checkpoint -- started doing some R4 encryption support

git-svn-id: svn+q:///qpdf/trunk@807 71b93d88-0707-0410-a8cf-f5a4172ac649

6 files changed, 204 insertions, 23 deletions

diff --git a/libqpdf/Pl_AES_PDF.cc b/libqpdf/Pl_AES_PDF.cc
new file mode 100644
index 00000000..f2e58af0
--- /dev/null
+++ b/libqpdf/Pl_AES_PDF.cc
@@ -0,0 +1,110 @@
+#include <qpdf/Pl_AES_PDF.hh>
+#include <qpdf/QUtil.hh>
+#include <cstring>
+#include <assert.h>
+#include <stdexcept>
+
+Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next,
+		       bool encrypt, unsigned char* key_data) :
+    Pipeline(identifier, next),
+    encrypt(encrypt),
+    offset(0)
+{
+    std::memset(this->buf, 0, this->buf_size);
+    // XXX init
+}
+
+Pl_AES_PDF::~Pl_AES_PDF()
+{
+    // XXX finalize
+}
+
+void
+Pl_AES_PDF::write(unsigned char* data, int len)
+{
+    unsigned int bytes_left = len;
+    unsigned char* p = data;
+
+    while (bytes_left > 0)
+    {
+	if (this->offset == this->buf_size)
+	{
+	    flush(false);
+	}
+
+	unsigned int available = this->buf_size - this->offset;
+	int bytes = (bytes_left < available ? bytes_left : available);
+	bytes_left -= bytes;
+	std::memcpy(this->buf + this->offset, p, bytes);
+	this->offset += bytes;
+	p += bytes;
+    }
+}
+
+void
+Pl_AES_PDF::finish()
+{
+    if (this->encrypt)
+    {
+	if (this->offset == this->buf_size)
+	{
+	    flush(false);
+	}
+	// Pad as described in section 3.5.1 of version 1.7 of the PDF
+	// specification, including providing an entire block of padding
+	// if the input was a multiple of 16 bytes.
+	unsigned char pad = this->buf_size - this->offset;
+	memset(this->buf + this->offset, pad, pad);
+	this->offset = this->buf_size;
+	flush(false);
+    }
+    else
+    {
+	if (this->offset != this->buf_size)
+	{
+	    throw std::runtime_error(
+		"aes encrypted stream length was not a multiple of " +
+		QUtil::int_to_string(this->buf_size) + " bytes (offset = " +
+		QUtil::int_to_string(this->offset) + ")");
+	}
+	flush(true);
+    }
+    getNext()->finish();
+}
+
+void
+Pl_AES_PDF::flush(bool strip_padding)
+{
+    assert(this->offset == this->buf_size);
+    if (this->encrypt)
+    {
+	// XXX encrypt this->buf
+    }
+    else
+    {
+	// XXX decrypt this->buf
+    }
+    unsigned int bytes = this->buf_size;
+    if (strip_padding)
+    {
+	unsigned char last = this->buf[this->buf_size - 1];
+	if (last <= this->buf_size)
+	{
+	    bool strip = true;
+	    for (unsigned int i = 1; i <= last; ++i)
+	    {
+		if (this->buf[this->buf_size - i] != last)
+		{
+		    strip = false;
+		    break;
+		}
+	    }
+	    if (strip)
+	    {
+		bytes -= last;
+	    }
+	}
+    }
+    getNext()->write(this->buf, bytes);
+    this->offset = 0;
+}
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 5bc89627..dd1fea56 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -253,6 +253,7 @@ QPDF::QPDF() :
     ignore_xref_streams(false),
     suppress_warnings(false),
     attempt_recovery(true),
+    encryption_use_aes(false),
     cached_key_objid(0),
     cached_key_generation(0),
     first_xref_item_offset(0),
diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 0ede7889..2a990fa3 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -326,7 +326,8 @@ QPDFWriter::setEncryptionParametersInternal(
     encryption_dictionary["/O"] = QPDF_String(O).unparse(true);
     encryption_dictionary["/U"] = QPDF_String(U).unparse(true);
     this->encrypted = true;
-    QPDF::EncryptionData encryption_data(V, R, key_len, P, O, U, this->id1);
+    QPDF::EncryptionData encryption_data(V, R, key_len, P, O, U, this->id1,
+					 /*XXX encrypt_metadata*/true);
     this->encryption_key = QPDF::compute_encryption_key(
 	user_password, encryption_data);
 }
@@ -335,7 +336,7 @@ void
 QPDFWriter::setDataKey(int objid)
 {
     this->cur_data_key = QPDF::compute_data_key(
-	this->encryption_key, objid, 0);
+	this->encryption_key, objid, 0, /*XXX use_aes */false);
 }
 
