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121 lines
4.5 KiB
Plaintext
121 lines
4.5 KiB
Plaintext
## Copyright (C) 2012 - 2018 ENCRYPTED SUPPORT LP <adrelanos@riseup.net>
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## See the file COPYING for copying conditions.
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Source: security-misc
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Section: misc
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Priority: optional
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Maintainer: Patrick Schleizer <adrelanos@riseup.net>
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Build-Depends: debhelper (>= 12), genmkfile, config-package-dev
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Homepage: https://github.com/Whonix/security-misc
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Vcs-Browser: https://github.com/Whonix/security-misc
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Vcs-Git: https://github.com/Whonix/security-misc.git
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Standards-Version: 4.3.0
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Package: security-misc
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Architecture: all
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Depends: python, libglib2.0-bin, ${misc:Depends}
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Replaces: tcp-timestamps-disable
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Description: enhances misc security settings
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The following settings are changed:
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.
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deactivates previews in Dolphin;
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deactivates previews in Nautilus;
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deactivates thumbnails in Thunar;
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deactivates TCP timestamps;
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deactivates Netfilter's connection tracking helper;
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implements some kernel hardening;
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prevents DMA attacks;
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.
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TCP time stamps (RFC 1323) allow for tracking clock
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information with millisecond resolution. This may or may not allow an
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attacker to learn information about the system clock at such
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a resolution, depending on various issues such as network lag.
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This information is available to anyone who monitors the network
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somewhere between the attacked system and the destination server.
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It may allow an attacker to find out how long a given
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system has been running, and to distinguish several
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systems running behind NAT and using the same IP address. It might
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also allow one to look for clocks that match an expected value to find the
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public IP used by a user.
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.
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Hence, this package disables this feature by shipping the
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/etc/sysctl.d/tcp_timestamps.conf configuration file.
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.
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Note that TCP time stamps normally have some usefulness. They are
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needed for:
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.
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* the TCP protection against wrapped sequence numbers; however, to
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trigger a wrap, one needs to send roughly 2^32 packets in one
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minute: as said in RFC 1700, "The current recommended default
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time to live (TTL) for the Internet Protocol (IP) [45,105] is 64".
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So, this probably won't be a practical problem in the context
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of Anonymity Distributions.
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.
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* "Round-Trip Time Measurement", which is only useful when the user
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manages to saturate their connection. When using Anonymity Distributions,
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probably the limiting factor for transmission speed is rarely the capacity
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of the user connection.
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.
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Netfilter's connection tracking helper module increases kernel attack
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surface by enabling superfluous functionality such as IRC parsing in
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the kernel. (!)
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.
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Hence, this package disables this feature by shipping the
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/etc/modprobe.d/30_nf_conntrack_helper_disable.conf configuration file.
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.
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Kernel symbols in /proc/kallsyms are hidden to prevent malware from
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reading them and using them to learn more about what to attack on your system.
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.
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Kexec is disabled as it can be used for live patching of the running kernel.
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.
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The BPF JIT compiler is restricted to the root user and is hardened.
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.
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ASLR effectiveness for mmap is increased.
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.
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The ptrace system call is restricted to the root user only.
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.
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The TCP/IP stack is hardened.
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.
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This package makes some data spoofing attacks harder.
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.
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SACK is disabled as it is commonly exploited and is rarely used.
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.
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This package disables the merging of slabs of similar sizes to prevent an
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attacker from exploiting them.
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.
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Sanity checks, redzoning, and memory poisoning are enabled.
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.
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The kernel now panics on uncorrectable errors in ECC memory which could
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be exploited.
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.
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Kernel Page Table Isolation is enabled to mitigate Meltdown and increase
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KASLR effectiveness.
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.
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SMT is disabled as it can be used to exploit the MDS vulnerability.
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.
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All mitigations for the MDS vulnerability are enabled.
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.
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DCCP, SCTP, TIPC, RDS and HDLC are blacklisted as they are rarely used and may have
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unknown vulnerabilities.
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.
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The kernel logs are restricted to root only.
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.
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A systemd service clears System.map on boot as these contain kernel symbols
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that could be useful to an attacker.
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.
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The SysRq key is restricted to only allow shutdowns/reboots.
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.
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The thunderbolt and firewire modules are blacklisted as they can be used for
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DMA (Direct Memory Access) attacks.
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.
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IOMMU is enabled with a boot parameter to prevent DMA attacks.
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.
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Coredumps are disabled as they may contain important information such as
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encryption keys or passwords.
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.
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A systemd service mounts /proc with hidepid=2 at boot to prevent users from
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seeing each other's processes.
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.
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The default umask is changed to 006. This allows only the owner and group to
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read and write to newly created files.
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