The CAA response checking method has been refactored to have a
easier to follow straight-line control flow. Several bugs in it have
been fixed:
- Firstly, parameters for issue and issuewild directives were not
parsed, so any attempt to specify parameters would result in
a string mismatch with the CA CAA identity (e.g. "letsencrypt.org").
Moreover, the syntax as specified permits leading and trailing
whitespace, so a parameter-free record such as
" letsencrypt.org ; " would not be considered a match.
This has been fixed by stripping whitespace and parameters. The RFC
does not specify the criticality of parameters, so unknown
parameters (currently all parameters) are considered noncritical.
I justify this as follows:
If someone decides to nominate a CA in a CAA record, they can,
with trivial research, determine what parameters, if any, that
CA supports, and presumably in trusting them in the first place
is able to adequately trust that the CA will continue to support
those parameters. The risk from other CAs is zero because other CAs
do not process the parameters because the records in which they
appear they do not relate to them.
- Previously, all of the flag bits were considered to effectively mean
'critical'. However, the RFC specifies that all bits except for the
actual critical bit (decimal 128) should be ignored. In practice,
many people have misunderstood the RFC to mean that the critical bit
is decimal 1, so both bits are interpreted to mean 'critical', but
this change ignores all of the other bits. This ensures that the
remaining six bits are reasonably usable for future standards action
if any need should arise.
- Previously, existence of an "issue" directive but no "issuewild"
directive was essentially equivalent to an unsatisfiable "issuewild"
directive, meaning that no wildcard identifiers could pass the CAA
check. This is contrary to the RFC, which states that issuewild
should default to what is specified for "issue" if no issuewild
directives are specified. (This is somewhat moot since boulder
doesn't currently support wildcard issuance.)
- Conversely, existence of an "issuewild" directive but no "issue"
directive would cause CAA validation for a non-wildcard identifier
to fail, which was contrary to the RFC. This has been fixed.
- More generally, existence of any unknown non-critical directive, say
"foobar", would cause the CAA checking code to act as though an
unsatisfiable "issue" directive existed, preventing any issuance.
This has been fixed.
Test coverage for corner cases is enhanced and provides regression
testing for these bugs.
statsd statistics have been added for tracking the relative frequency
of occurrence of different CAA features and outcomes. I added these on
a whim suspecting that they may be of interest.
Fixes#1436.
This is more what we expect from a dns server.
dig A nx.google.com @ns2.google.com
; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> A nx.google.com @ns2.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 28643
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;nx.google.com. IN A
;; AUTHORITY SECTION:
google.com. 60 IN SOA ns4.google.com. dns-admin.google.com. 112672771 900 900 1800 60
;; Query time: 13 msec
;; SERVER: 216.239.34.10#53(216.239.34.10)
;; WHEN: Thu Jan 21 14:44:06 CET 2016
;; MSG SIZE rcvd: 81
VS
dig A www.google.com @ns2.google.com
; <<>> DiG 9.9.5-3ubuntu0.7-Ubuntu <<>> A www.google.com @ns2.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18684
;; flags: qr aa rd; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available
;; QUESTION SECTION:
;www.google.com. IN A
;; ANSWER SECTION:
www.google.com. 300 IN A 64.233.184.99
www.google.com. 300 IN A 64.233.184.105
www.google.com. 300 IN A 64.233.184.106
www.google.com. 300 IN A 64.233.184.104
www.google.com. 300 IN A 64.233.184.147
www.google.com. 300 IN A 64.233.184.103
;; Query time: 13 msec
;; SERVER: 216.239.34.10#53(216.239.34.10)
;; WHEN: Thu Jan 21 14:44:32 CET 2016
;; MSG SIZE rcvd: 128
Previously we would return a detailed errorString, which ProblemDetailsFromDNSError
would turn into a generic, uninformative "Server failure at resolver".
Now we return a new internal dnsError type, which ProblemDetailsFromDNSError can
turn into a more informative message to be shown to the user.
This provides a means to add retries to DNS look ups, and, with some
future work, end retries early if our request deadline is blown. That
future work is tagged with #1292.
Updates #1258
This moves the RTT metrics calculation inside of the DNSResolver. This
cleans up code in the RA and VA and makes some adding retries to the
DNSResolver less ugly to do.
Note: this will put `Rate` and `RTT` after the name of DNS query
type (`A`, `MX`, etc.). I think that's fine and desirable. We aren't
using this data in alerts or many dashboards, yet, so a flag day is
okay.
Fixes#1124
Moves the DNS code from core to dns and renames the dns package to bdns
to be clearer.
Fixes#1260 and will be good to have while we add retries and such.
Hugo Landau