1 files changed, 345 insertions, 0 deletions

diff --git a/security/commoncap.c b/security/commoncap.c
new file mode 100644
index 00000000000..849b8c338ee
--- /dev/null
+++ b/security/commoncap.c
@@ -0,0 +1,345 @@
+/* Common capabilities, needed by capability.o and root_plug.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>
+#include <linux/xattr.h>
+#include <linux/hugetlb.h>
+
+int cap_netlink_send(struct sock *sk, struct sk_buff *skb)
+{
+	NETLINK_CB(skb).eff_cap = current->cap_effective;
+	return 0;
+}
+
+EXPORT_SYMBOL(cap_netlink_send);
+
+int cap_netlink_recv(struct sk_buff *skb)
+{
+	if (!cap_raised(NETLINK_CB(skb).eff_cap, CAP_NET_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+EXPORT_SYMBOL(cap_netlink_recv);
+
+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;
+	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))
+		return -EPERM;
+	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;
+}
+
+void cap_bprm_apply_creds (struct linux_binprm *bprm, int unsafe)
+{
+	/* 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);
+
+	if (bprm->e_uid != current->uid || bprm->e_gid != current->gid ||
+	    !cap_issubset (new_permitted, current->cap_permitted)) {
+		current->mm->dumpable = 0;
+
+		if (unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
+			if (!capable(CAP_SETUID)) {
+				bprm->e_uid = current->uid;
+				bprm->e_gid = current->gid;
+			}
+			if (!capable (CAP_SETPCAP)) {
+				new_permitted = cap_intersect (new_permitted,
+							current->cap_permitted);
+			}
+		}
+	}
+
+	current->suid = current->euid = current->fsuid = bprm->e_uid;
+	current->sgid = current->egid = current->fsgid = bprm->e_gid;
+
+	/* 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 */
+
+	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);
+}
+
+int cap_inode_setxattr(struct dentry *dentry, char *name, void *value,
+		       size_t size, int flags)
+{
+	if (!strncmp(name, XATTR_SECURITY_PREFIX,
+		     sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+int cap_inode_removexattr(struct dentry *dentry, char *name)
+{
+	if (!strncmp(name, XATTR_SECURITY_PREFIX,
+		     sizeof(XATTR_SECURITY_PREFIX) - 1)  &&
+	    !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+/* 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 && type != 10) && !capable(CAP_SYS_ADMIN))
+		return -EPERM;
+	return 0;
+}
+
+int cap_vm_enough_memory(long pages)
+{
+	int cap_sys_admin = 0;
+
+	if (cap_capable(current, CAP_SYS_ADMIN) == 0)
+		cap_sys_admin = 1;
+	return __vm_enough_memory(pages, cap_sys_admin);
+}
+
+EXPORT_SYMBOL(cap_capable);
+EXPORT_SYMBOL(cap_settime);
+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_apply_creds);
+EXPORT_SYMBOL(cap_bprm_secureexec);
+EXPORT_SYMBOL(cap_inode_setxattr);
+EXPORT_SYMBOL(cap_inode_removexattr);
+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");