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59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive<tr><th colspan="3" align="center"><span class="application">isc-hmac-fixup</span></th></tr>
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5a58787efeb02a1c3f06569d019ad81fd2efa06end<p><span class="application">isc-hmac-fixup</span> — fixes HMAC keys generated by older versions of BIND</p>
5a58787efeb02a1c3f06569d019ad81fd2efa06end<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>
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive Versions of BIND 9 up to and including BIND 9.6 had a bug causing
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive HMAC-SHA* TSIG keys which were longer than the digest length of the
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive hash algorithm (i.e., SHA1 keys longer than 160 bits, SHA256 keys
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive longer than 256 bits, etc) to be used incorrectly, generating a
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive message authentication code that was incompatible with other DNS
0e2778c974d0e3a799b138249013eba9400d36c9nd implementations.
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive This bug has been fixed in BIND 9.7. However, the fix may
0e2778c974d0e3a799b138249013eba9400d36c9nd cause incompatibility between older and newer versions of
0e2778c974d0e3a799b138249013eba9400d36c9nd BIND, when using long keys. <span class="command"><strong>isc-hmac-fixup</strong></span>
0e2778c974d0e3a799b138249013eba9400d36c9nd modifies those keys to restore compatibility.
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive To modify a key, run <span class="command"><strong>isc-hmac-fixup</strong></span> and
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive specify the key's algorithm and secret on the command line. If the
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive secret is longer than the digest length of the algorithm (64 bytes
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive for SHA1 through SHA256, or 128 bytes for SHA384 and SHA512), then a
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive new secret will be generated consisting of a hash digest of the old
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive secret. (If the secret did not require conversion, then it will be
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive printed without modification.)
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive<a name="id-1.14.30.8"></a><h2>SECURITY CONSIDERATIONS</h2>
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive Secrets that have been converted by <span class="command"><strong>isc-hmac-fixup</strong></span>
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive are shortened, but as this is how the HMAC protocol works in
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive operation anyway, it does not affect security. RFC 2104 notes,
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive "Keys longer than [the digest length] are acceptable but the
59879db9d12c2ea10f77b2c44d6d3aba89bb9cb3slive extra length would not significantly increase the function
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