diff options
Diffstat (limited to 'core/sysctl.html')
| -rw-r--r-- | core/sysctl.html | 484 |
1 files changed, 16 insertions, 468 deletions
diff --git a/core/sysctl.html b/core/sysctl.html index d06afde..afee463 100644 --- a/core/sysctl.html +++ b/core/sysctl.html @@ -2,24 +2,18 @@ <html dir="ltr" lang="en"> <head> <meta charset='utf-8'> - <title>2.2.2. Sysctl</title> + <title>2.6.2. Sysctl</title> </head> <body> <a href="index.html">Core OS Index</a> - <h1 id="sysctl">2.2.2. Sysctl</h1> + <h1 id="sysctl">2.6.2. Sysctl</h1> <p>Sysctl references <a href="https://wiki.archlinux.org/index.php/sysctl#TCP.2FIP_stack_hardening">Arch TCP/IP stack hardening</a>, <a href="http://www.cyberciti.biz/tips/linux-unix-bsd-nginx-webserver-security.html">Cyberciti Nginx Hardning</a>, - <a href="http://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/">Cyberciti Security Hardening</a>, - <a href="https://en.wikibooks.org/wiki/Grsecurity/Appendix/Grsecurity_and_PaX_Configuration_Options">Grsecurity and PaX Configuration</a>.</p> - - <p>Since kernels on machine-ports have <a href="pax.grsecurity.net">PaX</a> - and <a href="http://grsecurity.net/announce.php">grsecurity</a>, - <a href="conf/sysctl.conf">/etc/sysctl.conf</a> can have follow - values;</p> + <a href="http://www.cyberciti.biz/faq/linux-kernel-etcsysctl-conf-security-hardening/">Cyberciti Security Hardening</a>.</p> <pre> # @@ -27,49 +21,20 @@ # kernel.printk = 7 1 1 4 + kernel.randomize_va_space = 2 + # Shared Memory #kernel.shmmax = 500000000 # Total allocated file handlers that can be allocated # fs.file-nr= vm.mmap_min_addr=65536 + # Allow for more PIDs (to reduce rollover problems); may break some programs 32768 kernel.pid_max = 65536 - # - # Memory Protections - # - - # If you say Y here, all ioperm and iopl calls will return an error. - # Ioperm and iopl can be used to modify the running kernel. - # Unfortunately, some programs need this access to operate properly, - # the most notable of which are XFree86 and hwclock. hwclock can be - # remedied by having RTC support in the kernel, so real-time - # clock support is enabled if this option is enabled, to ensure - # that hwclock operates correctly. - # - # If you're using XFree86 or a version of Xorg from 2012 or earlier, - # you may not be able to boot into a graphical environment with this - # option enabled. In this case, you should use the RBAC system instead. - kernel.grsecurity.disable_priv_io = 1 - - # If you say Y here, attempts to bruteforce exploits against forking - # daemons such as apache or sshd, as well as against suid/sgid binaries - # will be deterred. When a child of a forking daemon is killed by PaX - # or crashes due to an illegal instruction or other suspicious signal, - # the parent process will be delayed 30 seconds upon every subsequent - # fork until the administrator is able to assess the situation and - # restart the daemon. - # In the suid/sgid case, the attempt is logged, the user has all their - # existing instances of the suid/sgid binary terminated and will - # be unable to execute any suid/sgid binaries for 15 minutes. - # - # It is recommended that you also enable signal logging in the auditing - # section so that logs are generated when a process triggers a suspicious - # signal. - # If the sysctl option is enabled, a sysctl option with name - # "deter_bruteforce" is created. - kernel.grsecurity.deter_bruteforce = 1 + #Yama LSM by default + kernel.yama.ptrace_scope = 1 # # Filesystem Protections @@ -79,345 +44,15 @@ # Increase system file descriptor limit fs.file-max = 65535 - # If you say Y here, /tmp race exploits will be prevented, since users - # will no longer be able to follow symlinks owned by other users in - # world-writable +t directories (e.g. /tmp), unless the owner of the - # symlink is the owner of the directory. users will also not be - # able to hardlink to files they do not own. If the sysctl option is - # enabled, a sysctl option with name "linking_restrictions" is created. - kernel.grsecurity.linking_restrictions = 1 - - - # Apache's SymlinksIfOwnerMatch option has an inherent race condition - # that prevents it from being used as a security feature. As Apache - # verifies the symlink by performing a stat() against the target of - # the symlink before it is