From 1f4568684341ec3a0abb0c7ce72580b07b73d646 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Fri, 22 Dec 2023 20:09:31 -0500
Subject: [PATCH] Handle --encrypt -- without crashing

---
 libqpdf/QPDFJob_argv.cc     | 1 +
 libqpdf/QPDFJob_config.cc   | 3 +++
 qpdf/qtest/arg-parsing.test | 7 ++++++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/libqpdf/QPDFJob_argv.cc b/libqpdf/QPDFJob_argv.cc
index 56acd7a9..3875474b 100644
--- a/libqpdf/QPDFJob_argv.cc
+++ b/libqpdf/QPDFJob_argv.cc
@@ -163,6 +163,7 @@ ArgParser::argShowCrypto()
 void
 ArgParser::argEncrypt()
 {
+    this->c_enc = c_main->encrypt(0, "", "");
     this->accumulated_args.clear();
     this->ap.selectOptionTable(O_ENCRYPTION);
 }
diff --git a/libqpdf/QPDFJob_config.cc b/libqpdf/QPDFJob_config.cc
index 834de9ab..4798ce9b 100644
--- a/libqpdf/QPDFJob_config.cc
+++ b/libqpdf/QPDFJob_config.cc
@@ -1042,6 +1042,9 @@ QPDFJob::EncConfig::EncConfig(Config* c) :
 QPDFJob::Config*
 QPDFJob::EncConfig::endEncrypt()
 {
+    if (config->o.m->keylen == 0) {
+        usage("encryption key length is required");
+    }
     config->o.m->encrypt = true;
     config->o.m->decrypt = false;
     config->o.m->copy_encryption = false;
diff --git a/qpdf/qtest/arg-parsing.test b/qpdf/qtest/arg-parsing.test
index 2f6bf621..aca8c7ef 100644
--- a/qpdf/qtest/arg-parsing.test
+++ b/qpdf/qtest/arg-parsing.test
@@ -15,7 +15,7 @@ cleanup();
 
 my $td = new TestDriver('arg-parsing');
 
-my $n_tests = 21;
+my $n_tests = 22;
 
 $td->runtest("required argument",
              {$td->COMMAND => "qpdf --password minimal.pdf"},
@@ -107,6 +107,11 @@ $td->runtest("empty and replace-input",
              {$td->REGEXP => ".*--replace-input may not be used with --empty.*",
                   $td->EXIT_STATUS => 2},
              $td->NORMALIZE_NEWLINES);
+$td->runtest("missing key length",
+             {$td->COMMAND => "qpdf --encrypt --"},
+             {$td->REGEXP => ".*encryption key length is required",
+                  $td->EXIT_STATUS => 2},
+             $td->NORMALIZE_NEWLINES);
 
 # Disallow mixing positional and flag-style encryption arguments.
 my @bad_enc = (