Lettre panics when there is an invalid certificate or invalid hostname match

[BlackDex]

When using STARTTLS and having a wrong host (or by using an IP) which doesn't match the one in the certificate a panic is generated.

To Reproduce
Make a connection to a STARTTLS enabled mail server, but instead of using the DNS/Hostname use it's IP instead.

Expected behavior
No panic, but a nice error which can be caught.
I know in the past this worked fine.

Environment (please complete the following information):

• Lettre version: 0.10.0-rc.3 and af157c5f2663d52aed1f3680ba72dc1c7f9fe6ec (Also 0.10.0-rc.2 and 0.10.0-rc.1)
• OS: Linux Ubuntu 20.04
• Cargo.toml: lettre = { version = "0.10.0-rc.3", features = ["smtp-transport", "builder", "serde", "native-tls", "hostname", "tracing"], default-features = false }

Backtrace

[panic][ERROR] thread 'unnamed' panicked at 'InnerNetworkStream::None must never be built': /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/net.rs:242
   0: vaultwarden::init_logging::{{closure}}
             at src/main.rs:179:25
   1: std::panicking::rust_panic_with_hook
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panicking.rs:628:17
   2: std::panicking::begin_panic::{{closure}}
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panicking.rs:544:9
   3: std::sys_common::backtrace::__rust_end_short_backtrace
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/sys_common/backtrace.rs:141:18
   4: std::panicking::begin_panic
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panicking.rs:543:12
   5: <lettre::transport::smtp::client::net::NetworkStream as std::io::Write>::write
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/net.rs:242:17
   6: std::io::Write::write_all
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/io/mod.rs:1527:19
   7: lettre::transport::smtp::client::connection::SmtpConnection::write
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/connection.rs:256:9
   8: lettre::transport::smtp::client::connection::SmtpConnection::command
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/connection.rs:250:9
   9: lettre::transport::smtp::client::connection::SmtpConnection::abort
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/connection.rs:179:21
  10: lettre::transport::smtp::client::connection::SmtpConnection::starttls
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/client/connection.rs:148:17
  11: lettre::transport::smtp::transport::SmtpClient::connection
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/transport.rs:222:17
  12: <lettre::transport::smtp::transport::SmtpTransport as lettre::transport::Transport>::send_raw
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/smtp/transport.rs:32:24
  13: lettre::transport::Transport::send
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/lettre-0.10.0-rc.3/src/transport/mod.rs:132:9
  14: vaultwarden::mail::send_email
             at src/mail.rs:471:11
  15: vaultwarden::mail::send_test
             at src/mail.rs:435:5
  16: vaultwarden::api::admin::test_smtp
             at src/api/admin.rs:288:9
  17: vaultwarden::api::admin::rocket_route_fn_test_smtp
             at src/api/admin.rs:284:4
  18: core::ops::function::Fn::call
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/core/src/ops/function.rs:70:5
  19: <F as rocket::handler::Handler>::handle
             at /home/mathijs/.cargo/git/checkouts/rocket-8bf16d9ca7e90bdc/263e39b/core/lib/src/handler.rs:177:9
  20: rocket::rocket::Rocket::route
             at /home/mathijs/.cargo/git/checkouts/rocket-8bf16d9ca7e90bdc/263e39b/core/lib/src/rocket.rs:297:27
  21: rocket::rocket::Rocket::route_and_process
             at /home/mathijs/.cargo/git/checkouts/rocket-8bf16d9ca7e90bdc/263e39b/core/lib/src/rocket.rs:243:34
  22: rocket::rocket::Rocket::dispatch
             at /home/mathijs/.cargo/git/checkouts/rocket-8bf16d9ca7e90bdc/263e39b/core/lib/src/rocket.rs:218:28
  23: <rocket::rocket::Rocket as hyper::server::Handler>::handle
             at /home/mathijs/.cargo/git/checkouts/rocket-8bf16d9ca7e90bdc/263e39b/core/lib/src/rocket.rs:83:24
  24: hyper::server::Worker<H>::keep_alive_loop
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/hyper-0.10.16/src/server/mod.rs:340:13
  25: hyper::server::Worker<H>::handle_connection
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/hyper-0.10.16/src/server/mod.rs:282:15
  26: hyper::server::handle::{{closure}}
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/hyper-0.10.16/src/server/mod.rs:242:34
  27: hyper::server::listener::spawn_with::{{closure}}
             at /home/mathijs/.cargo/registry/src/github.com-1ecc6299db9ec823/hyper-0.10.16/src/server/listener.rs:50:31
  28: std::sys_common::backtrace::__rust_begin_short_backtrace
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/sys_common/backtrace.rs:125:18
  29: std::thread::Builder::spawn_unchecked::{{closure}}::{{closure}}
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/thread/mod.rs:481:17
  30: <core::panic::unwind_safe::AssertUnwindSafe<F> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/core/src/panic/unwind_safe.rs:271:9
  31: std::panicking::try::do_call
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panicking.rs:403:40
  32: __rust_try
  33: std::panicking::try
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panicking.rs:367:19
  34: std::panic::catch_unwind
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/panic.rs:133:14
  35: std::thread::Builder::spawn_unchecked::{{closure}}
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/thread/mod.rs:480:30
  36: core::ops::function::FnOnce::call_once{{vtable.shim}}
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/core/src/ops/function.rs:227:5
  37: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/alloc/src/boxed.rs:1636:9
      <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/alloc/src/boxed.rs:1636:9
      std::sys::unix::thread::Thread::new::thread_start
             at /rustc/ac2d9fc509e36d1b32513744adf58c34bcc4f43c/library/std/src/sys/unix/thread.rs:106:17
  38: start_thread
             at /build/glibc-eX1tMB/glibc-2.31/nptl/pthread_create.c:477:8
  39: clone
             at /build/glibc-eX1tMB/glibc-2.31/misc/../sysdeps/unix/sysv/linux/x86_64/clone.S:95

[paolobarbolini]

Very strange. When compiling with --release it instead seems to return the correct error and not panic.

The InnerNetworkStream::None panic is caused by

lettre/src/transport/smtp/client/net.rs

Line 132 in af157c5

let tcp_stream = mem::replace(&mut self.inner, InnerNetworkStream::None);

lettre/src/transport/smtp/client/async_net.rs

Line 222 in af157c5

let tcp_stream = mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);

lettre/src/transport/smtp/client/async_net.rs

Line 245 in af157c5

let tcp_stream = mem::replace(&mut self.inner, InnerAsyncNetworkStream::None);

taking the connection out and not caring to put the connection back into self.inner if the TLS handshake fails, as propagating the error should be enough to cause the entire attempt to send the email to be dropped.

[BlackDex]

Quick fix people!
Works like a charm.