* Add editing for published statuses
* Fix change of multiple-choice boolean in poll not resetting votes
* Remove the ability to update existing media attachments for now
* Fix Sidekiq warnings about JSON serialization
This occurs on every symbol argument we pass, and every symbol key in hashes,
because Sidekiq expects strings instead.
See https://github.com/mperham/sidekiq/pull/5071
We do not need to change how workers parse their arguments because this has
not changed and we were already converting to symbols adequately or using
`with_indifferent_access`.
* Set Sidekiq to raise on unsafe arguments in test mode
In order to more easily catch issues that would produce warnings in production
code.
* Remove support for OAUTH_REDIRECT_AT_SIGN_IN
Fixes#15959
Introduced in #6540, OAUTH_REDIRECT_AT_SIGN_IN allowed skipping the log-in form
to instead redirect to the external OmniAuth login provider.
However, it did not prevent the log-in form on /about introduced by #10232 from
appearing, and completely broke with the introduction of #15228.
As I restoring that previous log-in flow without introducing a security
vulnerability may require extensive care and knowledge of how OmniAuth works,
this commit removes support for OAUTH_REDIRECT_AT_SIGN_IN instead for the time
being.
* Add OMNIAUTH_ONLY environment variable to enforce external log-in only
* Disable user registration when OMNIAUTH_ONLY is set to true
* Replace log-in links When OMNIAUTH_ONLY is set with exactly one OmniAuth provider
Fixes#15959
Introduced in #6540, OAUTH_REDIRECT_AT_SIGN_IN allowed skipping the log-in form
to instead redirect to the external OmniAuth login provider.
However, it did not prevent the log-in form on /about introduced by #10232 from
appearing, and completely broke with the introduction of #15228.
As I restoring that previous log-in flow without introducing a security
vulnerability may require extensive care and knowledge of how OmniAuth works,
this commit removes support for OAUTH_REDIRECT_AT_SIGN_IN instead for the time
being.
* Add support for editing for published statuses
* Fix references to stripped-out code
* Various fixes and improvements
* Further fixes and improvements
* Fix updates being potentially sent to unauthorized recipients
* Various fixes and improvements
* Fix wrong words in test
* Fix notifying accounts that were tagged but were not in the audience
* Fix mistake
* Add admin option to remove canonical email blocks from a deleted account
* Add tootctl canonical_email_blocks to inspect and remove canonical email blocks
* Add trending links
* Add overriding specific links trendability
* Add link type to preview cards and only trend articles
Change trends review notifications from being sent every 5 minutes to being sent every 2 hours
Change threshold from 5 unique accounts to 15 unique accounts
* Fix tests
Up until now, we have used Devise's Rememberable mechanism to re-log users
after the end of their browser sessions. This mechanism relies on a signed
cookie containing a token. That token was stored on the user's record,
meaning it was shared across all logged in browsers, meaning truly revoking
a browser's ability to auto-log-in involves revoking the token itself, and
revoking access from *all* logged-in browsers.
We had a session mechanism that dynamically checks whether a user's session
has been disabled, and would log out the user if so. However, this would only
clear a session being actively used, and a new one could be respawned with
the `remember_user_token` cookie.
In practice, this caused two issues:
- sessions could be revived after being closed from /auth/edit (security issue)
- auto-log-in would be disabled for *all* browsers after logging out from one
of them
This PR removes the `remember_token` mechanism and treats the `_session_id`
cookie/token as a browser-specific `remember_token`, fixing both issues.
* Add followed_by? to account_interactions
* Add RemoveFromFollowersService
* Fix AccountBatch to use RemoveFromFollowersService
* Add remove from followers API
* Add tests
* Add security-related tests
My first (unpublished) attempt at fixing the issues introduced (extremely
hard-to-exploit) security vulnerabilities, addressing them in a test.
