1 files changed, 94 insertions, 0 deletions
diff --git a/lib/glider/keys.py b/lib/glider/keys.py
new file mode 100644
index 0000000..1ff96f1
--- /dev/null
+++ b/lib/glider/keys.py
@@ -0,0 +1,94 @@
+
+# These require PyCrypto.
+import Crypto.PublicKey.RSA
+import Crypto.Hash.SHA256
+
+import sexp.access
+import sexp.encode
+import sexp.parse
+
+import binascii
+import os
+
+class CryptoError(Exception):
+    pass
+
+class PubkeyFormatException(Exception):
+    pass
+
+class UnknownMethod(Exception):
+    pass
+
+class PublicKey:
+    def format(self):
+        raise NotImplemented()
+    def sign(self, data):
+        # returns a list of method,signature tuples.
+        raise NotImplemented()
+    def checkSignature(self, method, data, signature):
+        # returns True, False, or raises UnknownMethod.
+        raise NotImplemented()
+    def getKeyID(self):
+        raise NotImplemented()
+    def getRoles(self):
+        raise NotImplemented()
+
+def intToBinary(number):
+    h = hex(number)
+    assert h[:2] == '0x'
+    return binascii.a2b_hex(h[2:])
+
+def binaryToInt(binary):
+    return int(binascii.b2a_hex(binary), 16)
+
+def _pkcs1_padding(m, size):
+
+    # I'd rather use OAEP+, but apparently PyCrypto barely supports
+    # signature verification, and doesn't seem to support signature
+    # verification with nondeterministic padding.  "argh."
+
+    s = [ "\x00\x01", "\xff"* (size-3-len(m)), "\x00", m ]
+    r = s.join()
+    return r
+
+class RSAKey(PublicKey):
+    def __init__(self, key):
+        self.key = key
+
+    @staticmethod
+    def generate(bits=2048):
+        key = Crypto.PublicKey.RSA.generate(bits=bits, randfunc=os.urandom)
+        return RSAKey(key)
+
+    @staticmethod
+    def fromSExpression(sexpr):
+        # sexpr must match PUBKEY_SCHEMA
+        typeattr = s_child(sexpr[1], "type")[1]
+        if typeattr[1] != "rsa":
+            return None
+        if len(sexpr[2]) != 2:
+            raise PubkeyFormatException("RSA keys must have an e,n pair")
+        e,n = sexpr[2]
+        key = Crypto.PublicKey.RSA.construct((binaryToInt(n), binaryToInt(e)))
+        return RSAKey(key)
+
+    def format(self):
+        n = intToBinary(self.key.n)
+        e = intToBinary(self.key.e)
+        return ("pubkey", [("type", "rsa")], (e, n))
+
+    def sign(self, sexpr):
+        d_obj = Crypto.Digest.SHA256.new()
+        sexpr.encode.hash_canonical(sexpr, d_obj)
+        m = _pkcs1_padding(d_obj.digest(), (self.key.size()+1) // 8)
+        return ("sha256-pkcs1", self.key.sign(m, "")[0])
+
+    def checkSignature(self, method, sexpr, sig):
+        if method != "sha256-pkcs1":
+            raise UnknownMethod("method")
+        d_obj = Crypto.Digest.SHA256.new()
+        sexpr.encode.hash_canonical(sexpr, d_obj)
+        m = _pkcs1_padding(d_obj.digest(), (self.key.size()+1) // 8)
+        return self.key.verify(sig, m)
+
+