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76 lines
2.7 KiB
Markdown
76 lines
2.7 KiB
Markdown
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DNSSEC and DANE
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===============
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[Back](index.md)
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**DNSSEC and DANE support in Smack and MiniDNS is still in its
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infancy. It should be considered experimental and not ready for
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production use at this time.** We would like to see more thorough
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testing and review by the security community. If you can help, then
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please do not hesitate to contact us.
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About
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-----
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DNSSEC ([RFC 4033](https://tools.ietf.org/html/rfc4033) and others)
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authenticates DNS answers, positive and negative ones. This means that
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if a DNS response secured by DNSSEC turns out to be authentic, then
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you can be sure that the domain either exists, and that the returned
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resource records (RRs) are the ones the domain owner authorized, or
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that the domain does not exists and that nobody tried to fake its non
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existence.
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The tricky part is that an application using DNSSEC can not determine
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whether a domain uses DNSSEC, does not use DNSSEC or if someone
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downgraded your DNS query using DNSSEC to a response without DNSSEC.
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[DANE](https://tools.ietf.org/html/rfc6698) allows the verification of
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a TLS certificate with information stored in the DNS system and
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secured by DNSSEC. Thus DANE requires DNSSEC.
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Prerequisites
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-------------
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From the three DNS resolver providers (MiniDNS, javax, dnsjava)
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supported by Smack only [MiniDNS](https://github.com/rtreffer/minidns)
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currently supports DNSSEC. MiniDNS is the default resolver when
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smack-android is used. For other configurations, make sure to add
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smack-resolver-minidns to your dependencies and call
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`MiniDnsResolver.setup()` prior using Smack (e.g. in a `static {}`
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code block).
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DNSSEC API
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----------
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Smack's DNSSEC API is very simple: Just use
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`ConnectionConfiguration.Builder..setDnssecMode(DnssecMode)` to enable
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DNSSEC. `DnssecMode` can be one of
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- `disabled`
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- `needsDnssec`
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- `needsDnssecAndDane`
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The default is `disabled`.
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If `needsDnssec` is used, then Smack will only connect if the DNS
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results required to determine a host for the XMPP domain could be
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verified using DNSSEC.
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If `needsDnssecAndDane` then DANE will be used to verify the XMPP
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service's TLS certificate if STARTTLS is used. Note that you may want
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to configure
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`ConnectionConfiguration.Builder.setSecurityMode(SecurityMode.required)`
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if you use this DNSSEC mode setting.
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Best practices
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--------------
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We recommend that applications using Smack's DNSSEC API do not ask the
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user if DNSSEC is avaialble. Instead they should check for DNSSEC
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suport on every connection attempt. Once DNSSEC support has been
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discovered, the application should use the `needsDnssec` mode for all
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future connection attempts. The same scheme can be applied when using
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DANE. This approach is similar to the scheme established by
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to
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["HTTP Strict Transport Security" (HSTS, RFC 6797)](https://tools.ietf.org/html/rfc6797).
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