* Fix authentication failures after going halfway through a sign-in attempt
* Refactor `authenticate_with_sign_in_token` and `authenticate_with_two_factor` to make the two authentication steps more obvious
The addition of authentication history broke the omniauth login with
the following error:
method=GET path=/auth/auth/cas/callback format=html
controller=Auth::OmniauthCallbacksController action=cas status=500
error='NameError: undefined local variable or method `user' for
#<Auth::OmniauthCallbacksController:0x00000000036290>
Did you mean? @user' duration=435.93 view=0.00 db=36.19
* app/controllers/auth/omniauth_callbacks_controller.rb: fix variable
name to `@user`
* Add account statuses cleanup policy model
* Record last inspected toot to delete to speed up successive calls to statuses_to_delete
* Add service to cleanup a given account's statuses within a budget
* Add worker to go through account policies and delete old toots
* Fix last inspected status id logic
All existing statuses older or equal to last inspected status id must be
kept by the current policy. This is an invariant that must be kept so that
resuming deletion from the last inspected status remains sound.
* Add tests
* Refactor scheduler and add tests
* Add user interface
* Add support for discriminating based on boosts/favs
* Add UI support for min_reblogs and min_favs, rework UI
* Address first round of review comments
* Replace Snowflake#id_at_start with with_random parameter
* Add tests
* Add tests for StatusesCleanupController
* Rework settings page
* Adjust load-avoiding mechanisms
* Please CodeClimate
* Fix anonymous access to outbox not being cached by the reverse proxy
Up until now, anonymous access to outbox was marked as public, but with a
0 duration for caching, which means remote proxies would only serve from cache
when the server was completely overwhelmed.
Changed that cache duration to one minute, so that repeated anonymous access
to one account's outbox can be appropriately cached.
Also added `Signature` to the `Vary` header in case a page is requested, so
that authenticated fetches are never served from cache (which only contains
public toots).
* Remove Vary: Accept header from webfinger controller
Indeed, we have stopped returning xrd, and only ever return jrd, so the
Accept request header does not matter anymore.
* Cache negative webfinger hits for 3 minutes
* Add tests
* Fix serialization of followers/following counts when user hides their network
Fixes#16382
Signed-off-by: Claire <claire.github-309c@sitedethib.com>
If a status with a hashtag becomes very popular, it stands to
reason that the hashtag should have a chance at trending
Fix no stats being recorded for hashtags that are not allowed
to trend, and stop ignoring bots
Remove references to hashtags in profile directory from the code
and the admin UI
* Fix issues with POSIX::Spawn, Terrapin and Ruby 3.0
Also improve the Terrapin monkey-patch for the stderr/stdout issue.
* Fix keyword argument handling throughout the codebase
* Monkey-patch Paperclip to fix keyword arguments handling in validators
* Change validation_extensions to please CodeClimate
* Bump microformats from 4.2.1 to 4.3.1
* Allow Ruby 3.0
* Add Ruby 3.0 test target to CircleCI
* Add test for admin dashboard warnings
* Fix admin dashboard warnings on Ruby 3.0
Database serialization failure occurs when a read-replica is used
and a query takes long enough that rows on the primary database
become unavailable. It should return HTTP 503 as it is temporary.
Re-order rescue definitions according to their status codes
Clicking the confirmation link multiple times currently leads to entering
account settings, which can be confusing. This commit changes that so that
it redirects to the root path, so it behaves the same way as clicking only
once in most cases.
* Update devise-two-factor to unreleased fork for Rails 6 support
Update tests to match new `rotp` version.
* Update nsa gem to unreleased fork for Rails 6 support
* Update rails to 6.1.3 and rails-i18n to 6.0
* Update to unreleased fork of pluck_each for Ruby 6 support
* Run "rails app:update"
* Add missing ActiveStorage config file
* Use config.ssl_options instead of removed ApplicationController#force_ssl
Disabled force_ssl-related tests as they do not seem to be easily testable
anymore.
* Fix nonce directives by removing Rails 5 specific monkey-patching
* Fix fixture_file_upload deprecation warning
* Fix yield-based test failing with Rails 6
* Use Rails 6's index_with when possible
* Use ActiveRecord::Cache::Store#delete_multi from Rails 6
This will yield better performances when deleting an account
* Disable Rails 6.1's automatic preload link headers
Since Rails 6.1, ActionView adds preload links for javascript files
in the Links header per default.
In our case, that will bloat headers too much and potentially cause
issues with reverse proxies. Furhermore, we don't need those links,
as we already output them as HTML link tags.
