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add derive_key(), use it for file-xfer bulk-encryption key

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This commit is contained in:
Brian Warner 2015-02-19 17:16:43 -08:00
parent 40e78ca839
commit 12845f191b
3 changed files with 12 additions and 8 deletions
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3
bin/receive_file.py
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@ -1,6 +1,5 @@
from __future__ import print_function
import sys, os, json
from binascii import unhexlify
from nacl.secret import SecretBox
from wormhole.blocking.transcribe import Receiver
from wormhole.blocking.transit import TransitReceiver
@ -23,7 +22,7 @@ data = json.loads(r.get_data().decode("utf-8"))
#print("their data: %r" % (data,))
file_data = data["file"]
xfer_key = unhexlify(file_data["key"].encode("ascii"))
xfer_key = r.derive_key(APPID+"/xfer-key", SecretBox.KEY_SIZE)
filename = os.path.basename(file_data["filename"]) # unicode
filesize = file_data["filesize"]
encrypted_filesize = filesize + SecretBox.NONCE_SIZE+16

3
bin/send_file.py
View File

@ -10,7 +10,6 @@ APPID = "lothar.com/wormhole/file-xfer"
# we're sending
filename = sys.argv[1]
assert os.path.isfile(filename)
xfer_key = os.urandom(SecretBox.KEY_SIZE)
transit_sender = TransitSender()
transit_key = transit_sender.get_transit_key()
direct_hints = transit_sender.get_direct_hints()
@ -19,7 +18,6 @@ relay_hints = transit_sender.get_relay_hints()
filesize = os.stat(filename).st_size
data = json.dumps({
"file": {
"key": hexlify(xfer_key),
"filename": os.path.basename(filename),
"filesize": filesize,
},
@ -38,6 +36,7 @@ print("")
them_bytes = i.get_data()
them_d = json.loads(them_bytes.decode("utf-8"))
#print("them: %r" % (them_d,))
xfer_key = i.derive_key(APPID+"/xfer-key", SecretBox.KEY_SIZE)
box = SecretBox(xfer_key)
with open(filename, "rb") as f:

14
src/wormhole/blocking/transcribe.py
View File

@ -82,6 +82,10 @@ class Common:
r = requests.post(self.url("deallocate"))
r.raise_for_status()
def derive_key(self, purpose, length=SecretBox.KEY_SIZE):
assert type(purpose) == type(b"")
return HKDF(self.key, length, CTXinfo=purpose)
class Initiator(Common):
def __init__(self, appid, data, relay=RELAY):
self.appid = appid
@ -104,13 +108,14 @@ class Initiator(Common):
def get_data(self):
key = self._poll_pake([])
self.key = key
try:
outbound_key = HKDF(key, SecretBox.KEY_SIZE, CTXinfo=b"sender")
outbound_key = self.derive_key(b"sender")
outbound_encrypted = self._encrypt_data(outbound_key, self.data)
other_msgs = self._post_data(outbound_encrypted)
inbound_encrypted = self._poll_data(other_msgs)
inbound_key = HKDF(key, SecretBox.KEY_SIZE, CTXinfo=b"receiver")
inbound_key = self.derive_key(b"receiver")
inbound_data = self._decrypt_data(inbound_key, inbound_encrypted)
finally:
self._deallocate()
@ -155,14 +160,15 @@ class Receiver(Common):
assert self.channel_id is not None
other_msgs = self._post_pake()
key = self._poll_pake(other_msgs)
self.key = key
try:
outbound_key = HKDF(key, SecretBox.KEY_SIZE, CTXinfo=b"receiver")
outbound_key = self.derive_key(b"receiver")
outbound_encrypted = self._encrypt_data(outbound_key, self.data)
other_msgs = self._post_data(outbound_encrypted)
inbound_encrypted = self._poll_data(other_msgs)
inbound_key = HKDF(key, SecretBox.KEY_SIZE, CTXinfo=b"sender")
inbound_key = self.derive_key(b"sender")
inbound_data = self._decrypt_data(inbound_key, inbound_encrypted)
finally:
self._deallocate()