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SubjectRe: [PATCH] LSM changes for 2.5.59
ChangeSet 1.984, 2003/02/05 14:37:12+11:00, sds@epoch.ncsc.mil

[PATCH] LSM: Add LSM syslog hook to 2.5.59

This patch adds the LSM security_syslog hook for controlling the
syslog(2) interface relative to 2.5.59 plus the previously posted
security_sysctl patch. In response to earlier comments by Christoph,
the existing capability check for syslog(2) is moved into the
capability security module hook function, and a corresponding dummy
security module hook function is defined that provides traditional
superuser behavior. The LSM hook is placed in do_syslog rather than
sys_syslog so that it is called when either the system call interface
or the /proc/kmsg interface is used. SELinux uses this hook to
control access to the kernel message ring and to the console log
level.


diff -Nru a/include/linux/security.h b/include/linux/security.h
--- a/include/linux/security.h Wed Feb 5 14:58:15 2003
+++ b/include/linux/security.h Wed Feb 5 14:58:15 2003
@@ -47,6 +47,7 @@
extern int cap_task_post_setuid (uid_t old_ruid, uid_t old_euid, uid_t old_suid, int flags);
extern void cap_task_kmod_set_label (void);
extern void cap_task_reparent_to_init (struct task_struct *p);
+extern int cap_syslog (int type);

/*
* Values used in the task_security_ops calls
@@ -778,6 +779,12 @@
* @tsk contains the task_struct for the process.
* @cap contains the capability <include/linux/capability.h>.
* Return 0 if the capability is granted for @tsk.
+ * @syslog:
+ * Check permission before accessing the kernel message ring or changing
+ * logging to the console.
+ * See the syslog(2) manual page for an explanation of the @type values.
+ * @type contains the type of action.
+ * Return 0 if permission is granted.
*
* @register_security:
* allow module stacking.
@@ -808,6 +815,7 @@
int (*capable) (struct task_struct * tsk, int cap);
int (*quotactl) (int cmds, int type, int id, struct super_block * sb);
int (*quota_on) (struct file * f);
+ int (*syslog) (int type);

int (*bprm_alloc_security) (struct linux_binprm * bprm);
void (*bprm_free_security) (struct linux_binprm * bprm);
@@ -1013,6 +1021,11 @@
return security_ops->quota_on (file);
}

+static inline int security_syslog(int type)
+{
+ return security_ops->syslog(type);
+}
+
static inline int security_bprm_alloc (struct linux_binprm *bprm)
{
return security_ops->bprm_alloc_security (bprm);
@@ -1625,6 +1638,11 @@
static inline int security_quota_on (struct file * file)
{
return 0;
+}
+
+static inline int security_syslog(int type)
+{
+ return cap_syslog(type);
}

static inline int security_bprm_alloc (struct linux_binprm *bprm)
diff -Nru a/kernel/printk.c b/kernel/printk.c
--- a/kernel/printk.c Wed Feb 5 14:58:15 2003
+++ b/kernel/printk.c Wed Feb 5 14:58:15 2003
@@ -28,6 +28,7 @@
#include <linux/config.h>
#include <linux/delay.h>
#include <linux/smp.h>
+#include <linux/security.h>

#include <asm/uaccess.h>

@@ -161,6 +162,10 @@
char c;
int error = 0;

+ error = security_syslog(type);
+ if (error)
+ return error;
+
switch (type) {
case 0: /* Close log */
break;
@@ -273,8 +278,6 @@

asmlinkage long sys_syslog(int type, char * buf, int len)
{
- if ((type != 3) && !capable(CAP_SYS_ADMIN))
- return -EPERM;
return do_syslog(type, buf, len);
}

diff -Nru a/security/capability.c b/security/capability.c
--- a/security/capability.c Wed Feb 5 14:58:15 2003
+++ b/security/capability.c Wed Feb 5 14:58:15 2003
@@ -262,6 +262,13 @@
return;
}

+int cap_syslog (int type)
+{
+ if ((type != 3) && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ return 0;
+}
+
EXPORT_SYMBOL(cap_capable);
EXPORT_SYMBOL(cap_ptrace);
EXPORT_SYMBOL(cap_capget);
@@ -272,6 +279,7 @@
EXPORT_SYMBOL(cap_task_post_setuid);
EXPORT_SYMBOL(cap_task_kmod_set_label);
EXPORT_SYMBOL(cap_task_reparent_to_init);
+EXPORT_SYMBOL(cap_syslog);

#ifdef CONFIG_SECURITY

@@ -289,6 +297,8 @@
.task_post_setuid = cap_task_post_setuid,
.task_kmod_set_label = cap_task_kmod_set_label,
.task_reparent_to_init = cap_task_reparent_to_init,
+
+ .syslog = cap_syslog,
};

#if defined(CONFIG_SECURITY_CAPABILITIES_MODULE)
diff -Nru a/security/dummy.c b/security/dummy.c
--- a/security/dummy.c Wed Feb 5 14:58:15 2003
+++ b/security/dummy.c Wed Feb 5 14:58:15 2003
@@ -90,6 +90,13 @@
return 0;
}

+static int dummy_syslog (int type)
+{
+ if ((type != 3) && current->euid)
+ return -EPERM;
+ return 0;
+}
+
static int dummy_bprm_alloc_security (struct linux_binprm *bprm)
{
return 0;
@@ -640,6 +647,7 @@
set_to_dummy_if_null(ops, quotactl);
set_to_dummy_if_null(ops, quota_on);
set_to_dummy_if_null(ops, sysctl);
+ set_to_dummy_if_null(ops, syslog);
set_to_dummy_if_null(ops, bprm_alloc_security);
set_to_dummy_if_null(ops, bprm_free_security);
set_to_dummy_if_null(ops, bprm_compute_creds);
-
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