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Share protected pages, images and feeds using signed URLs with the signing user's\nview permissions. Recipients do not need to log in as that user. Typical uses\ninclude private calendar feeds, HTML certificate rendering and sharing a survey\nwith people who do not have an account.<\/p>\n

Setup and administration<\/h2>\n

Install the zotonic_mod_access_url<\/code> application and enable mod_access_url<\/code> for\nthe site. The module adds a Share link to this page<\/strong> widget to the admin edit\nsidebar. An authenticated user who can view the resource can generate and copy\na link, choosing a duration or an indefinite link.<\/p>\n

There are no module configuration keys. Signing secrets are created on demand\nas mod_access_url<\/code> identities associated with the signing user.<\/p>\n

Generate a signed URL<\/h2>\n

Add z_access_url<\/code> to a dispatch URL generated in an authenticated context:<\/p>\n

{% url page id=id z_access_url absolute_url %}\n<\/code><\/pre>\n
To make the link valid for one hour:<\/p>\n
{% url page id=id z_access_url z_access_url_valid_for=3600 absolute_url %}\n<\/code><\/pre>\n
z_access_url_valid_for<\/code> accepts an integer duration in seconds or a binary date\nexpression understood by z_datetime:to_datetime\/1<\/code>, such as +day<\/code> or +week<\/code>.\nOmitting it creates a link without an expiry. The generated query contains the\nabsolute expiry timestamp; do not pass that timestamp back as an integer duration.<\/p>\n
The same arguments can be passed to z_dispatcher:url_for\/3<\/code>, or set on a context\nwhen generating resource page URLs. m_access_url:generate_url\/2,3<\/code> provides a\nconvenience API for absolute resource URLs. See m_access_url<\/code> for model calls.<\/p>\n
An integer z_access_url<\/code> selects another signing user only when the caller can\nedit that user's resource. Signing explicitly for user 1 requires the caller to\nbe user 1. Without a signing user, the URL is returned unsigned.<\/p>\n
Permissions and respondent identity<\/h2>\n
A valid link supplies an additional context for resource and property view<\/strong>\nchecks. It does not replace the visitor's logged-in identity or grant edit,\nupdate or delete permissions. Invalid, expired and unknown tokens leave normal\nrequest permissions in effect.<\/p>\n
For surveys using the standard submission handler, an anonymous recipient's\nanswers remain anonymous in the user_id<\/code> column and may be associated with a\nbrowser session. A logged-in recipient's answers belong to that recipient, not\nthe signer. Survey settings and custom submission handlers still apply; a signed\nlink is not a general authorization to perform writes.<\/p>\n
The module runs at priority 10 so its view grants can be evaluated before an ACL\nmodule returns a denial. Custom ACL integrations must preserve that ordering.<\/p>\n
Images, browser sessions and expiry<\/h2>\n
Image URLs generated through the image<\/code> dispatch while rendering a validated\naccess URL are signed using the validated signing user. They retain the parent\nlink's exact expiry, including the absence of an expiry. This allows renderers\nwithout the visitor's login cookies to fetch protected images.<\/p>\n
Resources granted view access can also be registered for the visitor's session\nfor four hours. These grants allow subsequent requests, such as survey pages,\nto access those resources without resending the original signature. Grants are\nkept in a site-specific ETS table on the current node and are lost when that\ntable is recreated. The four-hour grant period is independent of the signed\nURL's expiry and can outlast it.<\/p>\n
The _html_body.tpl<\/code> contribution uses m.access_url.reload_needed<\/code> to reload a\nsigned page after the Cotonic session cookie becomes available. Custom page\nlayouts should include the standard Zotonic body contributions for this behavior.\nImage signatures themselves do not require a browser session.<\/p>\n
Signature compatibility and diagnostics<\/h2>\n
Verification accepts current Base64URL signatures and earlier Base64 signatures.\nLinks without an expiry can also use the historical Erlang-term signatures,\nincluding the old use_absolute_url<\/code> variant. Compatibility checks reconstruct\nserver-side data; they never deserialize a term supplied by the requester.<\/p>\n
Failure logs distinguish expired<\/code>, invalid_expiry<\/code>, malformed_signature<\/code>,\nsignature_mismatch<\/code> and unknown_user_token<\/code>. Successful verification logs the\nsignature format at debug level. These logs omit tokens, signatures and secrets.\nAdded application parameters, including tracking parameters, invalidate a link.<\/p>\n
Sharing and scope<\/h2>\n
Anyone holding a valid link can use it. Share links only with intended recipients\nand avoid exposing them in public pages or logs. The signature binds the dispatch\nand application arguments; language and internal access-URL arguments are handled\nseparately. It does not turn arbitrary links on the page into signed links.\nValidated responses receive a noindex header.<\/p>\n
The public register_resource\/2<\/code> helper records a session grant without checking\nACLs itself. Use it only after authorizing access; is_resource_registered\/2<\/code>\nchecks whether that session grant is still valid.<\/p>","slug":"mod_access_url","doc_module_config":[],"is_protected":false,"visible_for":0,"tz":"UTC","language":["en"],"doc_source_hash":"66a08a21370fde286f76a04f0e5d6b5b9164db3ccf99a5d7deb8927011eb5077","doc_module_observers":[{"name":"acl_is_allowed","page_name":"doc_notification_acl_is_allowed"},{"name":"acl_is_allowed_prop","page_name":"doc_notification_acl_is_allowed_prop"},{"name":"middleware","page_name":"doc_notification_middleware"},{"name":"tick_24h","page_name":"doc_notification_tick_24h"},{"name":"url_rewrite","page_name":"doc_notification_url_rewrite"}],"is_featured":false,"content_group_id":{"id":2551,"is_a":["meta","content_group"],"name":"content_group_imported_docs","title":"Imported documentation","uri":"https:\/\/zotonic.com\/id\/content_group_imported_docs"},"external_module_id":{"id":5,"is_a":[],"name":null,"title":null,"uri":"https:\/\/zotonic.com\/id\/5"},"git_url":"https:\/\/github.com\/zotonic\/zotonic_mod_access_url","category_id":{"id":320,"is_a":["meta","category"],"name":"module","title":"Modules","uri":"https:\/\/test.zotonic.com\/id\/320"},"doc_source_path":".\/src\/mod_access_url.erl","publication_start":"2026-10-20T12:30:42Z","github_url":"https:\/\/github.com\/zotonic\/zotonic_mod_access_url","pivot_location_lng":null,"doc_source_kind":"external","name":"doc_external_5_mod_access_url","is_unfindable":false,"is_published":true,"pivot_geocode":null,"external_module_title":"Access URLs","created":"2026-10-20T12:30:42Z","uri":null,"doc_status":"current","is_dependent":false,"is_external_module":true,"publication_end":"9999-06-01T00:00:00Z","modifier_id":{"id":1,"is_a":["person"],"name":"administrator","title":"Site Administrator","uri":"https:\/\/zotonic.com\/id\/1"},"privacy":0,"doc_source_commit":"1f353ae6249143f0a1ae35b298a6210170607f71","creator_id":{"id":1,"is_a":["person"],"name":"administrator","title":"Site Administrator","uri":"https:\/\/zotonic.com\/id\/1"},"modified":"2026-10-20T12:30:42Z","title_slug":"mod_access_url"},"uri":"https:\/\/zotonic.com\/id\/3094","uri_template":"https:\/\/zotonic.com\/id\/:id","websub":{"hub":"https:\/\/zotonic.com\/.zotonic\/websub","topic":"https:\/\/zotonic.com\/.zotonic\/websub\/topic\/3094"}},"status":"ok"}