* Switch to Rails 6.0 default config
* Switch to Rails 6.1 default config
* Do not include autoload paths in the load path
* Use ActiveRecord::Result#to_ary instead of deprecated to_hash
They do the same thing, and to_hash has been removed from Rails 6.1
* Explicitly name polymorphic indexes to workaround a bug in Rails 6.1
cf. https://github.com/rails/rails/issues/41693
* Fix incorrect usage of “foreign_key” in migration script
* Use `ActiveModel::Errors#delete` instead of deprecated clear method
* Fix link headers tests on Rails 6.1
Rails 6.1 adds values to the Link header by default, thus it is not a
LinkHeader object anymore. Fix the test to parse the Link header instead
of assuming it is a LinkHeader.
* Fix crash on receiving requests with missing Digest header
Return an error pointing out that Digest is missing, instead of crashing.
Fixes#15743
* Fix from review feedback
An uncommon but somewhat difficult to digagnose issue is dealing with
improperly-seeded databases. In such cases, instance-signed fetches will
fail with a ActiveRecord::RecordNotFound error, usually caught and handled
as generic 404, leading people to think the remote resource itself has not
been found, while it's the local instance actor that does not exist.
This commit changes the code so that failure to find the instance actor
automatically creates a new one, so that improperly-seeded databases do
not cause any issue.
This also skips fetching the actor completely.
This will be useful if we end up distributing Update activities linked to
account suspensions more widely (they are currently only delivered to
the suspended account's followers), as currently, instances not knowing
about the suspended account would fetch it to then process the suspension.
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
* Add honeypot fields to limit non-specialized spam
Add two honeypot fields: a fake website input and a fake password confirmation
one. The label/placeholder/aria-label tells not to fill them, and they are
hidden in CSS, so legitimate users should not fall into these.
This should cut down on some non-Mastodon-specific spambots.
* Require a 3 seconds delay before submitting the registration form
* Fix tests
* Move registration form time check to model validation
* Give people a chance to clear the honeypot fields
* Refactor honeypot translation strings
Co-authored-by: Claire <claire.github-309c@sitedethib.com>
If someone tries logging in to an account and is prompted for a 2FA
code or sign-in token, even if the account's password or e-mail is
updated in the meantime, the session will show the prompt and allow
the login process to complete with a valid 2FA code or sign-in token
* Add more specific error message when request body digest is invalid
This may help other implementors debug their implementation.
* Relax Host parameter requirement to GET requests
The only POST requests processed by Mastodon need objects/actors (including
their host) to be explicitly mentioned in the request's body, so replaying
a legitimate request to another host should not be a security issue.
* Support Digest headers using multiple algorithms or lowercase alogirthm names
* Add support for followers synchronization on the receiving end
Check the `collectionSynchronization` attribute on `Create` and `Announce`
activities and synchronize followers from provided collection if possible.
* Add tests for followers synchronization on the receiving end
* Add support for follower synchronization on the sender's end
* Add tests for the sending end
* Switch from AS attributes to HTTP header
Replace the custom `collectionSynchronization` ActivityStreams attribute by
an HTTP header (`X-AS-Collection-Synchronization`) with the same syntax as
the `Signature` header and the following fields:
- `collectionId` to specify which collection to synchronize
- `digest` for the SHA256 hex-digest of the list of followers known on the
receiving instance (where “receiving instance” is determined by accounts
sharing the same host name for their ActivityPub actor `id`)
- `url` of a collection that should be fetched by the instance actor
Internally, move away from the webfinger-based `domain` attribute and use
account `uri` prefix to group accounts.
* Add environment variable to disable followers synchronization
Since the whole mechanism relies on some new preconditions that, in some
extremely rare cases, might not be met, add an environment variable
(DISABLE_FOLLOWERS_SYNCHRONIZATION) to disable the mechanism altogether and
avoid followers being incorrectly removed.
The current conditions are:
1. all managed accounts' actor `id` and inbox URL have the same URI scheme and
netloc.
2. all accounts whose actor `id` or inbox URL share the same URI scheme and
netloc as a managed account must be managed by the same Mastodon instance
as well.
As far as Mastodon is concerned, breaking those preconditions require extensive
configuration changes in the reverse proxy and might also cause other issues.
Therefore, this environment variable provides a way out for people with highly
unusual configurations, and can be safely ignored for the overwhelming majority
of Mastodon administrators.
