Improve password handling

Use --encryption-file-password, if given, in addition to --password as
a source for passwords for files specified in --pages.

manual/qpdf-manual.xml

@@ -586,20 +586,16 @@ make
    </para>
    <para>
     For each file that pages should be taken from, specify the file, a
-    password needed to open the file (if needed), and a page range.
-    If the primary input file file requires a password, that password
-    must be specified outside the <option>--pages</option> option and
-    does not need to be repeated inside the <option>--pages</option>.
-    The same file can be repeated multiple times.  If a file that is
-    repeated has a password, the password only has to be given the
-    first time.  All non-page data (info, outlines, page numbers,
-    etc.) are taken from the primary input file.  To discard these,
-    use <option>--empty</option> as the primary input.  One subtlety
-    about specifying passwords is that specifying a password as
-    <option>--encryption-file-password</option> doesn't prevent you
-    from having to repeat that password of that is also one of the
-    input files.  If in doubt, it's never an error to specify the
-    password multiple times.
+    password needed to open the file (if any), and a page range.  The
+    password needs to be given only once per file.  If any of the
+    input files are the same as the primary input file or the file
+    used to copy encryption parameters (if specified), you do not need
+    to repeat the password here.  The same file can be repeated
+    multiple times.  If a file that is repeated has a password, the
+    password only has to be given the first time.  All non-page data
+    (info, outlines, page numbers, etc.) are taken from the primary
+    input file.  To discard these, use <option>--empty</option> as the
+    primary input.
    </para>
    <para>
     It is not presently possible to specify the same page from the

qpdf/qpdf.cc

@@ -152,13 +152,14 @@ starting point, but its pages are replaced with pages as specified.\n\
 --pages file [ --password=password ] page-range ... --\n\
 \n\
 For each file that pages should be taken from, specify the file, a\n\
-password needed to open the file (if needed), and a page range.  The\n\
-password needs to be given only once per file.  If the input file file\n\
-requires a password, that password must be specified outside the\n\
---pages option and does not need to be repeated.  The same file can be\n\
-repeated multiple times.  All non-page data (info, outlines, page numbers,\n\
-etc. are taken from the primary input file.  To discard this, use --empty\n\
-as the primary input.\n\
+password needed to open the file (if any), and a page range.  The\n\
+password needs to be given only once per file.  If any of the input\n\
+files are the same as the primary input file or the file used to copy\n\
+encryption parameters (if specified), you do not need to repeat the\n\
+password here.  The same file can be repeated multiple times.  All\n\
+non-page data (info, outlines, page numbers, etc. are taken from the\n\
+primary input file.  To discard this, use --empty as the primary\n\
+input.\n\
 \n\
 The page range is a set of numbers separated by commas, ranges of\n\
 numbers separated dashes, or combinations of those.  The character\n\
@@ -880,13 +881,13 @@ int main(int argc, char* argv[])
 	exit(0);
     }
 
-    char const* password = "";
+    char const* password = 0;
     bool linearize = false;
     bool decrypt = false;
 
     bool copy_encryption = false;
     char const* encryption_file = 0;
-    char const* encryption_file_password = "";
+    char const* encryption_file_password = 0;
 
     bool encrypt = false;
     std::string user_password;
@@ -1282,7 +1283,7 @@ int main(int argc, char* argv[])
 			if (filter &&
 			    (! obj.pipeStreamData(0, true, false, false)))
 			{
-			    QTC::TC("qpdf", "unable to filter");
+			    QTC::TC("qpdf", "qpdf unable to filter");
 			    std::cerr << "Unable to filter stream data."
 				      << std::endl;
 			    exit(EXIT_ERROR);
@@ -1445,8 +1446,15 @@ int main(int argc, char* argv[])
                         PointerHolder<QPDF> qpdf_ph = new QPDF();
                         page_heap.push_back(qpdf_ph);
                         QPDF* qpdf = qpdf_ph.getPointer();
+                        char const* password = page_spec.password;
+                        if (encryption_file && (password == 0) &&
+                            (page_spec.filename == encryption_file))
+                        {
+                            QTC::TC("qpdf", "qpdf pages encryption password");
+                            password = encryption_file_password;
+                        }
                         qpdf->processFile(
-                            page_spec.filename.c_str(), page_spec.password);
+                            page_spec.filename.c_str(), password);
                         page_spec_qpdfs[page_spec.filename] = qpdf;
                     }
 

qpdf/qpdf.testcov

@@ -113,7 +113,7 @@ QPDFObjectHandle indirect to unknown 0
 QPDF_Stream pipeStreamData with null pipeline 0
 QPDFWriter not recompressing /FlateDecode 0
 QPDF_encryption xref stream from encrypted file 0
-unable to filter 0
+qpdf unable to filter 0
 QPDF_String non-trivial UTF-16 0
 QPDF xref overwrite object 0
 QPDF decoding error warning 0
@@ -237,3 +237,4 @@ QPDFWriter foreign object 0
 QPDFWriter copy use_aes 1
 QPDFObjectHandle indirect without context 0
 QPDFObjectHandle trailing data in parse 0
+qpdf pages encryption password 0

qpdf/qtest/qpdf.test

@@ -424,7 +424,7 @@ foreach my $d (@nrange_tests)
 
 # ----------
 $td->notify("--- Merging and Splitting ---");
-$n_tests += 4;
+$n_tests += 6;
 
 # Select pages from the same file multiple times including selecting
 # twice from an encrypted file and specifying the password only the
@@ -460,6 +460,15 @@ $td->runtest("merge three files",
 $td->runtest("check output",
              {$td->FILE => "a.pdf"},
              {$td->FILE => "merge-three-files-2.pdf"});
+$td->runtest("avoid respecification of password",
+             {$td->COMMAND =>
+                  "qpdf --empty a.pdf --copy-encryption=20-pages.pdf" .
+                  " --encryption-file-password=user" .
+                  " --pages 20-pages.pdf 1,z -- --static-id"},
+             {$td->STRING => "", $td->EXIT_STATUS => 0});
+$td->runtest("check output",
+             {$td->FILE => "a.pdf"},
+             {$td->FILE => "pages-copy-encryption.pdf"});
 # ----------
 $td->notify("--- PDF From Scratch ---");
 $n_tests += 2;