---

yaml --- r: 94058 b: refs/heads/master c: 3898b1b h: refs/heads/master v: v3
git-mirror · Apr 28, 2008 · 5cefd36 · 5cefd36
1 parent 12af452
commit 5cefd36
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Showing 13 changed files with 142 additions and 61 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 4016a1390d07f15b267eecb20e76a48fd5c524ef
+refs/heads/master: 3898b1b4ebff8dcfbcf1807e0661585e06c9a91c
diff --git a/trunk/include/linux/capability.h b/trunk/include/linux/capability.h
@@ -155,6 +155,7 @@ typedef struct kernel_cap_struct {
  *   Add any capability from current's capability bounding set
  *       to the current process' inheritable set
  *   Allow taking bits out of capability bounding set
+ *   Allow modification of the securebits for a process
  */
 
 #define CAP_SETPCAP          8
@@ -490,8 +491,6 @@ extern const kernel_cap_t __cap_init_eff_set;
 int capable(int cap);
 int __capable(struct task_struct *t, int cap);
 
-extern long cap_prctl_drop(unsigned long cap);
-
 #endif /* __KERNEL__ */
 
 #endif /* !_LINUX_CAPABILITY_H */
diff --git a/trunk/include/linux/init_task.h b/trunk/include/linux/init_task.h
@@ -9,6 +9,7 @@
 #include <linux/ipc.h>
 #include <linux/pid_namespace.h>
 #include <linux/user_namespace.h>
+#include <linux/securebits.h>
 #include <net/net_namespace.h>
 
 #define INIT_FDTABLE \
@@ -172,7 +173,7 @@ extern struct group_info init_groups;
 	.cap_inheritable = CAP_INIT_INH_SET,				\
 	.cap_permitted	= CAP_FULL_SET,					\
 	.cap_bset 	= CAP_INIT_BSET,				\
-	.keep_capabilities = 0,						\
+	.securebits     = SECUREBITS_DEFAULT,				\
 	.user		= INIT_USER,					\
 	.comm		= "swapper",					\
 	.thread		= INIT_THREAD,					\

diff --git a/trunk/include/linux/prctl.h b/trunk/include/linux/prctl.h
@@ -16,7 +16,8 @@
 # define PR_UNALIGN_NOPRINT	1	/* silently fix up unaligned user accesses */
 # define PR_UNALIGN_SIGBUS	2	/* generate SIGBUS on unaligned user access */
 
-/* Get/set whether or not to drop capabilities on setuid() away from uid 0 */
+/* Get/set whether or not to drop capabilities on setuid() away from
+ * uid 0 (as per security/commoncap.c) */
 #define PR_GET_KEEPCAPS   7
 #define PR_SET_KEEPCAPS   8
 
@@ -63,7 +64,7 @@
 #define PR_GET_SECCOMP	21
 #define PR_SET_SECCOMP	22
 
-/* Get/set the capability bounding set */
+/* Get/set the capability bounding set (as per security/commoncap.c) */
 #define PR_CAPBSET_READ 23
 #define PR_CAPBSET_DROP 24
 
@@ -73,4 +74,8 @@
 # define PR_TSC_ENABLE		1	/* allow the use of the timestamp counter */
 # define PR_TSC_SIGSEGV		2	/* throw a SIGSEGV instead of reading the TSC */
 
+/* Get/set securebits (as per security/commoncap.c) */
+#define PR_GET_SECUREBITS 27
+#define PR_SET_SECUREBITS 28
+
 #endif /* _LINUX_PRCTL_H */
diff --git a/trunk/include/linux/sched.h b/trunk/include/linux/sched.h
@@ -68,7 +68,6 @@ struct sched_param {
 #include <linux/smp.h>
 #include <linux/sem.h>
 #include <linux/signal.h>
-#include <linux/securebits.h>
 #include <linux/fs_struct.h>
 #include <linux/compiler.h>
 #include <linux/completion.h>
@@ -1133,7 +1132,7 @@ struct task_struct {
 	gid_t gid,egid,sgid,fsgid;
 	struct group_info *group_info;
 	kernel_cap_t   cap_effective, cap_inheritable, cap_permitted, cap_bset;
-	unsigned keep_capabilities:1;
+	unsigned securebits;
 	struct user_struct *user;
 #ifdef CONFIG_KEYS
 	struct key *request_key_auth;	/* assumed request_key authority */

diff --git a/trunk/include/linux/securebits.h b/trunk/include/linux/securebits.h
@@ -3,28 +3,39 @@
 
