Add digital signatures to PDF reports using OpenSSL-generated self-si…

…gned certificates

--

**Add digital signatures to PDF reports using OpenSSL-generated self-signed certificates**

- **Implemented digital signing of PDF erasure certificates**
  - Generates a self-signed X.509 certificate at runtime using OpenSSL.
  - Signs the generated PDF reports to ensure their authenticity and integrity.
- **Embedded the digital signature within the PDF documents**
  - Provides a method to verify that the reports are genuine and have not been tampered with.
- **Enhances security and trustworthiness of the PDF reports**
  - Ensures that recipients can validate the source and integrity of the reports.
- **Uses locally trusted PKI for proof of concept**
  - While a self-signed certificate is used for demonstration purposes, a certificate from a trusted Certificate Authority (CA) is recommended for production environments.

configure.ac

@@ -50,6 +50,24 @@ PKG_CHECK_MODULES(
 	)]
 )
 
+PKG_CHECK_MODULES(
+    [OPENSSL],
+    [openssl],
+    [
+            CFLAGS="${CFLAGS} ${OPENSSL_CFLAGS}"
+            LIBS="${LIBS} ${OPENSSL_LIBS}"
+    ],
+    [AC_CHECK_LIB([ssl], [SSL_library_init], [
+            LIBS="-lssl -lcrypto $LIBS"
+            AC_CHECK_HEADERS(openssl/ssl.h,, [
+                AC_CHECK_HEADERS(openssl/crypto.h, [
+                    AC_DEFINE([OPENSSL_IN_SUBDIR], [openssl/], [Look for openssl headers in subdir])
+                    ], [AC_MSG_ERROR([openssl headers not found])])
+            ])
+        ], [AC_MSG_ERROR([OpenSSL development library not found])]
+    )]
+)
+
 PKG_CHECK_MODULES(
 	[LIBCONFIG],
 	[libconfig],