IsDomainName: check for escape as last character

[miekg]

Keep track if the escape, if still true when returning isDomainName should return false.

TODO:

• Should still be done in packDomainName as well.
• And that should be tested
• Some tests now fail

There are multiple other places that supposedly also check for this, but they are not called in the parsing.

Fixes: #1528

Signed-off-by: Miek Gieben [email protected]

[miekg]

testing in my tree, yields:

--- FAIL: TestUpdate2NoRdataUnpack (0.00s)
    update2_test.go:72: failed to unpack RR with zero rdata: SOA: dns: overflow unpacking uint32
    update2_test.go:72: failed to unpack RR with zero rdata: TSIG: dns: overflow unpacking uint16
    update2_test.go:72: failed to unpack RR with zero rdata: TKEY: dns: overflow unpacking uint16
FAIL

[janik-cloudflare]

I've applied this to our DNS API repository which has a fairly extensive test suite, and everything looks good!

[janik-cloudflare]

Should still be done in packDomainName as well.

Maybe also on the lexer level so that . 1 IN TXT hello\ is also rejected? (I'd be happy to work on a PR for that, but it might take another two weeks or so.)

[miekg]

yes, please do. I've merged this for now, but there is indeed some followup work to be done