 #define SECUREBITS_DEFAULT 0x00000000
 
-extern unsigned securebits;
-
 /* When set UID 0 has no special privileges. When unset, we support
    inheritance of root-permissions and suid-root executable under
    compatibility mode. We raise the effective and inheritable bitmasks
    *of the executable file* if the effective uid of the new process is
    0. If the real uid is 0, we raise the inheritable bitmask of the
    executable file. */
-#define SECURE_NOROOT            0
+#define SECURE_NOROOT			0
+#define SECURE_NOROOT_LOCKED		1  /* make bit-0 immutable */
 
 /* When set, setuid to/from uid 0 does not trigger capability-"fixes"
    to be compatible with old programs relying on set*uid to loose
    privileges. When unset, setuid doesn't change privileges. */
-#define SECURE_NO_SETUID_FIXUP   2
+#define SECURE_NO_SETUID_FIXUP		2
+#define SECURE_NO_SETUID_FIXUP_LOCKED	3  /* make bit-2 immutable */
+
+/* When set, a process can retain its capabilities even after
+   transitioning to a non-root user (the set-uid fixup suppressed by
+   bit 2). Bit-4 is cleared when a process calls exec(); setting both
+   bit 4 and 5 will create a barrier through exec that no exec()'d
+   child can use this feature again. */
+#define SECURE_KEEP_CAPS		4
+#define SECURE_KEEP_CAPS_LOCKED		5  /* make bit-4 immutable */
 
 /* Each securesetting is implemented using two bits. One bit specify
    whether the setting is on or off. The other bit specify whether the
    setting is fixed or not. A setting which is fixed cannot be changed
    from user-level. */
+#define issecure_mask(X)	(1 << (X))
+#define issecure(X)		(issecure_mask(X) & current->securebits)
 
-#define issecure(X) ( (1 << (X+1)) & SECUREBITS_DEFAULT ? 	\
-		      (1 << (X)) & SECUREBITS_DEFAULT :		\
-		      (1 << (X)) & securebits )
+#define SECURE_ALL_BITS		(issecure_mask(SECURE_NOROOT) | \
+				 issecure_mask(SECURE_NO_SETUID_FIXUP) | \
+				 issecure_mask(SECURE_KEEP_CAPS))
+#define SECURE_ALL_LOCKS	(SECURE_ALL_BITS << 1)
 
 #endif /* !_LINUX_SECUREBITS_H */
diff --git a/trunk/include/linux/security.h b/trunk/include/linux/security.h
@@ -34,8 +34,6 @@
 #include <linux/xfrm.h>
 #include <net/flow.h>
 
-extern unsigned securebits;
-
 /* Maximum number of letters for an LSM name string */
 #define SECURITY_NAME_MAX	10
 
@@ -61,6 +59,8 @@ extern int cap_inode_need_killpriv(struct dentry *dentry);
 extern int cap_inode_killpriv(struct dentry *dentry);
 extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
 extern void cap_task_reparent_to_init (struct task_struct *p);
+extern int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+			  unsigned long arg4, unsigned long arg5, long *rc_p);
 extern int cap_task_setscheduler (struct task_struct *p, int policy, struct sched_param *lp);
 extern int cap_task_setioprio (struct task_struct *p, int ioprio);
 extern int cap_task_setnice (struct task_struct *p, int nice);
@@ -720,7 +720,9 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
  *	@arg3 contains a argument.
  *	@arg4 contains a argument.
  *	@arg5 contains a argument.
- *	Return 0 if permission is granted.
+ *      @rc_p contains a pointer to communicate back the forced return code
+ *	Return 0 if permission is granted, and non-zero if the security module
+ *      has taken responsibility (setting *rc_p) for the prctl call.
  * @task_reparent_to_init:
  * 	Set the security attributes in @p->security for a kernel thread that
  * 	is being reparented to the init task.
@@ -1420,7 +1422,7 @@ struct security_operations {
 	int (*task_wait) (struct task_struct * p);
 	int (*task_prctl) (int option, unsigned long arg2,
 			   unsigned long arg3, unsigned long arg4,
-			   unsigned long arg5);
+			   unsigned long arg5, long *rc_p);
 	void (*task_reparent_to_init) (struct task_struct * p);
 	void (*task_to_inode)(struct task_struct *p, struct inode *inode);
 
