Publish instructions on the new common/show_image.php

docs/abcd-advanced/format-language/viewer-central.md

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+---
+title: "Secure Image Viewer (Central show_image.php)"
+sidebar_label: Secure Image Viewer
+sidebar_position: 3
+---
+
+The `show_image.php` script located in the `central/common/` directory is a robust, security-hardened mechanism for displaying digital assets within the ABCD Central administrative interface and the OPAC. Unlike standard file links, this script is designed to serve media located **outside** the web server's public `DOCUMENT_ROOT`, protecting sensitive files from direct exposure.
+
+Recent updates have significantly improved its security posture, making it a "safe than sorry" solution against modern web vulnerabilities.
+
+## Key Security Features
+
+* **Path Traversal Prevention:** The script strictly forbids the use of `..` in URLs and uses PHP's `realpath()` to ensure requested files remain within the authorized base directory.
+* **Referrer Validation:** To prevent hotlinking and direct URL manipulation, the script only executes if the request originates from a recognized ABCD `central` or `opac` host.
+* **Session-Based Access:** For administrative requests, the script verifies that the user is actively logged into ABCD with a valid profile and permissions.
+* **Strict Sanitization:** Input parameters undergo rigorous cleaning; only alphanumeric characters, slashes (`/`), dots (`.`), underscores (`_`), and dashes (`-`) are permitted.
+* **MIME Type Whitelisting:** The script only serves files with recognized extensions (e.g., jpg, pdf, mp3, zip) and maps them to their correct Content-Type.
+
+---
+
+## Configuration
+
+To serve files, the script requires a defined **ROOT** directory. This is configured in the `dr_path.def` file located in your database folder:
+`.../bases/[database_name]/dr_path.def`.
+
+### The ROOT Parameter
+
+The `ROOT` parameter defines the starting point for media searches. It supports the `%path_database%` variable for portability.
+
+```ini
+/* Example 1: Standard images folder */
+ROOT=%path_database%nvbsodr/images
+
+/* Example 2: Secure FTP upload folder */
+ROOT=%path_database%nvbsodr/ftp_nvbsodr/files
+
+```
+
+:::important Configuration Logic
+
+1. **If `dr_path.def` exists:** The `ROOT` parameter is **mandatory**. If it is missing or empty, the script will terminate with a configuration error.
+2. **If `dr_path.def` does not exist:** The script defaults to the database's root folder (`%path_database%[databasename]`).
+:::
+
+---
+
+## Usage in PFT (ISIS Formatting Language)
+
+You can call this script within your `.pft` display files to render links or embedded media. The script requires two URL parameters: `image` (the path) and `base` (the database name).
+
+### 1. Simple Download/View Link
+
+This creates a text link that opens the file in the current window.
+
+```pft
+if p(v160) then 
+    '<tr><td><b>File:</b></td>'
+    '<td><a href="/central/common/show_image.php?image='v160'&base=nvbsodr">'v160'</a></td></tr>' 
+fi/
+
+```
+
+### 2. Intelligent Media Embedding (PDF vs. Images)
+
+This advanced example detects the file extension to decide whether to use an `<embed>` tag for PDFs or a clickable thumbnail for images.
+
+```pft
+'<tr><td style="text-align:center" width="250px">'
+(if right(v160,4)='.pdf' then 
+    /* PDF View */
+    '<a href="/central/common/show_image.php?image='v160'&base=nvbsodr">Show PDF</a>'
+    '<embed src="/central/common/show_image.php?image='v160'&base=nvbsodr" width=350 height=300>'
+else if p(v160) then 
+    /* Image View */
+    '<a href="/central/common/show_image.php?image='v160'&base=nvbsodr">'
+    '<embed src="/central/common/show_image.php?image='v160'&base=nvbsodr" width=225></a>' 
+fi/ /fi/)
+
+/* Default image if field is empty */
+(if a(v160) then '<img src="/assets/images/no_image_nl.jpg" width=120>' fi/)
+'</td>'
+
+```
+
+---
+
+## Technical Specifications
+
+### Supported File Types
+
+The script includes a comprehensive `switch` block to handle various formats:
+
+* **Images:** jpg, jpeg, gif, png, bmp, tiff.
+* **Documents:** pdf, doc, txt, rtf, html, xls, xlsx, ppt.
+* **Archives/Multimedia:** zip, exe, mp3, wav, avi, mpeg.
+
+### Security Updates
+
+* **2023-01-04:** Added lowercase extension conversion to ensure compatibility with Linux servers.
+* **2026-02-28:** Implemented `realpath` validation to block Path Traversal.
+* **2026-03-08:** Added `HTTP_REFERER` checks and enhanced filename sanitization.
+
+Would you like me to generate a specific PFT example for a different database field or explain how to customize the error messages in this script?
+
+Aliás, para liberar as funcionalidades de todos os apps, ative a [Atividade nos apps do Gemini](https://myactivity.google.com/product/gemini).