Add support for SSH private key passphrases (#2331)

This adds support for encrypted SSH keys via passphrase.

Co-authored-by: Louis Ruch <louisruch@gmail.com>
Co-authored-by: Michael Gaffney <mgaffney@users.noreply.github.com>

internal/proto/controller/api/resources/credentials/v1/credential.proto

@@ -135,4 +135,23 @@ message SshPrivateKeyAttributes {
       that: "PrivateKeyHmac"
     }
   ]; // @gotags: `class:"public"`
+
+  // Input only. The passphrase for the SSH private key associated with the credential.
+  google.protobuf.StringValue private_key_passphrase = 40 [
+    json_name = "private_key_passphrase",
+    (custom_options.v1.generate_sdk_option) = true,
+    (custom_options.v1.mask_mapping) = {
+      this: "attributes.private_key_passphrase"
+      that: "PrivateKeyPassphrase"
+    }
+  ]; // @gotags: `class:"secret"`
+
+  // Output only. The hmac value of the SSH private key passphrase.
+  string private_key_passphrase_hmac = 50 [
+    json_name = "private_key_passphrase_hmac",
+    (custom_options.v1.mask_mapping) = {
+      this: "attributes.private_key_passphrase_hmac"
+      that: "PrivateKeyPassphraseHmac"
+    }
+  ]; // @gotags: `class:"public"`
 }

internal/proto/controller/api/resources/targets/v1/target.proto

@@ -330,4 +330,7 @@ message SshPrivateKeyCredential {
 
   // Private key of the credential
   string private_key = 2; // @gotags: `class:"secret"`
+
+  // The optional passphrase of the private_key
+  string private_key_passphrase = 3; // @gotags: `class:"secret"`
 }