[PATCH] LSM root_plug fixup

[PATCH] LSM root_plug fixup

[bert hubert]

Greg,

For root_plug, which is a fun way to demonstrate LSM, depends on
capability.o, but when loaded, capability.o installs its own security module
which won't accept root_plug anymore.

This patch abstracts out the functionality of capability.o which is needed
by root_plug, but leaves the actual security module in capability.o.

This creates the new file commoncap.c, which contains the functions
capability.o and root_plug.o both need.

It also fixes a cosmetic oddity in root_plug.

Please apply.

diff -uBbrN linux-2.6.0-test1/security/Makefile linux-2.6.0-test2-ahu/security/Makefile
--- linux-2.6.0-test1/security/Makefile	Mon Jul 14 05:36:37 2003
+++ linux-2.6.0-test2-ahu/security/Makefile	Mon Aug  4 19:49:58 2003
@@ -4,10 +4,10 @@
 
 # if we don't select a security model, use the default capabilities
 ifneq ($(CONFIG_SECURITY),y)
-obj-y		+= capability.o
+obj-y		+= commoncap.c capability.o
 endif
 
 # Object file lists
 obj-$(CONFIG_SECURITY)			+= security.o dummy.o
-obj-$(CONFIG_SECURITY_CAPABILITIES)	+= capability.o
-obj-$(CONFIG_SECURITY_ROOTPLUG)		+= root_plug.o
+obj-$(CONFIG_SECURITY_CAPABILITIES)	+= commoncap.o capability.o
+obj-$(CONFIG_SECURITY_ROOTPLUG)		+= commoncap.o root_plug.o
diff -uBbrN linux-2.6.0-test1/security/capability.c linux-2.6.0-test2-ahu/security/capability.c
--- linux-2.6.0-test1/security/capability.c	Mon Jul 14 05:32:43 2003
+++ linux-2.6.0-test2-ahu/security/capability.c	Mon Aug  4 19:48:26 2003
@@ -23,333 +23,6 @@
 #include <linux/netlink.h>
 #include <linux/ptrace.h>
 
-int cap_capable (struct task_struct *tsk, int cap)
-{
-	/* Derived from include/linux/sched.h:capable. */
-	if (cap_raised (tsk->cap_effective, cap))
-		return 0;
-	else
-		return -EPERM;
-}
-
-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))
-		return -EPERM;
-	else
-		return 0;
-}
-
-int cap_capget (struct task_struct *target, kernel_cap_t *effective,
-		kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capget. */
-	*effective = cap_t (target->cap_effective);
-	*inheritable = cap_t (target->cap_inheritable);
-	*permitted = cap_t (target->cap_permitted);
-	return 0;
-}
-
-int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
-		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capset. */
-	/* verify restrictions on target's new Inheritable set */
-	if (!cap_issubset (*inheritable,
-			   cap_combine (target->cap_inheritable,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify restrictions on target's new Permitted set */
-	if (!cap_issubset (*permitted,
-			   cap_combine (target->cap_permitted,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
-	if (!cap_issubset (*effective, *permitted)) {
-		return -EPERM;
-	}
-
-	return 0;
-}
-
-void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
-		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	target->cap_effective = *effective;
-	target->cap_inheritable = *inheritable;
-	target->cap_permitted = *permitted;
-}
-
-int cap_bprm_set_security (struct linux_binprm *bprm)
-{
-	/* Copied from fs/exec.c:prepare_binprm. */
-
-	/* We don't have VFS support for capabilities yet */
-	cap_clear (bprm->cap_inheritable);
-	cap_clear (bprm->cap_permitted);
-	cap_clear (bprm->cap_effective);
-
-	/*  To support inheritance of root-permissions and suid-root
-	 *  executables under compatibility mode, we raise all three
-	 *  capability sets for the file.
-	 *
-	 *  If only the real uid is 0, we only raise the inheritable
-	 *  and permitted sets of the executable file.
-	 */
-
-	if (!issecure (SECURE_NOROOT)) {
-		if (bprm->e_uid == 0 || current->uid == 0) {
-			cap_set_full (bprm->cap_inheritable);
-			cap_set_full (bprm->cap_permitted);
-		}
-		if (bprm->e_uid == 0)
-			cap_set_full (bprm->cap_effective);
-	}
-	return 0;
-}
-
-/* Copied from fs/exec.c */
-static inline int must_not_trace_exec (struct task_struct *p)
-{
-	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
-}
-
-void cap_bprm_compute_creds (struct linux_binprm *bprm)
-{
-	/* Derived from fs/exec.c:compute_creds. */
-	kernel_cap_t new_permitted, working;
-
-	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
-	working = cap_intersect (bprm->cap_inheritable,
-				 current->cap_inheritable);
-	new_permitted = cap_combine (new_permitted, working);
-
-	task_lock(current);
-	if (!cap_issubset (new_permitted, current->cap_permitted)) {
-		current->mm->dumpable = 0;
-
-		if (must_not_trace_exec (current)
-		    || atomic_read (&current->fs->count) > 1
-		    || atomic_read (&current->files->count) > 1
-		    || atomic_read (&current->sighand->count) > 1) {
-			if (!capable (CAP_SETPCAP)) {
-				new_permitted = cap_intersect (new_permitted,
-							       current->
-							       cap_permitted);
-			}
-		}
-	}
-
-	/* For init, we want to retain the capabilities set
-	 * in the init_task struct. Thus we skip the usual
-	 * capability rules */
-	if (current->pid != 1) {
-		current->cap_permitted = new_permitted;
-		current->cap_effective =
-		    cap_intersect (new_permitted, bprm->cap_effective);
-	}
-
-	/* AUD: Audit candidate if current->cap_effective is set */
-	task_unlock(current);
-
-	current->keep_capabilities = 0;
-}
-
-int cap_bprm_secureexec (struct linux_binprm *bprm)
-{
-	/* If/when this module is enhanced to incorporate capability
-	   bits on files, the test below should be extended to also perform a 
-	   test between the old and new capability sets.  For now,
-	   it simply preserves the legacy decision algorithm used by
-	   the old userland. */
-	return (current->euid != current->uid ||
-		current->egid != current->gid);
-}
-
-/* moved from kernel/sys.c. */
-/* 
- * cap_emulate_setxuid() fixes the effective / permitted capabilities of
- * a process after a call to setuid, setreuid, or setresuid.
- *
- *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
- *  {r,e,s}uid != 0, the permitted and effective capabilities are
- *  cleared.
- *
- *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
- *  capabilities of the process are cleared.
- *
- *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
- *  capabilities are set to the permitted capabilities.
- *
- *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
- *  never happen.
- *
- *  -astor 
- *
- * cevans - New behaviour, Oct '99
- * A process may, via prctl(), elect to keep its capabilities when it
- * calls setuid() and switches away from uid==0. Both permitted and
- * effective sets will be retained.
- * Without this change, it was impossible for a daemon to drop only some
- * of its privilege. The call to setuid(!=0) would drop all privileges!
- * Keeping uid 0 is not an option because uid 0 owns too many vital
- * files..
- * Thanks to Olaf Kirch and Peter Benie for spotting this.
- */
-static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
-					int old_suid)
-{
-	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
-	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
-	    !current->keep_capabilities) {
-		cap_clear (current->cap_permitted);
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid == 0 && current->euid != 0) {
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid != 0 && current->euid == 0) {
-		current->cap_effective = current->cap_permitted;
-	}
-}
-
-int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
-			  int flags)
-{
-	switch (flags) {
-	case LSM_SETID_RE:
-	case LSM_SETID_ID:
-	case LSM_SETID_RES:
-		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
-		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
-		}
-		break;
-	case LSM_SETID_FS:
-		{
-			uid_t old_fsuid = old_ruid;
-
-			/* Copied from kernel/sys.c:setfsuid. */
-
-			/*
-			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
-			 *          if not, we might be a bit too harsh here.
-			 */
-
-			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-				if (old_fsuid == 0 && current->fsuid != 0) {
-					cap_t (current->cap_effective) &=
-					    ~CAP_FS_MASK;
-				}
-				if (old_fsuid != 0 && current->fsuid == 0) {
-					cap_t (current->cap_effective) |=
-					    (cap_t (current->cap_permitted) &
-					     CAP_FS_MASK);
-				}
-			}
-			break;
-		}
-	default:
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-void cap_task_reparent_to_init (struct task_struct *p)
-{
-	p->cap_effective = CAP_INIT_EFF_SET;
-	p->cap_inheritable = CAP_INIT_INH_SET;
-	p->cap_permitted = CAP_FULL_SET;
-	p->keep_capabilities = 0;
-	return;
-}
-
-int cap_syslog (int type)
-{
-	if ((type != 3) && !capable(CAP_SYS_ADMIN))
-		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
- * succeed and -ENOMEM implies there is not.
- *
- * We currently support three overcommit policies, which are set via the
- * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
- *
- * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
- * Additional code 2002 Jul 20 by Robert Love.
- */
-int cap_vm_enough_memory(long pages)
-{
-	unsigned long free, allowed;
-
-	vm_acct_memory(pages);
-
-        /*
-	 * Sometimes we want to use more memory than we have
-	 */
-	if (sysctl_overcommit_memory == 1)
-		return 0;
-
-	if (sysctl_overcommit_memory == 0) {
-		free = get_page_cache_size();
-		free += nr_free_pages();
-		free += nr_swap_pages;
-
-		/*
-		 * Any slabs which are created with the
-		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
-		 * which are reclaimable, under pressure.  The dentry
-		 * cache and most inode caches should fall into this
-		 */
-		free += atomic_read(&slab_reclaim_pages);
-
-		/*
-		 * Leave the last 3% for root
-		 */
-		if (!capable(CAP_SYS_ADMIN))
-			free -= free / 32;
-
-		if (free > pages)
-			return 0;
-		vm_unacct_memory(pages);
-		return -ENOMEM;
-	}
-
-	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
-	allowed += total_swap_pages;
-
-	if (atomic_read(&vm_committed_space) < allowed)
-		return 0;
-
-	vm_unacct_memory(pages);
-
-	return -ENOMEM;
-}
-
-EXPORT_SYMBOL(cap_capable);
-EXPORT_SYMBOL(cap_ptrace);
-EXPORT_SYMBOL(cap_capget);
-EXPORT_SYMBOL(cap_capset_check);
-EXPORT_SYMBOL(cap_capset_set);
-EXPORT_SYMBOL(cap_bprm_set_security);
-EXPORT_SYMBOL(cap_bprm_compute_creds);
-EXPORT_SYMBOL(cap_bprm_secureexec);
-EXPORT_SYMBOL(cap_task_post_setuid);
-EXPORT_SYMBOL(cap_task_reparent_to_init);
-EXPORT_SYMBOL(cap_syslog);
-EXPORT_SYMBOL(cap_vm_enough_memory);
-
 #ifdef CONFIG_SECURITY
 
