Fail if multiple matching devices are attached

Previously, we just applied our filter (if any) to all attached Nitrokey
devices and selected the first match when connection to a Nitrokey
device.  This may lead to unexpected behavior if multiple devices are
attached.  This patch changes the find_device function to return an
error if multiple matching devices are found.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/commands.rs b/src/commands.rs
index ac3d020..883110a 100644
--- a/src/commands.rs
+++ b/src/commands.rs
@@ -61,6 +61,13 @@ fn find_device(config: &config::Config) -> anyhow::Result<nitrokey::DeviceInfo>
   let device = iter
     .next()
     .with_context(|| format!("Nitrokey device not found{}", format_filter(config)))?;
+
+  anyhow::ensure!(
+    iter.next().is_none(),
+    "Multiple Nitrokey devices found{}.  Use the --model and --serial-number options to \
+    select one",
+    format_filter(config)
+  );
   Ok(device)
 }