Split the package into a shared library and separate per-device packages

libagent/gpg/client.py

@@ -0,0 +1,44 @@
+"""Device abstraction layer for GPG operations."""
+
+import logging
+
+from .. import device, formats, util
+
+log = logging.getLogger(__name__)
+
+
+class Client(object):
+    """Sign messages and get public keys from a hardware device."""
+
+    def __init__(self, user_id, curve_name, device_type):
+        """Connect to the device and retrieve required public key."""
+        self.device = device_type()
+        self.user_id = user_id
+        self.identity = device.interface.Identity(
+            identity_str='gpg://', curve_name=curve_name)
+        self.identity.identity_dict['host'] = user_id
+
+    def pubkey(self, ecdh=False):
+        """Return public key as VerifyingKey object."""
+        with self.device:
+            pubkey = self.device.pubkey(ecdh=ecdh, identity=self.identity)
+        return formats.decompress_pubkey(
+            pubkey=pubkey, curve_name=self.identity.curve_name)
+
+    def sign(self, digest):
+        """Sign the digest and return a serialized signature."""
+        log.info('please confirm GPG signature on %s for "%s"...',
+                 self.device, self.user_id)
+        if self.identity.curve_name == formats.CURVE_NIST256:
+            digest = digest[:32]  # sign the first 256 bits
+        log.debug('signing digest: %s', util.hexlify(digest))
+        with self.device:
+            sig = self.device.sign(blob=digest, identity=self.identity)
+        return (util.bytes2num(sig[:32]), util.bytes2num(sig[32:]))
+
+    def ecdh(self, pubkey):
+        """Derive shared secret using ECDH from remote public key."""
+        log.info('please confirm GPG decryption on %s for "%s"...',
+                 self.device, self.user_id)
+        with self.device:
+            return self.device.ecdh(pubkey=pubkey, identity=self.identity)