1 files changed, 57 insertions, 0 deletions
diff --git a/src/marlin.core/functional/SshKeyGitCredential.cs b/src/marlin.core/functional/SshKeyGitCredential.cs
new file mode 100644
index 0000000..9183a66
--- /dev/null
+++ b/src/marlin.core/functional/SshKeyGitCredential.cs
@@ -0,0 +1,57 @@
+namespace marlin.core.functional;
+
+using System.Diagnostics;
+
+/// <summary>
+/// SSH auth via a private key. The key is written to a per-invocation temp file
+/// (owner-read/write only) and deleted as soon as the git process that used it exits —
+/// ssh has no clean way to take key material via stdin/env, so a short-lived file is
+/// the least-bad option.
+/// </summary>
+public sealed class SshKeyGitCredential : IGitCredential
+{
+    private readonly string _privateKeyPem;
+
+    public SshKeyGitCredential(string privateKeyPem)
+    {
+        this._privateKeyPem = privateKeyPem;
+    }
+
+    public async Task<IAsyncDisposable> ApplyAsync(ProcessStartInfo psi)
+    {
+        string keyPath = Path.Combine(Path.GetTempPath(), $"marlin_{Guid.NewGuid():N}.key");
+        await File.WriteAllTextAsync(keyPath, this._privateKeyPem);
+
+        if (!OperatingSystem.IsWindows())
+            File.SetUnixFileMode(keyPath, UnixFileMode.UserRead | UnixFileMode.UserWrite);
+
+        psi.Environment["GIT_SSH_COMMAND"] =
+            $"ssh -i \"{keyPath}\" -o IdentitiesOnly=yes -o StrictHostKeyChecking=accept-new";
+
+        return new TempKeyFile(keyPath);
+    }
+
+    private sealed class TempKeyFile : IAsyncDisposable
+    {
+        private readonly string _path;
+
+        public TempKeyFile(string path)
+        {
+            this._path = path;
+        }
+
+        public ValueTask DisposeAsync()
+        {
+            try
+            {
+                File.Delete(this._path);
+            }
+            catch (IOException)
+            {
+                // best-effort cleanup; a leftover temp file is not worth failing the caller over
+            }
+
+            return ValueTask.CompletedTask;
+        }
+    }
+}