/contrib/bind9/bin/tools/isc-hmac-fixup.html

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  17. <html>
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  20. <title>isc-hmac-fixup</title>
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  23. <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="refentry" lang="en">
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  24. <a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
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  25. <div class="refnamediv">
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  26. <h2>Name</h2>
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  27. <p><span class="application">isc-hmac-fixup</span> &#8212; fixes HMAC keys generated by older versions of BIND</p>
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  28. </div>
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  29. <div class="refsynopsisdiv">
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  30. <h2>Synopsis</h2>
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  31. <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>
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  32. </div>
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  33. <div class="refsect1" lang="en">
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  34. <a name="id2543352"></a><h2>DESCRIPTION</h2>
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  35. <p>
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  36.       Versions of BIND 9 up to and including BIND 9.6 had a bug causing
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  37.       HMAC-SHA* TSIG keys which were longer than the digest length of the
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  38.       hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
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  39.       longer than 256 bits, etc) to be used incorrectly, generating a
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  40.       message authentication code that was incompatible with other DNS
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  41.       implementations.
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  42.     </p>
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  43. <p>
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  44.       This bug has been fixed in BIND 9.7.  However, the fix may
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  45.       cause incompatibility between older and newer versions of
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  46.       BIND, when using long keys.  <span><strong class="command">isc-hmac-fixup</strong></span>
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  47.       modifies those keys to restore compatibility.
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  48.     </p>
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  49. <p>
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  50.       To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
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  51.       specify the key's algorithm and secret on the command line.  If the
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  52.       secret is longer than the digest length of the algorithm (64 bytes
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  53.       for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
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  54.       new secret will be generated consisting of a hash digest of the old
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  55.       secret.  (If the secret did not require conversion, then it will be
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  56.       printed without modification.)
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  57.     </p>
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  58. </div>
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  59. <div class="refsect1" lang="en">
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  60. <a name="id2543376"></a><h2>SECURITY CONSIDERATIONS</h2>
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  61. <p>
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  62.       Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
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  63.       are shortened, but as this is how the HMAC protocol works in
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  64.       operation anyway, it does not affect security.  RFC 2104 notes,
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  65.       "Keys longer than [the digest length] are acceptable but the
    66. 

  66.       extra length would not significantly increase the function
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  67.       strength."
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  68.     </p>
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  69. </div>
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  70. <div class="refsect1" lang="en">
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  71. <a name="id2543389"></a><h2>SEE ALSO</h2>
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  72. <p>
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  73.       <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
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  74.       <em class="citetitle">RFC 2104</em>.
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  75.     </p>
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  76. </div>
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  77. <div class="refsect1" lang="en">
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  78. <a name="id2543406"></a><h2>AUTHOR</h2>
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  79. <p><span class="corpauthor">Internet Systems Consortium</span>
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  80.     </p>
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  81. </div>
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  82. </div></body>
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  83. </html>
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