Refactor encryption permissions handling by replacing integer-based logic with `…

…std::bitset`, reorganizing related methods, and simplifying access to improve clarity and maintainability.

Refactor encryption permissions handling by replacing integer-based logic with `…
…std::bitset`, reorganizing related methods, and simplifying access to improve clarity and maintainability.
m-holger
1 parent 34142a6c
Showing 3 changed files with 66 additions and 110 deletions
include/qpdf/QPDF.hh
libqpdf/QPDF_encryption.cc
libqpdf/qpdf/QPDF_private.hh
@@ -23,6 +23,7 @@
 #include <qpdf/DLL.h>
 #include <qpdf/Types.h>
+#include <bitset>
 #include <cstdio>
 #include <functional>
 #include <iostream>
@@ -465,7 +466,7 @@ class QPDF
             V(V),
             R(R),
             Length_bytes(Length_bytes),
-            P(P),
+            P(static_cast<unsigned long long>(P)),
             O(O),
             U(U),
             OE(OE),
@@ -480,6 +481,8 @@ class QPDF
         int getR() const;
         int getLengthBytes() const;
         int getP() const;
+        //  Bits in P are numbered from 1 as in the PDF spec.
+        bool getP(size_t bit) const;
         std::string const& getO() const;
         std::string const& getU() const;
         std::string const& getOE() const;
@@ -487,7 +490,8 @@ class QPDF
         std::string const& getPerms() const;
         std::string const& getId1() const;
         bool getEncryptMetadata() const;
-
+        //  Bits in P are numbered from 1 as in the PDF spec.
+        void setP(size_t bit, bool val);
         void setO(std::string const&);
         void setU(std::string const&);
         void setV5EncryptionParameters(
@@ -562,7 +566,7 @@ class QPDF
         int V;
         int R;
         int Length_bytes;
-        int P;
+        std::bitset<32> P{0xfffffffc}; // Specification always requires bits 1 and 2 to be cleared.
         std::string O;
         std::string U;
         std::string OE;
@@ -51,7 +51,21 @@ QPDF::EncryptionData::getLengthBytes() const
 int
 QPDF::EncryptionData::getP() const
 {
-    return this->P;
+    return static_cast<int>(P.to_ullong());
+}
+
+bool
+QPDF::EncryptionData::getP(size_t bit) const
+{
+    qpdf_assert_debug(bit);
+    return P.test(bit - 1);
+}
+
+bool
+QPDF::EncryptionParameters::P(size_t bit) const
+{
+    qpdf_assert_debug(bit);
+    return P_.test(bit - 1);
 }
 std::string const&
@@ -109,6 +123,13 @@ QPDF::EncryptionData::setU(std::string const&amp; U)
 }
 void
+QPDF::EncryptionData::setP(size_t bit, bool val)
+{
+    qpdf_assert_debug(bit);
+    P.set(bit - 1, val);
+}
+
+void
 QPDF::EncryptionData::setV5EncryptionParameters(
     std::string const& O,
     std::string const& OE,
@@ -782,7 +803,7 @@ QPDF::EncryptionParameters::initialize(QPDF&amp; qpdf)
     int R = encryption_dict.getKey("/R").getIntValueAsInt();
     std::string O = encryption_dict.getKey("/O").getStringValue();
     std::string U = encryption_dict.getKey("/U").getStringValue();
-    int P = static_cast<int>(encryption_dict.getKey("/P").getIntValue());
+    int p = static_cast<int>(encryption_dict.getKey("/P").getIntValue());
     // If supporting new encryption R/V values, remember to update error message inside this if
     // statement.
@@ -792,9 +813,9 @@ QPDF::EncryptionParameters::initialize(QPDF&amp; qpdf)
             " (max 6), V = " + std::to_string(V) + " (max 5)");
     }
-    encryption_P = P;
+    P_ = std::bitset<32>(static_cast<unsigned long long>(p));
     encryption_V = V;
-    encryption_R = R;
+    R_ = R;
     // OE, UE, and Perms are only present if V >= 5.
