Add replacement API for '*keys' and 'interface' key generation and import

docs/CRYPTO_SIGNER.md

@@ -0,0 +1,97 @@
+
+# CryptoSigner
+
+`CryptoSigner` is a modern replacement for the legacy `securesystemslib.keys`
+module. It can be used via the `Signer.from_priv_key_uri` API to load private
+*rsa*, *ecdsa* and *ed25519* keys from file. It also provides API to generate
+in-memory signers for ad-hoc signing.
+
+## Code examples
+
+### Example 1: Ad-hoc signing
+
+`CryptoSigner` provides `generate_{rsa, ed25519, ecdsa}` methods for ad-hoc
+signing and signature verification, e.g. in tests or demos.
+
+```python
+from securesystemslib.signer import CryptoSigner
+
+signer = CryptoSigner.generate_ed25519()
+signature = signer.sign(b"data")
+signer.public_key.verify_signature(signature, b"data")
+```
+
+### Example 2: Asynchronous key management and signing
+
+The typical Signer API usage is described in
+[this blog post](https://theupdateframework.github.io/python-tuf/2023/01/24/securesystemslib-signer-api.html)
+and outlined below for a file-based signer.
+
+#### 1. Generate key files
+*`CryptoSigner` does not provide API to generate key files. Compatible
+keys can be generated with standard tools like `openssl genpkey` (CLI) or
+`pyca/cryptography` (Python).*
+
+```python
+from cryptography.hazmat.primitives import asymmetric, serialization
+
+# Generate key pair
+private_key = asymmetric.ed25519.Ed25519PrivateKey.generate()
+
+# Serialize private key as encrypted PEM/PKCS8
+private_pem = private_key.private_bytes(
+    encoding=serialization.Encoding.PEM,
+    format=serialization.PrivateFormat.PKCS8,
+    encryption_algorithm=serialization.BestAvailableEncryption(b"hunter2"),
+)
+
+# Serialize public key as encrypted PEM/subjectPublicKeyInfo
+public_pem = private_key.public_key().public_bytes(
+    encoding=serialization.Encoding.PEM,
+    format=serialization.PublicFormat.SubjectPublicKeyInfo,
+)
+
+# Write key files
+with open("private.pem", "wb") as f:
+    f.write(private_pem)
+with open("public.pem", "wb") as f:
+    f.write(public_pem)
+```
+
+#### 2. Prepare signing environment
+
+```python
+import os
+from securesystemslib.signer import SSlibKey
+
+with open("public.pem", "rb") as f:
+    public_bytes = f.read()
+
+# Make public key, signer URI, and key decryption password available to the
+# signer, e.g. via environment variables. The private key file must also be
+# available to the signer at the specified path.
+os.environ.update({
+    "SIGNER_URI":  "file:private.pem?encrypted=true",
+    "SIGNER_PUBLIC": public_bytes.decode(),
+    "SIGNER_SECRET": "hunter2"
+})
+```
+
+#### 3. Load and use signer
+
+```python
+import os
+from securesystemslib.signer import SSlibKey, Signer, CryptoSigner, SIGNER_FOR_URI_SCHEME
+
+# NOTE: Registration becomes obsolete once CryptoSigner is the default file signer
+SIGNER_FOR_URI_SCHEME.update({CryptoSigner.FILE_URI_SCHEME: CryptoSigner})
+
+# Read signer details
+uri = os.environ["SIGNER_URI"]
+public_key = SSlibKey.from_pem(os.environ["SIGNER_PUBLIC"].encode())
+secrets_handler = lambda sec: os.environ["SIGNER_SECRET"]
+
+# Load and sign
+signer = Signer.from_priv_key_uri(uri, public_key, secrets_handler)
+signer.sign(b"data")
+```

securesystemslib/signer/__init__.py

@@ -6,6 +6,7 @@
 """
 from securesystemslib.signer._aws_signer import AWSSigner
 from securesystemslib.signer._azure_signer import AzureSigner
+from securesystemslib.signer._crypto_signer import CryptoSigner
 from securesystemslib.signer._gcp_signer import GCPSigner
 from securesystemslib.signer._gpg_signer import GPGKey, GPGSigner
 from securesystemslib.signer._hsm_signer import HSMSigner
@@ -15,14 +16,14 @@
     SIGNER_FOR_URI_SCHEME,
     SecretsHandler,
     Signer,
-    SSlibSigner,
 )
 from securesystemslib.signer._sigstore_signer import SigstoreKey, SigstoreSigner
 from securesystemslib.signer._spx_signer import (
     SpxKey,
     SpxSigner,
     generate_spx_key_pair,
 )
+from securesystemslib.signer._sslib_signer import SSlibSigner
 
 # Register supported private key uri schemes and the Signers implementing them
 SIGNER_FOR_URI_SCHEME.update(

securesystemslib/signer/_aws_signer.py

@@ -7,13 +7,9 @@
 import securesystemslib.hash as sslib_hash
 from securesystemslib import exceptions
 from securesystemslib.exceptions import UnsupportedLibraryError
-from securesystemslib.signer._key import Key
-from securesystemslib.signer._signer import (
-    SecretsHandler,
-    Signature,
-    Signer,
-    SSlibKey,
-)
+from securesystemslib.signer._key import Key, SSlibKey
+from securesystemslib.signer._signer import SecretsHandler, Signature, Signer
+from securesystemslib.signer._utils import compute_default_keyid
 
 logger = logging.getLogger(__name__)
 
@@ -127,7 +123,7 @@ def import_(cls, aws_key_id: str, local_scheme: str) -> Tuple[str, Key]:
             ) from e
 
         keyval = {"public": public_key_pem}
-        keyid = cls._get_keyid(keytype, local_scheme, keyval)
+        keyid = compute_default_keyid(keytype, local_scheme, keyval)
         public_key = SSlibKey(keyid, keytype, local_scheme, keyval)
         return f"{cls.SCHEME}:{aws_key_id}", public_key
 

securesystemslib/signer/_azure_signer.py

@@ -6,13 +6,9 @@
 
 import securesystemslib.hash as sslib_hash
 from securesystemslib.exceptions import UnsupportedLibraryError
-from securesystemslib.signer._key import Key
-from securesystemslib.signer._signer import (
-    SecretsHandler,
-    Signature,
-    Signer,
-    SSlibKey,
-)
+from securesystemslib.signer._key import Key, SSlibKey
+from securesystemslib.signer._signer import SecretsHandler, Signature, Signer
+from securesystemslib.signer._utils import compute_default_keyid
 
 AZURE_IMPORT_ERROR = None
 try:
@@ -231,7 +227,7 @@ def import_(cls, az_vault_name: str, az_key_name: str) -> Tuple[str, Key]:
 
         keytype, scheme = cls._get_keytype_and_scheme(key_vault_key.key.crv)
         keyval = {"public": pem.decode("utf-8")}
-        keyid = cls._get_keyid(keytype, scheme, keyval)
+        keyid = compute_default_keyid(keytype, scheme, keyval)
         public_key = SSlibKey(keyid, keytype, scheme, keyval)
         priv_key_uri = key_vault_key.key.kid.replace("https:", "azurekms:")