* Only set follower synchronization header on non-public statuses
This is to avoid unnecessary computations and allow Follow-related
activities to be handled by the usual codepath instead of going through
the synchronization mechanism (otherwise, any Follow/Undo/Accept activity
would trigger the synchronization mechanism even if processing the activity
itself would be enough to re-introduce synchronization)
* Change how ActivityPub::SynchronizeFollowersService handles follow requests
If the remote lists a local follower which we only know has sent a follow
request, consider the follow request as accepted instead of sending an Undo.
* Integrate review feeback
- rename X-AS-Collection-Synchronization to Collection-Synchronization
- various minor refactoring and code style changes
* Only select required fields when computing followers_hash
* Use actor URI rather than webfinger domain in synchronization endpoint
* Change hash computation to be a XOR of individual hashes
Makes it much easier to be memory-efficient, and avoid sorting discrepancy issues.
* Marginally improve followers_hash computation speed
* Further improve hash computation performances by using pluck_each
* Add bell button
Fix#4890
* Remove duplicate type from post-deployment migration
* Fix legacy class type mappings
* Improve query performance with better index
* Fix validation
* Remove redundant index from notifications
* Do not serve account actors at all in limited federation mode
When an account is fetched without a signature from an allowed instance,
return an error.
This isn't really an improvement in security, as the only information that was
previously returned was required protocol-level info, and the only personal bit
was the existence of the account. The existence of the account can still be
checked by issuing a webfinger query, as those are accepted without signatures.
However, this change makes it so that unallowed instances won't create account
records on their end when they find a reference to an unknown account.
The previous behavior of rendering a limited list of fields, instead of not
rendering the actor at all, was in order to prevent situations in which two
instances in Authorized Fetch mode or Limited Federation mode would fail to
reach each other because resolving an account would require a signed query…
from an account which can only be fetched with a signed query itself. However,
this should now be fine as fetching accounts is done by signing on behalf of
the special instance actor, which does not require any kind of valid signature
to be fetched.
* Fix tests
* Add database support for list show-reply preferences
* Add backend support to read and update list-specific show_replies settings
* Add basic UI to set list replies setting
* Add specs for list replies policy
* Switch "cycling" reply policy link to a set of radio inputs
* Capitalize replies_policy strings
* Change radio button design to be consistent with that of the directory explorer
* Make Array-creation behavior of Paginable more predictable
Paginable.paginate_by_id usually returns ActiveRecord::Relation, but it
returns an Array if min_id option is present. The behavior caused problems
fixed with the following commits:
- 552e886b64
- b63ede5005
- 64ef37b89d
To prevent from recurring similar problems, this commit introduces two
changes:
- The scope now always returns an Array whether min_id option is present
or not.
- The scope is renamed to to_a_paginated_by_id to clarify it returns an
Array.
* Transform Paginable.to_a_paginated_by_id from a scope to a class method
https://api.rubyonrails.org/classes/ActiveRecord/Scoping/Named/ClassMethods.html#method-i-scope
> The method is intended to return an ActiveRecord::Relation object, which
> is composable with other scopes.
Paginable.to_a_paginated_by_id returns an Array and is not appropriate
as a scope.
* Replace incorrect use of distinct with group
Some uses of ActiveRecord::QueryMethods#distinct pass field names but they
are incorrect for the current version of Rails.
ActiveRecord::QueryMethods#group provides the expected behavior and
benefits performance. See commit 6da24aad4cafdef8d8a2c92bac2002a5fc2fe9c8.
* Introduce ApplicationController#cache_collection_paginated_by_id
ApplicationController#cache_collection_paginated_by_id fuses
ApplicationController#cache_collection and Paginable.paginate_by_id.
An advantage of this method is that it prevents from modifying scope which
Paginable.paginate_by_id may provide.
ApplicationController#cache_collection always return an array and there
is no possibility of the scope modification. It is also clear for a
programmer, considering the implication of "cache".
This method can also emit more efficient queries by using
Cacheable.cache_ids before calling Paginable.paginate_by_id.
Some uses of ActiveRecord::QueryMethods#distinct pass field names but they
are incorrect for the current version of Rails.
ActiveRecord::QueryMethods#group provides the expected behavior and
benefits performance. See commit 6da24aad4cafdef8d8a2c92bac2002a5fc2fe9c8.
