first public version

LICENSE

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+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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README.md

@@ -1,2 +1,161 @@
-# sapp
-Simply a PDF Document Parser in PHP
+# SAPP - Simply A PDF Document Parser
+
+SAPP stands for Simply a PDF Parser and it makes what is name says: parsing PDF files. It also enables other cool features such as rebuilding documents (to make the content more clear or compact), adding images or digitally signing documents.
+
+# 1. Why SAPP
+I created SAPP because I wanted to programmatically sign documents, including **multiple signatures**.
+
+I tried [tcpdf](https://tcpdf.org/) along with [FPDI](https://www.setasign.com/products/fpdi/downloads/), but the results are not those expected. When importing a document using FPDI, the result is a new document with the pages of the original one, not the original document. So if the original document was signed, those signatures were lost.
+
+I read about [SetaPDF-Signer](https://www.setasign.com/products/setapdf-signer/details/), but it cannot be used for free. I also inspected some CLI tools such as [PortableSigner](https://github.com/pflaeging/PortableSigner2), but (1) it was Java based (and I really don't like java) and (2) it depends on iText and other libraries which don't seem to be free at this moment.
+
+At the end I got the [PDF 1.7 definition](https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/PDF32000_2008.pdf), and I learned about incremental PDF documents and its utility to include multiple signature in documents.
+
+# 2. Using SAPP
+
+To test the examples, you can clone the repository and use [composer](https://getcomposer.org/):
+
+```bash
+$ git clone https://github.com/dealfonso/sapp
+$ cd sapp
+$ composer dump-autoload
+$ php pdfrebuild.php examples/testdoc.pdf > testdoc-rebuilt.pdf
+``` 
+
+## 1.1. Examples
+
+In the root folder you can find two simple examples: 
+
+1. `pdfrebuild.php`: this example gets a PDF file, loads it and rebuilds it to make every PDF object to be in order, and also reducing the amount of text to define the document. 
+1. `pdfsign.php`: this example gets a PDF file and digitally signs it using a pkcs12 (pfx) certificate.
+
+### 2.1.1. Rebuild PDF files with `pdfrebuild.php`
+
+Once cloned the repository and generated the autoload content, it is possible to run the example:
+
+```bash
+$ php pdfrebuild.php examples/testdoc.pdf > testdoc-rebuilt.pdf
+```
+
+The result is a more ordered PDF document which is (problably) smaller. (e.g. rebuilding examples/testdoc.pdf provides a 50961 bytes document while the original was 51269 bytes).
+
+```
+$ ls -l examples/testdoc.pdf
+-rw-r--r--@ 1 calfonso  staff  51269  5 nov 14:01 examples/testdoc.pdf
+$ ls -l testdoc-rebuilt.pdf
+-rw-r--r--@ 1 calfonso  staff  50961  5 nov 14:22 testdoc-rebuilt.pdf
+```
+
+And the `xref` table looks significantly better ordered:
+```
+$ cat examples/testdoc.pdf
+...
+xref
+0 39
+0000000000 65535 f
+0000049875 00000 n
+0000002955 00000 n
+0000005964 00000 n
+0000000022 00000 n
+0000002935 00000 n
+0000003059 00000 n
+0000005928 00000 n
+...
+$ cat testdoc-rebuilt.pdf
+...
+xref
+0 8
+0000000000 65535 f
+0000000009 00000 n
+0000000454 00000 n
+0000000550 00000 n
+0000000623 00000 n
+0000003532 00000 n
+0000003552 00000 n
+0000003669 00000 n
+...
+```
+
+**The code:**
+
+```php
+use ddn\sapp\PDFDoc;
+
+require_once('vendor/autoload.php');
+
+if ($argc !== 2)
+    fwrite(STDERR, sprintf("usage: %s <filename>", $argv[0]));
+else {
+    if (!file_exists($argv[1]))
+        fwrite(STDERR, "failed to open file " . $argv[1]);
+    else {
+        $obj = PDFDoc::from_string(file_get_contents($argv[1]));
+
+        if ($obj === false)
+            fwrite(STDERR, "failed to parse file " . $argv[1]);
+        else
+            echo $obj->to_pdf_file_s(true);
+    }
+}
+```
+
+### 2.1.2. Sign PDF files with `pdfsign.php`
+
+To sign a PDF document, it is possible to use the script `pdfsign.php`:
+
+```bash
+$ php pdfsign.php examples/testdoc.pdf caralla.p12 > testdoc-signed.pdf
+```
+
+And now the document is signed. And if you wanted to add a second signature, it is as easy as signing the resulting document again:
+
+```bash
+$ php pdfsign.php testdoc-signed.pdf user.p12 > testdoc-resigned.pdf
+```
+
+**The code:**
+
+```php
+use ddn\sapp\PDFDoc;
+
+require_once('vendor/autoload.php');
+
+if ($argc !== 3)
+    fwrite(STDERR, sprintf("usage: %s <filename> <certfile>", $argv[0]));
+else {
+    if (!file_exists($argv[1]))
+        fwrite(STDERR, "failed to open file " . $argv[1]);
+    else {
+        // Silently prompt for the password
+        fwrite(STDERR, "Password: ");
+        system('stty -echo');
+        $password = trim(fgets(STDIN));
+        system('stty echo');
+        fwrite(STDERR, "\n");
+
+        $file_content = file_get_contents($argv[1]);
+        $obj = PDFDoc::from_string($file_content);
+
+        if ($obj === false)
+            fwrite(STDERR, "failed to parse file " . $argv[1]);
+        else {
+            if ($obj->sign_document($argv[2], $password) === false)
+                fwrite(STDERR, "could not sign the document");
+            else
+                echo $obj->to_pdf_file_s();
+        }
+    }
+}
+```
+
+# 3. Limitations
+
+At this time, the main limitations are:
+- Not dealing with **non-zero generation** pdf objects: they are uncommon, but according to the definition of the PDF structure, they are possible. If you find one non-zero generation object (you get an exception or error in that sense), please send me the document and I'll try to support it.
+- Not dealing with **encrypted documents**.
+- Other limitations, for sure :)
+
+# 4. Attributions
+
+1. The mechanism for calculating the signature hash is heavily inspired in tcpdf.
+1. Reading jpg and png files has been taken from fpdf.

composer.json

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+{
+    "name": "ddn/sapp",
+    "description": "Simply a PDF Parser",
+    "type": "library",
+    "license": "GNU/LGPLv3",
+    "authors": [
+        {
+            "name": "Carlos A.",
+            "email": "[email protected]"
+        }
+    ],
+    "require": {
+        "php": "^7.2"        
+    },
+    "autoload": {
+        "psr-4": {"ddn\\sapp\\": "src/"}
+    }
+}

pdfrebuild.php

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+<?php
+/*
+    This file is part of SAPP
+
+    Simply A PDF Parser (SAPP) - Parse PDF documents in PHP (and update them)
+    Copyright (C) 2020 - Carlos de Alfonso ([email protected])
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+use ddn\sapp\PDFDoc;
+
+require_once('vendor/autoload.php');
+
+if ($argc !== 2)
+    fwrite(STDERR, sprintf("usage: %s <filename>", $argv[0]));
+else {
+    if (!file_exists($argv[1]))
+        fwrite(STDERR, "failed to open file " . $argv[1]);
+    else {
+        $obj = PDFDoc::from_string(file_get_contents($argv[1]));
+
+        if ($obj === false)
+            fwrite(STDERR, "failed to parse file " . $argv[1]);
+        else
+            echo $obj->to_pdf_file_s(true);
+    }
+}