followed, an attacker can setup a symlink - # to point to a same-owned file, then replace the symlink with one - # that targets another user's file just after Apache "validates" the - # symlink -- a classic TOCTOU race. If you say Y here, a complete, - # race-free replacement for Apache's "SymlinksIfOwnerMatch" option - # will be in place for the group you specify. If the sysctl option - # is enabled, a sysctl option with name "enforce_symlinksifowner" is - # created. - kernel.grsecurity.enforce_symlinksifowner = 1 - kernel.grsecurity.symlinkown_gid = 15 - - # if you say Y here, users will not be able to write to FIFOs they don't - # own in world-writable +t directories (e.g. /tmp), unless the owner of - # the FIFO is the same owner of the directory it's held in. If the sysctl - # option is enabled, a sysctl option with name "fifo_restrictions" is - # created. - kernel.grsecurity.fifo_restrictions = 1 - - # If you say Y here, a sysctl option with name "romount_protect" will - # be created. By setting this option to 1 at runtime, filesystems - # will be protected in the following ways: - # * No new writable mounts will be allowed - # * Existing read-only mounts won't be able to be remounted read/write - # * Write operations will be denied on all block devices - # This option acts independently of grsec_lock: once it is set to 1, - # it cannot be turned off. Therefore, please be mindful of the resulting - # behavior if this option is enabled in an init script on a read-only - # filesystem. - # Also be aware that as with other root-focused features, GRKERNSEC_KMEM - # and GRKERNSEC_IO should be enabled and module loading disabled via - # config or at runtime. - # This feature is mainly intended for secure embedded systems. - #kernel.grsecurity.romount_protect = 1 - - # if you say Y here, the capabilities on all processes within a - # chroot jail will be lowered to stop module insertion, raw i/o, - # system and net admin tasks, rebooting the system, modifying immutable - # files, modifying IPC owned by another, and changing the system time. - # This is left an option because it can break some apps. Disable this - # if your chrooted apps are having problems performing those kinds of - # tasks. If the sysctl option is enabled, a sysctl option with - # name "chroot_caps" is created. - kernel.grsecurity.chroot_caps = 1 - - #kernel.grsecurity.chroot_deny_bad_rename = 1 - - # If you say Y here, processes inside a chroot will not be able to chmod - # or fchmod files to make them have suid or sgid bits. This protects - # against another published method of breaking a chroot. If the sysctl - # option is enabled, a sysctl option with name "chroot_deny_chmod" is - # created. - kernel.grsecurity.chroot_deny_chmod = 1 - - # If you say Y here, processes inside a chroot will not be able to chroot - # again outside the chroot. This is a widely used method of breaking - # out of a chroot jail and should not be allowed. If the sysctl - # option is enabled, a sysctl option with name - # "chroot_deny_chroot" is created. - kernel.grsecurity.chroot_deny_chroot = 1 - - # If you say Y here, a well-known method of breaking chroots by fchdir'ing - # to a file descriptor of the chrooting process that points to a directory - # outside the filesystem will be stopped. If the sysctl option - # is enabled, a sysctl option with name "chroot_deny_fchdir" is created. - kernel.grsecurity.chroot_deny_fchdir = 1 - - # If you say Y here, processes inside a chroot will not be allowed to - # mknod. The problem with using mknod inside a chroot is that it - # would allow an attacker to create a device entry that is the same - # as one on the physical root of your system, which could range from - # anything from the console device to a device for your harddrive (which - # they could then use to wipe the drive or steal data). It is recommended - # that you say Y here, unless you run into software incompatibilities. - # If the sysctl option is enabled, a sysctl option with name - # "chroot_deny_mknod" is created. - kernel.grsecurity.chroot_deny_mknod = 1 - - # If you say Y here, processes inside a chroot will not be able to - # mount or remount filesystems. If the sysctl option is enabled, a - # sysctl option with name "chroot_deny_mount" is created. - kernel.grsecurity.chroot_deny_mount = 1 - - # If you say Y here, processes inside a chroot will not be able to use - # a function called pivot_root() that was introduced in Linux 2.3.41. It - # works similar to chroot in that it changes the root filesystem. This - # function could be misused in a chrooted process to attempt to break out - # of the chroot, and therefore should not be allowed. If the sysctl - # option is enabled, a sysctl option with name "chroot_deny_pivot" is - # created. - kernel.grsecurity.chroot_deny_pivot = 1 - - # If you say Y here, processes inside a chroot will not be able to attach - # to shared memory segments that were created outside of the chroot jail. - # It is recommended that you say Y here. If the sysctl option is enabled, - # a sysctl option with name "chroot_deny_shmat" is created. - kernel.grsecurity.chroot_deny_shmat = 1 - - # If you say Y here, an attacker in a chroot will not be able to - # write to sysctl entries, either by sysctl(2) or through a /proc - # interface. It is strongly recommended that you say Y here. If the - # sysctl option is enabled, a sysctl option with name - # "chroot_deny_sysctl" is created. - kernel.grsecurity.chroot_deny_sysctl = 1 - - # If you say Y here, processes inside a chroot will not be able to - # connect to abstract (meaning not belonging to a filesystem) Unix - # domain sockets that were bound outside of a chroot. It is recommended - # that you say Y here. If the sysctl option is enabled, a sysctl option - # with name "chroot_deny_unix" is created. - kernel.grsecurity.chroot_deny_unix = 1 - - # If you say Y here, the current working directory of all newly-chrooted - # applications will be set to the the root directory of the chroot. - # The man page on chroot(2) states: - # Note that usually chhroot does not change the current working - # directory, so that `.' can be outside the tree rooted at - # `/'. In particular, the super-user can escape from a - # `chroot jail' by doing `mkdir foo; chroot foo; cd ..'. - # - # It is recommended that you say Y here, since it's not known to break - # any software. If the sysctl option is enabled, a sysctl option with - # name "chroot_enforce_chdir" is created. - kernel.grsecurity.chroot_enforce_chdir = 1 - - # If you say Y here, processes inside a chroot will not be able to - # kill, send signals with fcntl, ptrace, capget, getpgid, setpgid, - # getsid, or view any process outside of the chroot. If the sysctl - # option is enabled, a sysctl option with name "chroot_findtask" is - # created. - kernel.grsecurity.chroot_findtask = 1 - - # If you say Y here, processes inside a chroot will not be able to raise - # the priority of processes in the chroot, or alter the priority of - # processes outside the chroot. This provides more security than simply - # removing CAP_SYS_NICE from the process' capability set. If the - # sysctl option is enabled, a sysctl option with name "chroot_restrict_nice" - # is created. - kernel.grsecurity.chroot_restrict_nice = 1 - - # - # Kernel Auditing - # - - # If you say Y here, the exec and chdir logging features will only operate - # on a group you specify. This option is recommended if you only want to - # watch certain users instead of having a large amount of logs from the - # entire system. If the sysctl option is enabled, a sysctl option with - # name "audit_group" is created. - kernel.grsecurity.audit_group = 1 - - # If you say Y here, the exec and chdir logging features will only operate - # on a group you specify. This option is recommended if you only want to - # watch certain users instead of having a large amount of logs from the - # entire system. If the sysctl option is enabled, a sysctl option with - # name "audit_group" is created. - kernel.grsecurity.audit_gid = 99 - - # If you say Y here, all execve() calls will be logged (since the - # other exec*() calls are frontends to execve(), all execution - # will be logged). Useful for shell-servers that like to keep track - # of their users. If the sysctl option is enabled, a sysctl option with - # name "exec_logging" is created. - # WARNING: This option when enabled will produce a LOT of logs, especially - # on an active system. - kernel.grsecurity.exec_logging = 0 - - # If you say Y here, all attempts to overstep resource limits will - # be