From 7a3358b7875622c93853b76b6ec34f5c2edb1939 Mon Sep 17 00:00:00 2001
From: Chinmoy Ranjan Pradhan <chinmoyrp65@protonmail.com>
Date: Sat, 7 Apr 2018 17:40:24 +0000
Subject: [PATCH] Add ability to extract signature information to pdfsig tool

This patch adds '-dump' option to pdfsig tool which can be used to extract signatures
into the current working directory.
---
 poppler/Form.cc |  5 +++++
 poppler/Form.h  |  2 ++
 utils/pdfsig.cc | 30 +++++++++++++++++++++++++++++-
 3 files changed, 36 insertions(+), 1 deletion(-)

diff --git a/poppler/Form.cc b/poppler/Form.cc
index 6aff30d1..19088616 100644
--- a/poppler/Form.cc
+++ b/poppler/Form.cc
@@ -461,6 +461,11 @@ FormWidgetSignature::FormWidgetSignature(PDFDoc *docA, Object *aobj, unsigned nu
   type = formSignature;
 }
 
+GooString *FormWidgetSignature::getSignature()
+{
+    return static_cast<FormFieldSignature*>(field)->getSignature();
+}
+
 SignatureInfo *FormWidgetSignature::validateSignature(bool doVerifyCert, bool forceRevalidation, time_t validationTime)
 {
   return static_cast<FormFieldSignature*>(field)->validateSignature(doVerifyCert, forceRevalidation, validationTime);
diff --git a/poppler/Form.h b/poppler/Form.h
index 9df6b22e..3a85f094 100644
--- a/poppler/Form.h
+++ b/poppler/Form.h
@@ -283,6 +283,8 @@ public:
   // if the check passed (and the checked file size as output parameter in checkedFileSize)
   // otherwise a nullptr is returned
   GooString* getCheckedSignature(Goffset *checkedFileSize);
+
+  GooString *getSignature();
 };
 
 //------------------------------------------------------------------------
diff --git a/utils/pdfsig.cc b/utils/pdfsig.cc
index 2f08c82a..04bdd730 100644
--- a/utils/pdfsig.cc
+++ b/utils/pdfsig.cc
@@ -21,6 +21,7 @@
 #include <string.h>
 #include <time.h>
 #include <hasht.h>
+#include <fstream>
 #include "parseargs.h"
 #include "Object.h"
 #include "Array.h"
@@ -88,13 +89,32 @@ static char *getReadableTime(time_t unix_time)
   return time_str;
 }
 
+static void dumpSignature(int sig_num, FormWidgetSignature *sig_widget, const char *filename)
+{
+    GooString *signature = sig_widget->getSignature();
+    if (!signature) {
+        printf("Cannot dump signature #%d\n", sig_num);
+        return;
+    }
+
+    char buf[1024];
+    snprintf(buf, sizeof buf, "%s.sig%02u", basename(filename), sig_num);
+    printf("Signature #%d (%u bytes) => %s\n", sig_num, signature->getLength(), buf);
+    std::ofstream outfile(buf, std::ofstream::binary);
+    outfile.write(signature->getCString(), signature->getLength());
+    outfile.close();
+}
+
 static GBool printVersion = gFalse;
 static GBool printHelp = gFalse;
 static GBool dontVerifyCert = gFalse;
+static GBool dumpSignatures = gFalse;
 
 static const ArgDesc argDesc[] = {
   {"-nocert", argFlag,     &dontVerifyCert,     0,
    "don't perform certificate validation"},
+  {"-dump",   argFlag,     &dumpSignatures,     0,
+   "dump all signatures into current directory"},
 
   {"-v",      argFlag,     &printVersion,  0,
    "print copyright and version info"},
@@ -150,7 +170,15 @@ int main(int argc, char *argv[])
   sigCount = sig_widgets.size();
 
   if (sigCount >= 1) {
-    printf("Digital Signature Info of: %s\n", fileName->getCString());
+    if (dumpSignatures) {
+      printf("Dumping Signatures : %u\n", sigCount);
+      for (unsigned int i = 0; i < sigCount; i++) {
+        dumpSignature(i, sig_widgets.at(i), fileName->getCString());
+      }
+      goto end;
+    } else {
+      printf("Digital Signature Info of: %s\n", fileName->getCString());
+    }
   } else {
     printf("File '%s' does not contain any signatures\n", fileName->getCString());
     exitCode = 2;
-- 
2.15.1