Warn when -accessibility=n will be ignored

Also accept -accessibility=n with 256 bit keys even though it will be
ignored.

4 files changed, 73 insertions, 24 deletions

diff --git a/ChangeLog b/ChangeLog
index 951d9d03..460cdd89 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2013-10-18  Jay Berkenbilt  <ejb@ql.org>
+
+	* Warn when -accessibility=n is specified with a modern encryption
+	format (R > 3).  Also, accept this flag (and ignore with warning)
+	with 256-bit encryption.  qpdf has always ignored the
+	accessibility setting with R > 3, but it previously did so
+	silently.
+
 2013-10-05  Jay Berkenbilt  <ejb@ql.org>
 
 	* Replace operator[] in std::string and std::vector with "at" in
diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 833637d3..4e917469 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -462,7 +462,9 @@ QPDFWriter::setEncryptionParameters(
 
     if (R > 3)
     {
-        // Bit 10 is deprecated and should always be set.
+        // Bit 10 is deprecated and should always be set.  This used
+        // to mean accessibility.  There is no way to disable
+        // accessibility with R > 3.
         bits_to_clear.erase(10);
     }
 
diff --git a/qpdf/qpdf.cc b/qpdf/qpdf.cc
index ed648129..be8198e6 100644
--- a/qpdf/qpdf.cc
+++ b/qpdf/qpdf.cc
@@ -740,13 +740,13 @@ parse_encrypt_options(
 	    {
 		usage("invalid -accessibility parameter");
 	    }
-	    if (keylen == 128)
+	    if (keylen == 40)
 	    {
-		r3_accessibility = result;
+		usage("-accessibility invalid for 40-bit keys");
 	    }
 	    else
 	    {
-		usage("-accessibility invalid for 40-bit keys");
+		r3_accessibility = result;
 	    }
 	}
 	else if (strcmp(arg, "cleartext-metadata") == 0)
@@ -1730,49 +1730,77 @@ int main(int argc, char* argv[])
             }
 	    if (encrypt)
 	    {
+                int R = 0;
 		if (keylen == 40)
 		{
-		    w.setR2EncryptionParameters(
-			user_password.c_str(), owner_password.c_str(),
-			r2_print, r2_modify, r2_extract, r2_annotate);
+                    R = 2;
 		}
 		else if (keylen == 128)
 		{
 		    if (force_V4 || cleartext_metadata || use_aes)
 		    {
-			w.setR4EncryptionParameters(
-			    user_password.c_str(), owner_password.c_str(),
-			    r3_accessibility, r3_extract, r3_print, r3_modify,
-			    !cleartext_metadata, use_aes);
+                        R = 4;
 		    }
 		    else
 		    {
-			w.setR3EncryptionParameters(
-			    user_password.c_str(), owner_password.c_str(),
-			    r3_accessibility, r3_extract, r3_print, r3_modify);
+                        R = 3;
 		    }
 		}
 		else if (keylen == 256)
 		{
 		    if (force_R5)
                     {
-			w.setR5EncryptionParameters(
-			    user_password.c_str(), owner_password.c_str(),
-			    r3_accessibility, r3_extract, r3_print, r3_modify,
-			    !cleartext_metadata);
+                        R = 5;
 		    }
 		    else
 		    {
-			w.setR6EncryptionParameters(
-			    user_password.c_str(), owner_password.c_str(),
-			    r3_accessibility, r3_extract, r3_print, r3_modify,
-			    !cleartext_metadata);
+                        R = 6;
 		    }
 		}
 		else
 		{
 		    throw std::logic_error("bad encryption keylen");
 		}
+                if ((R > 3) && (r3_accessibility == false))
+                {
+                    std::cerr << whoami
+                              << ": -accessibility=n is ignored for modern"
+                              << " encryption formats" << std::endl;
+                }
+                switch (R)
+                {
+                  case 2:
+		    w.setR2EncryptionParameters(
+			user_password.c_str(), owner_password.c_str(),
+			r2_print, r2_modify, r2_extract, r2_annotate);
+                    break;
+                  case 3:
+                    w.setR3EncryptionParameters(
+                        user_password.c_str(), owner_password.c_str(),
+                        r3_accessibility, r3_extract, r3_print, r3_modify);
+                    break;
+                  case 4:
+                    w.setR4EncryptionParameters(
+                        user_password.c_str(), owner_password.c_str(),
+                        r3_accessibility, r3_extract, r3_print, r3_modify,
+                        !cleartext_metadata, use_aes);
+                    break;
+                  case 5:
+                    w.setR5EncryptionParameters(
+                        user_password.c_str(), owner_password.c_str(),
+                        r3_accessibility, r3_extract, r3_print, r3_modify,
+                        !cleartext_metadata);
+                    break;
+                  case 6:
+                    w.setR6EncryptionParameters(
+                        user_password.c_str(), owner_password.c_str(),
+                        r3_accessibility, r3_extract, r3_print, r3_modify,
+                        !cleartext_metadata);
+                    break;
+                  default:
+		    throw std::logic_error("bad encryption R value");
+                    break;
+                }
 	    }
 	    if (linearize)
 	    {
diff --git a/qpdf/qtest/qpdf.test b/qpdf/qtest/qpdf.test
index d07a54c5..1aff3d21 100644
--- a/qpdf/qtest/qpdf.test
+++ b/qpdf/qtest/qpdf.test
@@ -1399,6 +1399,9 @@ my @encrypted_files =
      ['XI-R6,V5,U=view,O=master', 'master',
       '-print=low', -2052,
       1, 1, 1, 0, 1, 1, 1, 1, 1],
+     ['XI-R6,V5,U=view,O=master', 'master',
+      '-accessibility=n', -4, # -accessibility=n has no effect
+      1, 1, 1, 1, 1, 1, 1, 1, 1],
      ['XI-long-password', 'qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnm'],
      ['XI-long-password', 'qwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcvbnmqwertyuiopasdfghjklzxcv'],
     );
@@ -1501,12 +1504,20 @@ foreach my $d (@encrypted_files)
             # password.
             $upass = "";
         }
+        my $accessibility_warning = "";
+        if (($R > 3) && ($eflags =~ /accessibility=n/))
+        {
+            $accessibility_warning =
+                "qpdf: -accessibility=n is ignored" .
+                " for modern encryption formats\n";
+        }
 	$td->runtest("encrypt $file",
 		     {$td->COMMAND =>
 			  "qpdf --static-id --no-original-object-ids -qdf" .
 			  " $eflags $file.enc $file.enc2"},
-		     {$td->STRING => "",
-		      $td->EXIT_STATUS => 0});
+		     {$td->STRING => $accessibility_warning,
+		      $td->EXIT_STATUS => 0},
+                     $td->NORMALIZE_NEWLINES);
 	$td->runtest("check /P",
 		     {$td->COMMAND =>
 			  "qpdf --show-encryption --password=\"$pass\"" .