Add newline to PublicKey::write_openssh_file output (#188)

Also adds an integration test to ensure that the file output matches
what `ssh-keygen` generates byte-for-byte.

The `ToString` impl still omits the newline.

To avoid making breaking changes, it always uses `\n` as the newline,
however perhaps in a future breaking release it could be changed to
accept `LineEnding` so as to match `PrivateKey::write_openssh_file`.

ssh-key/src/public.rs

@@ -232,7 +232,9 @@ impl PublicKey {
     /// Write public key as an OpenSSH-formatted file.
     #[cfg(feature = "std")]
     pub fn write_openssh_file(&self, path: &Path) -> Result<()> {
-        let encoded = self.to_openssh()?;
+        let mut encoded = self.to_openssh()?;
+        encoded.push('\n'); // TODO(tarcieri): OS-specific line endings?
+
         fs::write(path, encoded.as_bytes())?;
         Ok(())
     }

ssh-key/tests/private_key.rs

@@ -12,7 +12,7 @@ use ssh_key::LineEnding;
 #[cfg(all(feature = "std"))]
 use {
     ssh_key::PublicKey,
-    std::{io, process},
+    std::{io, path::PathBuf, process},
 };
 
 /// DSA OpenSSH-formatted public key
@@ -46,6 +46,12 @@ const OPENSSH_RSA_4096_EXAMPLE: &str = include_str!("examples/id_rsa_4096");
 #[cfg(feature = "alloc")]
 const OPENSSH_OPAQUE_EXAMPLE: &str = include_str!("examples/id_opaque");
 
+/// Get a path into the `tests/scratch` directory.
+#[cfg(feature = "std")]
+pub fn scratch_path(filename: &str) -> PathBuf {
+    PathBuf::from(&format!("tests/scratch/{}", filename))
+}
+
 #[cfg(feature = "alloc")]
 #[test]
 fn decode_dsa_openssh() {
@@ -468,7 +474,7 @@ fn encoding_integration_test(private_key: PrivateKey) {
         .replace(':', "-")
         .replace('/', "_");
 
-    let path = std::path::PathBuf::from(&format!("tests/scratch/{}", fingerprint));
+    let path = scratch_path(&fingerprint);
 
     private_key
         .write_openssh_file(&path, LineEnding::LF)

ssh-key/tests/public_key.rs

@@ -7,6 +7,9 @@ use std::collections::HashSet;
 #[cfg(feature = "ecdsa")]
 use ssh_key::EcdsaCurve;
 
+#[cfg(feature = "std")]
+use std::{fs, path::PathBuf};
+
 /// DSA OpenSSH-formatted public key
 #[cfg(feature = "alloc")]
 const OPENSSH_DSA_EXAMPLE: &str = include_str!("examples/id_dsa_1024.pub");
@@ -45,6 +48,12 @@ const OPENSSH_SK_ED25519_EXAMPLE: &str = include_str!("examples/id_sk_ed25519.pu
 #[cfg(feature = "alloc")]
 const OPENSSH_OPAQUE_EXAMPLE: &str = include_str!("examples/id_opaque.pub");
 
+/// Get a path into the `tests/scratch` directory.
+#[cfg(feature = "std")]
+pub fn scratch_path(filename: &str) -> PathBuf {
+    PathBuf::from(&format!("tests/scratch/{}.pub", filename))
+}
+
 #[cfg(feature = "alloc")]
 #[test]
 fn decode_dsa_openssh() {
@@ -386,3 +395,20 @@ fn public_keys_are_hashable() {
     let set = HashSet::from([&key]);
     assert_eq!(true, set.contains(&key));
 }
+
+#[cfg(feature = "std")]
+#[test]
+fn write_openssh_file() {
+    let example_key = OPENSSH_ED25519_EXAMPLE;
+    let key = PublicKey::from_openssh(example_key).unwrap();
+
+    let fingerprint = key
+        .fingerprint(Default::default())
+        .to_string()
+        .replace(':', "-")
+        .replace('/', "_");
+
+    let path = scratch_path(&fingerprint);
+    key.write_openssh_file(&path).unwrap();
+    assert_eq!(example_key, fs::read_to_string(&path).unwrap());
+}