Skip the implicit trailing `.` in `HumanReadableName`'s domain

Domain names implicitly have a trailing `.`, which we require in
bLIP 32 but generally shouldn't be exposing to the user in
`HumanReadableName`s (after all, they're human-readable). Here we
make sure the trailing `.` is dropped in `HumanReadableName`s
before we re-add them when building the bLIP 32 messages.

diff --git a/lightning/src/onion_message/dns_resolution.rs b/lightning/src/onion_message/dns_resolution.rs
index bbf8caa4f71923b246bea86c39ef007b630919b7..0f6071e73a3f05c753f5058af859fbbbc3d92b8a 100644 (file)
--- a/lightning/src/onion_message/dns_resolution.rs
+++ b/lightning/src/onion_message/dns_resolution.rs
@@ -198,7 +198,12 @@ pub struct HumanReadableName {
 impl HumanReadableName {
        /// Constructs a new [`HumanReadableName`] from the `user` and `domain` parts. See the
        /// struct-level documentation for more on the requirements on each.
-       pub fn new(user: String, domain: String) -> Result<HumanReadableName, ()> {
+       pub fn new(user: String, mut domain: String) -> Result<HumanReadableName, ()> {
+               // First normalize domain and remove the optional trailing `.`
+               if domain.ends_with(".") {
+                       domain.pop();
+               }
+               // Note that `REQUIRED_EXTRA_LEN` includes the (now implicit) trailing `.`
                const REQUIRED_EXTRA_LEN: usize = ".user._bitcoin-payment.".len() + 1;
                if user.len() + domain.len() + REQUIRED_EXTRA_LEN > 255 {
                        return Err(());