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fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte<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>
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte Versions of BIND 9 up to and including BIND 9.6 had a bug causing
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte HMAC-SHA* TSIG keys which were longer than the digest length of the
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte longer than 256 bits, etc) to be used incorrectly, generating a
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte message authentication code that was incompatible with other DNS
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte implementations.
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte This bug has been fixed in BIND 9.7. However, the fix may
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte cause incompatibility between older and newer versions of
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe BIND, when using long keys. <span><strong class="command">isc-hmac-fixup</strong></span>
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte modifies those keys to restore compatibility.
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte To modify a key, run <span><strong class="command">isc-hmac-fixup</strong></span> and
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe specify the key's algorithm and secret on the command line. If the
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe secret is longer than the digest length of the algorithm (64 bytes
7014882c6a3672fd0e5d60200af8643ae53c5928Richard Lowe for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte new secret will be generated consisting of a hash digest of the old
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte secret. (If the secret did not require conversion, then it will be
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte printed without modification.)
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte<a name="id2625249"></a><h2>SECURITY CONSIDERATIONS</h2>
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte Secrets that have been converted by <span><strong class="command">isc-hmac-fixup</strong></span>
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte are shortened, but as this is how the HMAC protocol works in
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte operation anyway, it does not affect security. RFC 2104 notes,
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte "Keys longer than [the digest length] are acceptable but the
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte extra length would not significantly increase the function
fcf3ce441efd61da9bb2884968af01cb7c1452ccJohn Forte <em class="citetitle">BIND 9 Administrator Reference Manual</em>,