 

diff -uBbrN linux-2.6.0-test1/security/commoncap.c linux-2.6.0-test2-ahu/security/commoncap.c
--- linux-2.6.0-test1/security/commoncap.c	Thu Jan  1 01:00:00 1970
+++ linux-2.6.0-test2-ahu/security/commoncap.c	Mon Aug  4 19:48:19 2003
@@ -0,0 +1,341 @@
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/smp_lock.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/ptrace.h>
+
+int cap_capable (struct task_struct *tsk, int cap)
+{
+	/* Derived from include/linux/sched.h:capable. */
+	if (cap_raised (tsk->cap_effective, cap))
+		return 0;
+	else
+		return -EPERM;
+}
+
+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))
+		return -EPERM;
+	else
+		return 0;
+}
+
+int cap_capget (struct task_struct *target, kernel_cap_t *effective,
+		kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capget. */
+	*effective = cap_t (target->cap_effective);
+	*inheritable = cap_t (target->cap_inheritable);
+	*permitted = cap_t (target->cap_permitted);
+	return 0;
+}
+
+int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
+		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capset. */
+	/* verify restrictions on target's new Inheritable set */
+	if (!cap_issubset (*inheritable,
+			   cap_combine (target->cap_inheritable,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify restrictions on target's new Permitted set */
+	if (!cap_issubset (*permitted,
+			   cap_combine (target->cap_permitted,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
+	if (!cap_issubset (*effective, *permitted)) {
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
+		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	target->cap_effective = *effective;
+	target->cap_inheritable = *inheritable;
+	target->cap_permitted = *permitted;
+}
+
+int cap_bprm_set_security (struct linux_binprm *bprm)
+{
+	/* Copied from fs/exec.c:prepare_binprm. */
+
+	/* We don't have VFS support for capabilities yet */
+	cap_clear (bprm->cap_inheritable);
+	cap_clear (bprm->cap_permitted);
+	cap_clear (bprm->cap_effective);
+
+	/*  To support inheritance of root-permissions and suid-root
+	 *  executables under compatibility mode, we raise all three
+	 *  capability sets for the file.
+	 *
+	 *  If only the real uid is 0, we only raise the inheritable
+	 *  and permitted sets of the executable file.
+	 */
+
+	if (!issecure (SECURE_NOROOT)) {
+		if (bprm->e_uid == 0 || current->uid == 0) {
+			cap_set_full (bprm->cap_inheritable);
+			cap_set_full (bprm->cap_permitted);
+		}
+		if (bprm->e_uid == 0)
+			cap_set_full (bprm->cap_effective);
+	}
+	return 0;
+}
+
+/* Copied from fs/exec.c */
+static inline int must_not_trace_exec (struct task_struct *p)
+{
+	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
+}
+
+void cap_bprm_compute_creds (struct linux_binprm *bprm)
+{
+	/* Derived from fs/exec.c:compute_creds. */
+	kernel_cap_t new_permitted, working;
+
+	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
+	working = cap_intersect (bprm->cap_inheritable,
+				 current->cap_inheritable);
+	new_permitted = cap_combine (new_permitted, working);
+
+	task_lock(current);
+	if (!cap_issubset (new_permitted, current->cap_permitted)) {
+		current->mm->dumpable = 0;
+
+		if (must_not_trace_exec (current)
+		    || atomic_read (&current->fs->count) > 1
+		    || atomic_read (&current->files->count) > 1
+		    || atomic_read (&current->sighand->count) > 1) {
+			if (!capable (CAP_SETPCAP)) {
+				new_permitted = cap_intersect (new_permitted,
+							       current->
+							       cap_permitted);
+			}
+		}
+	}
+
+	/* For init, we want to retain the capabilities set
+	 * in the init_task struct. Thus we skip the usual
+	 * capability rules */
+	if (current->pid != 1) {
+		current->cap_permitted = new_permitted;
+		current->cap_effective =
+		    cap_intersect (new_permitted, bprm->cap_effective);
+	}
+
+	/* AUD: Audit candidate if current->cap_effective is set */
+	task_unlock(current);
+
+	current->keep_capabilities = 0;
+}
+
+int cap_bprm_secureexec (struct linux_binprm *bprm)
+{
+	/* If/when this module is enhanced to incorporate capability
+	   bits on files, the test below should be extended to also perform a 
+	   test between the old and new capability sets.  For now,
+	   it simply preserves the legacy decision algorithm used by
+	   the old userland. */
+	return (current->euid != current->uid ||
+		current->egid != current->gid);
+}
+
+/* moved from kernel/sys.c. */
+/* 
+ * cap_emulate_setxuid() fixes the effective / permitted capabilities of
+ * a process after a call to setuid, setreuid, or setresuid.
+ *
+ *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
+ *  {r,e,s}uid != 0, the permitted and effective capabilities are
+ *  cleared.
+ *
+ *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
+ *  capabilities of the process are cleared.
+ *
+ *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
+ *  capabilities are set to the permitted capabilities.
+ *
+ *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
+ *  never happen.
+ *
+ *  -astor 
+ *
+ * cevans - New behaviour, Oct '99
+ * A process may, via prctl(), elect to keep its capabilities when it
+ * calls setuid() and switches away from uid==0. Both permitted and
+ * effective sets will be retained.
+ * Without this change, it was impossible for a daemon to drop only some
+ * of its privilege. The call to setuid(!=0) would drop all privileges!
+ * Keeping uid 0 is not an option because uid 0 owns too many vital
+ * files..
+ * Thanks to Olaf Kirch and Peter Benie for spotting this.
+ */
+static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
+					int old_suid)
+{
+	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
+	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
+	    !current->keep_capabilities) {
+		cap_clear (current->cap_permitted);
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid == 0 && current->euid != 0) {
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid != 0 && current->euid == 0) {
+		current->cap_effective = current->cap_permitted;
+	}
+}
+
+int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
+			  int flags)
+{
+	switch (flags) {
+	case LSM_SETID_RE:
+	case LSM_SETID_ID:
+	case LSM_SETID_RES:
+		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
+		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
+		}
+		break;
+	case LSM_SETID_FS:
+		{
+			uid_t old_fsuid = old_ruid;
+
+			/* Copied from kernel/sys.c:setfsuid. */
+
+			/*
+			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
+			 *          if not, we might be a bit too harsh here.
+			 */
+
+			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+				if (old_fsuid == 0 && current->fsuid != 0) {
+					cap_t (current->cap_effective) &=
+					    ~CAP_FS_MASK;
+				}
+				if (old_fsuid != 0 && current->fsuid == 0) {
+					cap_t (current->cap_effective) |=
+					    (cap_t (current->cap_permitted) &
+					     CAP_FS_MASK);
+				}
+			}
+			break;
+		}
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+void cap_task_reparent_to_init (struct task_struct *p)
+{
+	p->cap_effective = CAP_INIT_EFF_SET;
+	p->cap_inheritable = CAP_INIT_INH_SET;
+	p->cap_permitted = CAP_FULL_SET;
+	p->keep_capabilities = 0;
+	return;
+}
+
+int cap_syslog (int type)
+{
+	if ((type != 3) && !capable(CAP_SYS_ADMIN))
+		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
+ * succeed and -ENOMEM implies there is not.
+ *
+ * We currently support three overcommit policies, which are set via the
+ * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
+ *
+ * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
+ * Additional code 2002 Jul 20 by Robert Love.
+ */
+int cap_vm_enough_memory(long pages)
+{
+	unsigned long free, allowed;
+
+	vm_acct_memory(pages);
+
+        /*
+	 * Sometimes we want to use more memory than we have
+	 */
+	if (sysctl_overcommit_memory == 1)
+		return 0;
+
+	if (sysctl_overcommit_memory == 0) {
+		free = get_page_cache_size();
+		free += nr_free_pages();
+		free += nr_swap_pages;
+
+		/*
+		 * Any slabs which are created with the
+		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
+		 * which are reclaimable, under pressure.  The dentry
+		 * cache and most inode caches should fall into this
+		 */
+		free += atomic_read(&slab_reclaim_pages);
+
+		/*
+		 * Leave the last 3% for root
+		 */
+		if (!capable(CAP_SYS_ADMIN))
+			free -= free / 32;
+
+		if (free > pages)
+			return 0;
+		vm_unacct_memory(pages);
+		return -ENOMEM;
+	}
+
+	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
+	allowed += total_swap_pages;
+
+	if (atomic_read(&vm_committed_space) < allowed)
+		return 0;
+
+	vm_unacct_memory(pages);
+
+	return -ENOMEM;
+}
+
+EXPORT_SYMBOL(cap_capable);
+EXPORT_SYMBOL(cap_ptrace);
+EXPORT_SYMBOL(cap_capget);
+EXPORT_SYMBOL(cap_capset_check);
+EXPORT_SYMBOL(cap_capset_set);
+EXPORT_SYMBOL(cap_bprm_set_security);
+EXPORT_SYMBOL(cap_bprm_compute_creds);
+EXPORT_SYMBOL(cap_bprm_secureexec);
+EXPORT_SYMBOL(cap_task_post_setuid);
+EXPORT_SYMBOL(cap_task_reparent_to_init);
+EXPORT_SYMBOL(cap_syslog);
+EXPORT_SYMBOL(cap_vm_enough_memory);

