tools: add support for EC account keys

Allows usage of pre-generated EC account keys (P-256, P-384, P-521)
in addition to already supported RSA keys.

README.md

@@ -12,7 +12,7 @@ Requirements
 ------------
 
   * Python (2.7+ and 3.5+ should work)
-  * cryptography (includes the optional idna module)
+  * cryptography>=0.6 (includes the optional idna module)
 
 Optional packages (required to use specified features)
 ------------------------------------------------------
@@ -21,7 +21,7 @@ Optional packages (required to use specified features)
   * dnspython: used by dns.* challenge handlers
   * idna: to allow automatic conversion of unicode domain names to their IDNA2008 counterparts
   * cryptography>=2.1: for creating certificates with the OCSP must-staple flag (cert_must_staple)
-
+  
 Setup
 -----
 

acertmgr/tools.py

@@ -17,8 +17,10 @@ import traceback
 from cryptography import x509
 from cryptography.hazmat.backends import default_backend
 from cryptography.hazmat.primitives import hashes, serialization
-from cryptography.hazmat.primitives.asymmetric import rsa, padding
+from cryptography.hazmat.primitives.asymmetric import rsa, ec, padding
+from cryptography.hazmat.primitives.asymmetric.utils import decode_dss_signature
 from cryptography.x509.oid import NameOID, ExtensionOID
+from cryptography.utils import int_to_bytes
 
 try:
     from urllib.request import urlopen, Request  # Python 3
@@ -241,6 +243,24 @@ def get_key_alg_and_jwk(key):
         return "RS256", {"kty": "RSA",
                          "e": bytes_to_base64url(number_to_byte_format(numbers.e)),
                          "n": bytes_to_base64url(number_to_byte_format(numbers.n))}
+    elif isinstance(key, ec.EllipticCurvePrivateKey):
+        # See https://tools.ietf.org/html/rfc7518#section-6.2
+        numbers = key.public_key().public_numbers()
+        if isinstance(numbers.curve, ec.SECP256R1):
+            alg = 'ES256'
+            crv = 'P-256'
+        elif isinstance(numbers.curve, ec.SECP384R1):
+            alg = 'ES384'
+            crv = 'P-384'
+        elif isinstance(numbers.curve, ec.SECP521R1):
+            alg = 'ES512'
+            crv = 'P-521'
+        else:
+            raise ValueError("Unsupported EC curve in key: {}".format(key))
+        full_octets = (int(crv[2:]) + 7) // 8
+        return alg, {"kty": "EC", "crv": crv,
+                     "x": bytes_to_base64url(int_to_bytes(numbers.x, full_octets)),
+                     "y": bytes_to_base64url(int_to_bytes(numbers.y, full_octets))}
     else:
         raise ValueError("Unsupported key: {}".format(key))
 
@@ -251,6 +271,19 @@ def signature_of_str(key, string):
     data = string.encode('utf8')
     if alg == 'RS256':
         return key.sign(data, padding.PKCS1v15(), hashes.SHA256())
+    elif alg.startswith('ES'):
+        full_octets = (int(alg[2:]) + 7) // 8
+        if alg == 'ES256':
+            der_sig = key.sign(data, ec.ECDSA(hashes.SHA256()))
+        elif alg == 'ES384':
+            der_sig = key.sign(data, ec.ECDSA(hashes.SHA384()))
+        elif alg == 'ES512':
+            der_sig = key.sign(data, ec.ECDSA(hashes.SHA512()))
+        else:
+            raise ValueError("Unsupported EC signature algorithm: {}".format(alg))
+        # convert DER signature to RAW format (https://tools.ietf.org/html/rfc7518#section-3.4)
+        r, s = decode_dss_signature(der_sig)
+        return int_to_bytes(r, full_octets) + int_to_bytes(s, full_octets)
     else:
         raise ValueError("Unsupported signature algorithm: {}".format(alg))
 

docs/archlinux/python-acertmgr/PKGBUILD

@@ -6,11 +6,11 @@ pkgdesc='An automated certificate manager using ACME/letsencrypt'
 arch=('any')
 url='https://github.com/moepman/acertmgr'
 license=('ISC')
-depends=('python-cryptography')
+depends=('python-cryptography>=0.6')
 optdepends=('python-yaml: Support config files in YAML format'
             'python-idna: Support conversion of unicode domains'
-	    'python-dnspython: Support for dns challenge handlers'
-	    'python-cryptography>=2.1: Support for the OCSP must-staple flag'
+            'python-dnspython: Support for dns challenge handlers'
+            'python-cryptography>=2.1: Support for the OCSP must-staple flag'
 	   )
 makedepends=('git')
 conflicts=('python-acertmgr')

docs/archlinux/python2-acertmgr/PKGBUILD

@@ -6,11 +6,11 @@ pkgdesc='An automated certificate manager using ACME/letsencrypt'
 arch=('any')
 url='https://github.com/moepman/acertmgr'
 license=('ISC')
-depends=('python2-cryptography')
+depends=('python2-cryptography>=0.6')
 optdepends=('python2-yaml: Support config files in YAML format'
             'python2-idna: Support conversion of unicode domains'
-	    'python2-dnspython: Support for dns challenge handlers'
-	    'python2-cryptography>=2.1: Support for the OCSP must-staple flag'
+            'python2-dnspython: Support for dns challenge handlers'
+            'python2-cryptography>=2.1: Support for the OCSP must-staple flag'
 	   )
 makedepends=('git')
 conflicts=('python-acertmgr')

setup.py

@@ -65,7 +65,7 @@ setup(
         "License :: OSI Approved :: ISC License",
     ],
     install_requires=[
-        "cryptography",
+        "cryptography>=0.6",
     ],
     extras_require={
         "dns": [
@@ -80,6 +80,9 @@ setup(
         "ocsp-must-staple": [
             "cryptography>=2.1",
         ],
+        "ed25519": [
+            "cryptography>=2.6",
+        ],
     },
     entry_points={
         'console_scripts': [