The old implementation had two queries:
1. The query constructed in Api::V1::FavouritesController#results
2. The query constructed in #cached_favourites, which is merged with 1.
Both of them are issued againt PostgreSQL. The combination of the two
queries caused the following problems:
- The small window between the two queries involves race conditions.
- Minor performance inefficiency.
Moreover, the construction of query 2, which involves merging with query
1 has a bug. Query 1 is finalized with paginate_by_id, but paginate_by_id
returns an array when min_id parameter is specified. The behavior prevents
from merging the query, and in the real world, ActiveRecord simply ignores
the merge (!), which results in querying the entire scan of statuses and
favourites table.
This change fixes these issues by simply letting query 1 get all the works
done.
DISTINCT clause removes duplicated records according to all the selected
attributes. In reality, it can remove duplicated records only looking at
statuses.id, but the clause confuses the query planner and yields
insufficient performance.
The behavior is also problematic if the scope produced by HashQueryService
is used to query columns without id (using pluck method, for example). The
scope is expected to contain unique statuses, but the uniquness will be
evaluated with some arbitrary columns other than id.
GROUP BY clause resolves those problem by explicitly specifying the
column to take into account for the record distinction.
A workaround for the problem of DISTINCT clause in
Api::V1::Timelines::TagController is no longer necessary and removed.
* Add support for latest HTTP Signatures spec draft
https://www.ietf.org/id/draft-ietf-httpbis-message-signatures-00.html
- add support for the “hs2019” signature algorithm (assumed to be equivalent
to RSA-SHA256, since we do not have a mechanism to specify the algorithm
within the key metadata yet)
- add support for (created) and (expires) pseudo-headers and related
signature parameters, when using the hs2019 signature algorithm
- adjust default “headers” parameter while being backwards-compatible with
previous implementation
- change the acceptable time window logic from 12 hours surrounding the “date”
header to accepting signatures created up to 1 hour in the future and
expiring up to 1 hour in the past (but only allowing expiration dates up to
12 hours after the creation date)
This doesn't conform with the current draft, as it doesn't permit accounting
for clock skew.
This, however, should be addressed in a next version of the draft:
https://github.com/httpwg/http-extensions/pull/1235
* Add additional signature requirements
* Rewrite signature params parsing using Parslet
* Make apparent which signature algorithm Mastodon on verification failure
Mastodon uses RSASSA-PKCS1-v1_5, which is not recommended for new applications,
and new implementers may thus unknowingly use RSASSA-PSS.
* Add workaround for PeerTube's invalid signature header
The previous parser allowed incorrect Signature headers, such as
those produced by old versions of the `http-signature` node.js package,
and seemingly used by PeerTube.
This commit adds a workaround for that.
* Fix `signature_key_id` raising an exception
Previously, parsing failures would result in `signature_key_id` being nil,
but the parser changes made that result in an exception.
This commit changes the `signature_key_id` method to return `nil` in case
of parsing failures.
* Move extra HTTP signature helper methods to private methods
* Relax (request-target) requirement to (request-target) || digest
This lets requests from Plume work without lowering security significantly.
* feat: add possibility of adding WebAuthn security keys to use as 2FA
This adds a basic UI for enabling WebAuthn 2FA. We did a little refactor
to the Settings page for editing the 2FA methods – now it will list the
methods that are available to the user (TOTP and WebAuthn) and from
there they'll be able to add or remove any of them.
Also, it's worth mentioning that for enabling WebAuthn it's required to
have TOTP enabled, so the first time that you go to the 2FA Settings
page, you'll be asked to set it up.
This work was inspired by the one donde by Github in their platform, and
despite it could be approached in different ways, we decided to go with
this one given that we feel that this gives a great UX.
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* feat: add request for WebAuthn as second factor at login if enabled
This commits adds the feature for using WebAuthn as a second factor for
login when enabled.
If users have WebAuthn enabled, now a page requesting for the use of a
WebAuthn credential for log in will appear, although a link redirecting
to the old page for logging in using a two-factor code will also be
present.
