settime) (struct timespec *ts, struct timezone *tz);
 	int (*vm_enough_memory) (long pages);
 
 	int (*bprm_alloc_security) (struct linux_binprm * bprm);
@@ -1291,6 +1299,12 @@ static inline int security_syslog(int type)
 	return security_ops->syslog(type);
 }
 
+static inline int security_settime(struct timespec *ts, struct timezone *tz)
+{
+	return security_ops->settime(ts, tz);
+}
+
+
 static inline int security_vm_enough_memory(long pages)
 {
 	return security_ops->vm_enough_memory(pages);
@@ -1963,6 +1977,11 @@ static inline int security_syslog(int type)
 	return cap_syslog(type);
 }
 
+static inline int security_settime(struct timespec *ts, struct timezone *tz)
+{
+	return cap_settime(ts, tz);
+}
+
 static inline int security_vm_enough_memory(long pages)
 {
 	return cap_vm_enough_memory(pages);

kernel/time.c

@@ -32,6 +32,8 @@
 #include <linux/errno.h>
 #include <linux/smp_lock.h>
 #include <linux/syscalls.h>
+#include <linux/security.h>
+
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
 
@@ -78,13 +80,17 @@ asmlinkage long sys_time(int __user * tloc)
 asmlinkage long sys_stime(time_t __user *tptr)
 {
 	struct timespec tv;
+	int err;
 
-	if (!capable(CAP_SYS_TIME))
-		return -EPERM;
 	if (get_user(tv.tv_sec, tptr))
 		return -EFAULT;
 
 	tv.tv_nsec = 0;
+
+	err = security_settime(&tv, NULL);
+	if (err)
+		return err;
+
 	do_settimeofday(&tv);
 	return 0;
 }
@@ -146,10 +152,12 @@ inline static void warp_clock(void)
 int do_sys_settimeofday(struct timespec *tv, struct timezone *tz)
 {
 	static int firsttime = 1;
+	int error = 0;
+
+	error = security_settime(tv, tz);
+	if (error)
+		return error;
 
-	if (!capable(CAP_SYS_TIME))
-		return -EPERM;
-		
 	if (tz) {
 		/* SMP safe, global irq locking makes it work. */
 		sys_tz = *tz;

security/capability.c

@@ -30,6 +30,7 @@ static struct security_operations capability_ops = {
 	.capset_check =			cap_capset_check,
 	.capset_set =			cap_capset_set,
 	.capable =			cap_capable,
+	.settime =			cap_settime,
 	.netlink_send =			cap_netlink_send,
 	.netlink_recv =			cap_netlink_recv,
 

security/commoncap.c

@@ -27,20 +27,25 @@
 int cap_capable (struct task_struct *tsk, int cap)
 {
 	/* Derived from include/linux/sched.h:capable. */
-	if (cap_raised (tsk->cap_effective, cap))
+	if (cap_raised(tsk->cap_effective, cap))
 		return 0;
-	else
+	return -EPERM;
+}
+
+int cap_settime(struct timespec *ts, struct timezone *tz)
+{
+	if (!capable(CAP_SYS_TIME))
 		return -EPERM;
+	return 0;
 }
 
 int cap_ptrace (struct task_struct *parent, struct task_struct *child)
 {
 	/* Derived from arch/i386/kernel/ptrace.c:sys_ptrace. */
 	if (!cap_issubset (child->cap_permitted, current->cap_permitted) &&
-	    !capable (CAP_SYS_PTRACE))
+	    !capable(CAP_SYS_PTRACE))
 		return -EPERM;
-	else
-		return 0;
+	return 0;
 }
 
 int cap_capget (struct task_struct *target, kernel_cap_t *effective,
@@ -373,6 +378,7 @@ int cap_vm_enough_memory(long pages)
 }
 
 EXPORT_SYMBOL(cap_capable);
+EXPORT_SYMBOL(cap_settime);
 EXPORT_SYMBOL(cap_ptrace);
 EXPORT_SYMBOL(cap_capget);
 EXPORT_SYMBOL(cap_capset_check);

security/dummy.c

@@ -104,6 +104,13 @@ static int dummy_syslog (int type)
 	return 0;
 }
 
+static int dummy_settime(struct timespec *ts, struct timezone *tz)
+{
+	if (!capable(CAP_SYS_TIME))
+		return -EPERM;
+	return 0;
+}
+
 /*
  * Check that a process has enough memory to allocate a new virtual
  * mapping. 0 means there is enough memory for the allocation to
@@ -897,6 +904,7 @@ void security_fixup_ops (struct security_operations *ops)
 	set_to_dummy_if_null(ops, quota_on);
 	set_to_dummy_if_null(ops, sysctl);
 	set_to_dummy_if_null(ops, syslog);
+	set_to_dummy_if_null(ops, settime);
 	set_to_dummy_if_null(ops, vm_enough_memory);
 	set_to_dummy_if_null(ops, bprm_alloc_security);
 	set_to_dummy_if_null(ops, bprm_free_security);