 int
diff --git a/libqpdf/QPDF_encryption.cc b/libqpdf/QPDF_encryption.cc
index 7e45260f..190d2d6a 100644
--- a/libqpdf/QPDF_encryption.cc
+++ b/libqpdf/QPDF_encryption.cc
@@ -99,9 +99,10 @@ iterate_rc4(unsigned char* data, int data_len,
 
 std::string
 QPDF::compute_data_key(std::string const& encryption_key,
-		       int objid, int generation)
+		       int objid, int generation,
+		       bool use_aes)
 {
-    // Algorithm 3.1 from the PDF 1.4 Reference Manual
+    // Algorithm 3.1 from the PDF 1.7 Reference Manual
 
     std::string result = encryption_key;
 
@@ -111,6 +112,10 @@ QPDF::compute_data_key(std::string const& encryption_key,
     result += (char) ((objid >> 16) & 0xff);
     result += (char) (generation & 0xff);
     result += (char) ((generation >> 8) & 0xff);
+    if (use_aes)
+    {
+	result += "sAlT";
+    }
 
     MD5 md5;
     md5.encodeDataIncrementally(result.c_str(), result.length());
@@ -118,13 +123,16 @@ QPDF::compute_data_key(std::string const& encryption_key,
     md5.digest(digest);
     return std::string((char*) digest,
 		       std::min(result.length(), (size_t) 16));
+
+    // XXX Item 4 in Algorithm 3.1 mentions CBC and a random number.
+    // We still have to incorporate that.
 }
 
 std::string
 QPDF::compute_encryption_key(
     std::string const& password, EncryptionData const& data)
 {
-    // Algorithm 3.2 from the PDF 1.4 Reference Manual
+    // Algorithm 3.2 from the PDF 1.7 Reference Manual
 
     MD5 md5;
     md5.encodeDataIncrementally(
@@ -137,8 +145,14 @@ QPDF::compute_encryption_key(
     pbytes[3] = (char) ((data.P >> 24) & 0xff);
     md5.encodeDataIncrementally(pbytes, 4);
     md5.encodeDataIncrementally(data.id1.c_str(), id_bytes);
+    if ((data.R >= 4) && (! data.encrypt_metadata))
+    {
+	char bytes[4];
+	memset(bytes, 0xff, 4);
+	md5.encodeDataIncrementally(bytes, 4);
+    }
     MD5::Digest digest;
-    iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
+    iterate_md5_digest(md5, digest, ((data.R >= 3) ? 50 : 0));
     return std::string((char*)digest, data.Length_bytes);
 }
 
@@ -157,7 +171,7 @@ compute_O_rc4_key(std::string const& user_password,
     md5.encodeDataIncrementally(
 	pad_or_truncate_password(password).c_str(), key_bytes);
     MD5::Digest digest;
-    iterate_md5_digest(md5, digest, ((data.R == 3) ? 50 : 0));
+    iterate_md5_digest(md5, digest, ((data.R >= 3) ? 50 : 0));
     memcpy(key, digest, O_key_bytes);
 }
 
