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c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar - Copyright (C) 2004-2012 Internet Systems Consortium, Inc. ("ISC")
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar - Copyright (C) 2000-2003 Internet Software Consortium.
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c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar<div class="cmdsynopsis"><p><code class="command">isc-hmac-fixup</code> {<em class="replaceable"><code>algorithm</code></em>} {<em class="replaceable"><code>secret</code></em>}</p></div>
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar Versions of BIND 9 up to and including BIND 9.6 had a bug causing
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar HMAC-SHA* TSIG keys which were longer than the digest length of the
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar longer than 256 bits, etc) to be used incorrectly, generating a
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar message authentication code that was incompatible with other DNS
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar implementations.
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar This bug has been fixed in BIND 9.7. However, the fix may
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar cause incompatibility between older and newer versions of
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe modifies those keys to restore compatibility.
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar specify the key's algorithm and secret on the command line. If the
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar secret is longer than the digest length of the algorithm (64 bytes
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar new secret will be generated consisting of a hash digest of the old
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar secret. (If the secret did not require conversion, then it will be
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar printed without modification.)
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar<a name="id2657424"></a><h2>SECURITY CONSIDERATIONS</h2>
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar are shortened, but as this is how the HMAC protocol works in
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar operation anyway, it does not affect security. RFC 2104 notes,
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar "Keys longer than [the digest length] are acceptable but the
c39526b769298791ff5b0b6c5e761f49aabaeb4ePramod Gunjikar extra length would not significantly increase the function
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