/// <summary>
/// Computes the O(owner) value in the encryption dictionary.
/// </summary>
/// <remarks>
/// Corresponds to algorithm 3.3 on page 69 of the PDF specficiation.
/// </remarks>
/// <param name="options">
/// The user supplied PDF options that provides access to the passwords.
/// </param>
private void CreateOwnerEntry(SecurityOptions options)
{
// Pad or truncate the owner password string.
// If there is no owner password use the user password instead.
string password = options.OwnerPassword;
if (password == null)
{
password = options.UserPassword;
}
byte[] paddedPassword = PadPassword(password);
// Create an MD5 hash from the padded password.
// The first 5 bytes of this hash will be used as an ARC4 key.
MD5 md5 = MD5.Create();
byte[] hash = md5.ComputeHash(paddedPassword);
// Pad or truncate the user password string.
byte[] paddedUserPassword = PadPassword(options.UserPassword);
// Encrypt the padded user password using the key generated above.
Arc4 arc4 = new Arc4(hash, 0, 5);
ownerEntry = new byte[32];
arc4.Encrypt(paddedUserPassword, ownerEntry);
}
/// <summary>
/// Encrypts the passed byte array using the ARC4 cipher.
/// </summary>
public byte[] Encrypt(byte[] data, PdfObjectId objectId)
{
Arc4 arc4 = new Arc4(ComputeEncryptionKey31(masterKey, objectId));
arc4.Encrypt(data, data);
return(data);
}
/// <summary>
/// Computes the U(user) value in the encryption dictionary.
/// </summary>
/// <remarks>
/// Corresponds to algorithm 3.4 on page 70 of the PDF specficiation.
/// </remarks>
/// <param name="options">
/// The user supplied PDF options that provides access to the passwords.
/// </param>
private void CreateUserEntry(SecurityOptions options)
{
// Encrypt the 32-byte padding string using the master key.
Arc4 arc4 = new Arc4(masterKey);
userEntry = new byte[32];
arc4.Encrypt(Padding, userEntry);
}
/// <summary>
/// Performs the actual checking of the user password.
/// </summary>
private static bool CheckUserPassword(
byte[] paddedPassword, byte[] userEntry, byte[] ownerEntry, int permissions, byte[] fileId)
{
// Compute an encryption key from the supplied information.
byte[] key = ComputeEncryptionKey32(
paddedPassword, ownerEntry, permissions, fileId);
// Decrpt the User entry using the key.
Arc4 arc4 = new Arc4(key);
byte[] decryptedUserEntry = new byte[32];
arc4.Encrypt(userEntry, decryptedUserEntry);
// Compare the two arrays, if they match then the
// supplied password is correct.
return(CompareArray(Padding, decryptedUserEntry));
}
/// <summary>
/// Checks the owner password.
/// </summary>
internal static bool CheckOwnerPassword(
string password, byte[] userEntry, byte[] ownerEntry, int permissions, byte[] fileId)
{
// Compute an encryption key from the supplied information.
MD5 md5 = MD5.Create();
byte[] hash = md5.ComputeHash(PadPassword(password));
// Decrpt the Owner entry using the key.
Arc4 arc4 = new Arc4(hash, 0, 5);
byte[] decryptedOwnerEntry = new byte[32];
arc4.Encrypt(ownerEntry, decryptedOwnerEntry);
// The decryped owner entry is the correct user password,
// then the owner password is also correct.
return(CheckUserPassword(decryptedOwnerEntry, userEntry, ownerEntry, permissions, fileId));
}
/// <summary>
/// Computes the O(owner) value in the encryption dictionary.
/// </summary>
/// <remarks>
/// Corresponds to algorithm 3.3 on page 69 of the PDF specficiation.
/// </remarks>
/// <param name="options">
/// The user supplied PDF options that provides access to the passwords.
/// </param>
private void CreateOwnerEntry(SecurityOptions options)
{
// Pad or truncate the owner password string.
// If there is no owner password use the user password instead.
string password = options.OwnerPassword;
if (password == null)
{
password = options.UserPassword;
}
byte[] paddedPassword = PadPassword(password);
// Create an MD5 hash from the padded password.
// The first 5 bytes of this hash will be used as an ARC4 key.
MD5 md5 = MD5.Create();
byte[] hash = md5.ComputeHash(paddedPassword);
// Pad or truncate the user password string.
byte[] paddedUserPassword = PadPassword(options.UserPassword);
// Encrypt the padded user password using the key generated above.
Arc4 arc4 = new Arc4(hash, 0, 5);
ownerEntry = new byte[32];
arc4.Encrypt(paddedUserPassword, ownerEntry);
}
/// <summary>
/// Checks the owner password.
/// </summary>
internal static bool CheckOwnerPassword(
string password, byte[] userEntry, byte[] ownerEntry, int permissions, byte[] fileId)
{
// Compute an encryption key from the supplied information.
MD5 md5 = MD5.Create();
byte[] hash = md5.ComputeHash(PadPassword(password));
// Decrpt the Owner entry using the key.
Arc4 arc4 = new Arc4(hash, 0, 5);
byte[] decryptedOwnerEntry = new byte[32];
arc4.Encrypt(ownerEntry, decryptedOwnerEntry);
// The decryped owner entry is the correct user password,
// then the owner password is also correct.
return CheckUserPassword(decryptedOwnerEntry, userEntry, ownerEntry, permissions, fileId);
}
/// <summary>
/// Performs the actual checking of the user password.
/// </summary>
private static bool CheckUserPassword(
byte[] paddedPassword, byte[] userEntry, byte[] ownerEntry, int permissions, byte[] fileId)
{
// Compute an encryption key from the supplied information.
byte[] key = ComputeEncryptionKey32(
paddedPassword, ownerEntry, permissions, fileId);
// Decrpt the User entry using the key.
Arc4 arc4 = new Arc4(key);
byte[] decryptedUserEntry = new byte[32];
arc4.Encrypt(userEntry, decryptedUserEntry);
// Compare the two arrays, if they match then the
// supplied password is correct.
return CompareArray(Padding, decryptedUserEntry);
}
/// <summary>
/// Encrypts the passed byte array using the ARC4 cipher.
/// </summary>
public byte[] Encrypt(byte[] data, PdfObjectId objectId)
{
Arc4 arc4 = new Arc4(ComputeEncryptionKey31(masterKey, objectId));
arc4.Encrypt(data, data);
return data;
}
/// <summary>
/// Computes the U(user) value in the encryption dictionary.
/// </summary>
/// <remarks>
/// Corresponds to algorithm 3.4 on page 70 of the PDF specficiation.
/// </remarks>
/// <param name="options">
/// The user supplied PDF options that provides access to the passwords.
/// </param>
private void CreateUserEntry(SecurityOptions options)
{
// Encrypt the 32-byte padding string using the master key.
Arc4 arc4 = new Arc4(masterKey);
userEntry = new byte[32];
arc4.Encrypt(Padding, userEntry);
}
