| 1 |
<?php |
| 2 |
/** |
| 3 |
* Unauthenticated File Upload Helper Functions. |
| 4 |
* |
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* @package automattic/jetpack |
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*/ |
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|
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namespace Automattic\Jetpack\UnauthFileUpload; |
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|
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if ( ! defined( 'ABSPATH' ) ) { |
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exit( 0 ); |
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} |
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|
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add_action( 'wp_ajax_jetpack_unauth_file_download', __NAMESPACE__ . '\handle_file_download' ); |
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add_filter( 'jetpack_unauth_file_upload_get_file', __NAMESPACE__ . '\get_file_content', 10, 2 ); |
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add_filter( 'jetpack_unauth_file_download_url', __NAMESPACE__ . '\filter_get_download_url', 10, 2 ); |
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|
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/** |
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* The lifetime of a download link, in seconds. |
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* |
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* Kept generous enough that an editor returning to the responses dashboard days later still |
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* has a working link, short enough to limit the exposure of a leaked URL. |
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*/ |
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const DOWNLOAD_LINK_LIFETIME = 7 * DAY_IN_SECONDS; |
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|
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/** |
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* The token scheme version carried in download links. |
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* |
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* Travels in the URL as `token_version` and is bound into the signature, so the signing scheme |
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* can be changed in the future (bump this and branch on the value in authorize_file_download()) |
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* without older links being mistaken for the new format. |
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*/ |
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const DOWNLOAD_TOKEN_VERSION = 'v1'; |
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|
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/** |
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* Get the secret used to sign download links. |
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* |
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* Defaults to the Jetpack blog token, which this feature already depends on (the file content |
| 39 |
* is fetched from WP.com as the blog). There is nothing extra to store, and reconnecting |
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* Jetpack rotates the token and so invalidates any outstanding links. Only the secret portion |
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* of the token (after the publicly-visible key prefix) is used, matching the rest of the |
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* connection stack. |
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* |
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* @since 16.0 |
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* |
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* @return string The signing key, or an empty string if no secret is available. |
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*/ |
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function get_download_signing_key() { |
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$blog_token = ( new \Automattic\Jetpack\Connection\Tokens() )->get_access_token(); |
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$secret = ''; |
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|
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if ( $blog_token && ! is_wp_error( $blog_token ) && ! empty( $blog_token->secret ) ) { |
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// Blog tokens are stored as "key.secret"; sign with the secret part only, matching the |
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// rest of the connection stack. Require exactly two non-empty parts so a malformed token |
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// fails closed rather than signing links the fetch path could never honor. |
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$parts = explode( '.', (string) $blog_token->secret, 2 ); |
| 57 |
if ( count( $parts ) === 2 && '' !== $parts[0] && '' !== $parts[1] ) { |
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$secret = $parts[1]; |
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} |
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} |
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|
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/** |
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* Filters the secret used to sign Forms unauthenticated file-download links. |
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* |
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* Defaults to the Jetpack blog token secret. Environments without a usable blog token |
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* (e.g. WordPress.com Simple) can return their own stable, secret value here so that |
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* download links can still be signed and verified. |
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* |
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* @since 16.0 |
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* |
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* @param string $secret The signing secret. Empty string if none is available. |
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*/ |
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return (string) apply_filters( 'jetpack_unauth_file_download_signing_key', $secret ); |
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} |
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|
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/** |
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* Generate a signed token authorizing the download of a given file. |
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* |
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* Unlike a WordPress nonce, the token is not tied to a specific user or session, so a link |
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* generated by one logged-in editor works for any logged-in editor. The expiry timestamp is |
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* part of the signed payload, so it cannot be tampered with to extend access. |
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* |
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* @since 16.0 |
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* |
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* @param int $file_id The file ID. |
