Fri 29 Sep 2017

getdns-1.2.0 release

06e6494b5d8b9404f439d5a98a3ab8f1f4b3557fb7aa3db005b021a6289b4229

Dear all,

We have a new feature release version 1.2.0 of getdns.

This release contains two new features:

  • Built-in DNSSEC trust-anchor management:
    Zero configuration DNSSEC
  • Better TLS upstream failure management, more resilient to transient connectivity loss and laptop "sleeps" etc.

and

  • An updated version of Stubby (0.1.3) with YAML configuration files.

Zero configuration DNSSEC

Until now, we've assumed an external system component (like unbound-anchor) to do the trust-anchor management for getdns, but this is not optimal. Ideally applications that want to use DNSSEC validation, for example to perform DANE, would want to be able to rely on an application library to deliver DNSSEC, without requiring additional system configuration. This release includes a form of built-in trust-anchor management modelled on RFC7958, that is suitable for a resolver library which can not assume reliable up-time and which we have named: Zero configuration DNSSEC.

With Zero configuration DNSSEC, the "root-anchors.xml" file (from http://data.iana.org/root-anchors/root-anchors.xml) will be verified by validating the S/MIME signatures (stored separately in "root-anchors.p7s") with the ICANN Root Certificate Authority.

Trust anchors from "root-anchors.xml" will be used only when the accompanying "root-anchors.p7s" matches and validates and when either:

  • There were no other trust anchors provided, either by the default trust anchor file (likely either /etc/unbound/getdns-root.key or /usr/local/etc/unbound/getdns-root.key), or set explicitly by the application with the getdns_context_set_dnssec_trust_anchors() function, or
  • The available trust anchors (from the default location or set explicitly by the application) caused the root DNSKEY RRset to fail validation.

The "root-anchors.xml" and "root-anchors.p7s" files will be tried to read from a location for storing library specific data: ${HOME}/.getdns/ on Unix like systems (Linux, BSD's, MacOS) and %AppData%\getdns on Windows.

When trust anchors from "root-anchors.xml" are used, the root DNSKEY is also tracked (for changes) and a copy of it is stored in a "root.key" file in the library specific data directory.

A (new) version of "root-anchors.xml" and "root-anchors.p7s" will be retrieved from data.iana.org, when either:

  • The library specific data directory is (creatable and) writeable by the current user, but the "root-anchors.xml" or "root-anchors.p7s" files were absent, or
  • There is a new root DNSKEY RRset (or signature) and it contains keys with ID's which were not in "root-anchors.xml".

Zero configuration DNSSEC assumes DNSSEC with the ICANN root trust-anchors and is configured to use the ICANN defaults defined in RFC7958, but all default parameters can be adapted to fit alternate DNS(SEC) roots, with:

Better TLS upstream failure management

RFC7858 suggested a back-off period of one hour on failing TLS upstreams. However this is not a resilient and practical demeanor in practice when short-term network outages or connection loss caused, for example, by laptops going to sleep.

This release introduces a new TLS upstream failure management scheme in which the back-off time is incremented gradually from 1 second up, and doubled each retry with a maximum set by the getdns_context_set_tls_backoff_time() function. Also, back-off time is ignored when there are no more responding TLS upstreams and the upstream with the least amount of retries will be used for retrying first.

Stubby will be much more resilient against short term outages and connection losses with this scheme.

YAML configuration files for Stubby

This release comes with an updated version of Stubby (version 0.1.3) with the new improvement to read configuration files in YAML format.

Previously Stubby would read configuration files in the JSON like format that is understood by getdns. However, the necessity to deal with opening and closing brackets and the lack of comments make it unsuitable for human consumption. YAML is much better readable and most importantly: can be annotated with comments and is as such a good fit for configuration files.

Stubby configuration files are now specified in YAML format by default. JSON format can still be used if it is given on the command line with the -C flag.

Don't forget that the --with-stubby option needs to be used with configure when you want to build Stubby alongside the library. When build with Stubby, there is an additional dependency on libyaml for the stubby binary only.

Also note that the primary location for Stubby has moved to the dnsprivacy.org website.


ChangeLog:
* 2017-09-29: Version 1.2.0
  * Bugfix of rc1: authentication of first query with TLS
    Thanks Travis Burtrum
  * A function to set the location for library specific data,
    like trust-anchors: getdns_context_set_appdata().
  * Zero configuration DNSSEC - build upon the scheme
    described in RFC7958.  The URL from which to fetch
    the trust anchor, the verification CA and email
    can be set with the new getdns_context_set_trust_anchor_url(),
    getdns_context_set_trust_anchor_verify_CA() and
    getdns_context_set_trust_anchor_verify_email() functions.
    The default values are to fetch from IANA and to validate
    with the ICANN CA.
  * Update of Stubby with yaml configuration file and
    logging from a certain severity support.
  * Fix tpkg exit status on test failure. Thanks Jim Hague.
  * Refined logging levels for upstream statistics
  * Reuse (best behaving) backed-off TLS upstreams when non are usable.
  * Let TLS upstreams back-off a incremental amount of time.
    Back-off time starts with 1 second and is doubled each failure, but
    will not exceed the time given by getdns_context_set_tls_backoff_time()
  * Make TLS upstream management more resilient to temporary outages
    (like laptop sleeps)

Related

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