logged with the resource name, the requested size, and the current - # limit. It is highly recommended that you say Y here. If the sysctl - # option is enabled, a sysctl option with name "resource_logging" is - # created. If the RBAC system is enabled, the sysctl value is ignored. - kernel.grsecurity.resource_logging = 1 - - # If you say Y here, all executions inside a chroot jail will be logged - # to syslog. This can cause a large amount of logs if certain - # applications (eg. djb's daemontools) are installed on the system, and - # is therefore left as an option. If the sysctl option is enabled, a - # sysctl option with name "chroot_execlog" is created. - kernel.grsecurity.chroot_execlog = 0 - - # If you say Y here, all attempts to attach to a process via ptrace - # will be logged. If the sysctl option is enabled, a sysctl option - # with name "audit_ptrace" is created. - #kernel.grsecurity.audit_ptrace = 1 - - # If you say Y here, all attempts to attach to a process via ptrace - # will be logged. If the sysctl option is enabled, a sysctl option - # with name "audit_ptrace" is created. - kernel.grsecurity.audit_chdir = 0 - - # If you say Y here, all mounts and unmounts will be logged. If the - # sysctl option is enabled, a sysctl option with name "audit_mount" is - # created. - kernel.grsecurity.audit_mount = 1 - - # If you say Y here, certain important signals will be logged, such as - # SIGSEGV, which will as a result inform you of when a error in a program - # occurred, which in some cases could mean a possible exploit attempt. - # If the sysctl option is enabled, a sysctl option with name - # "signal_logging" is created. - kernel.grsecurity.signal_logging = 1 - - # If you say Y here, all failed fork() attempts will be logged. - # This could suggest a fork bomb, or someone attempting to overstep - # their process limit. If the sysctl option is enabled, a sysctl option - # with name "forkfail_logging" is created. - kernel.grsecurity.forkfail_logging = 1 - - # If you say Y here, any changes of the system clock will be logged. - # If the sysctl option is enabled, a sysctl option with name - # "timechange_logging" is created. - kernel.grsecurity.timechange_logging = 1 - - # if you say Y here, calls to mmap() and mprotect() with explicit - # usage of PROT_WRITE and PROT_EXEC together will be logged when - # denied by the PAX_MPROTECT feature. This feature will also - # log other problematic scenarios that can occur when PAX_MPROTECT - # is enabled on a binary, like textrels and PT_GNU_STACK. If the - # sysctl option is enabled, a sysctl option with name "rwxmap_logging" - # is created. - kernel.grsecurity.rwxmap_logging = 1 - - # - # Executable Protections - # - - - # if you say Y here, non-root users will not be able to use dmesg(8) - # to view the contents of the kernel's circular log buffer. - # The kernel's log buffer often contains kernel addresses and other - # identifying information useful to an attacker in fingerprinting a - # system for a targeted exploit. - # If the sysctl option is enabled, a sysctl option with name "dmesg" is - # created. - kernel.grsecurity.dmesg = 1 - # Hide symbol addresses in /proc/kallsyms kernel.kptr_restrict = 2 - # If you say Y here, TTY sniffers and other malicious monitoring - # programs implemented through ptrace will be defeated. If you - # have been using the RBAC system, this option has already been - # enabled for several years for all users, with the ability to make - # fine-grained exceptions. - # - # This option only affects the ability of non-root users to ptrace - # processes that are not a descendent of the ptracing process. - # This means that strace ./binary and gdb ./binary will still work, - # but attaching to arbitrary processes will not. If the sysctl - # option is enabled, a sysctl option with name "harden_ptrace" is - # created. - kernel.grsecurity.harden_ptrace = 1 - - # If you say Y here, unprivileged users will not be able to ptrace unreadable - # binaries. This option is useful in environments that - # remove the read bits (e.g. file mode 4711) from suid binaries to - # prevent infoleaking of their contents. This option adds - # consistency to the use of that file mode, as the binary could normally - # be read out when run without privileges while