     std::string OE;
@@ -891,7 +912,7 @@ QPDF::EncryptionParameters::initialize(QPDF&amp; qpdf)
         }
     }
-    EncryptionData data(V, R, Length / 8, P, O, U, OE, UE, Perms, id1, encrypt_metadata);
+    EncryptionData data(V, R, Length / 8, p, O, U, OE, UE, Perms, id1, encrypt_metadata);
     if (qm.provided_password_is_hex_key) {
         // ignore passwords in file
         encryption_key = QUtil::hex_decode(provided_password);
@@ -942,12 +963,7 @@ QPDF::getKeyForObject(std::shared_ptr&lt;EncryptionParameters&gt; encp, QPDFObjGen og,
     if (og != encp->cached_key_og) {
         encp->cached_object_encryption_key = compute_data_key(
-            encp->encryption_key,
-            og.getObj(),
-            og.getGen(),
-            use_aes,
-            encp->encryption_V,
-            encp->encryption_R);
+            encp->encryption_key, og.getObj(), og.getGen(), use_aes, encp->encryption_V, encp->R());
         encp->cached_key_og = og;
     }
@@ -1239,8 +1255,8 @@ QPDF::isEncrypted(int&amp; R, int&amp; P)
     if (!m->encp->encrypted) {
         return false;
     }
-    P = m->encp->encryption_P;
-    R = m->encp->encryption_R;
+    P = m->encp->P();
+    R = m->encp->R();
     return true;
 }
@@ -1256,8 +1272,8 @@ QPDF::isEncrypted(
     if (!m->encp->encrypted) {
         return false;
     }
-    P = m->encp->encryption_P;
-    R = m->encp->encryption_R;
+    P = m->encp->P();
+    R = m->encp->R();
     V = m->encp->encryption_V;
     stream_method = m->encp->cf_stream;
     string_method = m->encp->cf_string;
@@ -1277,135 +1293,57 @@ QPDF::userPasswordMatched() const
     return m->encp->user_password_matched;
 }
-static bool
-is_bit_set(int P, int bit)
-{
-    // Bits in P are numbered from 1 in the spec
-    return ((P & (1 << (bit - 1))) != 0);
-}
-
 bool
 QPDF::allowAccessibility()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        if (R < 3) {
-            status = is_bit_set(P, 5);
-        } else {
-            status = is_bit_set(P, 10);
-        }
-    }
-    return status;
+    return m->encp->R() < 3 ? m->encp->P(5) : m->encp->P(10);
 }
 bool
 QPDF::allowExtractAll()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = is_bit_set(P, 5);
-    }
-    return status;
+    return m->encp->P(5);
 }
 bool
 QPDF::allowPrintLowRes()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = is_bit_set(P, 3);
-    }
-    return status;
+    return m->encp->P(3);
 }
 bool
 QPDF::allowPrintHighRes()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = is_bit_set(P, 3);
-        if ((R >= 3) && (!is_bit_set(P, 12))) {
-            status = false;
-        }
-    }
-    return status;
+    return allowPrintLowRes() && (m->encp->R() < 3 ? true : m->encp->P(12));
 }
 bool
 QPDF::allowModifyAssembly()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        if (R < 3) {
-            status = is_bit_set(P, 4);
-        } else {
-            status = is_bit_set(P, 11);
-        }
-    }
-    return status;
+    return m->encp->R() < 3 ? m->encp->P(4) : m->encp->P(11);
 }
 bool
 QPDF::allowModifyForm()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        if (R < 3) {
-            status = is_bit_set(P, 6);
-        } else {
-            status = is_bit_set(P, 9);
-        }
-    }
-    return status;
+    return m->encp->R() < 3 ? m->encp->P(6) : m->encp->P(9);
 }
 bool
 QPDF::allowModifyAnnotation()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = is_bit_set(P, 6);
-    }
-    return status;
+    return m->encp->P(6);
 }
 bool
 QPDF::allowModifyOther()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = is_bit_set(P, 4);
-    }
-    return status;
+    return m->encp->P(4);
 }
 bool
 QPDF::allowModifyAll()
 {
-    int R = 0;
-    int P = 0;
-    bool status = true;
-    if (isEncrypted(R, P)) {
-        status = (is_bit_set(P, 4) && is_bit_set(P, 6));
-        if (R >= 3) {
-            status = status && (is_bit_set(P, 9) && is_bit_set(P, 11));
-        }
-    }
-    return status;
+    return allowModifyAnnotation() && allowModifyOther() &&
+        (m->encp->R() < 3 ? true : allowModifyForm() && allowModifyAssembly());
 }
@@ -187,16 +187,30 @@ class QPDF::EncryptionParameters
   public:
     EncryptionParameters() = default;
-    encryption_method_e interpretCF(QPDFObjectHandle const& cf) const;
+    int
+    P() const
+    {
+        return static_cast<int>(P_.to_ullong());
+    }
+
+    //  Bits in P are numbered from 1 as in the PDF spec.
+    bool P(size_t bit) const;
+
+    int
+    R()
+    {
+        return R_;
+    }
-  private:
     void initialize(QPDF& qpdf);
+    encryption_method_e interpretCF(QPDFObjectHandle const& cf) const;
+  private:
     bool encrypted{false};
     bool encryption_initialized{false};
-    int encryption_P{0};
+    std::bitset<32> P_{0xfffffffc}; // Specification always requires bits 1 and 2 to be cleared.
     int encryption_V{0};
-    int encryption_R{0};
+    int R_{0};
     bool encrypt_metadata{true};
     std::map<std::string, encryption_method_e> crypt_filters;
     encryption_method_e cf_stream{e_none};