Improve IPv6 address handling in ocspserve

[jonathanio]

When setting an IPv6 address to listing on via the -address command-line argument for both serve and ocspserve, the latter errors unless the address is escaped:

# cfssl ocspserve -db-config=db-config.json -responses=responses.txt -address=::1 -port=8889
2021/05/08 17:00:00 [INFO] Now listening on ::1:8889
listen tcp: address ::1:8889: too many colons in address

However, serve uses the net library to process the address and port, which results in the enforced escaping of IPv6 addresses regardless of if the address is already enclosed in square brackets (e.g. [::1]):

# cfssl serve -config=config.json -db-config=db-config.json -ca=ca.pem -ca-key=ca-key.pem -address=::1 -port 8888
2021/05/08 17:00:00 [INFO] Now listening on [::1]:8888
# cfssl serve -config=config.json -db-config=db-config.json -ca=ca.pem -ca-key=ca-key.pem -address=[::1] -port 8888
2021/05/08 17:00:00 [INFO] Now listening on [[::1]]:8888
listen tcp: address [[::1]]:8888: missing port in address

This Pull Request changes oscpserve to use the same net library call as serve to provide consistency between the two modes when handling IPv6 addresses.

I'm unsure as to the level of "breaking change" this could be considered as. This does directly change the handling of an already existing command-line argument, but there is no documentation that I can see regarding -address (other than it exists and defaults to 127.0.0.1 if not set). More importantly, I don't see anything specific to -address and IPv6 addresses, or the differences in handling between serve and ocspserve.

I don't know if some more specific configuration on the handling of -address may be required as part of this to clean up handling between the modes?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.91%. Comparing base (6dd12c2) to head (00a28f6).
Report is 222 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1187      +/-   ##
==========================================
+ Coverage   54.72%   54.91%   +0.19%     
==========================================
  Files          77       77              
  Lines        6668     6668              
==========================================
+ Hits         3649     3662      +13     
+ Misses       2561     2551      -10     
+ Partials      458      455       -3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[thaJeztah]

LGTM (not a maintainer)

[thaJeztah]

/cc @nickysemenza (easy review)

[nickysemenza]

thanks!