diff -uBbrN linux-2.6.0-test1/security/root_plug.c linux-2.6.0-test2-ahu/security/root_plug.c
--- linux-2.6.0-test1/security/root_plug.c	Mon Jul 14 05:38:46 2003
+++ linux-2.6.0-test2-ahu/security/root_plug.c	Mon Aug  4 19:42:52 2003
@@ -108,7 +108,7 @@
 		/* try registering with primary module */
 		if (mod_reg_security (MY_NAME, &rootplug_security_ops)) {
 			printk (KERN_INFO "Failure registering Root Plug "
-				" module with primary security module.\n");
+				"module with primary security module.\n");
 			return -EINVAL;
 		}
 		secondary = 1;
@@ -124,7 +124,7 @@
 	if (secondary) {
 		if (mod_unreg_security (MY_NAME, &rootplug_security_ops))
 			printk (KERN_INFO "Failure unregistering Root Plug "
-				" module with primary module.\n");
+				"module with primary module.\n");
 	} else { 
 		if (unregister_security (&rootplug_security_ops)) {
 			printk (KERN_INFO "Failure unregistering Root Plug "


-- 
http://www.PowerDNS.com      Open source, database driven DNS Software 
http://lartc.org           Linux Advanced Routing & Traffic Control HOWTO

[PATCH] (improved) LSM root_plug fixup

[bert hubert]

Stephen Smalley noticed a typo in my new Makefile and suggested rediffing
against bitkeeper which now has SELinux merged. 

Further changes, added small comment, added module license & description,
actually tested compiling the kernel with different security settings.

Please consider applying.

To recap, this patch allows root_plug to work again. It needs functions that
used to reside in capability.c but linking in capability.c, disabled
root_plug from loading, as a security module is already present then. This
patch splits out the functions root_plug needs from capability.c.

diff -uBbrNw -X ./dontdiff linux-2.6.0-test2-bk/security/Makefile linux-2.6.0-test2-bk-ahu/security/Makefile
--- linux-2.6.0-test2-bk/security/Makefile	2003-08-05 09:46:54.000000000 +0200
+++ linux-2.6.0-test2-bk-ahu/security/Makefile	2003-08-05 09:51:14.000000000 +0200
@@ -6,7 +6,7 @@
 
 # if we don't select a security model, use the default capabilities
 ifneq ($(CONFIG_SECURITY),y)
-obj-y		+= capability.o
+obj-y		+= commoncap.o capability.o
 endif
 
 # Object file lists
@@ -15,5 +15,5 @@
 ifeq ($(CONFIG_SECURITY_SELINUX),y)
 	obj-$(CONFIG_SECURITY_SELINUX)	+= selinux/built-in.o
 endif
-obj-$(CONFIG_SECURITY_CAPABILITIES)	+= capability.o
-obj-$(CONFIG_SECURITY_ROOTPLUG)		+= root_plug.o
+obj-$(CONFIG_SECURITY_CAPABILITIES)	+= commoncap.o capability.o
+obj-$(CONFIG_SECURITY_ROOTPLUG)		+= commoncap.o root_plug.o
diff -uBbrNw -X ./dontdiff linux-2.6.0-test2-bk/security/capability.c linux-2.6.0-test2-bk-ahu/security/capability.c
--- linux-2.6.0-test2-bk/security/capability.c	2003-08-05 09:45:07.000000000 +0200
+++ linux-2.6.0-test2-bk-ahu/security/capability.c	2003-08-05 11:03:58.000000000 +0200
@@ -6,6 +6,7 @@
  *	the Free Software Foundation; either version 2 of the License, or
  *	(at your option) any later version.
  *
+ *	2003-08-05	Split out common functions to commoncap.c (ahu@ds9a.nl)
  */
 
 #include <linux/config.h>
@@ -23,333 +24,6 @@
 #include <linux/netlink.h>
 #include <linux/ptrace.h>
 