@@ -1684,7 +1686,7 @@ int security_task_kill(struct task_struct *p, struct siginfo *info,
 			int sig, u32 secid);
 int security_task_wait(struct task_struct *p);
 int security_task_prctl(int option, unsigned long arg2, unsigned long arg3,
-			 unsigned long arg4, unsigned long arg5);
+			 unsigned long arg4, unsigned long arg5, long *rc_p);
 void security_task_reparent_to_init(struct task_struct *p);
 void security_task_to_inode(struct task_struct *p, struct inode *inode);
 int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag);
@@ -2271,9 +2273,9 @@ static inline int security_task_wait (struct task_struct *p)
 static inline int security_task_prctl (int option, unsigned long arg2,
 				       unsigned long arg3,
 				       unsigned long arg4,
-				       unsigned long arg5)
+				       unsigned long arg5, long *rc_p)
 {
-	return 0;
+	return cap_task_prctl(option, arg2, arg3, arg3, arg5, rc_p);
 }
 
 static inline void security_task_reparent_to_init (struct task_struct *p)

diff --git a/trunk/kernel/sys.c b/trunk/kernel/sys.c
@@ -1632,10 +1632,9 @@ asmlinkage long sys_umask(int mask)
 asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 			  unsigned long arg4, unsigned long arg5)
 {
-	long error;
+	long uninitialized_var(error);
 
-	error = security_task_prctl(option, arg2, arg3, arg4, arg5);
-	if (error)
+	if (security_task_prctl(option, arg2, arg3, arg4, arg5, &error))
 		return error;
 
 	switch (option) {
@@ -1688,17 +1687,6 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 				error = -EINVAL;
 			break;
 
-		case PR_GET_KEEPCAPS:
-			if (current->keep_capabilities)
-				error = 1;
-			break;
-		case PR_SET_KEEPCAPS:
-			if (arg2 != 0 && arg2 != 1) {
-				error = -EINVAL;
-				break;
-			}
-			current->keep_capabilities = arg2;
-			break;
 		case PR_SET_NAME: {
 			struct task_struct *me = current;
 			unsigned char ncomm[sizeof(me->comm)];
@@ -1732,17 +1720,6 @@ asmlinkage long sys_prctl(int option, unsigned long arg2, unsigned long arg3,
 		case PR_SET_SECCOMP:
 			error = prctl_set_seccomp(arg2);
 			break;
-
-		case PR_CAPBSET_READ:
-			if (!cap_valid(arg2))
-				return -EINVAL;
-			return !!cap_raised(current->cap_bset, arg2);
-		case PR_CAPBSET_DROP:
-#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
-			return cap_prctl_drop(arg2);
-#else
-			return -EINVAL;
-#endif
 		case PR_GET_TSC:
 			error = GET_TSC_CTL(arg2);
 			break;

diff --git a/trunk/security/capability.c b/trunk/security/capability.c
@@ -44,6 +44,7 @@ static struct security_operations capability_ops = {
 	.task_setioprio =		cap_task_setioprio,
 	.task_setnice =			cap_task_setnice,
 	.task_post_setuid =		cap_task_post_setuid,
+	.task_prctl =                   cap_task_prctl,
 	.task_reparent_to_init =	cap_task_reparent_to_init,
 
 	.syslog =                       cap_syslog,

diff --git a/trunk/security/commoncap.c b/trunk/security/commoncap.c
@@ -24,11 +24,8 @@
 #include <linux/hugetlb.h>
 #include <linux/mount.h>
 #include <linux/sched.h>
-
-/* Global security state */
-
-unsigned securebits = SECUREBITS_DEFAULT; /* systemwide security settings */
-EXPORT_SYMBOL(securebits);
+#include <linux/prctl.h>
+#include <linux/securebits.h>
 
 int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
 {
@@ -368,7 +365,7 @@ void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
 
