Check PTR against FQDN (including dot at the end)

[fabian-z]

PTR records are returned with a dot at the end (as FQDN) by hickory_resolver.
Without this fix, SPF checks for some mail providers (for example Yahoo and OVH) will fail without indicating errors.

Example program, showing the issue for Yahoo (easy testing due to free / open registration)

use mail_auth::Resolver;

// This is the main function.
#[tokio::main]
async fn main() {
    let resolver = Resolver::new_google().unwrap();

    let result = resolver
        .verify_spf_sender("87.248.110.31".parse().unwrap(), "sonic307-54.consmr.mail.ir2.yahoo.com", "my-local-domain.org", "testmail@yahoo.com")
        .await;
    println!("{}", result.result());

}

Expected result: Pass
Actual Result without this fix: Neutral (due to failure checking PTR records)

Thanks for your efforts!

[fabian-z]

@mdecimus Again thanks for your efforts! Would be great to get this in for Stalwart mail-server 0.7.0, too. Please let me know if I can provide further assistance.

Tests are passing after providing test records matching those returned by hickory_resolver:

running 33 tests
test common::headers::test::chained_header_iterator ... ok
test common::headers::test::header_iterator ... ok
test common::headers::test::header_parser ... ok
test common::resolver::test::reverse_lookup_addr ... ok
test common::base32::tests::base32_hash ... ok
test common::auth_results::test::authentication_results ... ok
test dkim::parse::test::dkim_report_record_parse ... ok
test dkim::canonicalize::test::dkim_canonicalize ... ok
test dkim::parse::test::dkim_record_parse ... ok
test dkim::verify::test::dkim_strip_signature ... ok
test dkim::parse::test::dkim_signature_parse ... ok
test dmarc::parse::test::parse_dmarc ... ok
test dmarc::verify::test::dmarc_verify ... ok
test mta_sts::parse::tests::mta_sts_record_parse ... ok
test mta_sts::parse::tests::tlsrpt_parse ... ok
test dkim::sign::test::dkim_sign ... ok
test report::arf::generate::test::arf_report_generate ... ok
test dmarc::verify::test::dmarc_verify_report_address ... ok
test report::arf::parse::test::arf_report_parse ... ok
test arc::verify::test::arc_verify ... ok
test report::tlsrpt::parse::tests::tlsrpt_parse ... ok
test report::dmarc::parse::test::dmarc_report_parse ... ok
test spf::parse::test::parse_ip4 ... ok
test spf::macros::test::expand_macro ... ok
test spf::parse::test::parse_ip6 ... ok
test report::dmarc::generate::test::dmarc_report_generate ... ok
test spf::parse::test::parse_spf ... ok
test report::tlsrpt::generate::test::tlsrpt_generate ... ok
test report::dmarc::parse::test::dmarc_report_eml_parse ... ok
test dkim::verify::test::dkim_verify ... ok
test dkim::sign::test::dkim_sign_verify ... ok
test spf::verify::test::spf_verify ... ok
test arc::seal::test::arc_seal ... ok

test result: ok. 33 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.65s

[mdecimus]

Hi @fabian-z , thanks for reporting this and also the PR! I have fixed this bug by stripping the dot from Hickory's response.

This fix will be included in version 0.7.0 of Stalwart Mail Server.