-int cap_capable (struct task_struct *tsk, int cap)
-{
-	/* Derived from include/linux/sched.h:capable. */
-	if (cap_raised (tsk->cap_effective, cap))
-		return 0;
-	else
-		return -EPERM;
-}
-
-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))
-		return -EPERM;
-	else
-		return 0;
-}
-
-int cap_capget (struct task_struct *target, kernel_cap_t *effective,
-		kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capget. */
-	*effective = cap_t (target->cap_effective);
-	*inheritable = cap_t (target->cap_inheritable);
-	*permitted = cap_t (target->cap_permitted);
-	return 0;
-}
-
-int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
-		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capset. */
-	/* verify restrictions on target's new Inheritable set */
-	if (!cap_issubset (*inheritable,
-			   cap_combine (target->cap_inheritable,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify restrictions on target's new Permitted set */
-	if (!cap_issubset (*permitted,
-			   cap_combine (target->cap_permitted,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
-	if (!cap_issubset (*effective, *permitted)) {
-		return -EPERM;
-	}
-
-	return 0;
-}
-
-void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
-		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	target->cap_effective = *effective;
-	target->cap_inheritable = *inheritable;
-	target->cap_permitted = *permitted;
-}
-
-int cap_bprm_set_security (struct linux_binprm *bprm)
-{
-	/* Copied from fs/exec.c:prepare_binprm. */
-
-	/* We don't have VFS support for capabilities yet */
-	cap_clear (bprm->cap_inheritable);
-	cap_clear (bprm->cap_permitted);
-	cap_clear (bprm->cap_effective);
-
-	/*  To support inheritance of root-permissions and suid-root
-	 *  executables under compatibility mode, we raise all three
-	 *  capability sets for the file.
-	 *
-	 *  If only the real uid is 0, we only raise the inheritable
-	 *  and permitted sets of the executable file.
-	 */
-
-	if (!issecure (SECURE_NOROOT)) {
-		if (bprm->e_uid == 0 || current->uid == 0) {
-			cap_set_full (bprm->cap_inheritable);
-			cap_set_full (bprm->cap_permitted);
-		}
-		if (bprm->e_uid == 0)
-			cap_set_full (bprm->cap_effective);
-	}
-	return 0;
-}
-
-/* Copied from fs/exec.c */
-static inline int must_not_trace_exec (struct task_struct *p)
-{
-	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
-}
-
-void cap_bprm_compute_creds (struct linux_binprm *bprm)
-{
-	/* Derived from fs/exec.c:compute_creds. */
-	kernel_cap_t new_permitted, working;
-
-	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
-	working = cap_intersect (bprm->cap_inheritable,
-				 current->cap_inheritable);
-	new_permitted = cap_combine (new_permitted, working);
-
-	task_lock(current);
-	if (!cap_issubset (new_permitted, current->cap_permitted)) {
-		current->mm->dumpable = 0;
-
-		if (must_not_trace_exec (current)
-		    || atomic_read (&current->fs->count) > 1
-		    || atomic_read (&current->files->count) > 1
-		    || atomic_read (&current->sighand->count) > 1) {
-			if (!capable (CAP_SETPCAP)) {
-				new_permitted = cap_intersect (new_permitted,
-							       current->
-							       cap_permitted);
-			}
-		}
-	}
-
-	/* For init, we want to retain the capabilities set
-	 * in the init_task struct. Thus we skip the usual
-	 * capability rules */
-	if (current->pid != 1) {
-		current->cap_permitted = new_permitted;
-		current->cap_effective =
-		    cap_intersect (new_permitted, bprm->cap_effective);
-	}
-
-	/* AUD: Audit candidate if current->cap_effective is set */
-	task_unlock(current);
-
-	current->keep_capabilities = 0;
-}
-
-int cap_bprm_secureexec (struct linux_binprm *bprm)
-{
-	/* If/when this module is enhanced to incorporate capability
-	   bits on files, the test below should be extended to also perform a 
-	   test between the old and new capability sets.  For now,
-	   it simply preserves the legacy decision algorithm used by
-	   the old userland. */
-	return (current->euid != current->uid ||
-		current->egid != current->gid);
-}
-
-/* moved from kernel/sys.c. */
-/* 
- * cap_emulate_setxuid() fixes the effective / permitted capabilities of
- * a process after a call to setuid, setreuid, or setresuid.
- *
- *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
- *  {r,e,s}uid != 0, the permitted and effective capabilities are
- *  cleared.
- *
- *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
- *  capabilities of the process are cleared.
- *
- *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
- *  capabilities are set to the permitted capabilities.
- *
- *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
- *  never happen.
- *
- *  -astor 
- *
- * cevans - New behaviour, Oct '99
- * A process may, via prctl(), elect to keep its capabilities when it
- * calls setuid() and switches away from uid==0. Both permitted and
- * effective sets will be retained.
- * Without this change, it was impossible for a daemon to drop only some
- * of its privilege. The call to setuid(!=0) would drop all privileges!
- * Keeping uid 0 is not an option because uid 0 owns too many vital
- * files..
- * Thanks to Olaf Kirch and Peter Benie for spotting this.
- */
-static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
-					int old_suid)
-{
-	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
-	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
-	    !current->keep_capabilities) {
-		cap_clear (current->cap_permitted);
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid == 0 && current->euid != 0) {
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid != 0 && current->euid == 0) {
-		current->cap_effective = current->cap_permitted;
-	}
-}
-
-int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
-			  int flags)
-{
-	switch (flags) {
-	case LSM_SETID_RE:
-	case LSM_SETID_ID:
-	case LSM_SETID_RES:
-		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
-		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
-		}
-		break;
-	case LSM_SETID_FS:
-		{
-			uid_t old_fsuid = old_ruid;
-
-			/* Copied from kernel/sys.c:setfsuid. */
-
-			/*
-			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
-			 *          if not, we might be a bit too harsh here.
-			 */
-
-			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-				if (old_fsuid == 0 && current->fsuid != 0) {
-					cap_t (current->cap_effective) &=
-					    ~CAP_FS_MASK;
-				}
-				if (old_fsuid != 0 && current->fsuid == 0) {
-					cap_t (current->cap_effective) |=
-					    (cap_t (current->cap_permitted) &
-					     CAP_FS_MASK);
-				}
-			}
-			break;
-		}
-	default:
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-void cap_task_reparent_to_init (struct task_struct *p)
-{
-	p->cap_effective = CAP_INIT_EFF_SET;
-	p->cap_inheritable = CAP_INIT_INH_SET;
-	p->cap_permitted = CAP_FULL_SET;
-	p->keep_capabilities = 0;
-	return;
-}
-
-int cap_syslog (int type)
-{
-	if ((type != 3) && !capable(CAP_SYS_ADMIN))
-		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
- * succeed and -ENOMEM implies there is not.
- *
- * We currently support three overcommit policies, which are set via the
- * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
- *
- * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
- * Additional code 2002 Jul 20 by Robert Love.
- */
-int cap_vm_enough_memory(long pages)
-{
-	unsigned long free, allowed;
-
-	vm_acct_memory(pages);
-
-        /*
-	 * Sometimes we want to use more memory than we have
-	 */
-	if (sysctl_overcommit_memory == 1)
-		return 0;
-
-	if (sysctl_overcommit_memory == 0) {
-		free = get_page_cache_size();
-		free += nr_free_pages();
-		free += nr_swap_pages;
-
-		/*
-		 * Any slabs which are created with the
-		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
-		 * which are reclaimable, under pressure.  The dentry
-		 * cache and most inode caches should fall into this
-		 */
-		free += atomic_read(&slab_reclaim_pages);
-
-		/*
-		 * Leave the last 3% for root
-		 */
-		if (!capable(CAP_SYS_ADMIN))
-			free -= free / 32;
-
-		if (free > pages)
-			return 0;
-		vm_unacct_memory(pages);
-		return -ENOMEM;
-	}
-
-	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
-	allowed += total_swap_pages;
-
-	if (atomic_read(&vm_committed_space) < allowed)
-		return 0;
-
-	vm_unacct_memory(pages);
-
-	return -ENOMEM;
-}
-
-EXPORT_SYMBOL(cap_capable);
-EXPORT_SYMBOL(cap_ptrace);
-EXPORT_SYMBOL(cap_capget);
-EXPORT_SYMBOL(cap_capset_check);
-EXPORT_SYMBOL(cap_capset_set);
-EXPORT_SYMBOL(cap_bprm_set_security);
-EXPORT_SYMBOL(cap_bprm_compute_creds);
-EXPORT_SYMBOL(cap_bprm_secureexec);
-EXPORT_SYMBOL(cap_task_post_setuid);
-EXPORT_SYMBOL(cap_task_reparent_to_init);
-EXPORT_SYMBOL(cap_syslog);
-EXPORT_SYMBOL(cap_vm_enough_memory);
-
 #ifdef CONFIG_SECURITY
 
