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use database to prevent double-spending of hashcash

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This commit is contained in:
Seth Schoen 2012-07-14 17:16:51 -07:00
parent 0b1b8e42d5
commit 088c97bbf5
1 changed files with 9 additions and 3 deletions
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12
server-ca/chocolate.py
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@ -140,6 +140,14 @@ class session(object):
self.die(r, r.BadRequest, uri="https://ca.example.com/failures/internalerror")
return
def check_hashcash(self, h):
"""Is the hashcash string h valid for a request to this server?"""
# TODO: should enforce hashcash expiry.
if hashcash.check(h, chocolate_server_name, difficulty):
# sessions.sadd returns True upon adding to a set and
# False if the item was already in the set.
return sessions.sadd("spent-hashcash", h)
def handlesession(self, m, r):
if r.failure.IsInitialized(): return
# Note that m.challenge and m.completedchallenge present
@ -205,9 +213,7 @@ class session(object):
self.die(r, r.BadRequest, uri="https://ca.example.com/failures/missingrequest")
return
# Check hashcash before doing any crypto or database access.
if not m.request.clientpuzzle or not hashcash.check(m.request.clientpuzzle, chocolate_server_name, difficulty):
# TODO: should enforce hashcash expiry and use the database to store valid
# ones in order to prevent double-spending.
if not m.request.clientpuzzle or not self.check_hashcash(h):
self.die(r, r.NeedClientPuzzle, uri="https://ca.example.com/failures/hashcash")
return
if self.request_made():