diff options
| -rw-r--r-- | Documentation/sysctl/kernel.txt | 14 | ||||
| -rw-r--r-- | include/linux/kernel.h | 1 | ||||
| -rw-r--r-- | kernel/printk.c | 6 | ||||
| -rw-r--r-- | kernel/sysctl.c | 9 | ||||
| -rw-r--r-- | security/Kconfig | 12 | ||||
| -rw-r--r-- | security/commoncap.c | 2 |
6 files changed, 44 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 3894eaa..209e158 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -28,6 +28,7 @@ show up in /proc/sys/kernel: - core_uses_pid - ctrl-alt-del - dentry-state +- dmesg_restrict - domainname - hostname - hotplug @@ -213,6 +214,19 @@ to decide what to do with it. ============================================================== +dmesg_restrict: + +This toggle indicates whether unprivileged users are prevented from using +dmesg(8) to view messages from the kernel's log buffer. When +dmesg_restrict is set to (0) there are no restrictions. When +dmesg_restrict is set set to (1), users must have CAP_SYS_ADMIN to use +dmesg(8). + +The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default +value of dmesg_restrict. + +============================================================== + domainname & hostname: These files can be used to set the NIS/YP domainname and the diff --git a/include/linux/kernel.h b/include/linux/kernel.h index b526947..fc3da9e 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -293,6 +293,7 @@ extern bool printk_timed_ratelimit(unsigned long *caller_jiffies, unsigned int interval_msec); extern int printk_delay_msec; +extern int dmesg_restrict; /* * Print a one-time message (analogous to WARN_ONCE() et al): diff --git a/kernel/printk.c b/kernel/printk.c index b2ebaee..38e7d58 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -261,6 +261,12 @@ static inline void boot_delay_msec(void) } #endif +#ifdef CONFIG_SECURITY_DMESG_RESTRICT +int dmesg_restrict = 1; +#else +int dmesg_restrict; +#endif + int do_syslog(int type, char __user *buf, int len, bool from_file) { unsigned i, j, limit, count; diff --git a/kernel/sysctl.c b/kernel/sysctl.c index c33a1ed..b65bf63 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -704,6 +704,15 @@ static struct ctl_table kern_table[] = { }, #endif { + .procname = "dmesg_restrict", + .data = &dmesg_restrict, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = &zero, + .extra2 = &one, + }, + { .procname = "ngroups_max", .data = &ngroups_max, .maxlen = sizeof (int), diff --git a/security/Kconfig b/security/Kconfig index bd72ae6..e80da95 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -39,6 +39,18 @@ config KEYS_DEBUG_PROC_KEYS If you are unsure as to whether this is required, answer N. +config SECURITY_DMESG_RESTRICT + bool "Restrict unprivileged access to the kernel syslog" + default n + help + This enforces restrictions on unprivileged users reading the kernel + syslog via dmesg(8). + + If this option is not selected, no restrictions will be enforced + unless the dmesg_restrict sysctl is explicitly set to (1). + + If you are unsure how to answer this question, answer N. + config SECURITY bool "Enable different security models" depends on SYSFS diff --git a/security/commoncap.c b/security/commoncap.c index 5e632b4..04b80f9 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -895,6 +895,8 @@ int cap_syslog(int type, bool from_file) { if (type != SYSLOG_ACTION_OPEN && from_file) return 0; + if (dmesg_restrict && !capable(CAP_SYS_ADMIN)) + return -EPERM; if ((type != SYSLOG_ACTION_READ_ALL && type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN)) return -EPERM; |