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* @param int $expires Unix timestamp at which the link stops being valid. |
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* @param string $version The token scheme version. Defaults to the current scheme. |
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* |
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* @return string The hex-encoded HMAC-SHA256 token, or an empty string if there is no signing key. |
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*/ |
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function generate_download_token( $file_id, $expires, $version = DOWNLOAD_TOKEN_VERSION ) { |
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$key = get_download_signing_key(); |
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|
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if ( '' === $key ) { |
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return ''; |
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} |
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|
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$payload = 'jetpack_unauth_file_download|' . $version . '|' . (int) $file_id . '|' . (int) $expires; |
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return hash_hmac( 'sha256', $payload, $key ); |
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} |
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|
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/** |
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* Verify a download token against the expected signature using a constant-time comparison. |
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* |
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* Expiry is checked separately by the caller so it can surface a distinct "expired" message. |
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* Fails closed when no signing key is available (i.e. the site is not connected). |
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* |
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* @since 16.0 |
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* |
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* @param int $file_id The file ID. |
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* @param int $expires Unix timestamp the token was signed with. |
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* @param string $token The token supplied in the request. |
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* @param string $version The token scheme version the token was signed with. |
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* |
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* @return bool True if the token matches. |
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*/ |
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function verify_download_token( $file_id, $expires, $token, $version = DOWNLOAD_TOKEN_VERSION ) { |
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$expected = generate_download_token( $file_id, $expires, $version ); |
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|
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return '' !== $expected |
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&& is_string( $token ) && '' !== $token |
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&& hash_equals( $expected, $token ); |
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} |
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|
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/** |
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* Get the file download URL filter callback. |
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* |
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* @param string $url The file download URL. |
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* @param int $file_id The file ID. |
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* |
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* @return string The file download URL. |
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*/ |
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function filter_get_download_url( $url, $file_id ) { |
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$expires = time() + DOWNLOAD_LINK_LIFETIME; |
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$token = generate_download_token( $file_id, $expires ); |
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|
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if ( '' === $token ) { |
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// No signing key (disconnected site, or WP.com Simple without the signing-key filter |
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// wired). Return the passthrough so callers omit the link instead of handing out one |
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// that can never work, and leave a breadcrumb for operators. |
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error_log( 'Jetpack Forms: unable to sign file download link; no signing key available.' ); // phpcs:ignore WordPress.PHP.DevelopmentFunctions.error_log_error_log |
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return $url; |
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} |
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|
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return add_query_arg( |
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array( |
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'action' => 'jetpack_unauth_file_download', |
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'file_id' => $file_id, |
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'expires' => $expires, |
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'token_version' => DOWNLOAD_TOKEN_VERSION, |
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'token' => $token, |
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), |
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admin_url( 'admin-ajax.php' ) |
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); |
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} |
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|
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/** |
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* Reject a download request with the generic invalid-link error and a debug code, then exit. |
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* |
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* The message stays generic so it leaks nothing to the requester and stays actionable (a token |
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* can be rejected simply because the blog token rotated on reconnect), while the appended code |
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* identifies which check failed, so a user-reported screenshot is enough to locate the cause: |
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* |
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* 1 - Missing or unrecognized token_version. |
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* 2 - Token signature did not verify. |
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* 3 - Legacy nonce did not verify. |
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* 4 - No token and no legacy nonce supplied. |
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* |
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* @since 16.0 |