 
diff -uBbrNw -X ./dontdiff linux-2.6.0-test2-bk/security/commoncap.c linux-2.6.0-test2-bk-ahu/security/commoncap.c
--- linux-2.6.0-test2-bk/security/commoncap.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.0-test2-bk-ahu/security/commoncap.c	2003-08-05 11:04:01.000000000 +0200
@@ -0,0 +1,354 @@
+/* Common capabilities, needed by capability.o and root_cap.o 
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ *	2003-08-05	Split out from capability.c (ahu@ds9a.nl)
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/smp_lock.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/ptrace.h>
+
+int cap_capable (struct task_struct *tsk, int cap)
+{
+	/* Derived from include/linux/sched.h:capable. */
+	if (cap_raised (tsk->cap_effective, cap))
+		return 0;
+	else
+		return -EPERM;
+}
+
+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))
+		return -EPERM;
+	else
+		return 0;
+}
+
+int cap_capget (struct task_struct *target, kernel_cap_t *effective,
+		kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capget. */
+	*effective = cap_t (target->cap_effective);
+	*inheritable = cap_t (target->cap_inheritable);
+	*permitted = cap_t (target->cap_permitted);
+	return 0;
+}
+
+int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
+		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capset. */
+	/* verify restrictions on target's new Inheritable set */
+	if (!cap_issubset (*inheritable,
+			   cap_combine (target->cap_inheritable,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify restrictions on target's new Permitted set */
+	if (!cap_issubset (*permitted,
+			   cap_combine (target->cap_permitted,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
+	if (!cap_issubset (*effective, *permitted)) {
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
+		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	target->cap_effective = *effective;
+	target->cap_inheritable = *inheritable;
+	target->cap_permitted = *permitted;
+}
+
+int cap_bprm_set_security (struct linux_binprm *bprm)
+{
+	/* Copied from fs/exec.c:prepare_binprm. */
+
+	/* We don't have VFS support for capabilities yet */
+	cap_clear (bprm->cap_inheritable);
+	cap_clear (bprm->cap_permitted);
+	cap_clear (bprm->cap_effective);
+
+	/*  To support inheritance of root-permissions and suid-root
+	 *  executables under compatibility mode, we raise all three
+	 *  capability sets for the file.
+	 *
+	 *  If only the real uid is 0, we only raise the inheritable
+	 *  and permitted sets of the executable file.
+	 */
+
+	if (!issecure (SECURE_NOROOT)) {
+		if (bprm->e_uid == 0 || current->uid == 0) {
+			cap_set_full (bprm->cap_inheritable);
+			cap_set_full (bprm->cap_permitted);
+		}
+		if (bprm->e_uid == 0)
+			cap_set_full (bprm->cap_effective);
+	}
+	return 0;
+}
+
+/* Copied from fs/exec.c */
+static inline int must_not_trace_exec (struct task_struct *p)
+{
+	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
+}
+
+void cap_bprm_compute_creds (struct linux_binprm *bprm)
+{
+	/* Derived from fs/exec.c:compute_creds. */
+	kernel_cap_t new_permitted, working;
+
+	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
+	working = cap_intersect (bprm->cap_inheritable,
+				 current->cap_inheritable);
+	new_permitted = cap_combine (new_permitted, working);
+
+	task_lock(current);
+	if (!cap_issubset (new_permitted, current->cap_permitted)) {
+		current->mm->dumpable = 0;
+
+		if (must_not_trace_exec (current)
+		    || atomic_read (&current->fs->count) > 1
+		    || atomic_read (&current->files->count) > 1
+		    || atomic_read (&current->sighand->count) > 1) {
+			if (!capable (CAP_SETPCAP)) {
+				new_permitted = cap_intersect (new_permitted,
+							       current->
+							       cap_permitted);
+			}
+		}
+	}
+
+	/* For init, we want to retain the capabilities set
+	 * in the init_task struct. Thus we skip the usual
+	 * capability rules */
+	if (current->pid != 1) {
+		current->cap_permitted = new_permitted;
+		current->cap_effective =
+		    cap_intersect (new_permitted, bprm->cap_effective);
+	}
+
+	/* AUD: Audit candidate if current->cap_effective is set */
+	task_unlock(current);
+
+	current->keep_capabilities = 0;
+}
+
+int cap_bprm_secureexec (struct linux_binprm *bprm)
+{
+	/* If/when this module is enhanced to incorporate capability
+	   bits on files, the test below should be extended to also perform a 
+	   test between the old and new capability sets.  For now,
+	   it simply preserves the legacy decision algorithm used by
+	   the old userland. */
+	return (current->euid != current->uid ||
+		current->egid != current->gid);
+}
+
+/* moved from kernel/sys.c. */
+/* 
+ * cap_emulate_setxuid() fixes the effective / permitted capabilities of
+ * a process after a call to setuid, setreuid, or setresuid.
+ *
+ *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
+ *  {r,e,s}uid != 0, the permitted and effective capabilities are
+ *  cleared.
+ *
+ *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
+ *  capabilities of the process are cleared.
+ *
+ *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
+ *  capabilities are set to the permitted capabilities.
+ *
+ *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
+ *  never happen.
+ *
+ *  -astor 
+ *
+ * cevans - New behaviour, Oct '99
+ * A process may, via prctl(), elect to keep its capabilities when it
+ * calls setuid() and switches away from uid==0. Both permitted and
+ * effective sets will be retained.
+ * Without this change, it was impossible for a daemon to drop only some
+ * of its privilege. The call to setuid(!=0) would drop all privileges!
+ * Keeping uid 0 is not an option because uid 0 owns too many vital
+ * files..
+ * Thanks to Olaf Kirch and Peter Benie for spotting this.
+ */
+static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
+					int old_suid)
+{
+	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
+	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
+	    !current->keep_capabilities) {
+		cap_clear (current->cap_permitted);
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid == 0 && current->euid != 0) {
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid != 0 && current->euid == 0) {
+		current->cap_effective = current->cap_permitted;
+	}
+}
+
+int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
+			  int flags)
+{
+	switch (flags) {
+	case LSM_SETID_RE:
+	case LSM_SETID_ID:
+	case LSM_SETID_RES:
+		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
+		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
+		}
+		break;
+	case LSM_SETID_FS:
+		{
+			uid_t old_fsuid = old_ruid;
+
+			/* Copied from kernel/sys.c:setfsuid. */
+
+			/*
+			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
+			 *          if not, we might be a bit too harsh here.
+			 */
+
+			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+				if (old_fsuid == 0 && current->fsuid != 0) {
+					cap_t (current->cap_effective) &=
+					    ~CAP_FS_MASK;
+				}
+				if (old_fsuid != 0 && current->fsuid == 0) {
+					cap_t (current->cap_effective) |=
+					    (cap_t (current->cap_permitted) &
+					     CAP_FS_MASK);
+				}
+			}
+			break;
+		}
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+void cap_task_reparent_to_init (struct task_struct *p)
+{
+	p->cap_effective = CAP_INIT_EFF_SET;
+	p->cap_inheritable = CAP_INIT_INH_SET;
+	p->cap_permitted = CAP_FULL_SET;
+	p->keep_capabilities = 0;
+	return;
+}
+
+int cap_syslog (int type)
+{
+	if ((type != 3) && !capable(CAP_SYS_ADMIN))
+		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
+ * succeed and -ENOMEM implies there is not.
+ *
+ * We currently support three overcommit policies, which are set via the
+ * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
+ *
+ * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
+ * Additional code 2002 Jul 20 by Robert Love.
+ */
+int cap_vm_enough_memory(long pages)
+{
+	unsigned long free, allowed;
+
+	vm_acct_memory(pages);
+
+        /*
+	 * Sometimes we want to use more memory than we have
+	 */
+	if (sysctl_overcommit_memory == 1)
+		return 0;
+
+	if (sysctl_overcommit_memory == 0) {
+		free = get_page_cache_size();
+		free += nr_free_pages();
+		free += nr_swap_pages;
+
+		/*
+		 * Any slabs which are created with the
+		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
+		 * which are reclaimable, under pressure.  The dentry
+		 * cache and most inode caches should fall into this
+		 */
+		free += atomic_read(&slab_reclaim_pages);
+
+		/*
+		 * Leave the last 3% for root
+		 */
+		if (!capable(CAP_SYS_ADMIN))
+			free -= free / 32;
+
+		if (free > pages)
+			return 0;
+		vm_unacct_memory(pages);
+		return -ENOMEM;
+	}
+
+	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
+	allowed += total_swap_pages;
+
+	if (atomic_read(&vm_committed_space) < allowed)
+		return 0;
+
+	vm_unacct_memory(pages);
+
+	return -ENOMEM;
+}
+
+EXPORT_SYMBOL(cap_capable);
+EXPORT_SYMBOL(cap_ptrace);
+EXPORT_SYMBOL(cap_capget);
+EXPORT_SYMBOL(cap_capset_check);
+EXPORT_SYMBOL(cap_capset_set);
+EXPORT_SYMBOL(cap_bprm_set_security);
+EXPORT_SYMBOL(cap_bprm_compute_creds);
+EXPORT_SYMBOL(cap_bprm_secureexec);
+EXPORT_SYMBOL(cap_task_post_setuid);
+EXPORT_SYMBOL(cap_task_reparent_to_init);
+EXPORT_SYMBOL(cap_syslog);
+EXPORT_SYMBOL(cap_vm_enough_memory);
+
+MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
+MODULE_LICENSE("GPL");

-- 
http://www.PowerDNS.com      Open source, database driven DNS Software 
http://lartc.org           Linux Advanced Routing & Traffic Control HOWTO

Re: [PATCH] (improved) LSM root_plug fixup

[James Morris]

On Tue, 5 Aug 2003, bert hubert wrote:

> Further changes, added small comment, added module license & description,
> actually tested compiling the kernel with different security settings.

Looks good to me.


- James
-- 
James Morris
<jmorris@intercode.com.au>

Re: [PATCH] (improved) LSM root_plug fixup

[Greg KH]

On Tue, Aug 05, 2003 at 11:58:40AM +0200, bert hubert wrote:
> Stephen Smalley noticed a typo in my new Makefile and suggested rediffing
> against bitkeeper which now has SELinux merged. 
> 
> Further changes, added small comment, added module license & description,
> actually tested compiling the kernel with different security settings.
> 
> Please consider applying.