ptracing. - # - # If the sysctl option is enabled, a sysctl option with name "ptrace_readexec" - # is created. - kernel.grsecurity.ptrace_readexec = 1 - - # If you say Y here, a change from a root uid to a non-root uid - # in a multithreaded application will cause the resulting uids, - # gids, supplementary groups, and capabilities in that thread - # to be propagated to the other threads of the process. In most - # cases this is unnecessary, as glibc will emulate this behavior - # on behalf of the application. Other libcs do not act in the - # same way, allowing the other threads of the process to continue - # running with root privileges. If the sysctl option is enabled, - # a sysctl option with name "consistent_setxid" is created. - kernel.grsecurity.consistent_setxid = 1 - - # If you say Y here, access to overly-permissive IPC objects (shared - # memory, message queues, and semaphores) will be denied for processes - # given the following criteria beyond normal permission checks: - # 1) If the IPC object is world-accessible and the euid doesn't match - # that of the creator or current uid for the IPC object - # 2) If the IPC object is group-accessible and the egid doesn't - # match that of the creator or current gid for the IPC object - # It's a common error to grant too much permission to these objects, - # with impact ranging from denial of service and information leaking to - # privilege escalation. This feature was developed in response to - # research by Tim Brown: - # http://labs.portcullis.co.uk/whitepapers/memory-squatting-attacks-on-system-v-shared-memory/ - # who found hundreds of such insecure usages. Processes with - # CAP_IPC_OWNER are still permitted to access these IPC objects. - # If the sysctl option is enabled, a sysctl option with name - # "harden_ipc" is created. - kernel.grsecurity.harden_ipc = 1 - - # If you say Y here, you will be able to choose a gid to add to the - # supplementary groups of users you want to mark as "untrusted." - # These users will not be able to execute any files that are not in - # root-owned directories writable only by root. If the sysctl option - # is enabled, a sysctl option with name "tpe" is created. - kernel.grsecurity.tpe = 1 - kernel.grsecurity.tpe_gid = 100 - - # If you say Y here, the group you specify in the TPE configuration will - # decide what group TPE restrictions will be *disabled* for. This - # option is useful if you want TPE restrictions to be applied to most - # users on the system. If the sysctl option is enabled, a sysctl option - # with name "tpe_invert" is created. Unlike other sysctl options, this - # entry will default to on for backward-compatibility. - kernel.grsecurity.tpe_invert = 1 - - # If you say Y here, all non-root users will be covered under - # a weaker TPE restriction. This is separate from, and in addition to, - # the main TPE options that you have selected elsewhere. Thus, if a - # "trusted" GID is chosen, this restriction applies to even that GID. - # Under this restriction, all non-root users will only be allowed to - # execute files in directories they own that are not group or - # world-writable, or in directories owned by root and writable only by - # root. If the sysctl option is enabled, a sysctl option with name - # "tpe_restrict_all" is created. - kernel.grsecurity.tpe_restrict_all = 1 - - - kernel.grsecurity.harden_tty = 1 - # # Network Protections # + net.core.bpf_jit_enable = 0 + # Increase Linux auto tuning TCP buffer limits # min, default, and max number of bytes to use # set max to at least 4MB, or higher if you use very high BDP paths @@ -519,105 +154,18 @@ # Sen SynAck retries to 3 net.ipv4.tcp_synack_retries = 3 - # If you say Y here, neither TCP resets nor ICMP - # destination-unreachable packets will be sent in response to packets - # sent to ports for which no associated listening process exists. - # This feature supports both IPV4 and IPV6 and exempts the - # loopback interface from blackholing. Enabling this feature - # makes a host more resilient to DoS attacks and reduces network - # visibility against scanners. - # - # The blackhole feature as-implemented is equivalent to the FreeBSD - # blackhole feature, as it prevents RST responses to all packets, not - # just SYNs. Under most application behavior this