Test private key parsing for commentless edge case

ssh-encoding/src/reader.rs

@@ -178,6 +178,10 @@ pub struct NestedReader<'r, R: Reader> {
 
 impl<'r, R: Reader> Reader for NestedReader<'r, R> {
     fn read<'o>(&mut self, out: &'o mut [u8]) -> Result<&'o [u8]> {
+        if out.is_empty() {
+            return Ok(out);
+        }
+
         let remaining_len = self
             .remaining_len
             .checked_sub(out.len())

ssh-key/tests/examples/padless_wonder

@@ -0,0 +1,8 @@
+-----BEGIN OPENSSH PRIVATE KEY-----
+b3BlbnNzaC1rZXktdjEAAAAABG5vbmUAAAAEbm9uZQAAAAAAAAABAAAAaAAAABNlY2RzYS
+1zaGEyLW5pc3RwMjU2AAAACG5pc3RwMjU2AAAAQQRx3l5o/ZI7bNGXguxVI/VmDd/SIwUo
+nlZHbHSmwBSeHPT7RisjBbiXnS829RrZ2o+Ix34GFtLN7z+SBHViPRVuAAAAmOCDDMLggw
+zCAAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBHHeXmj9kjts0ZeC
+7FUj9WYN39IjBSieVkdsdKbAFJ4c9PtGKyMFuJedLzb1Gtnaj4jHfgYW0s3vP5IEdWI9FW
+4AAAAgNEF96jnfIuhkq4ECZqNPe98Fv1SFb5evUQAq3/MtkKEAAAAA
+-----END OPENSSH PRIVATE KEY-----

ssh-key/tests/private_key.rs

@@ -46,6 +46,11 @@ 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");
 
+/// OpenSSH-formatted private key with no internal or external padding, and no comment
+/// Trips a corner case in base64ct
+#[cfg(feature = "ecdsa")]
+const OPENSSH_PADLESS_WONDER_EXAMPLE: &str = include_str!("examples/padless_wonder");
+
 /// Get a path into the `tests/scratch` directory.
 #[cfg(feature = "std")]
 pub fn scratch_path(filename: &str) -> PathBuf {
@@ -129,6 +134,24 @@ fn decode_ecdsa_p256_openssh() {
     assert_eq!("[email protected]", key.comment());
 }
 
+#[cfg(feature = "ecdsa")]
+#[test]
+fn decode_padless_wonder_openssh() {
+    let key = PrivateKey::from_openssh(OPENSSH_PADLESS_WONDER_EXAMPLE).unwrap();
+    assert_eq!(
+        Algorithm::Ecdsa {
+            curve: EcdsaCurve::NistP256
+        },
+        key.algorithm(),
+    );
+    assert_eq!(Cipher::None, key.cipher());
+    assert_eq!(KdfAlg::None, key.kdf().algorithm());
+    assert!(key.kdf().is_none());
+
+    #[cfg(feature = "alloc")]
+    assert_eq!("", key.comment());
+}
+
 #[cfg(feature = "ecdsa")]
 #[test]
 fn decode_ecdsa_p384_openssh() {