Relax the EncryptMetadata check.chromium/2957

BUG=pdfium:644

Review-Url: https://codereview.chromium.org/2581873002

2 files changed, 27 insertions, 4 deletions

diff --git a/core/fpdfapi/parser/cpdf_security_handler.cpp b/core/fpdfapi/parser/cpdf_security_handler.cpp
index 5476b5485e..61834fca13 100644
--- a/core/fpdfapi/parser/cpdf_security_handler.cpp
+++ b/core/fpdfapi/parser/cpdf_security_handler.cpp
@@ -386,10 +386,11 @@ bool CPDF_SecurityHandler::AES256_CheckPassword(const uint8_t* password,
   if (FXDWORD_GET_LSBFIRST(buf) != m_Permissions)
     return false;
 
-  bool encrypted = IsMetadataEncrypted();
-  if ((buf[8] == 'T' && !encrypted) || (buf[8] == 'F' && encrypted))
-    return false;
-  return true;
+  // Relax this check as there appear to be some non-conforming documents
+  // in the wild. The value in the buffer is the truth; if it requires us
+  // to encrypt metadata, but the dictionary says otherwise, then we may
+  // have a tampered doc.  Otherwise, give it a pass.
+  return buf[8] == 'F' || IsMetadataEncrypted();
 }
 
 bool CPDF_SecurityHandler::CheckPassword(const uint8_t* password,
diff --git a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
index 37b6d8fc33..c6c6217e2c 100644
--- a/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
+++ b/core/fpdfapi/parser/cpdf_security_handler_embeddertest.cpp
@@ -21,6 +21,10 @@ TEST_F(CPDFSecurityHandlerEmbeddertest, NoPassword) {
   EXPECT_FALSE(OpenDocument("encrypted.pdf"));
 }
 
+TEST_F(CPDFSecurityHandlerEmbeddertest, BadPassword) {
+  EXPECT_FALSE(OpenDocument("encrypted.pdf", "tiger"));
+}
+
 TEST_F(CPDFSecurityHandlerEmbeddertest, UserPassword) {
   ASSERT_TRUE(OpenDocument("encrypted.pdf", "1234"));
   EXPECT_EQ(0xFFFFF2C0, FPDF_GetDocPermissions(document()));
@@ -30,3 +34,21 @@ TEST_F(CPDFSecurityHandlerEmbeddertest, OwnerPassword) {
   ASSERT_TRUE(OpenDocument("encrypted.pdf", "5678"));
   EXPECT_EQ(0xFFFFFFFC, FPDF_GetDocPermissions(document()));
 }
+
+TEST_F(CPDFSecurityHandlerEmbeddertest, NoPasswordVersion5) {
+  ASSERT_FALSE(OpenDocument("bug_644.pdf"));
+}
+
+TEST_F(CPDFSecurityHandlerEmbeddertest, BadPasswordVersion5) {
+  ASSERT_FALSE(OpenDocument("bug_644.pdf", "tiger"));
+}
+
+TEST_F(CPDFSecurityHandlerEmbeddertest, OwnerPasswordVersion5) {
+  ASSERT_TRUE(OpenDocument("bug_644.pdf", "a"));
+  EXPECT_EQ(0xFFFFFFFC, FPDF_GetDocPermissions(document()));
+}
+
+TEST_F(CPDFSecurityHandlerEmbeddertest, UserPasswordVersion5) {
+  ASSERT_TRUE(OpenDocument("bug_644.pdf", "b"));
+  EXPECT_EQ(0xFFFFFFFC, FPDF_GetDocPermissions(document()));
+}