Package org.apache.poi.poifs.crypt

Class CryptoFunctions

  • @Internal
public final class CryptoFunctions
extends Object
    Helper functions used for standard and agile encryption

    • Method Detail

      • setMaxRecordLength

        public static void setMaxRecordLength​(int length)
        Parameters:
        length - the max record length allowed for CryptoFunctions

      • getMaxRecordLength

        public static int getMaxRecordLength()
        Returns:
        the max record length allowed for CryptoFunctions

      • hashPassword

        public static byte[] hashPassword​(String password,
                                  HashAlgorithm hashAlgorithm,
                                  byte[] salt,
                                  int spinCount)

        2.3.4.7 ECMA-376 Document Encryption Key Generation (Standard Encryption)
        2.3.4.11 Encryption Key Generation (Agile Encryption)

        The encryption key for ECMA-376 document encryption [ECMA-376] using agile encryption MUST be generated by using the following method, which is derived from PKCS #5: Password-Based Cryptography Version 2.0 [RFC2898].

        Let H() be a hashing algorithm as determined by the PasswordKeyEncryptor.hashAlgorithm element, H_n be the hash data of the n-th iteration, and a plus sign (+) represent concatenation. The password MUST be provided as an array of Unicode characters. Limitations on the length of the password and the characters used by the password are implementation-dependent. The initial password hash is generated as follows:

        H_0 = H(salt + password)

        The salt used MUST be generated randomly. The salt MUST be stored in the PasswordKeyEncryptor.saltValue element contained within the \EncryptionInfo stream as specified in section 2.3.4.10. The hash is then iterated by using the following approach:

        H_n = H(iterator + H_n-1)

        where iterator is an unsigned 32-bit value that is initially set to 0x00000000 and then incremented monotonically on each iteration until PasswordKey.spinCount iterations have been performed. The value of iterator on the last iteration MUST be one less than PasswordKey.spinCount.

        For POI, H_final will be calculated by generateKey(byte[],HashAlgorithm,byte[],int)

        Parameters:
        password - the password
        hashAlgorithm - the hash algorithm
        salt - the initial salt value
        spinCount - the repetition count
        Returns:
        the hashed password

      • hashPassword

        public static byte[] hashPassword​(String password,
                                  HashAlgorithm hashAlgorithm,
                                  byte[] salt,
                                  int spinCount,
                                  boolean iteratorFirst)
        Generalized method for read and write protection hash generation. The difference is, read protection uses the order iterator then hash in the hash loop, whereas write protection uses first the last hash value and then the current iterator value
        Parameters:
        password - the pasword
        hashAlgorithm - the hash algorighm
        salt - the initial salt value
        spinCount - the repetition count
        iteratorFirst - if true, the iterator is hashed before the n-1 hash value, if false the n-1 hash value is applied first
        Returns:
        the hashed password

      • generateIv

        public static byte[] generateIv​(HashAlgorithm hashAlgorithm,
                                byte[] salt,
                                byte[] blockKey,
                                int blockSize)

        2.3.4.12 Initialization Vector Generation (Agile Encryption)

        Initialization vectors are used in all cases for agile encryption. An initialization vector MUST be generated by using the following method, where H() is a hash function that MUST be the same as specified in section 2.3.4.11 and a plus sign (+) represents concatenation:

        • If a blockKey is provided, let IV be a hash of the KeySalt and the following value:
          blockKey: IV = H(KeySalt + blockKey)
        • If a blockKey is not provided, let IV be equal to the following value:
          KeySalt:IV = KeySalt
        • If the number of bytes in the value of IV is less than the value of the blockSize attribute corresponding to the cipherAlgorithm attribute, pad the array of bytes by appending 0x36 until the array is blockSize bytes. If the array of bytes is larger than blockSize bytes, truncate the array to blockSize bytes.

      • generateKey

        public static byte[] generateKey​(byte[] passwordHash,
                                 HashAlgorithm hashAlgorithm,
                                 byte[] blockKey,
                                 int keySize)

        2.3.4.11 Encryption Key Generation (Agile Encryption)

        The final hash data that is used for an encryption key is then generated by using the following method:

        H_final = H(H_n + blockKey)

        where blockKey represents an array of bytes used to prevent two different blocks from encrypting to the same cipher text.

        If the size of the resulting H_final is smaller than that of PasswordKeyEncryptor.keyBits, the key MUST be padded by appending bytes with a value of 0x36. If the hash value is larger in size than PasswordKeyEncryptor.keyBits, the key is obtained by truncating the hash value.

        Parameters:
        passwordHash - the hashed password byte
        hashAlgorithm - the hash algorithm
        blockKey - the block key
        keySize - the key size
        Returns:
        intermediate key

      • getCipher

        public static Cipher getCipher​(SecretKey key,
                               CipherAlgorithm cipherAlgorithm,
                               ChainingMode chain,
                               byte[] vec,
                               int cipherMode)
        Initialize a new cipher object with the given cipher properties and no padding If the given algorithm is not implemented in the JCE, it will try to load it from the bouncy castle provider.
        Parameters:
        key - the secret key
        cipherAlgorithm - the cipher algorithm
        chain - the chaining mode
        vec - the initialization vector (IV), can be null
        cipherMode - Cipher.DECRYPT_MODE or Cipher.ENCRYPT_MODE
        Returns:
        the requested cipher
        Throws:
        EncryptedDocumentException - if the initialization failed or if an algorithm was specified, which depends on a missing bouncy castle provider

      • getCipher

        public static Cipher getCipher​(Key key,
                               CipherAlgorithm cipherAlgorithm,
                               ChainingMode chain,
                               byte[] vec,
                               int cipherMode,
                               String padding)
        Initialize a new cipher object with the given cipher properties If the given algorithm is not implemented in the JCE, it will try to load it from the bouncy castle provider.
        Parameters:
        key - the secret key
        cipherAlgorithm - the cipher algorithm
        chain - the chaining mode
        vec - the initialization vector (IV), can be null
        cipherMode - Cipher.DECRYPT_MODE or Cipher.ENCRYPT_MODE
        padding - the padding (null = NOPADDING, ANSIX923Padding, PKCS5Padding, PKCS7Padding, ISO10126Padding, ...)
        Returns:
        the requested cipher
        Throws:
        EncryptedDocumentException - if the initialization failed or if an algorithm was specified, which depends on a missing bouncy castle provider

      • getBlock0

        public static byte[] getBlock0​(byte[] hash,
                               int size)
        Returns a new byte array with a truncated to the given size. If the hash has less than size bytes, it will be filled with 0-bytes
        Parameters:
        hash - the to be truncated/filled hash byte array
        size - the size of the returned byte array
        Returns:
        the padded hash

      • registerBouncyCastle

        public static void registerBouncyCastle()

      • xorHashPassword

        public static String xorHashPassword​(String password)
        This method generates the xored-hashed password for word documents < 2007.

      • xorHashPasswordReversed

        public static String xorHashPasswordReversed​(String password)
        Convenience function which returns the reversed xored-hashed password for further processing in word documents 2007 and newer, which utilize a real hashing algorithm like sha1.