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c63ebf815c8a874525cf18670ad74847f7fc7b26Christian Maeder - Copyright (C) 2004-2009 Internet Systems Consortium, Inc. ("ISC")
456238178f89e5a3de2988ee6c8af924297d52d9Christian Maeder - Copyright (C) 2000-2003 Internet Software Consortium.
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5191fa24c532d1f67e7a642e9aece65efb8a0975Christian Maeder - purpose with or without fee is hereby granted, provided that the above
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1aee4aaddde105264c1faf394d88e302c05094ffChristian Maeder<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
f4a2a20e49f41b2afa657e5e64d9e349c7faa091Christian Maeder<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>
1aee4aaddde105264c1faf394d88e302c05094ffChristian Maeder Versions of BIND 9 up to and including BIND 9.6 had a bug causing
8b767d09a78927b111f5596fdff9ca7d2c1a439fChristian Maeder HMAC-SHA* TSIG keys which were longer than the digest length of the
8b767d09a78927b111f5596fdff9ca7d2c1a439fChristian Maeder hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
8b767d09a78927b111f5596fdff9ca7d2c1a439fChristian Maeder longer than 256 bits, etc) to be used incorrectly, generating a
8b767d09a78927b111f5596fdff9ca7d2c1a439fChristian Maeder message authentication code that was incompatible with other DNS
8b767d09a78927b111f5596fdff9ca7d2c1a439fChristian Maeder implementations.
d54cd08a4cfa26256c38d8ed12c343adbfe1a0e3Christian Maeder This bug has been fixed in BIND 9.7. However, the fix may
23b4e542dca35852f58d1fb3f7d9078c1de5ab06Christian Maeder cause incompatibility between older and newer versions of
8a78868bae2ec6838c87366c35c57e109154c51eChristian Maeder BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
8cacad2a09782249243b80985f28e9387019fe40Christian Maeder modifies those keys to restore compatibility.
363939beade943a02b31004cea09dec34fa8a6d9Christian Maeder To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
014dc30f64ec25e4790cca987d4d1e6635430510Christian Maeder specify the key's algorithm and secret on the command line. If the
f04e8f3ff56405901be968fd4c6e9769239f1a9bKlaus Luettich secret is longer than the digest length of the algorithm (64 bytes
6aea82c63ba1d2efc0329bc784a14e521469ec20Christian Maeder for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
6aea82c63ba1d2efc0329bc784a14e521469ec20Christian Maeder new secret will be generated consisting of a hash digest of the old
431d34c7007a787331c4e5ec997badb0f8190fc7Christian Maeder secret. (If the secret did not require conversion, then it will be
f1541d4a151dbd08002dbd14e7eb1d5dde253689Christian Maeder printed without modification.)
6dc9bc98d0854fe2e3dd3bfc4275096a0c28ee1cChristian Maeder<a name="id272868"></a><h2>SECURITY CONSIDERATIONS</h2>
63f0e65a37b95621334db9ee4ba0cd9d826f5c0fChristian Maeder Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
61fa0ac06ede811c7aad54ec4c4202346727368eChristian Maeder are shortened, but as this is how the HMAC protocol works in
c0c2380bced8159ff0297ece14eba948bd236471Christian Maeder operation anyway, it does not affect security. RFC 2104 notes,
63f0e65a37b95621334db9ee4ba0cd9d826f5c0fChristian Maeder "Keys longer than [the digest length] are acceptable but the
63f0e65a37b95621334db9ee4ba0cd9d826f5c0fChristian Maeder extra length would not significantly increase the function
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