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readme
This commit is contained in:
Patrick Schleizer
parent
ea90f95f1c
commit
c13485f532
131
README.md
131
README.md
@ -7,43 +7,14 @@ 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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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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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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Note that TCP time stamps normally have some usefulness. They are
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needed for:
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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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* "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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implements some kernel hardening;
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prevents DMA attacks;
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restricts access to the root account;
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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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Hence, this package disables this feature by shipping the
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/etc/sysctl.d/nf_conntrack_helper.conf configuration file.
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the kernel. (!) 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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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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@ -77,8 +48,96 @@ SMT is disabled as it can be used to exploit the MDS vulnerability.
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All mitigations for the MDS vulnerability are enabled.
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DCCP, SCTP, TIPC and RDS are blacklisted as they are rarely used and may have
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unknown vulnerabilities.
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Uncommon network protocols are blacklisted in
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/etc/modprobe.d/uncommon-network-protocols.conf as they are rarely used and
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may have unknown vulnerabilities.
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The network protocols that are blacklisted are:
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* DCCP - Datagram Congestion Control Protocol
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* SCTP - Stream Control Transmission Protocol
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* RDS - Reliable Datagram Sockets
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* TIPC - Transparent Inter-process Communication
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* HDLC - High-Level Data Link Control
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* AX25 - Amateur X.25
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* NetRom
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* X25
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* ROSE
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* DECnet
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* Econet
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* af_802154 - IEEE 802.15.4
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* IPX - Internetwork Packet Exchange
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* AppleTalk
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* PSNAP - Subnetwork Access Protocol
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* p8023 - Novell raw IEEE 802.3
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* LLC - IEEE 802.2
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* p8022 - IEEE 802.2
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The kernel logs are restricted to root only.
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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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The SysRq key is restricted to only allow shutdowns/reboots.
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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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IOMMU is enabled with a boot parameter to prevent DMA attacks.
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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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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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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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Removes read, write and execute access for others for all users who have home
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folders under folder /home by running for example "chmod o-rwx /home/user"
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during package installation or upgrade. This will be done only once per folder
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in folder /home so users who wish to relax file permissions are free to do so.
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This is to protect previously created files in user home folder which were
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previously created with lax file permissions prior installation of this
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package.
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The kernel now panics on oopses to prevent it from continuing running a
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flawed process.
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Su is restricted to only users within the root group which prevents users from
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using su to gain root access or switch user accounts.
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Logging into the root account from a terminal is prevented.
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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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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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Note that TCP time stamps normally have some usefulness. They are
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needed for:
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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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* "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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## How to install `security-misc` using apt-get ##
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1\. Add [Whonix's Signing Key](https://www.whonix.org/wiki/Whonix_Signing_Key).
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