external/bsd/bind/dist/bin/tools/isc-hmac-fixup.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">
  24 <a name="man.isc-hmac-fixup"></a><div class="titlepage"></div>
  25 <div class="refnamediv">
  26 <h2>Name</h2>
  27 <p><span class="application">isc-hmac-fixup</span> &#8212; fixes HMAC keys generated by older versions of BIND</p>
  28 </div>
  29 <div class="refsynopsisdiv">
  30 <h2>Synopsis</h2>
  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>
  32 </div>
  33 <div class="refsect1" lang="en">
  34 <a name="id2543366"></a><h2>DESCRIPTION</h2>
  35 <p>
  36       Versions of BIND 9 up to and including BIND 9.6 had a bug causing
  37       HMAC-SHA* TSIG keys which were longer than the digest length of the
  38       hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
  39       longer than 256 bits, etc) to be used incorrectly, generating a
  40       message authentication code that was incompatible with other DNS
  41       implementations.
  42     </p>
  43 <p>
  44       This bug has been fixed in BIND 9.7.  However, the fix may
  45       cause incompatibility between older and newer versions of
  46       BIND, when using long keys.  <span><strong class="command">isc-hmac-fixup</strong></span>
  47       modifies those keys to restore compatibility.
  48     </p>
  49 <p>
  50       To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
  51       specify the key's algorithm and secret on the command line.  If the
  52       secret is longer than the digest length of the algorithm (64 bytes
  53       for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
  54       new secret will be generated consisting of a hash digest of the old
  55       secret.  (If the secret did not require conversion, then it will be
  56       printed without modification.)
  57     </p>
  58 </div>
  59 <div class="refsect1" lang="en">
  60 <a name="id2543389"></a><h2>SECURITY CONSIDERATIONS</h2>
  61 <p>
  62       Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
  63       are shortened, but as this is how the HMAC protocol works in
  64       operation anyway, it does not affect security.  RFC 2104 notes,
  65       "Keys longer than [the digest length] are acceptable but the
  66       extra length would not significantly increase the function
  67       strength."
  68     </p>
  69 </div>
  70 <div class="refsect1" lang="en">
  71 <a name="id2543403"></a><h2>SEE ALSO</h2>
  72 <p>
  73       <em class="citetitle">BIND 9 Administrator Reference Manual</em>,
  74       <em class="citetitle">RFC 2104</em>.
  75     </p>
  76 </div>
  77 <div class="refsect1" lang="en">
  78 <a name="id2543489"></a><h2>AUTHOR</h2>
  79 <p><span class="corpauthor">Internet Systems Consortium</span>
  80     </p>
  81 </div>
  82 </div></body>
  83 </html>