Sorry for the long delay, I've been busy with other stuff.

Yes, you are correct, this kind of change is necessary in order to get
root_plug working again.

I only have one very tiny, cosmetic, problem with the patch:


> --- linux-2.6.0-test2-bk/security/capability.c	2003-08-05 09:45:07.000000000 +0200
> +++ linux-2.6.0-test2-bk-ahu/security/capability.c	2003-08-05 11:03:58.000000000 +0200
> @@ -6,6 +6,7 @@
>   *	the Free Software Foundation; either version 2 of the License, or
>   *	(at your option) any later version.
>   *
> + *	2003-08-05	Split out common functions to commoncap.c (ahu@ds9a.nl)
>   */
>  
>  #include <linux/config.h>
> @@ -23,333 +24,6 @@

and:

> --- linux-2.6.0-test2-bk/security/commoncap.c	1970-01-01 01:00:00.000000000 +0100
> +++ linux-2.6.0-test2-bk-ahu/security/commoncap.c	2003-08-05 11:04:01.000000000 +0200
> @@ -0,0 +1,354 @@
> +/* Common capabilities, needed by capability.o and root_cap.o 
> + *
> + *	This program is free software; you can redistribute it and/or modify
> + *	it under the terms of the GNU General Public License as published by
> + *	the Free Software Foundation; either version 2 of the License, or
> + *	(at your option) any later version.
> + *
> + *	2003-08-05	Split out from capability.c (ahu@ds9a.nl)
> + */

Please do not add "changelog" type comments to files that do not already
have changelogs in them.  They are unmaintainable within the kernel and
do nothing to help anyone out.

Rely on the change history that we now have due to the use of bitkeeper,
which shows your name associated with a specific changeset.

If you take these lines out, I have no problem with the patch.

thanks,

greg k-h

Re: [PATCH] (improved) LSM root_plug fixup

[bert hubert]

[-- Attachment #1: Type: text/plain, Size: 629 bytes --]

On Thu, Sep 04, 2003 at 04:47:38PM -0700, Greg KH wrote:

> Please do not add "changelog" type comments to files that do not already
> have changelogs in them.  They are unmaintainable within the kernel and
> do nothing to help anyone out.

Ok - that was just my lame attempt to grafitti my name into the kernel :-)

Please find new patch attached, rediffed against test5. The directory in the
patch says 2.6.0-test2, but it is against test5. Compiles & works for me.

Thanks.


-- 
http://www.PowerDNS.com      Open source, database driven DNS Software 
http://lartc.org           Linux Advanced Routing & Traffic Control HOWTO

[-- Attachment #2: root-plug-fix-for-2.6.0-test5 --]
[-- Type: text/plain, Size: 21270 bytes --]

diff -urNBbw -X dontdiff linux-2.6.0-test2-bk/security/Makefile linux-2.6.0-test2-bk-ahu/security/Makefile
--- linux-2.6.0-test2-bk/security/Makefile	2003-08-05 09:46:54.000000000 +0200
+++ linux-2.6.0-test2-bk-ahu/security/Makefile	2003-09-09 10:12:37.000000000 +0200
@@ -6,7 +6,7 @@
 
 # if we don't select a security model, use the default capabilities
 ifneq ($(CONFIG_SECURITY),y)
-obj-y		+= capability.o
+obj-y		+= commoncap.o capability.o
 endif
 
 # Object file lists
@@ -15,5 +15,5 @@
 ifeq ($(CONFIG_SECURITY_SELINUX),y)
 	obj-$(CONFIG_SECURITY_SELINUX)	+= selinux/built-in.o
 endif
-obj-$(CONFIG_SECURITY_CAPABILITIES)	+= capability.o
-obj-$(CONFIG_SECURITY_ROOTPLUG)		+= root_plug.o
+obj-$(CONFIG_SECURITY_CAPABILITIES)	+= commoncap.o capability.o
+obj-$(CONFIG_SECURITY_ROOTPLUG)		+= commoncap.o root_plug.o
diff -urNBbw -X dontdiff linux-2.6.0-test2-bk/security/capability.c linux-2.6.0-test2-bk-ahu/security/capability.c
--- linux-2.6.0-test2-bk/security/capability.c	2003-09-09 10:10:13.000000000 +0200
+++ linux-2.6.0-test2-bk-ahu/security/capability.c	2003-09-09 09:57:08.000000000 +0200
@@ -23,334 +23,6 @@
 #include <linux/netlink.h>
 #include <linux/ptrace.h>
 
