Use hostname-validator crate for hostname validation

Cargo.lock

@@ -154,6 +154,7 @@ dependencies = [
  "educe",
  "fs-mistrust",
  "futures",
+ "hostname-validator",
  "humantime-serde",
  "libc",
  "once_cell",
@@ -1489,6 +1490,12 @@ dependencies = [
  "digest 0.10.3",
 ]
 
+[[package]]
+name = "hostname-validator"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f558a64ac9af88b5ba400d99b579451af0d39c6d360980045b91aac966d705e2"
+
 [[package]]
 name = "http"
 version = "0.2.8"

crates/arti-client/Cargo.toml

@@ -60,6 +60,7 @@ directories = "4"
 educe = "0.4.6"
 fs-mistrust = { path = "../fs-mistrust", version = "0.5.0", features = ["serde"] }
 futures = "0.3.14"
+hostname-validator = "1.1.1"
 humantime-serde = "1.1.1"
 libc = "0.2"
 pin-project = "1"

crates/arti-client/src/address.rs

@@ -363,25 +363,8 @@ impl DangerouslyIntoTorAddr for SocketAddrV6 {
 /// Check whether `hostname` is a valid hostname or not.
 ///
 /// (Note that IPv6 addresses don't follow these rules.)
-///
-/// TODO: Check whether the rules given here are in fact the same rules
-/// as Tor follows, and whether they conform to anything.
 fn is_valid_hostname(hostname: &str) -> bool {
-    /// Check if we have the valid characters for a hostname
-    fn is_valid_char(byte: u8) -> bool {
-        ((b'a'..=b'z').contains(&byte))
-            || ((b'A'..=b'Z').contains(&byte))
-            || ((b'0'..=b'9').contains(&byte))
-            || byte == b'-'
-            || byte == b'.'
-    }
-
-    !(hostname.bytes().any(|byte| !is_valid_char(byte))
-        || hostname.ends_with('-')
-        || hostname.starts_with('-')
-        || hostname.ends_with('.')
-        || hostname.starts_with('.')
-        || hostname.is_empty())
+    hostname_validator::is_valid(hostname)
 }
 
 #[cfg(test)]