diff options
Diffstat (limited to 'core/src/main/java/org/spongycastle/crypto/paddings/PaddedBufferedBlockCipher.java')
| -rw-r--r-- | core/src/main/java/org/spongycastle/crypto/paddings/PaddedBufferedBlockCipher.java | 299 |
1 files changed, 299 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/paddings/PaddedBufferedBlockCipher.java b/core/src/main/java/org/spongycastle/crypto/paddings/PaddedBufferedBlockCipher.java new file mode 100644 index 00000000..c479a062 --- /dev/null +++ b/core/src/main/java/org/spongycastle/crypto/paddings/PaddedBufferedBlockCipher.java @@ -0,0 +1,299 @@ +package org.spongycastle.crypto.paddings; + +import org.spongycastle.crypto.BlockCipher; +import org.spongycastle.crypto.BufferedBlockCipher; +import org.spongycastle.crypto.CipherParameters; +import org.spongycastle.crypto.DataLengthException; +import org.spongycastle.crypto.InvalidCipherTextException; +import org.spongycastle.crypto.OutputLengthException; +import org.spongycastle.crypto.params.ParametersWithRandom; + +/** + * A wrapper class that allows block ciphers to be used to process data in + * a piecemeal fashion with padding. The PaddedBufferedBlockCipher + * outputs a block only when the buffer is full and more data is being added, + * or on a doFinal (unless the current block in the buffer is a pad block). + * The default padding mechanism used is the one outlined in PKCS5/PKCS7. + */ +public class PaddedBufferedBlockCipher + extends BufferedBlockCipher +{ + BlockCipherPadding padding; + + /** + * Create a buffered block cipher with the desired padding. + * + * @param cipher the underlying block cipher this buffering object wraps. + * @param padding the padding type. + */ + public PaddedBufferedBlockCipher( + BlockCipher cipher, + BlockCipherPadding padding) + { + this.cipher = cipher; + this.padding = padding; + + buf = new byte[cipher.getBlockSize()]; + bufOff = 0; + } + + /** + * Create a buffered block cipher PKCS7 padding + * + * @param cipher the underlying block cipher this buffering object wraps. + */ + public PaddedBufferedBlockCipher( + BlockCipher cipher) + { + this(cipher, new PKCS7Padding()); + } + + /** + * initialise the cipher. + * + * @param forEncryption if true the cipher is initialised for + * encryption, if false for decryption. + * @param params the key and other data required by the cipher. + * @exception IllegalArgumentException if the params argument is + * inappropriate. + */ + public void init( + boolean forEncryption, + CipherParameters params) + throws IllegalArgumentException + { + this.forEncryption = forEncryption; + + reset(); + + if (params instanceof ParametersWithRandom) + { + ParametersWithRandom p = (ParametersWithRandom)params; + + padding.init(p.getRandom()); + + cipher.init(forEncryption, p.getParameters()); + } + else + { + padding.init(null); + + cipher.init(forEncryption, params); + } + } + + /** + * return the minimum size of the output buffer required for an update + * plus a doFinal with an input of len bytes. + * + * @param len the length of the input. + * @return the space required to accommodate a call to update and doFinal + * with len bytes of input. + */ + public int getOutputSize( + int len) + { + int total = len + bufOff; + int leftOver = total % buf.length; + + if (leftOver == 0) + { + if (forEncryption) + { + return total + buf.length; + } + + return total; + } + + return total - leftOver + buf.length; + } + + /** + * return the size of the output buffer required for an update + * an input of len bytes. + * + * @param len the length of the input. + * @return the space required to accommodate a call to update + * with len bytes of input. + */ + public int getUpdateOutputSize( + int len) + { + int total = len + bufOff; + int leftOver = total % buf.length; + + if (leftOver == 0) + { + return Math.max(0, total - buf.length); + } + + return total - leftOver; + } + + /** + * process a single byte, producing an output block if neccessary. + * + * @param in the input byte. + * @param out the space for any output that might be produced. + * @param outOff the offset from which the output will be copied. + * @return the number of output bytes copied to out. + * @exception DataLengthException if there isn't enough space in out. + * @exception IllegalStateException if the cipher isn't initialised. + */ + public int processByte( + byte in, + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException + { + int resultLen = 0; + + if (bufOff == buf.length) + { + resultLen = cipher.processBlock(buf, 0, out, outOff); + bufOff = 0; + } + + buf[bufOff++] = in; + + return resultLen; + } + + /** + * process an array of bytes, producing output if necessary. + * + * @param in the input byte array. + * @param inOff the offset at which the input data starts. + * @param len the number of bytes to be copied out of the input array. + * @param out the space for any output that might be produced. + * @param outOff the offset from which the output will be copied. + * @return the number of output bytes copied to out. + * @exception DataLengthException if there isn't enough space in out. + * @exception IllegalStateException if the cipher isn't initialised. + */ + public int processBytes( + byte[] in, + int inOff, + int len, + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException + { + if (len < 0) + { + throw new IllegalArgumentException("Can't have a negative input length!"); + } + + int blockSize = getBlockSize(); + int length = getUpdateOutputSize(len); + + if (length > 0) + { + if ((outOff + length) > out.length) + { + throw new OutputLengthException("output buffer too short"); + } + } + + int resultLen = 0; + int gapLen = buf.length - bufOff; + + if (len > gapLen) + { + System.arraycopy(in, inOff, buf, bufOff, gapLen); + + resultLen += cipher.processBlock(buf, 0, out, outOff); + + bufOff = 0; + len -= gapLen; + inOff += gapLen; + + while (len > buf.length) + { + resultLen += cipher.processBlock(in, inOff, out, outOff + resultLen); + + len -= blockSize; + inOff += blockSize; + } + } + + System.arraycopy(in, inOff, buf, bufOff, len); + + bufOff += len; + + return resultLen; + } + + /** + * Process the last block in the buffer. If the buffer is currently + * full and padding needs to be added a call to doFinal will produce + * 2 * getBlockSize() bytes. + * + * @param out the array the block currently being held is copied into. + * @param outOff the offset at which the copying starts. + * @return the number of output bytes copied to out. + * @exception DataLengthException if there is insufficient space in out for + * the output or we are decrypting and the input is not block size aligned. + * @exception IllegalStateException if the underlying cipher is not + * initialised. + * @exception InvalidCipherTextException if padding is expected and not found. + */ + public int doFinal( + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException, InvalidCipherTextException + { + int blockSize = cipher.getBlockSize(); + int resultLen = 0; + + if (forEncryption) + { + if (bufOff == blockSize) + { + if ((outOff + 2 * blockSize) > out.length) + { + reset(); + + throw new OutputLengthException("output buffer too short"); + } + + resultLen = cipher.processBlock(buf, 0, out, outOff); + bufOff = 0; + } + + padding.addPadding(buf, bufOff); + + resultLen += cipher.processBlock(buf, 0, out, outOff + resultLen); + + reset(); + } + else + { + if (bufOff == blockSize) + { + resultLen = cipher.processBlock(buf, 0, buf, 0); + bufOff = 0; + } + else + { + reset(); + + throw new DataLengthException("last block incomplete in decryption"); + } + + try + { + resultLen -= padding.padCount(buf); + + System.arraycopy(buf, 0, out, outOff, resultLen); + } + finally + { + reset(); + } + } + + return resultLen; + } +} |