From 549bf773efb041f39bd9d5a7eb96934c6af1862c Mon Sep 17 00:00:00 2001
From: Lukas Puehringer <lukas.puehringer@nyu.edu>
Date: Thu, 25 Apr 2024 13:56:33 +0200
Subject: [PATCH] Add basic VaultSigner (WIP)

VaultSigner.import_ already works for ed25519 keys,
and can be tested via

  tox -e local-vault

TODO:
- sign
- from_priv_key_uri
- test on CI

Signed-off-by: Lukas Puehringer <lukas.puehringer@nyu.edu>
---
 securesystemslib/signer/__init__.py      |  1 +
 securesystemslib/signer/_vault_signer.py | 51 ++++++++++++++++++++++++
 tests/check_vault_signer.py              | 40 +++++++++++++++++++
 tox.ini                                  | 12 +++---
 4 files changed, 98 insertions(+), 6 deletions(-)
 create mode 100644 securesystemslib/signer/_vault_signer.py
 create mode 100644 tests/check_vault_signer.py

diff --git a/securesystemslib/signer/__init__.py b/securesystemslib/signer/__init__.py
index e210090f..65abd2ca 100644
--- a/securesystemslib/signer/__init__.py
+++ b/securesystemslib/signer/__init__.py
@@ -11,6 +11,7 @@
 from securesystemslib.signer._gcp_signer import GCPSigner
 from securesystemslib.signer._gpg_signer import GPGKey, GPGSigner
 from securesystemslib.signer._hsm_signer import HSMSigner
+from securesystemslib.signer._vault_signer import VaultSigner
 from securesystemslib.signer._key import KEY_FOR_TYPE_AND_SCHEME, Key, SSlibKey
 from securesystemslib.signer._signature import Signature
 from securesystemslib.signer._signer import (
diff --git a/securesystemslib/signer/_vault_signer.py b/securesystemslib/signer/_vault_signer.py
new file mode 100644
index 00000000..887e59a8
--- /dev/null
+++ b/securesystemslib/signer/_vault_signer.py
@@ -0,0 +1,51 @@
+"""Signer implementation for HashiCorp Vault (Transit secrets engine)"""
+
+from typing import Tuple
+from base64 import b64decode
+
+from securesystemslib.exceptions import UnsupportedLibraryError
+from securesystemslib.signer._key import Key, SSlibKey
+from securesystemslib.signer._signer import SecretsHandler, Signature, Signer
+from securesystemslib.signer._utils import compute_default_keyid
+
+
+VAULT_IMPORT_ERROR = None
+try:
+    import hvac
+    from cryptography.hazmat.primitives.asymmetric.ed25519 import (
+        Ed25519PublicKey,
+    )
+
+except ImportError:
+    VAULT_IMPORT_ERROR = "Signing with HashiCorp Vault requires hvac and cryptography."
+
+
+class VaultSigner(Signer):
+    """HashiCorp Vault Signer (Transit secrets engine) """
+    SCHEME = "hv"
+
+    @classmethod
+    def import_(cls, hv_key_name: str) -> Tuple[str, Key]:
+        """Load key and signer details from vault.
+
+        Supported keytypes:
+        * ed25519
+
+        """
+        if VAULT_IMPORT_ERROR:
+            raise UnsupportedLibraryError(VAULT_IMPORT_ERROR)
+
+        client = hvac.Client()
+
+        resp = client.secrets.transit.read_key(hv_key_name)
+
+        # Extract "newest" key from response
+        pub_b64 = sorted(resp["data"]["keys"].items())[-1][1]["public_key"]
+        pub_raw = b64decode(pub_b64)
+        pub_crypto = Ed25519PublicKey.from_public_bytes(pub_raw)
+
+        pub = SSlibKey.from_crypto(pub_crypto)
+        uri = f"{VaultSigner.SCHEME}:{hv_key_name}"
+
+        return uri, pub
+
diff --git a/tests/check_vault_signer.py b/tests/check_vault_signer.py
new file mode 100644
index 00000000..88f989da
--- /dev/null
+++ b/tests/check_vault_signer.py
@@ -0,0 +1,40 @@
+"""Test AWSSigner
+
+"""
+
+import unittest
+
+from securesystemslib.signer import VaultSigner
+
+
+class TestVaultSigner(unittest.TestCase):
+    """Test VaultSigner"""
+
+    def test_vault_import_sign_verify(self):
+        # Test full signer flow with vault
+        # - see tests/scripts/init-vault.sh for how keys are created
+        # - see tox.ini for how credentials etc. are passed via env vars
+        keys_and_schemes = [
+            ("test-key-ed25519", "ed25519")
+        ]
+        for hv_key_name, scheme in keys_and_schemes:
+            # Test import
+            uri, public_key = VaultSigner.import_(hv_key_name)
+            self.assertEqual(uri, f"{VaultSigner.SCHEME}:{hv_key_name}")
+            self.assertEqual(scheme, public_key.scheme)
+
+            # # Test load
+            # signer = Signer.from_priv_key_uri(uri, public_key)
+            # self.assertIsInstance(signer, VaultSigner)
+
+            # # Test sign and verify
+            # signature = signer.sign(b"DATA")
+            # self.assertIsNone(
+            #     public_key.verify_signature(signature, b"DATA")
+            # )
+            # with self.assertRaises(UnverifiedSignatureError):
+            #     public_key.verify_signature(signature, b"NOT DATA")
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=1)
diff --git a/tox.ini b/tox.ini
index 13b4ffbc..b85f94ae 100644
--- a/tox.ini
+++ b/tox.ini
@@ -107,10 +107,12 @@ commands_post =
     localstack stop
 
 
-# Requires docker running
+# Requires `vault`
+# https://developer.hashicorp.com/vault/tutorials/getting-started/getting-started-install
 [testenv:local-vault]
-; deps =
-;     hvac
+deps =
+    -r{toxinidir}/requirements-pinned.txt
+    hvac
 
 allowlist_externals =
     bash
@@ -123,9 +125,7 @@ commands_pre =
     bash {toxinidir}/tests/scripts/init-vault.sh
 
 commands =
-    ; TODO: Test AWSSigner.import_, from_priv_key_uri and sign here
-    ; curl --header "X-Vault-Token: test-root-token" \
-    ;     http://127.0.0.1:8200/v1/transit/export/public-key/test-key-ed25519
+     python -m tests.check_vault_signer
 
 commands_post =
     bash {toxinidir}/tests/scripts/stop-vault.sh