From 1cd797252bcf1c9b51a4bd5d7f7f42e34484b2cf Mon Sep 17 00:00:00 2001
From: Jean-Paul Calderone <exarkun@twistedmatrix.com>
Date: Mon, 15 Jul 2019 12:24:16 -0400
Subject: [PATCH] Add some comments to this Foolscap constraint stuff
---
.../_storage_server.py | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/src/_secureaccesstokenauthorizer/_storage_server.py b/src/_secureaccesstokenauthorizer/_storage_server.py
index a237e47..46907a2 100644
--- a/src/_secureaccesstokenauthorizer/_storage_server.py
+++ b/src/_secureaccesstokenauthorizer/_storage_server.py
@@ -46,9 +46,25 @@ from allmydata.interfaces import (
RIStorageServer,
)
+# The Foolscap convention seems to be to try to constrain inputs to valid
+# values. So we'll try to limit the number of tokens a client can supply.
+# Foolscap may be moving away from this so we may eventually drop this as
+# well. Though it may still make sense on a non-Foolscap protocol (eg HTTP)
+# which Tahoe-LAFS may eventually support.
+#
+# In any case, for now, pick some fairly arbitrary value. I am deliberately
+# picking a small number here and expect to have to raise. However, ideally,
+# a client could accomplish a lot with a few tokens while also not wasting a
+# lot of value.
MAXIMUM_TOKENS_PER_CALL = 10
+
+# This is the length of a serialized PrivacyPass pass (there's a lot of
+# confusion between "tokens" and "passes" here, sadly).
TOKEN_LENGTH = 97
+# Take those values and turn them into the appropriate Foolscap constraint
+# objects. Foolscap seems to have a convention of representing these as
+# CamelCase module-level values so I replicate that here.
Token = ByteStringConstraint(maxLength=TOKEN_LENGTH, minLength=TOKEN_LENGTH)
TokenList = ListOf(Token, maxLength=MAXIMUM_TOKENS_PER_CALL)
--
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