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* feat: add possibility of deleting WebAuthn Credentials
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* feat: disable WebAuthn when an Admin disables 2FA for a user
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* feat: remove ability to disable TOTP leaving only WebAuthn as 2FA
Following examples form other platforms like Github, we decided to make
Webauthn 2FA secondary to 2FA with TOTP, so that we removed the
possibility of removing TOTP authentication only, leaving users with
just WEbAuthn as 2FA. Instead, users will have to click on 'Disable 2FA'
in order to remove second factor auth.
The reason for WebAuthn being secondary to TOPT is that in that way,
users will still be able to log in using their code from their phone's
application if they don't have their security keys with them – or maybe
even lost them.
* We had to change a little the flow for setting up TOTP, given that now
it's possible to setting up again if you already had TOTP, in order to
let users modify their authenticator app – given that now it's not
possible for them to disable TOTP and set it up again with another
authenticator app.
So, basically, now instead of storing the new `otp_secret` in the
user, we store it in the session until the process of set up is
finished.
This was because, as it was before, when users clicked on 'Edit' in
the new two-factor methods lists page, but then went back without
finishing the flow, their `otp_secret` had been changed therefore
invalidating their previous authenticator app, making them unable to
log in again using TOTP.
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* refactor: fix eslint errors
The PR build was failing given that linting returning some errors.
This commit attempts to fix them.
* refactor: normalize i18n translations
The build was failing given that i18n translations files were not
normalized.
This commits fixes that.
* refactor: avoid having the webauthn gem locked to a specific version
* refactor: use symbols for routes without '/'
* refactor: avoid sending webauthn disabled email when 2FA is disabled
When an admins disable 2FA for users, we were sending two mails
to them, one notifying that 2FA was disabled and the other to notify
that WebAuthn was disabled.
As the second one is redundant since the first email includes it, we can
remove it and send just one email to users.
* refactor: avoid creating new env variable for webauthn_origin config
* refactor: improve flash error messages for webauthn pages
Co-authored-by: Facundo Padula <facundo.padula@cedarcode.com>
* Increase DNS timeout from 1 second to 5 seconds for MX check
1 seconds is rather short when using a recursive DNS resolver which
hasn't got a cached result already available. Use 5 seconds instead,
which is the timeout value we use for outgoing HTTP queries.
* Add more precise error messages for invalid e-mail addresses
* Add tests for some cachable responses
This only covers responses that we should have managed to make cachable
so far. It's not the case of all responses that should be cachable in
the end.
* Fix RSS feeds not being cachable
* Add toot send by current user at local state after send a new toot
Related to #14021
* Decrement toot counter at profile when remove a toot
Related to #14021
* Remove semicolon at end of line
While OAuth tokens were immediately revoked, accessing the home
controller immediately generated new OAuth tokens and "revived"
the session due to a combination of using remember_me tokens and
overwriting the `authenticate_user!` method
* Add UserNote model
* Add UI for user notes
* Put comment in relationships entity
* Add API to create user notes
* Copy user notes to new account when receiving a Move activity
* Address some of the review remarks
* Replace modal by inline edition
* Please CodeClimate
* Button design changes
* Change design again
* Cancel note edition when pressing Escape
* Fixes
* Tweak design again
* Move “Add note” item, and allow users to add notes to themselves
* Rename UserNote into AccountNote, rename “comment” Relationship attribute to “note”
- Change audio files to not be stripped of metadata
- Automatically extract cover art from audio if it exists
- Add `thumbnail` parameter to `POST /api/v1/media`, `POST /api/v2/media` and `PUT /api/v1/media/:id`
- Add `icon` to represent it in attachments in ActivityPub
- Fix `preview_url` containing URL of missing missing image when there is no thumbnail instead of null
- Fix duration of audio not being displayed on public pages until the file is loaded
* Display appropriate error when performing unpermitted operation on custom emoji
Fixes#13897
* Remove links to custom emoji actions not performable by moderators
When attempting to access the log-in page while already logged in,
Devise's `require_no_authentication` kicks in and sets a flash
message “You are already signed in.”
In almost all cases, this also causes a redirect to /web, which
does not display or clear flash messages, thus leaving the message
to a potentially much later date, like for instance, accessing
/preferences several minutes after being redirected to /web.
This is achieved by sending a DELETE request to
/settings/profile/pictures/{avatar,header} via a link that is part of
the upload form's hint of the respective picture.