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* |
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* @param int $code Number identifying the failing check. |
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* |
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* @return void Terminates the request via wp_die(). |
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*/ |
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function invalid_download_link( $code ) { |
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wp_die( |
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esc_html( |
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sprintf( |
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/* translators: %d: error code used for debugging. */ |
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__( 'This download link is no longer valid. Reload the responses page to get a fresh link. (%d)', 'jetpack' ), |
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(int) $code |
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) |
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), |
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'', |
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array( 'response' => 403 ) |
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); |
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} |
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|
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/** |
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* Authorize a download request and return the requested file ID. |
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* |
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* Holds the security-critical gate (capability check, then either the current signed-token |
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* scheme or the legacy nonce fallback). Terminates the request via wp_die() on any failure and |
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* only returns when the caller is allowed to download the file. Kept separate from the |
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* file-serving logic in handle_file_download() so each branch is unit-testable without the |
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* headers/exit of the serving path. |
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* |
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* @since 16.0 |
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* |
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* @return int The validated file ID. |
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*/ |
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function authorize_file_download() { |
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if ( ! current_user_can( 'edit_pages' ) ) { |
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wp_die( esc_html__( 'Sorry, you are not allowed to access this page.', 'jetpack' ), '', array( 'response' => 403 ) ); |
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} |
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|
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$file_id = isset( $_GET['file_id'] ) ? absint( wp_unslash( $_GET['file_id'] ) ) : 0; |
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|
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if ( ! $file_id ) { |
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wp_die( esc_html__( 'Invalid file request.', 'jetpack' ), '', array( 'response' => 400 ) ); |
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} |
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|
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$token = isset( $_GET['token'] ) ? sanitize_text_field( wp_unslash( $_GET['token'] ) ) : ''; |
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|
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if ( '' !== $token ) { |
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// Current scheme: a site-signed, expiring token. Future schemes can branch on the version. |
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$token_version = isset( $_GET['token_version'] ) ? sanitize_text_field( wp_unslash( $_GET['token_version'] ) ) : ''; |
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|
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if ( DOWNLOAD_TOKEN_VERSION !== $token_version ) { |
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invalid_download_link( 1 ); |
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} |
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|
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$expires = isset( $_GET['expires'] ) ? absint( wp_unslash( $_GET['expires'] ) ) : 0; |
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|
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// A link is valid up to and including its expiry second; expired once time passes it. |
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if ( ! $expires || $expires < time() ) { |
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wp_die( esc_html__( 'This download link has expired. Reload the responses page to get a fresh link.', 'jetpack' ), '', array( 'response' => 410 ) ); |
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} |
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|
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// $token_version was asserted equal to DOWNLOAD_TOKEN_VERSION above; pass the constant so |
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// a future multi-version branch can't accidentally feed the request value back in. |
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if ( ! verify_download_token( $file_id, $expires, $token, DOWNLOAD_TOKEN_VERSION ) ) { |
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invalid_download_link( 2 ); |
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} |
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} elseif ( isset( $_GET['_wpnonce'] ) ) { |
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/* |
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* Backward compatibility for legacy per-file nonce links that may still be circulating |
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* in already-sent emails. WordPress nonces are only valid for ~24h, so these links |
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* expire on their own shortly after the signed-token scheme ships. |
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* |
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* @todo Remove this legacy nonce fallback in Jetpack 16.3 or later; links signed under |
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* the old scheme self-expire within ~24h of the signed-token scheme shipping. |
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*/ |
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if ( ! wp_verify_nonce( sanitize_text_field( wp_unslash( $_GET['_wpnonce'] ) ), 'jetpack_unauth_file_download_nonce_' . $file_id ) ) { |
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invalid_download_link( 3 ); |
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} |
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} else { |
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invalid_download_link( 4 ); |
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} |
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|
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return $file_id; |
