[Bug]: Name collision of shared folders

aslfv commented 2 years ago

⚠️ This issue respects the following points: ⚠️

[X] This is a bug, not a question or a configuration/webserver/proxy issue.
[X] This issue is not already reported on Github (I've searched it).
[X] Nextcloud Server is up to date. See Maintenance and Release Schedule for supported versions.
[X] Nextcloud Server is running on 64bit capable CPU, PHP and OS.
[X] I agree to follow Nextcloud's Code of Conduct.

Bug description

When two or more (sending) users share a folder with the same (receiving) user, that receiving user will only see the folder of the latest (sending) user under the "shared" folder, without necessarily being aware of it. The other folders will only reappear if the receiving user renames the folder seen.

The issue was originally raised at https://help.nextcloud.com/t/shared-folder-with-same-name-starts-override-each-other-at-recipient-view/142574/3.

IMHO this is a critical bug, which could pose a major digital security risk that could be exploited to inject malicious files in another user's folder.

But irrespective of this, users that share their (default) folders should not have to worry about name collisions.

Steps to reproduce

1.Alice shares her "Document" folder with Charly => Charly sees Alice's "Document" folder 2.Bob shares his "Document" folder with Charly => Charly only sees Bob's "Document" folder. 3.Mallory shares his "Document" folder, which contains malware with Charly => Charly only sees Mallory's "Document" folder and may believe this is still Alice's Document folder.

Expected behavior

Charly should see all three folders: Alice's, Bob's and Mallory's "Document" folders, which may be renamed as "Document (Alice)", "Document (Bob)" and "Document (Mallory)" respectively.

Installation method

Community Docker image

Operating system

Fedora 36

PHP engine version

PHP 8.0

Web server

Apache (supported)

Database engine version

PostgreSQL

Is this bug present after an update or on a fresh install?

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

Encryption is Enabled

What user-backends are you using?

[X] Default user-backend (database)
[ ] LDAP/ Active Directory
[ ] SSO - SAML
[ ] Other

Configuration report

{
    "system": {
        "memcache.local": "\\OC\\Memcache\\APCu",
        "apps_paths": [
            {
                "path": "\/var\/www\/html\/apps",
                "url": "\/apps",
                "writable": false
            },
            {
                "path": "\/var\/www\/html\/custom_apps",
                "url": "\/custom_apps",
                "writable": true
            }
        ],
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "password": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        },
        "overwritehost": "***REMOVED SENSITIVE VALUE***",
        "overwriteprotocol": "https",
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "localhost",
            "***REMOVED SENSITIVE VALUE***"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "pgsql",
        "version": "24.0.4.1",
        "overwrite.cli.url": "***REMOVED SENSITIVE VALUE***",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbport": "",
        "dbtableprefix": "oc_",
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "loglevel": "2",
        "log_type": "file",
        "logfile": "\/var\/www\/html\/data\/nextcloud.log",
        "log_rotate_size": "10485760",
        "log.condition": {
            "apps": [
                "admin_audit"
            ]
        },
        "preview_max_x": "2048",
        "preview_max_y": "2048",
        "jpeg_quality": "60",
        "enabledPreviewProviders": {
            "1": "OC\\Preview\\Image",
            "2": "OC\\Preview\\MarkDown",
            "3": "OC\\Preview\\MP3",
            "4": "OC\\Preview\\TXT",
            "5": "OC\\Preview\\OpenDocument",
            "6": "OC\\Preview\\Movie"
        },
        "enable_previews": true,
        "upgrade.disable-web": true,
        "mail_smtpmode": "smtp",
        "trashbin_retention_obligation": "auto, 30",
        "versions_retention_obligation": "auto, 30",
        "activity_expire_days": "30",
        "simpleSignUpLink.shown": false,
        "share_folder": "\/Shared",
        "one-click-instance": true,
        "one-click-instance.user-limit": 100,
        "htaccess.RewriteBase": "\/",
        "files_external_allow_create_new_local": false,
        "trusted_proxies": "***REMOVED SENSITIVE VALUE***"
    }
}