-int cap_capable (struct task_struct *tsk, int cap)
-{
-	/* Derived from include/linux/sched.h:capable. */
-	if (cap_raised (tsk->cap_effective, cap))
-		return 0;
-	else
-		return -EPERM;
-}
-
-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))
-		return -EPERM;
-	else
-		return 0;
-}
-
-int cap_capget (struct task_struct *target, kernel_cap_t *effective,
-		kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capget. */
-	*effective = cap_t (target->cap_effective);
-	*inheritable = cap_t (target->cap_inheritable);
-	*permitted = cap_t (target->cap_permitted);
-	return 0;
-}
-
-int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
-		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	/* Derived from kernel/capability.c:sys_capset. */
-	/* verify restrictions on target's new Inheritable set */
-	if (!cap_issubset (*inheritable,
-			   cap_combine (target->cap_inheritable,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify restrictions on target's new Permitted set */
-	if (!cap_issubset (*permitted,
-			   cap_combine (target->cap_permitted,
-					current->cap_permitted))) {
-		return -EPERM;
-	}
-
-	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
-	if (!cap_issubset (*effective, *permitted)) {
-		return -EPERM;
-	}
-
-	return 0;
-}
-
-void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
-		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
-{
-	target->cap_effective = *effective;
-	target->cap_inheritable = *inheritable;
-	target->cap_permitted = *permitted;
-}
-
-int cap_bprm_set_security (struct linux_binprm *bprm)
-{
-	/* Copied from fs/exec.c:prepare_binprm. */
-
-	/* We don't have VFS support for capabilities yet */
-	cap_clear (bprm->cap_inheritable);
-	cap_clear (bprm->cap_permitted);
-	cap_clear (bprm->cap_effective);
-
-	/*  To support inheritance of root-permissions and suid-root
-	 *  executables under compatibility mode, we raise all three
-	 *  capability sets for the file.
-	 *
-	 *  If only the real uid is 0, we only raise the inheritable
-	 *  and permitted sets of the executable file.
-	 */
-
-	if (!issecure (SECURE_NOROOT)) {
-		if (bprm->e_uid == 0 || current->uid == 0) {
-			cap_set_full (bprm->cap_inheritable);
-			cap_set_full (bprm->cap_permitted);
-		}
-		if (bprm->e_uid == 0)
-			cap_set_full (bprm->cap_effective);
-	}
-	return 0;
-}
-
-/* Copied from fs/exec.c */
-static inline int must_not_trace_exec (struct task_struct *p)
-{
-	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
-}
-
-void cap_bprm_compute_creds (struct linux_binprm *bprm)
-{
-	/* Derived from fs/exec.c:compute_creds. */
-	kernel_cap_t new_permitted, working;
-
-	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
-	working = cap_intersect (bprm->cap_inheritable,
-				 current->cap_inheritable);
-	new_permitted = cap_combine (new_permitted, working);
-
-	task_lock(current);
-	if (!cap_issubset (new_permitted, current->cap_permitted)) {
-		current->mm->dumpable = 0;
-
-		if (must_not_trace_exec (current)
-		    || atomic_read (&current->fs->count) > 1
-		    || atomic_read (&current->files->count) > 1
-		    || atomic_read (&current->sighand->count) > 1) {
-			if (!capable (CAP_SETPCAP)) {
-				new_permitted = cap_intersect (new_permitted,
-							       current->
-							       cap_permitted);
-			}
-		}
-	}
-
-	/* For init, we want to retain the capabilities set
-	 * in the init_task struct. Thus we skip the usual
-	 * capability rules */
-	if (current->pid != 1) {
-		current->cap_permitted = new_permitted;
-		current->cap_effective =
-		    cap_intersect (new_permitted, bprm->cap_effective);
-	}
-
-	/* AUD: Audit candidate if current->cap_effective is set */
-	task_unlock(current);
-
-	current->keep_capabilities = 0;
-}
-
-int cap_bprm_secureexec (struct linux_binprm *bprm)
-{
-	/* If/when this module is enhanced to incorporate capability
-	   bits on files, the test below should be extended to also perform a 
-	   test between the old and new capability sets.  For now,
-	   it simply preserves the legacy decision algorithm used by
-	   the old userland. */
-	return (current->euid != current->uid ||
-		current->egid != current->gid);
-}
-
-/* moved from kernel/sys.c. */
-/* 
- * cap_emulate_setxuid() fixes the effective / permitted capabilities of
- * a process after a call to setuid, setreuid, or setresuid.
- *
- *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
- *  {r,e,s}uid != 0, the permitted and effective capabilities are
- *  cleared.
- *
- *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
- *  capabilities of the process are cleared.
- *
- *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
- *  capabilities are set to the permitted capabilities.
- *
- *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
- *  never happen.
- *
- *  -astor 
- *
- * cevans - New behaviour, Oct '99
- * A process may, via prctl(), elect to keep its capabilities when it
- * calls setuid() and switches away from uid==0. Both permitted and
- * effective sets will be retained.
- * Without this change, it was impossible for a daemon to drop only some
- * of its privilege. The call to setuid(!=0) would drop all privileges!
- * Keeping uid 0 is not an option because uid 0 owns too many vital
- * files..
- * Thanks to Olaf Kirch and Peter Benie for spotting this.
- */
-static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
-					int old_suid)
-{
-	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
-	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
-	    !current->keep_capabilities) {
-		cap_clear (current->cap_permitted);
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid == 0 && current->euid != 0) {
-		cap_clear (current->cap_effective);
-	}
-	if (old_euid != 0 && current->euid == 0) {
-		current->cap_effective = current->cap_permitted;
-	}
-}
-
-int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
-			  int flags)
-{
-	switch (flags) {
-	case LSM_SETID_RE:
-	case LSM_SETID_ID:
-	case LSM_SETID_RES:
-		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
-		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
-		}
-		break;
-	case LSM_SETID_FS:
-		{
-			uid_t old_fsuid = old_ruid;
-
-			/* Copied from kernel/sys.c:setfsuid. */
-
-			/*
-			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
-			 *          if not, we might be a bit too harsh here.
-			 */
-
-			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
-				if (old_fsuid == 0 && current->fsuid != 0) {
-					cap_t (current->cap_effective) &=
-					    ~CAP_FS_MASK;
-				}
-				if (old_fsuid != 0 && current->fsuid == 0) {
-					cap_t (current->cap_effective) |=
-					    (cap_t (current->cap_permitted) &
-					     CAP_FS_MASK);
-				}
-			}
-			break;
-		}
-	default:
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
-void cap_task_reparent_to_init (struct task_struct *p)
-{
-	p->cap_effective = CAP_INIT_EFF_SET;
-	p->cap_inheritable = CAP_INIT_INH_SET;
-	p->cap_permitted = CAP_FULL_SET;
-	p->keep_capabilities = 0;
-	return;
-}
-
-int cap_syslog (int type)
-{
-	if ((type != 3) && !capable(CAP_SYS_ADMIN))
-		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
- * succeed and -ENOMEM implies there is not.
- *
- * We currently support three overcommit policies, which are set via the
- * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
- *
- * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
- * Additional code 2002 Jul 20 by Robert Love.
- */
-int cap_vm_enough_memory(long pages)
-{
-	unsigned long free, allowed;
-
-	vm_acct_memory(pages);
-
-	/* We estimate memory ourselves (common case) */
-	if (sysctl_overcommit_memory == 0) {
-		free = get_page_cache_size();
-		free += nr_free_pages();
-		free += nr_swap_pages;
-
-		/*
-		 * Any slabs which are created with the
-		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
-		 * which are reclaimable, under pressure.  The dentry
-		 * cache and most inode caches should fall into this
-		 */
-		free += atomic_read(&slab_reclaim_pages);
-
-		/*
-		 * Leave the last 3% for root
-		 */
-		if (!capable(CAP_SYS_ADMIN))
-			free -= free / 32;
-
-		if (free > pages)
-			return 0;
-
-		vm_unacct_memory(pages);
-		return -ENOMEM;
-	}
-
-	/* Kernel assumes allocation */
-	if (sysctl_overcommit_memory == 1)
-		return 0;
-
-	/* sysctl_overcommit_memory must be 2 which means strict_overcommit*/
-	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
-	allowed += total_swap_pages;
-
-	if (atomic_read(&vm_committed_space) < allowed)
-		return 0;
-
-	vm_unacct_memory(pages);
-
-	return -ENOMEM;
-}
-
-EXPORT_SYMBOL(cap_capable);
-EXPORT_SYMBOL(cap_ptrace);
-EXPORT_SYMBOL(cap_capget);
-EXPORT_SYMBOL(cap_capset_check);
-EXPORT_SYMBOL(cap_capset_set);
-EXPORT_SYMBOL(cap_bprm_set_security);
-EXPORT_SYMBOL(cap_bprm_compute_creds);
-EXPORT_SYMBOL(cap_bprm_secureexec);
-EXPORT_SYMBOL(cap_task_post_setuid);
-EXPORT_SYMBOL(cap_task_reparent_to_init);
-EXPORT_SYMBOL(cap_syslog);
-EXPORT_SYMBOL(cap_vm_enough_memory);
-
 #ifdef CONFIG_SECURITY
 
