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<title>Crypto Policy</title>
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<para>Beginning in Fedora 21, a system-wide crypto policy will be available for users to quickly setup the cryptographic options for their systems.  Users that must meet certain cryptographic standards can make the policy change in <filename>//etc/crypto-policies/config</filename>, and run update-crypto-policies. At this point applications that utilize the default set of ciphers in the GnuTLS and OpenSSL libraries will follow the policy requirements.</para>


== Hardlink and symlink restrictions ==
<para>The available options are: (1) <literal>LEGACY</literal>, which ensures compatibility with legacy systems - 64-bit security, (2) <literal>DEFAULT</literal>, a reasonable default for today's standards - 80-bit security, and (3) <literal>FUTURE</literal>, a conservative level that is believed to withstand any near-term future attacks - 128-bit security.  These levels affect SSL/TLS settings, including elliptic curve, signature hash functions, and ciphersuites and key sizes.</para>


A long-standing class of security issues is the link-based time-of-check-time-of-use race, most commonly seen in world-writable directories like /tmp. The common method of exploitation of this flaw is to cross privilege boundaries when following a given link (i.e. a root process follows a link belonging to another user).  In Fedora 19,  we permit links to only be followed when outside a sticky world-writable directory, or when the uid of the link and follower match, or when the directory owner matches the link's owner. In previous releases, this was enforced by SELinux policy and in this release, we have enabled these restrictions via the following sysctl settings in /usr/lib/sysctl.d/00-system.conf as an additional layer of protection:
<para>Additional information on this new feature can be found on the <ulink url="https://fedoraproject.org/wiki/Changes/CryptoPolicy">CryptoPolicy Changes wiki page</ulink>.</para>


fs.protected_hardlinks = 1
fs.protected_symlinks = 1


Refer to http://lwn.net/Articles/503660/ and https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=800179c9b8a1e796e441674776d11cd4c05d61d7 for more detailed information about this change.  Note that in addition to this,
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[[Category:Draft documentation]]
[[Category:Documentation beats]]

Revision as of 07:03, 4 June 2014

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<title>Crypto Policy</title>

<para>Beginning in Fedora 21, a system-wide crypto policy will be available for users to quickly setup the cryptographic options for their systems. Users that must meet certain cryptographic standards can make the policy change in <filename>//etc/crypto-policies/config</filename>, and run update-crypto-policies. At this point applications that utilize the default set of ciphers in the GnuTLS and OpenSSL libraries will follow the policy requirements.</para>

<para>The available options are: (1) <literal>LEGACY</literal>, which ensures compatibility with legacy systems - 64-bit security, (2) <literal>DEFAULT</literal>, a reasonable default for today's standards - 80-bit security, and (3) <literal>FUTURE</literal>, a conservative level that is believed to withstand any near-term future attacks - 128-bit security. These levels affect SSL/TLS settings, including elliptic curve, signature hash functions, and ciphersuites and key sizes.</para>

<para>Additional information on this new feature can be found on the <ulink url="https://fedoraproject.org/wiki/Changes/CryptoPolicy">CryptoPolicy Changes wiki page</ulink>.</para>