From 20c2f021b230112b08162237162ecd0f2e5f2aca Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Sun, 6 Jul 2025 21:15:27 +0100
Subject: [PATCH] Refactor encryption handling to streamline key computation, centralize version-based logic in `setEncryptionMinimumVersion`, and reduce redundancy across `QPDFWriter` methods.

---
 include/qpdf/QPDFWriter.hh |  3 +--
 libqpdf/QPDFWriter.cc      | 23 +++++++----------------
 libqpdf/QPDF_encryption.cc |  2 +-
 qpdf/qpdf.testcov          |  1 -
 4 files changed, 9 insertions(+), 20 deletions(-)

diff --git a/include/qpdf/QPDFWriter.hh b/include/qpdf/QPDFWriter.hh
index ffdec53..b26be87 100644
--- a/include/qpdf/QPDFWriter.hh
+++ b/include/qpdf/QPDFWriter.hh
@@ -523,8 +523,7 @@ class QPDFWriter
     void parseVersion(std::string const& version, int& major, int& minor) const;
     int compareVersions(int major1, int minor1, int major2, int minor2) const;
     void setEncryptionParameters(char const* user_password, char const* owner_password);
-    void setEncryptionParametersInternal(
-        std::string const& user_password, std::string const& encryption_key);
+    void setEncryptionMinimumVersion();
     void setDataKey(int objid);
     int openObject(int objid = 0);
     void closeObject(int objid);
diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 7823446..68ab329 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -655,8 +655,8 @@ QPDFWriter::setEncryptionParameters(char const* user_password, char const* owner
 {
     generateID();
     m->encryption->setId1(m->id1);
-    auto encryption_key = m->encryption->compute_parameters(user_password, owner_password);
-    setEncryptionParametersInternal(user_password, encryption_key);
+    m->encryption_key = m->encryption->compute_parameters(user_password, owner_password);
+    setEncryptionMinimumVersion();
 }
 
 void
@@ -686,11 +686,6 @@ QPDFWriter::copyEncryptionParameters(QPDF& qpdf)
         }
         QTC::TC("qpdf", "QPDFWriter copy encrypt metadata", encrypt_metadata ? 0 : 1);
         QTC::TC("qpdf", "QPDFWriter copy use_aes", m->encrypt_use_aes ? 0 : 1);
-        std::string encryption_key;
-        if (V >= 5) {
-            QTC::TC("qpdf", "QPDFWriter copy V5");
-            encryption_key = qpdf.getEncryptionKey();
-        }
 
         m->encryption = std::make_unique<QPDF::EncryptionData>(
             V,
@@ -704,7 +699,10 @@ QPDFWriter::copyEncryptionParameters(QPDF& qpdf)
             V < 5 ? "" : encrypt.getKey("/Perms").getStringValue(),
             m->id1, // m->id1 == the other file's id1
             encrypt_metadata);
-        setEncryptionParametersInternal(qpdf.getPaddedUserPassword(), encryption_key);
+        m->encryption_key = V >= 5
+            ? qpdf.getEncryptionKey()
+            : m->encryption->compute_encryption_key(qpdf.getPaddedUserPassword());
+        setEncryptionMinimumVersion();
     }
 }
 
@@ -779,8 +777,7 @@ QPDFWriter::compareVersions(int major1, int minor1, int major2, int minor2) cons
 }
 
 void
-QPDFWriter::setEncryptionParametersInternal(
-    std::string const& user_password, std::string const& encryption_key)
+QPDFWriter::setEncryptionMinimumVersion()
 {
     auto const R = m->encryption->getR();
     if (R >= 6) {
@@ -794,12 +791,6 @@ QPDFWriter::setEncryptionParametersInternal(
     } else {
         setMinimumPDFVersion("1.3");
     }
-
-    if (m->encryption->getV() < 5) {
-        m->encryption_key = m->encryption->compute_encryption_key(user_password);
-    } else {
-        m->encryption_key = encryption_key;
-    }
 }
 
 void
diff --git a/libqpdf/QPDF_encryption.cc b/libqpdf/QPDF_encryption.cc
index 23c4215..dcfd5ca 100644
--- a/libqpdf/QPDF_encryption.cc
+++ b/libqpdf/QPDF_encryption.cc
@@ -1201,7 +1201,7 @@ QPDF::EncryptionData::compute_parameters(char const* user_password, char const* 
 {
     if (V < 5) {
         compute_encryption_O_U(user_password, owner_password);
-        return {};
+        return compute_encryption_key(user_password);
     } else {
         return compute_encryption_parameters_V5(user_password, owner_password);
     }
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index 4e90b10..c3fd781 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -228,7 +228,6 @@ QPDFWriter extra header text no newline 0
 QPDFWriter extra header text add newline 0
 QPDF bogus 0 offset 0
 QPDF global offset 0
-QPDFWriter copy V5 0
 QPDFWriter increasing extension level 0
 QPDFWriter make Extensions direct 0
 QPDFWriter make ADBE direct 1
--
libgit2 0.21.4