isc-hmac-fixup.docbook revision 83a28ca274521e15086fc39febde507bcc4e145e
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein - Copyright (C) 2010, 2013-2016 Internet Systems Consortium, Inc. ("ISC")
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b0fb330a8581c8bfab5e523084f9f39264a52b12gstein<!-- Converted by db4-upgrade version 1.0 -->
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein<refentry xmlns:db="http://docbook.org/ns/docbook" version="5.0" xml:id="man.isc-hmac-fixup">
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refentryinfo>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <corpauthor>Internet Systems Consortium, Inc.</corpauthor>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein </refentryinfo>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refentrytitle><application>isc-hmac-fixup</application></refentrytitle>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refnamediv>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refname><application>isc-hmac-fixup</application></refname>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refpurpose>fixes HMAC keys generated by older versions of BIND</refpurpose>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein </refnamediv>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <copyright>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein </copyright>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <refsynopsisdiv>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <arg choice="req" rep="norepeat"><replaceable class="parameter">algorithm</replaceable></arg>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein <arg choice="req" rep="norepeat"><replaceable class="parameter">secret</replaceable></arg>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein </cmdsynopsis>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein </refsynopsisdiv>
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein Versions of BIND 9 up to and including BIND 9.6 had a bug causing
b0fb330a8581c8bfab5e523084f9f39264a52b12gstein HMAC-SHA* TSIG keys which were longer than the digest length of the
f4c310fd2555c6faca1f980f00b161eadb089023gstein hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
f4c310fd2555c6faca1f980f00b161eadb089023gstein longer than 256 bits, etc) to be used incorrectly, generating a
f4c310fd2555c6faca1f980f00b161eadb089023gstein message authentication code that was incompatible with other DNS
f4c310fd2555c6faca1f980f00b161eadb089023gstein implementations.
f4c310fd2555c6faca1f980f00b161eadb089023gstein This bug has been fixed in BIND 9.7. However, the fix may
1f6e6566a4ce31a0b95d5400c36d0aaff7a6e94agstein cause incompatibility between older and newer versions of
f4c310fd2555c6faca1f980f00b161eadb089023gstein BIND, when using long keys. <command>isc-hmac-fixup</command>
1a9d922232824a7cc008d4f74e48bd82adf5bdedgstein modifies those keys to restore compatibility.
f4c310fd2555c6faca1f980f00b161eadb089023gstein To modify a key, run <command>isc-hmac-fixup</command> and
f4c310fd2555c6faca1f980f00b161eadb089023gstein specify the key's algorithm and secret on the command line. If the
f4c310fd2555c6faca1f980f00b161eadb089023gstein secret is longer than the digest length of the algorithm (64 bytes
f4c310fd2555c6faca1f980f00b161eadb089023gstein for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
f4c310fd2555c6faca1f980f00b161eadb089023gstein new secret will be generated consisting of a hash digest of the old
f4c310fd2555c6faca1f980f00b161eadb089023gstein secret. (If the secret did not require conversion, then it will be
f4c310fd2555c6faca1f980f00b161eadb089023gstein printed without modification.)
f4c310fd2555c6faca1f980f00b161eadb089023gstein </refsection>
f4c310fd2555c6faca1f980f00b161eadb089023gstein <refsection><info><title>SECURITY CONSIDERATIONS</title></info>
f4c310fd2555c6faca1f980f00b161eadb089023gstein Secrets that have been converted by <command>isc-hmac-fixup</command>
f4c310fd2555c6faca1f980f00b161eadb089023gstein are shortened, but as this is how the HMAC protocol works in
f4c310fd2555c6faca1f980f00b161eadb089023gstein operation anyway, it does not affect security. RFC 2104 notes,
f4c310fd2555c6faca1f980f00b161eadb089023gstein "Keys longer than [the digest length] are acceptable but the
f4c310fd2555c6faca1f980f00b161eadb089023gstein extra length would not significantly increase the function
f4c310fd2555c6faca1f980f00b161eadb089023gstein </refsection>
f4c310fd2555c6faca1f980f00b161eadb089023gstein <citetitle>BIND 9 Administrator Reference Manual</citetitle>,
f4c310fd2555c6faca1f980f00b161eadb089023gstein </refsection>