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

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  19. <!-- $Id: isc-hmac-fixup.docbook,v 1.2 2010/01/07 21:52:11 each Exp $ -->
  20. <refentry id="man.isc-hmac-fixup">
  21. <refentryinfo>
  22. <date>January 5, 2010</date>
  23. </refentryinfo>
  24. <refmeta>
  25. <refentrytitle><application>isc-hmac-fixup</application></refentrytitle>
  26. <manvolnum>1</manvolnum>
  27. <refmiscinfo>BIND9</refmiscinfo>
  28. </refmeta>
  29. <refnamediv>
  30. <refname><application>isc-hmac-fixup</application></refname>
  31. <refpurpose>fixes HMAC keys generated by older versions of BIND</refpurpose>
  32. </refnamediv>
  33. <docinfo>
  34. <copyright>
  35. <year>2010</year>
  36. <holder>Internet Systems Consortium, Inc. ("ISC")</holder>
  37. </copyright>
  38. </docinfo>
  39. <refsynopsisdiv>
  40. <cmdsynopsis>
  41. <command>isc-hmac-fixup</command>
  42. <arg choice="req"><replaceable class="parameter">algorithm</replaceable></arg>
  43. <arg choice="req"><replaceable class="parameter">secret</replaceable></arg>
  44. </cmdsynopsis>
  45. </refsynopsisdiv>
  46. <refsect1>
  47. <title>DESCRIPTION</title>
  48. <para>
  49. Versions of BIND 9 up to and including BIND 9.6 had a bug causing
  50. HMAC-SHA* TSIG keys which were longer than the digest length of the
  51. hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
  52. longer than 256 bits, etc) to be used incorrectly, generating a
  53. message authentication code that was incompatible with other DNS
  54. implementations.
  55. </para>
  56. <para>
  57. This bug has been fixed in BIND 9.7. However, the fix may
  58. cause incompatibility between older and newer versions of
  59. BIND, when using long keys. <command>isc-hmac-fixup</command>
  60. modifies those keys to restore compatibility.
  61. </para>
  62. <para>
  63. To modify a key, run <command>isc-hmac-fixup</command> and
  64. specify the key's algorithm and secret on the command line. If the
  65. secret is longer than the digest length of the algorithm (64 bytes
  66. for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
  67. new secret will be generated consisting of a hash digest of the old
  68. secret. (If the secret did not require conversion, then it will be
  69. printed without modification.)
  70. </para>
  71. </refsect1>
  72. <refsect1>
  73. <title>SECURITY CONSIDERATIONS</title>
  74. <para>
  75. Secrets that have been converted by <command>isc-hmac-fixup</command>
  76. are shortened, but as this is how the HMAC protocol works in
  77. operation anyway, it does not affect security. RFC 2104 notes,
  78. "Keys longer than [the digest length] are acceptable but the
  79. extra length would not significantly increase the function
  80. strength."
  81. </para>
  82. </refsect1>
  83. <refsect1>
  84. <title>SEE ALSO</title>
  85. <para>
  86. <citetitle>BIND 9 Administrator Reference Manual</citetitle>,
  87. <citetitle>RFC 2104</citetitle>.
  88. </para>
  89. </refsect1>
  90. <refsect1>
  91. <title>AUTHOR</title>
  92. <para><corpauthor>Internet Systems Consortium</corpauthor>
  93. </para>
  94. </refsect1>
  95. </refentry><!--
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