 
diff -urNBbw -X dontdiff linux-2.6.0-test2-bk/security/commoncap.c linux-2.6.0-test2-bk-ahu/security/commoncap.c
--- linux-2.6.0-test2-bk/security/commoncap.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.0-test2-bk-ahu/security/commoncap.c	2003-09-09 09:56:53.000000000 +0200
@@ -0,0 +1,353 @@
+/* Common capabilities, needed by capability.o and root_cap.o 
+ *
+ *	This program is free software; you can redistribute it and/or modify
+ *	it under the terms of the GNU General Public License as published by
+ *	the Free Software Foundation; either version 2 of the License, or
+ *	(at your option) any later version.
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/security.h>
+#include <linux/file.h>
+#include <linux/mm.h>
+#include <linux/mman.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/smp_lock.h>
+#include <linux/skbuff.h>
+#include <linux/netlink.h>
+#include <linux/ptrace.h>
+
+int cap_capable (struct task_struct *tsk, int cap)
+{
+	/* Derived from include/linux/sched.h:capable. */
+	if (cap_raised (tsk->cap_effective, cap))
+		return 0;
+	else
+		return -EPERM;
+}
+
+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))
+		return -EPERM;
+	else
+		return 0;
+}
+
+int cap_capget (struct task_struct *target, kernel_cap_t *effective,
+		kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capget. */
+	*effective = cap_t (target->cap_effective);
+	*inheritable = cap_t (target->cap_inheritable);
+	*permitted = cap_t (target->cap_permitted);
+	return 0;
+}
+
+int cap_capset_check (struct task_struct *target, kernel_cap_t *effective,
+		      kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	/* Derived from kernel/capability.c:sys_capset. */
+	/* verify restrictions on target's new Inheritable set */
+	if (!cap_issubset (*inheritable,
+			   cap_combine (target->cap_inheritable,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify restrictions on target's new Permitted set */
+	if (!cap_issubset (*permitted,
+			   cap_combine (target->cap_permitted,
+					current->cap_permitted))) {
+		return -EPERM;
+	}
+
+	/* verify the _new_Effective_ is a subset of the _new_Permitted_ */
+	if (!cap_issubset (*effective, *permitted)) {
+		return -EPERM;
+	}
+
+	return 0;
+}
+
+void cap_capset_set (struct task_struct *target, kernel_cap_t *effective,
+		     kernel_cap_t *inheritable, kernel_cap_t *permitted)
+{
+	target->cap_effective = *effective;
+	target->cap_inheritable = *inheritable;
+	target->cap_permitted = *permitted;
+}
+
+int cap_bprm_set_security (struct linux_binprm *bprm)
+{
+	/* Copied from fs/exec.c:prepare_binprm. */
+
+	/* We don't have VFS support for capabilities yet */
+	cap_clear (bprm->cap_inheritable);
+	cap_clear (bprm->cap_permitted);
+	cap_clear (bprm->cap_effective);
+
+	/*  To support inheritance of root-permissions and suid-root
+	 *  executables under compatibility mode, we raise all three
+	 *  capability sets for the file.
+	 *
+	 *  If only the real uid is 0, we only raise the inheritable
+	 *  and permitted sets of the executable file.
+	 */
+
+	if (!issecure (SECURE_NOROOT)) {
+		if (bprm->e_uid == 0 || current->uid == 0) {
+			cap_set_full (bprm->cap_inheritable);
+			cap_set_full (bprm->cap_permitted);
+		}
+		if (bprm->e_uid == 0)
+			cap_set_full (bprm->cap_effective);
+	}
+	return 0;
+}
+
+/* Copied from fs/exec.c */
+static inline int must_not_trace_exec (struct task_struct *p)
+{
+	return (p->ptrace & PT_PTRACED) && !(p->ptrace & PT_PTRACE_CAP);
+}
+
+void cap_bprm_compute_creds (struct linux_binprm *bprm)
+{
+	/* Derived from fs/exec.c:compute_creds. */
+	kernel_cap_t new_permitted, working;
+
+	new_permitted = cap_intersect (bprm->cap_permitted, cap_bset);
+	working = cap_intersect (bprm->cap_inheritable,
+				 current->cap_inheritable);
+	new_permitted = cap_combine (new_permitted, working);
+
+	task_lock(current);
+	if (!cap_issubset (new_permitted, current->cap_permitted)) {
+		current->mm->dumpable = 0;
+
+		if (must_not_trace_exec (current)
+		    || atomic_read (&current->fs->count) > 1
+		    || atomic_read (&current->files->count) > 1
+		    || atomic_read (&current->sighand->count) > 1) {
+			if (!capable (CAP_SETPCAP)) {
+				new_permitted = cap_intersect (new_permitted,
+							       current->
+							       cap_permitted);
+			}
+		}
+	}
+
+	/* For init, we want to retain the capabilities set
+	 * in the init_task struct. Thus we skip the usual
+	 * capability rules */
+	if (current->pid != 1) {
+		current->cap_permitted = new_permitted;
+		current->cap_effective =
+		    cap_intersect (new_permitted, bprm->cap_effective);
+	}
+
+	/* AUD: Audit candidate if current->cap_effective is set */
+	task_unlock(current);
+
+	current->keep_capabilities = 0;
+}
+
+int cap_bprm_secureexec (struct linux_binprm *bprm)
+{
+	/* If/when this module is enhanced to incorporate capability
+	   bits on files, the test below should be extended to also perform a 
+	   test between the old and new capability sets.  For now,
+	   it simply preserves the legacy decision algorithm used by
+	   the old userland. */
+	return (current->euid != current->uid ||
+		current->egid != current->gid);
+}
+
+/* moved from kernel/sys.c. */
+/* 
+ * cap_emulate_setxuid() fixes the effective / permitted capabilities of
+ * a process after a call to setuid, setreuid, or setresuid.
+ *
+ *  1) When set*uiding _from_ one of {r,e,s}uid == 0 _to_ all of
+ *  {r,e,s}uid != 0, the permitted and effective capabilities are
+ *  cleared.
+ *
+ *  2) When set*uiding _from_ euid == 0 _to_ euid != 0, the effective
+ *  capabilities of the process are cleared.
+ *
+ *  3) When set*uiding _from_ euid != 0 _to_ euid == 0, the effective
+ *  capabilities are set to the permitted capabilities.
+ *
+ *  fsuid is handled elsewhere. fsuid == 0 and {r,e,s}uid!= 0 should 
+ *  never happen.
+ *
+ *  -astor 
+ *
+ * cevans - New behaviour, Oct '99
+ * A process may, via prctl(), elect to keep its capabilities when it
+ * calls setuid() and switches away from uid==0. Both permitted and
+ * effective sets will be retained.
+ * Without this change, it was impossible for a daemon to drop only some
+ * of its privilege. The call to setuid(!=0) would drop all privileges!
+ * Keeping uid 0 is not an option because uid 0 owns too many vital
+ * files..
+ * Thanks to Olaf Kirch and Peter Benie for spotting this.
+ */
+static inline void cap_emulate_setxuid (int old_ruid, int old_euid,
+					int old_suid)
+{
+	if ((old_ruid == 0 || old_euid == 0 || old_suid == 0) &&
+	    (current->uid != 0 && current->euid != 0 && current->suid != 0) &&
+	    !current->keep_capabilities) {
+		cap_clear (current->cap_permitted);
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid == 0 && current->euid != 0) {
+		cap_clear (current->cap_effective);
+	}
+	if (old_euid != 0 && current->euid == 0) {
+		current->cap_effective = current->cap_permitted;
+	}
+}
+
+int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid,
+			  int flags)
+{
+	switch (flags) {
+	case LSM_SETID_RE:
+	case LSM_SETID_ID:
+	case LSM_SETID_RES:
+		/* Copied from kernel/sys.c:setreuid/setuid/setresuid. */
+		if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+			cap_emulate_setxuid (old_ruid, old_euid, old_suid);
+		}
+		break;
+	case LSM_SETID_FS:
+		{
+			uid_t old_fsuid = old_ruid;
+
+			/* Copied from kernel/sys.c:setfsuid. */
+
+			/*
+			 * FIXME - is fsuser used for all CAP_FS_MASK capabilities?
+			 *          if not, we might be a bit too harsh here.
+			 */
+
+			if (!issecure (SECURE_NO_SETUID_FIXUP)) {
+				if (old_fsuid == 0 && current->fsuid != 0) {
+					cap_t (current->cap_effective) &=
+					    ~CAP_FS_MASK;
+				}
+				if (old_fsuid != 0 && current->fsuid == 0) {
+					cap_t (current->cap_effective) |=
+					    (cap_t (current->cap_permitted) &
+					     CAP_FS_MASK);
+				}
+			}
+			break;
+		}
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+void cap_task_reparent_to_init (struct task_struct *p)
+{
+	p->cap_effective = CAP_INIT_EFF_SET;
+	p->cap_inheritable = CAP_INIT_INH_SET;
+	p->cap_permitted = CAP_FULL_SET;
+	p->keep_capabilities = 0;
+	return;
+}
+
+int cap_syslog (int type)
+{
+	if ((type != 3) && !capable(CAP_SYS_ADMIN))
+		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
+ * succeed and -ENOMEM implies there is not.
+ *
+ * We currently support three overcommit policies, which are set via the
+ * vm.overcommit_memory sysctl.  See Documentation/vm/overcommit-acounting
+ *
+ * Strict overcommit modes added 2002 Feb 26 by Alan Cox.
+ * Additional code 2002 Jul 20 by Robert Love.
+ */
+int cap_vm_enough_memory(long pages)
+{
+	unsigned long free, allowed;
+
+	vm_acct_memory(pages);
+
+        /*
+	 * Sometimes we want to use more memory than we have
+	 */
+	if (sysctl_overcommit_memory == 1)
+		return 0;
+
+	if (sysctl_overcommit_memory == 0) {
+		free = get_page_cache_size();
+		free += nr_free_pages();
+		free += nr_swap_pages;
+
+		/*
+		 * Any slabs which are created with the
+		 * SLAB_RECLAIM_ACCOUNT flag claim to have contents
+		 * which are reclaimable, under pressure.  The dentry
+		 * cache and most inode caches should fall into this
+		 */
+		free += atomic_read(&slab_reclaim_pages);
+
+		/*
+		 * Leave the last 3% for root
+		 */
+		if (!capable(CAP_SYS_ADMIN))
+			free -= free / 32;
+
+		if (free > pages)
+			return 0;
+		vm_unacct_memory(pages);
+		return -ENOMEM;
+	}
+
+	allowed = totalram_pages * sysctl_overcommit_ratio / 100;
+	allowed += total_swap_pages;
+
+	if (atomic_read(&vm_committed_space) < allowed)
+		return 0;
+
+	vm_unacct_memory(pages);
+
+	return -ENOMEM;
+}
+
+EXPORT_SYMBOL(cap_capable);
+EXPORT_SYMBOL(cap_ptrace);
+EXPORT_SYMBOL(cap_capget);
+EXPORT_SYMBOL(cap_capset_check);
+EXPORT_SYMBOL(cap_capset_set);
+EXPORT_SYMBOL(cap_bprm_set_security);
+EXPORT_SYMBOL(cap_bprm_compute_creds);
+EXPORT_SYMBOL(cap_bprm_secureexec);
+EXPORT_SYMBOL(cap_task_post_setuid);
+EXPORT_SYMBOL(cap_task_reparent_to_init);
+EXPORT_SYMBOL(cap_syslog);
+EXPORT_SYMBOL(cap_vm_enough_memory);
+
+MODULE_DESCRIPTION("Standard Linux Common Capabilities Security Module");
+MODULE_LICENSE("GPL");

Re: [PATCH] (improved) LSM root_plug fixup

[Chris Wright]

* bert hubert (ahu@ds9a.nl) wrote:
> Please find new patch attached, rediffed against test5. The directory in the
> patch says 2.6.0-test2, but it is against test5. Compiles & works for me.

It's working for me.  I put it in the LSM tree with one minor typo fixed:

> +++ linux-2.6.0-test2-bk-ahu/security/commoncap.c	2003-09-09 09:56:53.000000000 +0200
> @@ -0,0 +1,353 @@
> +/* Common capabilities, needed by capability.o and root_cap.o 

s/root_cap/root_plug/

thanks,
-chris
-- 
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