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62 lines
2.5 KiB
Plaintext
62 lines
2.5 KiB
Plaintext
## Copyright (C) 2012 - 2014 Patrick Schleizer <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 (>= 9), genmkfile
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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: 3.9.8
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Package: security-misc
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Architecture: all
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Depends: ${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 TCP timestamps;
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deactivates Netfilter's connection tracking helper;
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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/sysctl.d/nf_conntrack_helper.conf configuration file.
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