-
Notifications
You must be signed in to change notification settings - Fork 36
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
8 changed files
with
190 additions
and
132 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,126 @@ | ||
| import os | ||
| import base64 | ||
| import hashlib | ||
| from zope.interface import ( | ||
| Interface, | ||
| Attribute, | ||
| implementer, | ||
| ) | ||
|
|
||
|
|
||
| class IPermission(Interface): | ||
| """ | ||
| A server-side method of granting permission to a client. | ||
| """ | ||
| name = Attribute("name") | ||
|
|
||
| def get_welcome_data(): | ||
| """ | ||
| return a dict of information to include under the name of this | ||
| Permission granter (under "permission-required" in the Welcome) | ||
| """ | ||
|
|
||
| def verify_permission(submit_permission): | ||
| """ | ||
| return a bool indicating if the submit_permission data is a valid | ||
| permission (or not) | ||
| """ | ||
|
|
||
|
|
||
| def create_permission_provider(kind): | ||
| """ | ||
| returns a permissions-provider | ||
| """ | ||
| if kind == "none": | ||
| return NoPermission | ||
| elif kind == "hashcash": | ||
| return HashcashPermission | ||
| raise ValueError( | ||
| "Unknown permission provider '{}'".format(kind) | ||
| ) | ||
|
|
||
|
|
||
| @implementer(IPermission) | ||
| class NoPermission(object): | ||
| """ | ||
| A no-op permission provider used to grant any client access (the | ||
| default). | ||
| """ | ||
| name = "none" | ||
|
|
||
| def get_welcome_data(self): | ||
| return {} | ||
|
|
||
| def verify_permission(self, submit_permission): | ||
| return True | ||
|
|
||
|
|
||
| @implementer(IPermission) | ||
| class HashcashPermission(object): | ||
| """ | ||
| A permission provider that generates a random 'resource' string | ||
| and checks a proof-of-work from the client. | ||
| """ | ||
| name = "hashcash" | ||
|
|
||
| def __init__(self, bits=20): | ||
| self._bits = bits | ||
|
|
||
| def get_welcome_data(self): | ||
| """ | ||
| Generate the data to include under this method's key in the | ||
| `permission-required` value of the welcome message. | ||
| Should be called at most once per connection. | ||
| """ | ||
| self._hashcash_resource = base64.b64encode(os.urandom(8)).decode("utf8") | ||
| return { | ||
| "bits": self._bits, | ||
| "resource": self._hashcash_resource, | ||
| } | ||
|
|
||
| def verify_permission(self, perms): | ||
| """ | ||
| :returns bool: an indication of whether the provided permissions | ||
| reply from a client is valid | ||
| """ | ||
| # XXX THINK do we need this whole method to be constant-time? | ||
| # (basically impossible if it's not even syntactially valid?) | ||
| stamp = perms.get("stamp", "") | ||
| fields = stamp.split(":") | ||
| if len(fields) != 7: | ||
| return False | ||
| vers, claimed_bits, date, resource, ext, rand, counter = fields | ||
| vers = int(vers) | ||
| if vers != 1: | ||
| return False | ||
| if resource != self._hashcash_resource: | ||
| return False | ||
|
|
||
| claimed_bits = int(claimed_bits) | ||
| if claimed_bits < self._bits: | ||
| return False | ||
|
|
||
| h = hashlib.sha1() | ||
| h.update(stamp.encode("utf8")) | ||
| measured_hash = h.digest() | ||
| if leading_zero_bits(measured_hash) < claimed_bits: | ||
| return False | ||
| return True | ||
|
|
||
|
|
||
| def leading_zero_bits(bytestring): | ||
| """ | ||
| :returns int: the number of leading zeros in the given byte-string | ||
| """ | ||
| measured_bits = 0 | ||
| for byte in bytestring: | ||
| bit = 1 << 7 | ||
| while bit: | ||
| if byte & bit: | ||
| return measured_bits | ||
| else: | ||
| measured_bits += 1 | ||
| bit = bit >> 1 | ||
|
|
||
|
|
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Oops, something went wrong.