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} |
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|
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/** |
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* Handle file download requests from the admin page. |
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* |
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* @return never This method never returns as it exits directly |
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*/ |
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function handle_file_download() { |
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$file_id = authorize_file_download(); |
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|
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/** |
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* Get the file content that we send to the user to download. |
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* |
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* @since 14.6 |
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* |
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* @param array $file_content The file content. |
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* @param string $file_id The file ID. |
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* |
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* @return array|\WP_Error The file array, containing the content, name and type. |
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*/ |
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$file = apply_filters( 'jetpack_unauth_file_upload_get_file', array(), $file_id ); |
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|
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if ( is_wp_error( $file ) || empty( $file ) || ! is_array( $file ) ) { |
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wp_die( esc_html__( 'Error retrieving file content.', 'jetpack' ) ); |
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} |
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|
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// Given $file can be manipulated by a filter, make sure everything is as it should be. |
| 279 |
$file['content'] ??= ''; |
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$file['type'] ??= 'application/octet-stream'; |
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$file['name'] ??= ''; |
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|
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// phpcs:ignore WordPress.Security.NonceVerification.Recommended -- The request is already authorized in authorize_file_download() before reaching here. |
| 284 |
$is_preview = isset( $_GET['preview'] ) && 'true' === $_GET['preview'] && is_file_type_previewable( $file['type'] ); |
| 285 |
|
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// Clean output buffer |
| 287 |
if ( ob_get_length() ) { |
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ob_clean(); |
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} |
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// Set headers for download |
| 291 |
header( 'Content-Type: ' . $file['type'] ); |
| 292 |
|
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if ( ! $is_preview ) { |
| 294 |
// Forcing the file to be downloaded is important to prevent XSS attacks. |
| 295 |
header( 'Content-Disposition: attachment; filename="' . sanitize_file_name( $file['name'] ) . '"' ); |
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} else { |
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// For preview mode, use inline disposition |
| 298 |
header( 'Content-Disposition: inline; filename="' . sanitize_file_name( $file['name'] ) . '"' ); |
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} |
| 300 |
header( 'Content-Length: ' . strlen( $file['content'] ) ); |
| 301 |
header( 'Content-Transfer-Encoding: binary' ); |
| 302 |
header( 'Cache-Control: no-cache, must-revalidate, max-age=0' ); |
| 303 |
header( 'Pragma: no-cache' ); |
| 304 |
header( 'Expires: 0' ); |
| 305 |
|
| 306 |
// Output file content and exit |
| 307 |
echo $file['content']; // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- Binary file data |
| 308 |
exit( 0 ); |
| 309 |
} |
| 310 |
|
| 311 |
/** |
| 312 |
* Get the file content. |
| 313 |
* |
| 314 |
* @param array $file_content The file content, name and type. |
| 315 |
* @param integer $file_id The file ID. |
| 316 |
* @return array|\WP_Error The file content, name and type |
| 317 |
*/ |
| 318 |
function get_file_content( $file_content, $file_id ) { |
| 319 |
if ( ( new \Automattic\Jetpack\Status\Host() )->is_wpcom_simple() ) { |
| 320 |
return $file_content; |
| 321 |
} |
| 322 |
|
| 323 |
$blog_id = \Jetpack_Options::get_option( 'id' ); |
| 324 |
$request_url = sprintf( '/sites/%d/unauth-file-upload/%s', $blog_id, $file_id ); |
| 325 |
|
| 326 |
$response = \Automattic\Jetpack\Connection\Client::wpcom_json_api_request_as_blog( |
| 327 |
$request_url, |
| 328 |
'v2', |
| 329 |
array( |
| 330 |
'method' => 'GET', |
| 331 |
), |
| 332 |
null, |
| 333 |
'wpcom' |
| 334 |
); |
| 335 |
|
| 336 |
$file_content = wp_remote_retrieve_body( $response ); |
| 337 |
|
| 338 |
if ( is_wp_error( $response ) || empty( $file_content ) ) { |
| 339 |
return new \WP_Error( 'jetpack_unauth_file_upload_error', esc_html__( 'Error retrieving file content.', 'jetpack' ) ); |
| 340 |
} |
| 341 |
|
| 342 |
try { |
| 343 |
$content = json_decode( $file_content, true, 3, defined( 'JSON_THROW_ON_ERROR' ) ? \JSON_THROW_ON_ERROR : 0 ); // phpcs:ignore PHPCompatibility.Constants.NewConstants.json_throw_on_errorFound |
| 344 |
if ( isset( $content['message'] ) ) { |
| 345 |
return new \WP_Error( 'jetpack_unauth_file_upload_error', esc_html__( 'Error retrieving file content.', 'jetpack' ) ); |
| 346 |
} |
| 347 |
} catch ( \Exception $e ) { // phpcs:ignore Generic.CodeAnalysis.EmptyStatement.DetectedCatch |
| 348 |
// If the file is not JSON, we assume it's a binary file. |
| 349 |
} |
| 350 |
|
| 351 |
$content_disposition = wp_remote_retrieve_header( $response, 'content-disposition' ); |
| 352 |
$filename = ''; |
| 353 |
if ( $content_disposition ) { |
| 354 |
// Match the filename using a regular expression |
| 355 |
if ( preg_match( '/filename="([^"]+)"/', $content_disposition, $matches ) ) { |
| 356 |
$filename = $matches[1]; // Extract the filename |
| 357 |
} |
| 358 |
} |
| 359 |
|
| 360 |
$type = wp_remote_retrieve_header( $response, 'content-type' ); |
| 361 |
if ( empty( $type ) ) { |
| 362 |
$type = 'application/octet-stream'; // Default to binary if no content type is found |
| 363 |
} |
| 364 |
|
| 365 |
return array( |
| 366 |
'content' => $file_content, |
| 367 |
'type' => $type, |
| 368 |
'name' => $filename, |
| 369 |
); |
| 370 |
} |
| 371 |
|
| 372 |
/** |
| 373 |
* Check which file type is previewable in the browser without downloading them. |
| 374 |
* |
| 375 |
* Allow images with extensions jpg, jpeg, png, gif, webp and pdf files. |
| 376 |
* |
| 377 |
* @param string $file_type The MIME type of the file. |
| 378 |
* @return bool True if the file is previable, false otherwise. |
| 379 |
*/ |
| 380 |
function is_file_type_previewable( $file_type ) { |
| 381 |
$previable_types = array( |
| 382 |
'image/jpeg', |
| 383 |
'image/png', |
| 384 |
'image/gif', |
| 385 |
'image/webp', |
| 386 |
'application/pdf', |
| 387 |
); |
| 388 |
|
| 389 |
return in_array( $file_type, $previable_types, true ); |
| 390 |
} |
| 391 |
|
