Support for CNAME records

README.md

@@ -61,7 +61,10 @@ service:
 
   # DNS records which users must add to their domain's DNS so that
   # Domani can serve the domains. All records given must route to this Domani
-  # instance. At least one record must be given.
+  # instance.
+  #
+  # A CNAME record with the primary_domain of this server is automatically
+  # included.
   dns_records:
     #- type: A
     #  addr: 127.0.0.1
@@ -69,6 +72,10 @@ service:
     #- type: AAAA
     #  addr: ::1
 
+    # NOTE that the name given here must resolve to the Domani server.
+    #- type: CNAME
+    #  name: domain.com
+
   # The domain name which will be used to serve the web interface of Domani. If
   # service.http.https_addr is enabled then an HTTPS certificate for this domain
   # will be retrieved automatically.
@@ -116,9 +123,14 @@ Within the shell which opens you can do `cargo run` to start a local instance.
 
 ## Roadmap
 
-* Support for CNAME records
 * Support for more backends than just git repositories, including:
     * IPFS/IPNS
     * Alternative URLs (reverse proxy)
     * Google Drive
     * Dropbox
+
+* Better support for dDNS servers. If a server is behind dDNS then users can
+  only add it to their domain via CNAME. If they add the CNAME (or ALIAS or
+  whatever) to the zone apex then Domani can't see that actual CNAME record (the
+  DNS server will flatten it to A records). This breaks Domani.
+

src/domain/checker.rs

@@ -24,9 +24,33 @@ pub enum CheckDomainError {
 pub enum DNSRecord {
     A(net::Ipv4Addr),
     AAAA(net::Ipv6Addr),
+    CNAME(domain::Name),
 }
 
 impl DNSRecord {
+    async fn check_a(
+        client: &mut AsyncClient,
+        domain: &trust_dns_client::rr::Name,
+        addr: &net::Ipv4Addr,
+    ) -> Result<bool, unexpected::Error> {
+        let response = client
+            .query(domain.clone(), DNSClass::IN, RecordType::A)
+            .await
+            .or_unexpected_while("querying A record")?;
+
+        let records = response.answers();
+
+        for record in records {
+            if let Some(RData::A(record_addr)) = record.data() {
+                if record_addr == addr {
+                    return Ok(true);
+                }
+            }
+        }
+
+        return Ok(false);
+    }
+
     async fn check_aaaa(
         client: &mut AsyncClient,
         domain: &trust_dns_client::rr::Name,
@@ -35,42 +59,42 @@ impl DNSRecord {
         let response = client
             .query(domain.clone(), DNSClass::IN, RecordType::AAAA)
             .await
-            .or_unexpected_while("querying A record")?;
+            .or_unexpected_while("querying AAAA record")?;
 
         let records = response.answers();
 
-        if records.len() != 1 {
-            return Ok(false);
+        for record in records {
+            if let Some(RData::AAAA(record_addr)) = record.data() {
+                if record_addr == addr {
+                    return Ok(true);
+                }
+            }
         }
 
-        // if the single record isn't a AAAA, or it's not the target AAAA, then return false
-        match records[0].data() {
-            Some(RData::AAAA(remote_addr)) if remote_addr == addr => Ok(true),
-            _ => return Ok(false),
-        }
+        return Ok(false);
     }
 
-    async fn check_a(
+    async fn check_cname(
         client: &mut AsyncClient,
         domain: &trust_dns_client::rr::Name,
-        addr: &net::Ipv4Addr,
+        cname: &trust_dns_client::rr::Name,
     ) -> Result<bool, unexpected::Error> {
         let response = client
-            .query(domain.clone(), DNSClass::IN, RecordType::A)
+            .query(domain.clone(), DNSClass::IN, RecordType::CNAME)
             .await
-            .or_unexpected_while("querying A record")?;
+            .or_unexpected_while("querying CNAME record")?;
 
         let records = response.answers();
 
-        if records.len() != 1 {
-            return Ok(false);
+        for record in records {
+            if let Some(RData::CNAME(record_cname)) = record.data() {
+                if record_cname == cname {
+                    return Ok(true);
+                }
+            }
         }
 
-        // if the single record isn't a A, or it's not the target A, then return false
-        match records[0].data() {
-            Some(RData::A(remote_addr)) if remote_addr == addr => Ok(true),
-            _ => return Ok(false),
-        }
+        return Ok(false);
     }
 
     async fn check(
@@ -81,6 +105,7 @@ impl DNSRecord {
         match self {
             Self::A(addr) => Self::check_a(client, domain, &addr).await,
             Self::AAAA(addr) => Self::check_aaaa(client, domain, &addr).await,
+            Self::CNAME(name) => Self::check_cname(client, domain, name.as_rr()).await,
         }
     }
 }

src/domain/name.rs

@@ -1,5 +1,5 @@
-use std::fmt;
 use std::str::FromStr;
+use std::{cmp, fmt};
 
 use serde::{de, Deserialize, Deserializer, Serialize, Serializer};
 use trust_dns_client::rr as trust_dns_rr;
@@ -40,6 +40,12 @@ impl FromStr for Name {
     }
 }
 