@@ -166,7 +180,7 @@ compute_O_value(std::string const& user_password,
 		std::string const& owner_password,
 		QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.3 from the PDF 1.4 Reference Manual
+    // Algorithm 3.3 from the PDF 1.7 Reference Manual
 
     unsigned char O_key[O_key_bytes];
     compute_O_rc4_key(user_password, owner_password, data, O_key);
@@ -174,7 +188,7 @@ compute_O_value(std::string const& user_password,
     char upass[key_bytes];
     pad_or_truncate_password(user_password, upass);
     iterate_rc4((unsigned char*) upass, key_bytes,
-		O_key, data.Length_bytes, (data.R == 3) ? 20 : 1, false);
+		O_key, data.Length_bytes, (data.R >= 3) ? 20 : 1, false);
     return std::string(upass, key_bytes);
 }
 
@@ -183,7 +197,7 @@ std::string
 compute_U_value_R2(std::string const& user_password,
 		   QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.4 from the PDF 1.4 Reference Manual
+    // Algorithm 3.4 from the PDF 1.7 Reference Manual
 
     std::string k1 = QPDF::compute_encryption_key(user_password, data);
     char udata[key_bytes];
@@ -198,7 +212,7 @@ std::string
 compute_U_value_R3(std::string const& user_password,
 		   QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.5 from the PDF 1.4 Reference Manual
+    // Algorithm 3.5 from the PDF 1.7 Reference Manual
 
     std::string k1 = QPDF::compute_encryption_key(user_password, data);
     MD5 md5;
@@ -224,7 +238,7 @@ static std::string
 compute_U_value(std::string const& user_password,
 		QPDF::EncryptionData const& data)
 {
-    if (data.R == 3)
+    if (data.R >= 3)
     {
 	return compute_U_value_R3(user_password, data);
     }
@@ -236,10 +250,10 @@ static bool
 check_user_password(std::string const& user_password,
 		    QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.6 from the PDF 1.4 Reference Manual
+    // Algorithm 3.6 from the PDF 1.7 Reference Manual
 
     std::string u_value = compute_U_value(user_password, data);
-    int to_compare = ((data.R == 3) ? sizeof(MD5::Digest) : key_bytes);
+    int to_compare = ((data.R >= 3) ? sizeof(MD5::Digest) : key_bytes);
     return (memcmp(data.U.c_str(), u_value.c_str(), to_compare) == 0);
 }
 
@@ -248,14 +262,14 @@ check_owner_password(std::string& user_password,
 		     std::string const& owner_password,
 		     QPDF::EncryptionData const& data)
 {
-    // Algorithm 3.7 from the PDF 1.4 Reference Manual
+    // Algorithm 3.7 from the PDF 1.7 Reference Manual
 
     unsigned char key[O_key_bytes];
     compute_O_rc4_key(user_password, owner_password, data, key);
     unsigned char O_data[key_bytes];
     memcpy(O_data, (unsigned char*) data.O.c_str(), key_bytes);
     iterate_rc4(O_data, key_bytes, key, data.Length_bytes,
-		(data.R == 3) ? 20 : 1, true);
+		(data.R >= 3) ? 20 : 1, true);
     std::string new_user_password =
 	std::string((char*)O_data, key_bytes);
     bool result = false;
@@ -339,13 +353,20 @@ QPDF::initializeEncryption()
     std::string U = encryption_dict.getKey("/U").getStringValue();
     unsigned int P = (unsigned int) encryption_dict.getKey("/P").getIntValue();
 
-    if (! (((R == 2) || (R == 3)) &&
-	   ((V == 1) || (V == 2))))
+    if (! (((R == 2) || (R == 3) || (R == 4)) &&
+	   ((V == 1) || (V == 2) || (V == 4))))
     {
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
 		      "Unsupported /R or /V in encryption dictionary");
     }
 
+    // XXX remove this check to continue implementing R4.
+    if ((R == 4) || (V == 4))
+    {
+	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
+		      "PDF >= 1.5 encryption support is not fully implemented");
+    }
+
     if (! ((O.length() == key_bytes) && (U.length() == key_bytes)))
     {
 	throw QPDFExc(this->file.getName(), this->file.getLastOffset(),
@@ -364,7 +385,18 @@ QPDF::initializeEncryption()
 	}
     }
 