 	/* AUD: Audit candidate if current->cap_effective is set */
 
-	current->keep_capabilities = 0;
+	current->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
 }
 
 int cap_bprm_secureexec (struct linux_binprm *bprm)
@@ -448,7 +445,7 @@ static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
 {
 	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
 	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
-	    !current->keep_capabilities) {
+	    !issecure(SECURE_KEEP_CAPS)) {
 		cap_clear (current->cap_permitted);
 		cap_clear (current->cap_effective);
 	}
@@ -547,7 +544,7 @@ int cap_task_setnice (struct task_struct *p, int nice)
  * this task could get inconsistent info.  There can be no
  * racing writer bc a task can only change its own caps.
  */
-long cap_prctl_drop(unsigned long cap)
+static long cap_prctl_drop(unsigned long cap)
 {
 	if (!capable(CAP_SETPCAP))
 		return -EPERM;
@@ -556,6 +553,7 @@ long cap_prctl_drop(unsigned long cap)
 	cap_lower(current->cap_bset, cap);
 	return 0;
 }
+
 #else
 int cap_task_setscheduler (struct task_struct *p, int policy,
 			   struct sched_param *lp)
@@ -572,12 +570,99 @@ int cap_task_setnice (struct task_struct *p, int nice)
 }
 #endif
 
+int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+		   unsigned long arg4, unsigned long arg5, long *rc_p)
+{
+	long error = 0;
+
+	switch (option) {
+	case PR_CAPBSET_READ:
+		if (!cap_valid(arg2))
+			error = -EINVAL;
+		else
+			error = !!cap_raised(current->cap_bset, arg2);
+		break;
+#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
+	case PR_CAPBSET_DROP:
+		error = cap_prctl_drop(arg2);
+		break;
+
+	/*
+	 * The next four prctl's remain to assist with transitioning a
+	 * system from legacy UID=0 based privilege (when filesystem
+	 * capabilities are not in use) to a system using filesystem
+	 * capabilities only - as the POSIX.1e draft intended.
+	 *
+	 * Note:
+	 *
+	 *  PR_SET_SECUREBITS =
+	 *      issecure_mask(SECURE_KEEP_CAPS_LOCKED)
+	 *    | issecure_mask(SECURE_NOROOT)
+	 *    | issecure_mask(SECURE_NOROOT_LOCKED)
+	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP)
+	 *    | issecure_mask(SECURE_NO_SETUID_FIXUP_LOCKED)
+	 *
+	 * will ensure that the current process and all of its
+	 * children will be locked into a pure
+	 * capability-based-privilege environment.
+	 */
+	case PR_SET_SECUREBITS:
+		if ((((current->securebits & SECURE_ALL_LOCKS) >> 1)
+		     & (current->securebits ^ arg2))                  /*[1]*/
+		    || ((current->securebits & SECURE_ALL_LOCKS
+			 & ~arg2))                                    /*[2]*/
+		    || (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
+		    || (cap_capable(current, CAP_SETPCAP) != 0)) {    /*[4]*/
+			/*
+			 * [1] no changing of bits that are locked
+			 * [2] no unlocking of locks
+			 * [3] no setting of unsupported bits
+			 * [4] doing anything requires privilege (go read about
+			 *     the "sendmail capabilities bug")
+			 */
+			error = -EPERM;  /* cannot change a locked bit */
+		} else {
+			current->securebits = arg2;
+		}
+		break;
+	case PR_GET_SECUREBITS:
+		error = current->securebits;
+		break;
+
+#endif /* def CONFIG_SECURITY_FILE_CAPABILITIES */
+
+	case PR_GET_KEEPCAPS:
+		if (issecure(SECURE_KEEP_CAPS))
+			error = 1;
+		break;
+	case PR_SET_KEEPCAPS:
+		if (arg2 > 1) /* Note, we rely on arg2 being unsigned here */
+			error = -EINVAL;
+		else if (issecure(SECURE_KEEP_CAPS_LOCKED))
+			error = -EPERM;
+		else if (arg2)
+			current->securebits |= issecure_mask(SECURE_KEEP_CAPS);
+		else
+			current->securebits &=
+				~issecure_mask(SECURE_KEEP_CAPS);
+		break;
+
+	default:
+		/* No functionality available - continue with default */
+		return 0;
+	}
+
+	/* Functionality provided */
+	*rc_p = error;
+	return 1;
+}
+
 void cap_task_reparent_to_init (struct task_struct *p)
 {
 	cap_set_init_eff(p->cap_effective);
 	cap_clear(p->cap_inheritable);
 	cap_set_full(p->cap_permitted);
-	p->keep_capabilities = 0;
+	p->securebits = SECUREBITS_DEFAULT;
 	return;
 }