+impl cmp::PartialEq for Name {
+    fn eq(&self, other: &Self) -> bool {
+        self.inner == other.inner
+    }
+}
+
 impl Serialize for Name {
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
     where

src/main.rs

@@ -34,14 +34,6 @@ struct Cli {
 async fn main() {
     let cli = Cli::parse();
 
-    let config: domani::config::Config = {
-        let path = &cli.config_path;
-        let f = std::fs::File::open(path)
-            .unwrap_or_else(|e| panic!("failed to open config file at {}: {e}", path.display()));
-        serde_yaml::from_reader(f)
-            .unwrap_or_else(|e| panic!("failed to parse config file at {}: {e}", path.display()))
-    };
-
     env_logger::Builder::new()
         .filter_level(cli.log_level)
         .format_timestamp(
@@ -50,14 +42,47 @@ async fn main() {
         )
         .init();
 
+    let config = {
+        let mut config: domani::config::Config = {
+            let path = &cli.config_path;
+            let f = std::fs::File::open(path).unwrap_or_else(|e| {
+                panic!("failed to open config file at {}: {e}", path.display())
+            });
+            serde_yaml::from_reader(f).unwrap_or_else(|e| {
+                panic!("failed to parse config file at {}: {e}", path.display())
+            })
+        };
+
+        // primary_cname is a CNAME record which points to the primary domain of the service. Since
+        // the primary domain _must_ point to the service (otherwise HTTPS wouldn't work) it's
+        // reasonable to assume that a CNAME on any domain would suffice to point that domain to
+        // the service.
+        let primary_cname = domani::service::ConfigDNSRecord::CNAME {
+            name: config.service.primary_domain.clone(),
+        };
+
+        let dns_records_have_primary_cname = config
+            .service
+            .dns_records
+            .iter()
+            .any(|r| r == &primary_cname);
+
+        if !dns_records_have_primary_cname {
+            log::info!(
+                "Adding 'CNAME {}' to service.dns_records",
+                &config.service.primary_domain
+            );
+            config.service.dns_records.push(primary_cname);
+        }
+
+        config
+    };
+
     let origin_store = domani::origin::git::FSStore::new(&config.origin)
         .expect("git origin store initialization failed");
 
     let domain_checker = {
         let dns_records = config.service.dns_records.clone();
-        if dns_records.len() == 0 {
-            panic!("service.dns_records must have at least one record defined")
-        }
 
         domani::domain::checker::DNSChecker::new(
             &config.domain.dns,

src/service.rs

@@ -9,11 +9,12 @@ fn default_primary_domain() -> domain::Name {
     domain::Name::from_str("localhost").unwrap()
 }
 
-#[derive(Serialize, Deserialize, Clone)]
+#[derive(Serialize, Deserialize, Clone, PartialEq)]
 #[serde(tag = "type")]
 pub enum ConfigDNSRecord {
     A { addr: net::Ipv4Addr },
     AAAA { addr: net::Ipv6Addr },
+    CNAME { name: domain::Name },
 }
 
 impl From<ConfigDNSRecord> for domain::checker::DNSRecord {
@@ -21,6 +22,7 @@ impl From<ConfigDNSRecord> for domain::checker::DNSRecord {
         match r {
             ConfigDNSRecord::A { addr } => Self::A(addr),
             ConfigDNSRecord::AAAA { addr } => Self::AAAA(addr),
+            ConfigDNSRecord::CNAME { name } => Self::CNAME(name),
         }
     }
 }

src/service/http.rs

@@ -230,6 +230,9 @@ impl<'svc> Service {
             flat_config: service::util::FlatConfig,
             dns_records: &'a [service::ConfigDNSRecord],
             challenge_token: String,
+
+            domain_is_zone_apex: bool,
+            dns_records_have_cname: bool,
         }
 
         let config: domain::Domain = match domain_config.try_into() {
@@ -249,6 +252,12 @@ impl<'svc> Service {
             }
         };
 
+        let domain_is_zone_apex = args.domain.as_rr().num_labels() == 2;
+        let dns_records_have_cname = self.config.dns_records.iter().any(|r| match r {
+            service::ConfigDNSRecord::CNAME { .. } => true,
+            _ => false,
+        });
+
         self.render_page(
             "/domain_init.html",
             Response {
@@ -256,6 +265,9 @@ impl<'svc> Service {
                 flat_config: config.into(),
                 dns_records: &self.config.dns_records,
                 challenge_token: config_hash,
+
+                domain_is_zone_apex,
+                dns_records_have_cname,
             },
         )
     }

src/service/http/tpl/domain_init.html

@@ -49,11 +49,21 @@ query for your domain name. It can be <strong>one or more of</strong>:</p>
   <tr>
     <td>{{ this.type }}</td>
     <td>{{ lookup ../data "domain" }}</td>
+    {{ #if this.name }}
+    <td>{{ this.name }}</td>
+    {{ else }}
     <td>{{ this.addr }}</td>
+    {{ /if }}
   </tr>
   {{ /each }}
 </table>
 
+{{ #if data.domain_is_zone_apex }}{{ #if data.dns_records_have_cname }}
+<p>(Please note that not all DNS providers support putting a CNAME at the zone
+apex, while others support it via an alternative record type like ALIAS or
+ANAME.)</p>
+{{ /if }}{{ /if }}
+
 <p>Once both entries are installed, you can hit the following button to check
 your configuration and set up your domain.</p>