-    EncryptionData data(V, R, Length / 8, P, O, U, id1);
+    bool encrypt_metadata = true;
+    if ((V >= 4) && (encryption_dict.getKey("/EncryptMetadata").isBool()))
+    {
+	encrypt_metadata =
+	    encryption_dict.getKey("/EncryptMetadata").getBoolValue();
+    }
+    // XXX not really...
+    if (R >= 4)
+    {
+	this->encryption_use_aes = true;
+    }
+    EncryptionData data(V, R, Length / 8, P, O, U, id1, encrypt_metadata);
     if (check_owner_password(this->user_password, this->provided_password, data))
     {
 	// password supplied was owner password; user_password has
@@ -395,7 +427,8 @@ QPDF::getKeyForObject(int objid, int generation)
 	   (generation == this->cached_key_generation)))
     {
 	this->cached_object_encryption_key =
-	    compute_data_key(this->encryption_key, objid, generation);
+	    compute_data_key(this->encryption_key, objid, generation,
+			     this->encryption_use_aes);
 	this->cached_key_objid = objid;
 	this->cached_key_generation = generation;
     }
@@ -424,8 +457,15 @@ QPDF::decryptStream(Pipeline*& pipeline, int objid, int generation,
 		    std::vector<PointerHolder<Pipeline> >& heap)
 {
     std::string key = getKeyForObject(objid, generation);
-    pipeline = new Pl_RC4("stream decryption", pipeline,
-			  (unsigned char*) key.c_str(), key.length());
+    if (this->encryption_use_aes)
+    {
+	throw std::logic_error("aes not yet implemented"); // XXX
+    }
+    else
+    {
+	pipeline = new Pl_RC4("RC4 stream decryption", pipeline,
+			      (unsigned char*) key.c_str(), key.length());
+    }
     heap.push_back(pipeline);
 }
 
@@ -435,7 +475,8 @@ QPDF::compute_encryption_O_U(
     int V, int R, int key_len, int P,
     std::string const& id1, std::string& O, std::string& U)
 {
-    EncryptionData data(V, R, key_len, P, "", "", id1);
+    EncryptionData data(V, R, key_len, P, "", "", id1,
+			/*XXX encrypt_metadata*/true);
     data.O = compute_O_value(user_password, owner_password, data);
     O = data.O;
     U = compute_U_value(user_password, data);
diff --git a/libqpdf/build.mk b/libqpdf/build.mk
index 6d6b3ae7..7b71cf61 100644
--- a/libqpdf/build.mk
+++ b/libqpdf/build.mk
@@ -13,6 +13,7 @@ SRCS_libqpdf = \
 	libqpdf/MD5.cc \
 	libqpdf/PCRE.cc \
 	libqpdf/Pipeline.cc \
+	libqpdf/Pl_AES_PDF.cc \
 	libqpdf/Pl_ASCII85Decoder.cc \
 	libqpdf/Pl_ASCIIHexDecoder.cc \
 	libqpdf/Pl_Buffer.cc \
diff --git a/libqpdf/qpdf/Pl_AES_PDF.hh b/libqpdf/qpdf/Pl_AES_PDF.hh
new file mode 100644
index 00000000..6939abb8
--- /dev/null
+++ b/libqpdf/qpdf/Pl_AES_PDF.hh
@@ -0,0 +1,27 @@
+#ifndef __PL_AES_PDF_HH__
+#define __PL_AES_PDF_HH__
+
+#include <qpdf/Pipeline.hh>
+
+class DLL_EXPORT Pl_AES_PDF: public Pipeline
+{
+  public:
+    // key_data should be a pointer to key_size bytes of data
+    static unsigned int const key_size = 16;
+    Pl_AES_PDF(char const* identifier, Pipeline* next,
+	       bool encrypt, unsigned char* key_data);
+    virtual ~Pl_AES_PDF();
+
+    virtual void write(unsigned char* data, int len);
+    virtual void finish();
+
+  private:
+    void flush(bool discard_padding);
+
+    bool encrypt;
+    unsigned int offset;
+    static unsigned int const buf_size = 16;
+    unsigned char buf[buf_size];
+};
+
+#endif // __PL_AES_PDF_HH__