Allow overriding domain used for TLS hostname verification

src/conn/mod.rs

@@ -550,7 +550,10 @@ impl Conn {
             self.write_struct(&ssl_request).await?;
             let conn = self;
             let ssl_opts = conn.opts().ssl_opts().cloned().expect("unreachable");
-            let domain = conn.opts().ip_or_hostname().into();
+            let domain = ssl_opts
+                .tls_hostname_override()
+                .unwrap_or_else(|| conn.opts().ip_or_hostname())
+                .into();
             conn.stream_mut()?.make_secure(domain, ssl_opts).await?;
             Ok(())
         } else {

src/io/tls/rustls_io.rs

@@ -136,8 +136,7 @@ impl ServerCertVerifier for DangerousVerifier {
             ) {
                 Ok(assertion) => Ok(assertion),
                 Err(ref e)
-                    if e.to_string().contains("NotValidForName")
-                        && self.skip_domain_validation =>
+                    if e.to_string().contains("NotValidForName") && self.skip_domain_validation =>
                 {
                     Ok(rustls::client::ServerCertVerified::assertion())
                 }

src/opts/mod.rs

@@ -144,6 +144,7 @@ pub struct SslOpts {
     root_cert_path: Option<Cow<'static, Path>>,
     skip_domain_validation: bool,
     accept_invalid_certs: bool,
+    tls_hostname_override: Option<Cow<'static, str>>,
 }
 
 impl SslOpts {
@@ -178,6 +179,18 @@ impl SslOpts {
         self
     }
 
+    /// If set, will override the hostname used to verify the server's certificate.
+    ///
+    /// This is useful when connecting to a server via a tunnel, where the server hostname
+    /// name is different from the hostname used to connect to the tunnel.
+    pub fn with_tls_hostname_override<T: Into<Cow<'static, str>>>(
+        mut self,
+        domain: Option<T>,
+    ) -> Self {
+        self.tls_hostname_override = domain.map(Into::into);
+        self
+    }
+
     #[cfg(any(feature = "native-tls", feature = "rustls-tls"))]
     pub fn client_identity(&self) -> Option<&ClientIdentity> {
         self.client_identity.as_ref()
@@ -194,6 +207,10 @@ impl SslOpts {
     pub fn accept_invalid_certs(&self) -> bool {
         self.accept_invalid_certs
     }
+
+    pub fn tls_hostname_override(&self) -> Option<&str> {
+        self.tls_hostname_override.as_ref().map(AsRef::as_ref)
+    }
 }
 
 /// Connection pool options.