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diff --git a/core/linux.html b/core/linux.html index 53fc304..0304884 100644 --- a/core/linux.html +++ b/core/linux.html @@ -2,12 +2,12 @@ <html dir="ltr" lang="en"> <head> <meta charset='utf-8'> - <title>2.3. Kernel Linux</title> + <title>2.1. Kernel Linux</title> </head> <body> <a href="index.html">Core OS Index</a> - <h1 id="kernel">2.3. Kernel Linux</h1> + <h1 id="kernel">2.1. Kernel Linux</h1> <p>Linux is a monolith kernel, a big one ! Visit <a href="http://www.fsfla.org/ikiwiki/selibre/linux-libre/">Linux Libre</a> @@ -15,58 +15,41 @@ <a href="https://www.kernel.org/">Linux Non-Libre</a> pages for more links and information.</p> - <h2 id="#linuxlibre">2.3.1. Port Linux Libre</h2> + <h2 id="#linuxlibre">2.1.1. Port Linux Libre</h2> - <p>Collection c9-ports have linux-libre port with default crux - configuration, this port depends on dracut and grub but is not - required to install them. To build and install this port using - prt-get;</p> + <p>Default crux configuration can be obtained from iso, this port depends + on dracut and grub but is not required to install them. To build and install + this port using prt-get;</p> <pre> $ prt-get depinst linux-libre </pre> - <h2 id="kinstall">2.3.2. Manual Install</h2> + <h2 id="kinstall">2.1.2. Manual Install</h2> <p>Download Linux Source from <a href="http://linux-libre.fsfla.org/pub/linux-libre/releases/">linux libre</a>, or using the port system;</p> - <pre> - $ cd /usr/ports/c9-ports/linux-libre - $ sudo -u pkgmk pkgmk -do - </pre> - - <p>Crux iso comes with config that is used in this port, is - a good starting point to personalize according to your needs;</p> + <p>Crux iso comes with config that is more generic than used on linux-libre + port, crux default is a good starting point to personalize according to your + needs (build default, detect modules needed);</p> <pre> $ mkdir ~/kernel $ cd ~/kernel - $ cp /usr/ports/c9-ports/linux-libre/linux-4.1.32.defconfig . - $ cp /usr/ports/distfiles/linux-libre-4.1.32-gnu.tar.xz . - $ tar xf linux-libre-4.1.32-gnu.tar.xz - $ cp linux-4.1.32.defconfig linux-4.1.32/.config + $ cp /usr/ports/distfiles/linux-libre-4.9.11-gnu.tar.xz . + $ tar xf linux-libre-4.9.11-gnu.tar.xz + $ cd linux-4.9.11/ </pre> - <p>If you like <a href="https://github.com/graysky2/kernel_gcc_patch/">graysky2</a> kernel_gcc_patch (<a href="https://github.com/graysky2/kernel_gcc_patch/archive/master.zip">download master</a>) that adds more cpu options (FLAGS native)</p> - - <pre> - $ cp /usr/ports/distfiles/enable_additional_cpu_optimizations_for_gcc_v4.9%2B_kernel_v3.15%2B.patch cpu_optimizations.patch - </pre> - - <pre> - $ cd ~/linux-4.1.32/ - $ patch -p1 < ../cpu_optimizations.patch - patching file arch/x86/include/asm/module.h - patching file arch/x86/Kconfig.cpu - patching file arch/x86/Makefile - Hunk #1 succeeded at 85 with fuzz 1 (offset -9 lines). - patching file arch/x86/Makefile_32.cpu - $ - </pre> - - <p>Read <a href="https://en.wikibooks.org/wiki/Grsecurity/Configuring_and_Installing_grsecurity#Patching_Your_Kernel_with_grsecurity">Gresecurity</a>.</p> + <p><a href="grsecurity.net">Grsecurity</a> patch for + <a href="https://grsecurity.net/test/grsecurity-3.1-4.9.9-201702122044.patch">4.9.11</a>. + Gcc <a href="https://github.com/graysky2/kernel_gcc_patch/">graysky2</a> kernel_gcc_patch (<a href="https://github.com/graysky2/kernel_gcc_patch/archive/master.zip">master.zip</a>) + that adds more cpu options (FLAGS native). + Check <a href="ports/linux-libre/Pkgfile">Pkgfile</a> for instructions and + more patches used on linux-libre port. Read patching your kernel with + <a href="https://en.wikibooks.org/wiki/Grsecurity/Configuring_and_Installing_grsecurity#Patching_Your_Kernel_with_grsecurity">gresecurity</a>.</p> <p>Configure kernel according to your current kernel hardware support;</p> @@ -77,11 +60,10 @@ <p>This will disable all unloaded modules, you can use localyesconfig mark all loaded - to be built in the kernel.</p> - - <p>To get information about your hardware, - for example information about which graphic - module (driver) is in use as root run;</p> + to be built in the kernel. To get information + about your hardware, for example information + about which graphic module (driver) is in use + as root run;</p> <pre> # lspci -nnk | grep -i vga -A3 | grep 'in use' @@ -95,16 +77,16 @@ </pre> <pre> - $ make -j $(nproc) all + $ make -j $(nproc) bzImage modules $ sudo make modules_install - $ sudo cp arch/x86/boot/bzImage /boot/vmlinuz-4.1.32-gnu_crux - $ sudo cp System.map /boot/System.map-4.1.32-gnu_crux + $ sudo cp arch/x86/boot/bzImage /boot/vmlinuz-4.9.11-gnu + $ sudo cp System.map /boot/System.map-4.9.11-gnu </pre> <p>Create dracut initramfs;</p> <pre> - $sudo dracut --fstab /boot/initramfs-4.1.32-gnu_crux.img 4.1.32-gnu_crux + $sudo dracut --fstab /boot/initramfs-4.9.11-gnu.img 4.9.11-gnu </pre> <p>Update grub;</p> @@ -113,17 +95,609 @@ # grub-mkconfig -o /boot/grub/grub.cfg </pre> - <h2 id="kuninstall">2.3.3. Manual Remove</h2> + <h2 id="kuninstall">2.1.3. Manual Remove</h2> <pre> - $ sudo rm -r /lib/modules/4.1.12-gnu_crux - $ sudo rm /boot/vmlinuz-4.1.12-gnu_crux - $ sudo rm /boot/System.map-4.1.12-gnu_crux + $ sudo rm -r /lib/modules/4.9.11-gnu + $ sudo rm /boot/vmlinuz-4.9.11-gnu + $ sudo rm /boot/System.map-4.9.11-gnu </pre> + <h2 id="sysctl">2.1.4. Sysctl</h2> + + <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 c9-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> + + <pre> + # + # /etc/sysctl.conf: configuration for system variables, see sysctl.conf(5) + # + + kernel.printk = 15 1 1 4 + kernel.randomize_va_space = 1 + kernel.shmmax = 500000000 + # 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 + kernel.grsecurity.disable_priv_io = 0 + + # 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 + + # + # Filesystem Protections + # + + # Optimization for port usefor LBs + # 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 = 33 + + # 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 = 0 + + # 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 = 0 + + # 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 = 201 + + # 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 + kernel.grsecurity.resource_logging = 0 + + # 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 + kernel.grsecurity.audit_ptrace = 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_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 + kernel.grsecurity.audit_mount = 0 + + # 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 = 0 + + # 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 + kernel.grsecurity.forkfail_logging = 0 + + # 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 = 1 + + # 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 = 101 + + # 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 = 0 + + + #kernel.grsecurity.harden_tty = 1 + # + # Network Protections + # + + # 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 + # Tcp Windows etc + net.core.rmem_max = 8388608 + net.core.wmem_max = 8388608 + net.core.netdev_max_backlog = 5000 + net.ipv4.tcp_window_scaling = 1 + + # Both ports linux-blob and linux-libre don't build with ipv6 + # Disable ipv6 + net.ipv6.conf.all.disable_ipv6 = 1 + net.ipv6.conf.default.disable_ipv6 = 1 + net.ipv6.conf.lo.disable_ipv6 = 1 + + # Tuen IPv6 + #net.ipv6.conf.default.router_solicitations = 0 + #net.ipv6.conf.default.accept_ra_rtr_pref = 0 + #net.ipv6.conf.default.accept_ra_pinfo = 0 + #net.ipv6.conf.default.accept_ra_defrtr = 0 + #net.ipv6.conf.default.autoconf = 0 + #net.ipv6.conf.default.dad_transmits = 0 + #net.ipv6.conf.default.max_addresses = 0 + + # Avoid a smurf attack + net.ipv4.icmp_echo_ignore_broadcasts = 1 + + # Turn on protection for bad icmp error messages + net.ipv4.icmp_ignore_bogus_error_responses = 1 + + # Turn on syncookies for SYN flood attack protection + net.ipv4.tcp_syncookies = 1 + + ## protect against tcp time-wait assassination hazards + ## drop RST packets for sockets in the time-wait state + ## (not widely supported outside of linux, but conforms to RFC) + net.ipv4.tcp_rfc1337 = 1 + + ## tcp timestamps + ## + protect against wrapping sequence numbers (at gigabit speeds) + ## + round trip time calculation implemented in TCP + ## - causes extra overhead and allows uptime detection by scanners like nmap + ## enable @ gigabit speeds + net.ipv4.tcp_timestamps = 0 + #net.ipv4.tcp_timestamps = 1 + + # Turn on and log spoofed, source routed, and redirect packets + net.ipv4.conf.all.log_martians = 1 + net.ipv4.conf.default.log_martians = 1 + + ## ignore echo broadcast requests to prevent being part of smurf attacks (default) + net.ipv4.icmp_echo_ignore_broadcasts = 1 + + # No source routed packets here + net.ipv4.conf.all.accept_source_route = 0 + net.ipv4.conf.default.accept_source_route = 0 + + ## sets the kernels reverse path filtering mechanism to value 1(on) + ## will do source validation of the packet's recieved from all the interfaces on the machine + ## protects from attackers that are using ip spoofing methods to do harm + net.ipv4.conf.all.rp_filter = 1 + net.ipv4.conf.default.rp_filter = 1 + #net.ipv6.conf.default.rp_filter = 1 + #net.ipv6.conf.all.rp_filter = 1 + + # Make sure no one can alter the routing tables + net.ipv4.conf.all.accept_redirects = 0 + net.ipv4.conf.default.accept_redirects = 0 + net.ipv4.conf.all.secure_redirects = 0 + net.ipv4.conf.default.secure_redirects = 0 + + # Act as a router, necessary for Access Point + net.ipv4.ip_forward = 1 + net.ipv4.conf.all.send_redirects = 1 + net.ipv4.conf.default.send_redirects = 1 + + # Increase system IP port limits + net.ipv4.ip_local_port_range = 2000 65000 + + # Increase TCP max buffer size setable using setsockopt() + net.ipv4.tcp_rmem = 4096 87380 8388608 + net.ipv4.tcp_wmem = 4096 87380 8388608 + + + # 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 = 202 + + # 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 = 203 + + # 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 = 204 + + # + # 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 = 1 + + + + # End of file + </pre> + + <a href="index.html">Core OS Index</a> <p>This is part of the c9-doc Manual. -Copyright (C) 2016 +Copyright (C) 2017 c9 team. See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a> for copying conditions.</p> |