List of activated Apps

Enabled:
  - accessibility: 1.10.0
  - activity: 2.16.0
  - admin_audit: 1.14.0
  - apporder: 0.15.0
  - bruteforcesettings: 2.4.0
  - calendar: 3.5.0
  - circles: 24.0.1
  - cloud_federation_api: 1.7.0
  - comments: 1.14.0
  - contacts: 4.2.0
  - contactsinteraction: 1.5.0
  - dashboard: 7.4.0
  - dav: 1.22.0
  - deck: 1.7.1
  - encryption: 2.12.0
  - event_update_notification: 1.5.0
  - federatedfilesharing: 1.14.0
  - federation: 1.14.0
  - files: 1.19.0
  - files_external: 1.16.1
  - files_pdfviewer: 2.5.0
  - files_rightclick: 1.3.0
  - files_sharing: 1.16.2
  - files_trashbin: 1.14.0
  - files_versions: 1.17.0
  - files_videoplayer: 1.13.0
  - firstrunwizard: 2.13.0
  - logreader: 2.9.0
  - lookup_server_connector: 1.12.0
  - nextcloud-aio: 0.2.0
  - nextcloud_announcements: 1.13.0
  - notes: 4.5.1
  - notifications: 2.12.0
  - notify_push: 0.4.0
  - oauth2: 1.12.0
  - password_policy: 1.14.0
  - phonetrack: 0.7.0
  - photos: 1.6.0
  - privacy: 1.8.0
  - provisioning_api: 1.14.0
  - recommendations: 1.3.0
  - serverinfo: 1.14.0
  - settings: 1.6.0
  - sharebymail: 1.14.0
  - socialsharing_email: 2.5.0
  - support: 1.7.0
  - survey_client: 1.12.0
  - systemtags: 1.14.0
  - tasks: 0.14.4
  - text: 3.5.1
  - theming: 1.15.0
  - twofactor_backupcodes: 1.13.0
  - twofactor_totp: 6.4.0
  - user_status: 1.4.0
  - viewer: 1.8.0
  - weather_status: 1.4.0
  - workflowengine: 2.6.0
Disabled:
  - cookbook: 0.9.14
  - grauphel
  - socialsharing_diaspora: 2.5.0
  - user_ldap

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

kesselb commented 2 years ago

If you believe, that something is a "major digital security risk", please report it to https://hackerone.com/nextcloud.

yahesh commented 2 years ago

Currently running into the same problem. This needs to be fixed.

kesselb commented 2 years ago

Hi,

thanks @aslfv for reporting the issue to h1 :+1:

On my test instance a suffix is automatically appended when a share with the same name already exist.

@yahesh do you have any idea why it's different on your instance?

yahesh commented 2 years ago

@kesselb Could you try what happens when one sending user shares a subfolder with the same name to the same receiving user (e.g foldera/shared/ and folderb/shared/)? That's what's happening in our case.

kesselb commented 2 years ago

I shared admin/TestA/Contracts and bob/TestB/Contracts to alice and see both folders. bob's with a suffix.

vitrex commented 1 year ago

I can confirm the issue:

An external folder named Photos, which is accessible by Alice and Bob. The structure is:

Photos
├── Holiday_1
│   └── Best
└── Holiday_2
    └── Best

Alice shares Holiday_1/Best with Charly.
Charly can see Best
Bob shares Holiday_2/Best with Charly.
Charly can no longer see (Holiday_1/)Best, it gets overwritten with (Holiday_2/)Best

My workaround was, that Charly renames the first shared folder to Best-Holiday_1. Afterwards he can get the next share.

I would also call it a possible security issue. Maybe it only happens on external shares?

kesselb commented 1 year ago

Hi,

Current status is that we don't know how to reproduce. If you observed something helpful, please let us know.

stefanvi commented 1 year ago

I can reproduce this as well. My installation is running the Nextcloud AIO (24.0.7) image with standard configurations, with the only exception being that the 'Shared' folder has a different default name. When one account shares a folder with a certain group, and another account shares a folder with the same name to the same group, the entire group will only see the new folder. That is to say, there are no suffixes added to either folder, it simply shows the most recent share.

stefanvi commented 1 year ago

I ran some tests to see when exactly a collision occurs that replaces an existing share. In the table below, the left column indicates that there is an existing shared folder with user Alice, by user Bob. This share can be personal, meaning Alice is the only recipient, it can be a share with a group that Alice is in, or both. The middle column indicates that Eve, a malicious user, shares a folder with the same name to Alice personally, or to a group that contains Alice. The right column shows when a collision occurs.

Alice is in a shared folder	Eve shares to	Collision
personal	personal	yes
personal	group	yes
group	personal	no
group	group	yes
personal, group	personal	yes
personal, group	group	yes

In the case where there is no collision, Alice does get an email notification about a new shared folder. Clicking the "Open >>Folder<<" button, opens Nextcloud, but fails to open the Folder itself. File could not be found

Edit: I completely reinstalled Nextcloud-aio via docker and the issue still occurs.

Edit 2: It also happens on a fresh install of the latest docker image (v25). I really don't understand what's going on anymore, but at this point I don't think I can trust this software.

PanieriLorenzo commented 1 year ago

Having the same issue here, on a new Docker deployment of nextcloud-apache 25 sharing SMB mounts.

kesselb commented 1 year ago

Thanks for your input :+1:

I will forward it accordingly.

nickvergessen commented 1 year ago

This was solved in 25.0.3 and the matching 24 version

nextcloud / server