causes no - # problems, but applications (like haproxy) may not close certain - # connections in a way that cleanly terminates them on the remote - # end, leaving the remote host in LAST_ACK state. Because of this - # side-effect and to prevent intentional LAST_ACK DoSes, this - # feature also adds automatic mitigation against such attacks. - # The mitigation drastically reduces the amount of time a socket - # can spend in LAST_ACK state. If you're using haproxy and not - # all servers it connects to have this option enabled, consider - # disabling this feature on the haproxy host. - # - # If the sysctl option is enabled, two sysctl options with names - # "ip_blackhole" and "lastack_retries" will be created. - # While "ip_blackhole" takes the standard zero/non-zero on/off - # toggle, "lastack_retries" uses the same kinds of values as - # "tcp_retries1" and "tcp_retries2". The default value of 4 - # prevents a socket from lasting more than 45 seconds in LAST_ACK - # state. - kernel.grsecurity.ip_blackhole = 1 - kernel.grsecurity.lastack_retries = 4 - - # If you say Y here, you will be able to choose a GID of whose users will - # be unable to connect to other hosts from your machine or run server - # applications from your machine. If the sysctl option is enabled, a - # sysctl option with name "socket_all" is created. - kernel.grsecurity.socket_all = 1 - - # Here you can choose the GID to disable socket access for. Remember to - # add the users you want socket access disabled for to the GID - # specified here. If the sysctl option is enabled, a sysctl option - # with name "socket_all_gid" is created. - kernel.grsecurity.socket_all_gid = 200 - - # If you say Y here, you will be able to choose a GID of whose users will - # be unable to connect to other hosts from your machine, but will be - # able to run servers. If this option is enabled, all users in the group - # you specify will have to use passive mode when initiating ftp transfers - # from the shell on your machine. If the sysctl option is enabled, a - # sysctl option with name "socket_client" is created. - kernel.grsecurity.socket_client = 1 - - # Here you can choose the GID to disable client socket access for. - # Remember to add the users you want client socket access disabled for to - # the GID specified here. If the sysctl option is enabled, a sysctl - # option with name "socket_client_gid" is created. - kernel.grsecurity.socket_client_gid = 201 - - # If you say Y here, you will be able to choose a GID of whose users will - # be unable to connect to other hosts from your machine, but will be - # able to run servers. If this option is enabled, all users in the group - # you specify will have to use passive mode when initiating ftp transfers - # from the shell on your machine. If the sysctl option is enabled, a - # sysctl option with name "socket_client" is created. - kernel.grsecurity.socket_server = 1 - - # Here you can choose the GID to disable server socket access for. - # Remember to add the users you want server socket access disabled for to - # the GID specified here. If the sysctl option is enabled, a sysctl - # option with name "socket_server_gid" is created. - kernel.grsecurity.socket_server_gid = 99 - - # - # Physical Protections - # - - # If you say Y here, a new sysctl option with name "deny_new_usb" - # will be created. Setting its value to 1 will prevent any new - # USB devices from being recognized by the OS. Any attempted USB - # device insertion will be logged. This option is intended to be - # used against custom USB devices designed to exploit vulnerabilities - # in various USB device drivers. - # - # For greatest effectiveness, this sysctl should be set after any - # relevant init scripts. This option is safe to enable in distros - # as each user can choose whether or not to toggle the sysctl. - kernel.grsecurity.deny_new_usb = 0 - - # - # Restrict grsec sysctl changes after this was set - # - kernel.grsecurity.grsec_lock = 0 - # End of file </pre> + <p>Reload sysctl settings;</p> + + <pre> + # sysctl --system + </pre> <a href="index.html">Core OS Index</a> <p>This is part of the Hive System Documentation. - Copyright (C) 2018 + Copyright (C) 2019 Hive Team. See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a> for copying conditions.</p> |