/contrib/bind9/doc/arm/man.isc-hmac-fixup.html

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  43. <a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
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  44. <div class="refnamediv">
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  45. <h2>Name</h2>
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  46. <p><span class="application">isc-hmac-fixup</span> &#8212; fixes HMAC keys generated by older versions of BIND</p>
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  47. </div>
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  48. <div class="refsynopsisdiv">
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  49. <h2>Synopsis</h2>
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  50. <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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  51. </div>
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  52. <div class="refsect1" lang="en">
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  53. <a name="id2615000"></a><h2>DESCRIPTION</h2>
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  54. <p>
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  55.       Versions of BIND 9 up to and including BIND 9.6 had a bug causing
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  56.       HMAC-SHA* TSIG keys which were longer than the digest length of the
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  57.       hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
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  58.       longer than 256 bits, etc) to be used incorrectly, generating a
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  59.       message authentication code that was incompatible with other DNS
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  60.       implementations.
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  61.     </p>
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  62. <p>
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  63.       This bug has been fixed in BIND 9.7.  However, the fix may
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  64.       cause incompatibility between older and newer versions of
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  65.       BIND, when using long keys.  <span><strong class="command">isc-hmac-fixup</strong></span>
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  66.       modifies those keys to restore compatibility.
    67. 

  67.     </p>
    68. 

  68. <p>
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  69.       To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
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  70.       specify the key's algorithm and secret on the command line.  If the
    71. 

  71.       secret is longer than the digest length of the algorithm (64 bytes
    72. 

  72.       for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
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  73.       new secret will be generated consisting of a hash digest of the old
    74. 

  74.       secret.  (If the secret did not require conversion, then it will be
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  75.       printed without modification.)
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  76.     </p>
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  77. </div>
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  78. <div class="refsect1" lang="en">
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  79. <a name="id2653052"></a><h2>SECURITY CONSIDERATIONS</h2>
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  80. <p>
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  81.       Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
    82. 

  82.       are shortened, but as this is how the HMAC protocol works in
    83. 

  83.       operation anyway, it does not affect security.  RFC 2104 notes,
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  84.       "Keys longer than [the digest length] are acceptable but the
    85. 

  85.       extra length would not significantly increase the function
    86. 

  86.       strength."
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  87.     </p>
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  88. </div>
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  89. <div class="refsect1" lang="en">
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  90. <a name="id2653068"></a><h2>SEE ALSO</h2>
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  91. <p>
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  92.       <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
    93. 

  93.       <em class="citetitle">RFC 2104</em>.
    94. 

  94.     </p>
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  95. </div>
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  96. <div class="refsect1" lang="en">
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  97. <a name="id2653085"></a><h2>AUTHOR</h2>
    98. 

  98. <p><span class="corpauthor">Internet Systems Consortium</span>
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