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From "Jason Smith (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (COUCHDB-1287) Inbox Database ("write-only" mode)
Date Mon, 21 Nov 2011 05:19:51 GMT

    [ https://issues.apache.org/jira/browse/COUCHDB-1287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13153991#comment-13153991
] 

Jason Smith commented on COUCHDB-1287:
--------------------------------------

I hope outside observers would see a spirited debate, neither nasty nor personal.

Benoit, I have no -1 veto power. However I hope to hear a response to my critique: special-case
"dropbox" handling must be sprinkled all over the code base. We cannot prove that this feature
is 100% secure; we can only make as many unit tests as possible, to be reasonably confident.

Authorization should not be decided at the HTTP level; however, in the current code base,
that is the only choke-point. Once you couch_db:open(), there are two problems:

1. Read and write access is unrestricted
2. Subsequent code has lost the Req object, so there is no context to decide yes/no
                
> Inbox Database ("write-only" mode)
> ----------------------------------
>
>                 Key: COUCHDB-1287
>                 URL: https://issues.apache.org/jira/browse/COUCHDB-1287
>             Project: CouchDB
>          Issue Type: New Feature
>          Components: HTTP Interface
>    Affects Versions: 1.2
>            Reporter: Jason Smith
>            Priority: Minor
>         Attachments: 0001-handle-dropbox-db.-Add-dropbox-true-to-security-obje.patch,
0001-handle-dropbox-db.-Add-dropbox-true-to-security-obje.patch, A_0001-Refactor-reader_acl-test-functions-into-a-loop.patch,
A_0002-Refactor-the-actual-read-check-out-of-the-member-che.patch, A_0003-Allow-non-member-writes-if-_security.members.allow_a.patch,
B_0001-Refactor-reader_acl-test-functions-into-a-loop.patch, B_0002-Refactor-the-actual-read-check-out-of-the-member-che.patch,
B_0003-Allow-non-member-updates-if-_security.members.allow_.patch
>
>
> Currently, we can only grant combined read+write access in the _security object "members"
section. A user can either do both or neither. This prevents a very common requirement for
couch apps: sending private information from less-privileged users to more-privileged users.
> There is no (reasonable) way to make an "inbox" where anybody may create a doc for me,
but only I may read it. An inbox database allows user-to-user, or user-to-admin private messages.
(Not only chat messages, but asynchronous notifications--with a per-user inbox, perhaps even
service requests and responses.)
> There is no reason _security.members (formerly .readers) should control write access.
validate_doc_update() functions do this better.
> I propose a boolean flag, _security.members.allow_anonymous_writes. If it is true, then
CouchDB will allow document updates from non-members, giving validate_doc_update() the final
word on accepting or rejecting the update.
> Requirements:
> 1. Everything about _security stays the same (backward-compatible)
> 2. If members.allow_anonymous_writes === true, then most PUT and POSTs may proceed
> 3. All updates are still subject to approval by all validate_doc_update functions, same
as before.
> These are the known changes to the security model. I consider these all to be either
very unlikely in practice, or worth the trade-off.
> * If you write to an inbox DB, you know, for a time, a subset of its documents (but that's
the point)
> * An _update function could reveal a document to the user, with or without changing it.
However, an admin must install such a misguided update function.
> * You can launch timing attacks to learn information about validate_doc_update
>   * You might discover whether doc IDs exist in the DB or not
>   * You might discover a well-known open source validation function. You can look for
bugs in its source code.
> * Zero or more things which Jason can't think of

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