[Add] First commit

scripts/imgtool/imglib/keys/ecdsa.py

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+"""
+ECDSA key management
+"""
+
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives.hashes import SHA256
+
+from .general import KeyClass
+
+class ECDSAUsageError(Exception):
+    pass
+
+class ECDSA256P1Public(KeyClass):
+    def __init__(self, key):
+        self.key = key
+
+    def shortname(self):
+        return "ecdsa"
+
+    def _unsupported(self, name):
+        raise ECDSAUsageError("Operation {} requires private key".format(name))
+
+    def _get_public(self):
+        return self.key
+
+    def get_public_bytes(self):
+        # The key is embedded into MBUboot in "SubjectPublicKeyInfo" format
+        return self._get_public().public_bytes(
+                encoding=serialization.Encoding.DER,
+                format=serialization.PublicFormat.SubjectPublicKeyInfo)
+
+    def export_private(self, path, passwd=None):
+        self._unsupported('export_private')
+
+    def export_public(self, path):
+        """Write the public key to the given file."""
+        pem = self._get_public().public_bytes(
+                encoding=serialization.Encoding.PEM,
+                format=serialization.PublicFormat.SubjectPublicKeyInfo)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def sig_type(self):
+        return "ECDSA256_SHA256"
+
+    def sig_tlv(self):
+        return "ECDSA256"
+
+    def sig_len(self):
+        # The DER encoding depends on the high bit, and can be
+        # anywhere from 70 to 72 bytes.  Because we have to fill in
+        # the length field before computing the signature, however,
+        # we'll give the largest, and the sig checking code will allow
+        # for it to be up to two bytes larger than the actual
+        # signature.
+        return 72
+
+class ECDSA256P1(ECDSA256P1Public):
+    """
+    Wrapper around an ECDSA private key.
+    """
+
+    def __init__(self, key):
+        """key should be an instance of EllipticCurvePrivateKey"""
+        self.key = key
+
+    @staticmethod
+    def generate():
+        pk = ec.generate_private_key(
+                ec.SECP256R1(),
+                backend=default_backend())
+        return ECDSA256P1(pk)
+
+    def _get_public(self):
+        return self.key.public_key()
+
+    def export_private(self, path, passwd=None):
+        """Write the private key to the given file, protecting it with the optional password."""
+        if passwd is None:
+            enc = serialization.NoEncryption()
+        else:
+            enc = serialization.BestAvailableEncryption(passwd)
+        pem = self.key.private_bytes(
+                encoding=serialization.Encoding.PEM,
+                format=serialization.PrivateFormat.PKCS8,
+                encryption_algorithm=enc)
+        with open(path, 'wb') as f:
+            f.write(pem)
+
+    def raw_sign(self, payload):
+        """Return the actual signature"""
+        return self.key.sign(
+                data=payload,
+                signature_algorithm=ec.ECDSA(SHA256()))
+
+    def sign(self, payload):
+        # To make fixed length, pad with one or two zeros.
+        sig = self.raw_sign(payload)
+        sig += b'\000' * (self.sig_len() - len(sig))
+        return sig