diff options
Diffstat (limited to 'core/src/main/jdk1.1/org/spongycastle/crypto/encodings/PKCS1Encoding.java')
| -rw-r--r-- | core/src/main/jdk1.1/org/spongycastle/crypto/encodings/PKCS1Encoding.java | 410 |
1 files changed, 410 insertions, 0 deletions
diff --git a/core/src/main/jdk1.1/org/spongycastle/crypto/encodings/PKCS1Encoding.java b/core/src/main/jdk1.1/org/spongycastle/crypto/encodings/PKCS1Encoding.java new file mode 100644 index 00000000..7af31f36 --- /dev/null +++ b/core/src/main/jdk1.1/org/spongycastle/crypto/encodings/PKCS1Encoding.java @@ -0,0 +1,410 @@ +package org.spongycastle.crypto.encodings; + +import java.security.SecureRandom; + +import org.spongycastle.crypto.AsymmetricBlockCipher; +import org.spongycastle.crypto.CipherParameters; +import org.spongycastle.crypto.InvalidCipherTextException; +import org.spongycastle.crypto.params.AsymmetricKeyParameter; +import org.spongycastle.crypto.params.ParametersWithRandom; + +/** + * this does your basic PKCS 1 v1.5 padding - whether or not you should be using this + * depends on your application - see PKCS1 Version 2 for details. + */ +public class PKCS1Encoding + implements AsymmetricBlockCipher +{ + /** + * some providers fail to include the leading zero in PKCS1 encoded blocks. If you need to + * work with one of these set the system property org.spongycastle.pkcs1.strict to false. + * <p> + * The system property is checked during construction of the encoding object, it is set to + * true by default. + * </p> + */ + public static final String STRICT_LENGTH_ENABLED_PROPERTY = "org.spongycastle.pkcs1.strict"; + + private static final int HEADER_LENGTH = 10; + + private SecureRandom random; + private AsymmetricBlockCipher engine; + private boolean forEncryption; + private boolean forPrivateKey; + private boolean useStrictLength; + private int pLen = -1; + private byte[] fallback = null; + + /** + * Basic constructor. + * @param cipher + */ + public PKCS1Encoding( + AsymmetricBlockCipher cipher) + { + this.engine = cipher; + this.useStrictLength = useStrict(); + } + + /** + * Constructor for decryption with a fixed plaintext length. + * + * @param cipher The cipher to use for cryptographic operation. + * @param pLen Length of the expected plaintext. + */ + public PKCS1Encoding( + AsymmetricBlockCipher cipher, + int pLen) + { + this.engine = cipher; + this.useStrictLength = useStrict(); + this.pLen = pLen; + } + + /** + * Constructor for decryption with a fixed plaintext length and a fallback + * value that is returned, if the padding is incorrect. + * + * @param cipher + * The cipher to use for cryptographic operation. + * @param fallback + * The fallback value, we don't to a arraycopy here. + */ + public PKCS1Encoding( + AsymmetricBlockCipher cipher, + byte[] fallback) + { + this.engine = cipher; + this.useStrictLength = useStrict(); + this.fallback = fallback; + this.pLen = fallback.length; + } + + + + // + // for J2ME compatibility + // + private boolean useStrict() + { + // required if security manager has been installed. + String strict = System.getProperty(STRICT_LENGTH_ENABLED_PROPERTY); + + return strict == null || strict.equals("true"); + } + + public AsymmetricBlockCipher getUnderlyingCipher() + { + return engine; + } + + public void init( + boolean forEncryption, + CipherParameters param) + { + AsymmetricKeyParameter kParam; + + if (param instanceof ParametersWithRandom) + { + ParametersWithRandom rParam = (ParametersWithRandom)param; + + this.random = rParam.getRandom(); + kParam = (AsymmetricKeyParameter)rParam.getParameters(); + } + else + { + this.random = new SecureRandom(); + kParam = (AsymmetricKeyParameter)param; + } + + engine.init(forEncryption, param); + + this.forPrivateKey = kParam.isPrivate(); + this.forEncryption = forEncryption; + } + + public int getInputBlockSize() + { + int baseBlockSize = engine.getInputBlockSize(); + + if (forEncryption) + { + return baseBlockSize - HEADER_LENGTH; + } + else + { + return baseBlockSize; + } + } + + public int getOutputBlockSize() + { + int baseBlockSize = engine.getOutputBlockSize(); + + if (forEncryption) + { + return baseBlockSize; + } + else + { + return baseBlockSize - HEADER_LENGTH; + } + } + + public byte[] processBlock( + byte[] in, + int inOff, + int inLen) + throws InvalidCipherTextException + { + if (forEncryption) + { + return encodeBlock(in, inOff, inLen); + } + else + { + return decodeBlock(in, inOff, inLen); + } + } + + private byte[] encodeBlock( + byte[] in, + int inOff, + int inLen) + throws InvalidCipherTextException + { + if (inLen > getInputBlockSize()) + { + throw new IllegalArgumentException("input data too large"); + } + + byte[] block = new byte[engine.getInputBlockSize()]; + + if (forPrivateKey) + { + block[0] = 0x01; // type code 1 + + for (int i = 1; i != block.length - inLen - 1; i++) + { + block[i] = (byte)0xFF; + } + } + else + { + random.nextBytes(block); // random fill + + block[0] = 0x02; // type code 2 + + // + // a zero byte marks the end of the padding, so all + // the pad bytes must be non-zero. + // + for (int i = 1; i != block.length - inLen - 1; i++) + { + while (block[i] == 0) + { + block[i] = (byte)random.nextInt(); + } + } + } + + block[block.length - inLen - 1] = 0x00; // mark the end of the padding + System.arraycopy(in, inOff, block, block.length - inLen, inLen); + + return engine.processBlock(block, 0, block.length); + } + + /** + * Checks if the argument is a correctly PKCS#1.5 encoded Plaintext + * for encryption. + * + * @param encoded The Plaintext. + * @param pLen Expected length of the plaintext. + * @return Either 0, if the encoding is correct, or -1, if it is incorrect. + */ + private static int checkPkcs1Encoding(byte[] encoded, int pLen) { + int correct = 0; + /* + * Check if the first two bytes are 0 2 + */ + correct |= (encoded[0] ^ 2); + + /* + * Now the padding check, check for no 0 byte in the padding + */ + int plen = encoded.length - ( + pLen /* Lenght of the PMS */ + + 1 /* Final 0-byte before PMS */ + ); + + for (int i = 1; i < plen; i++) { + int tmp = encoded[i]; + tmp |= tmp >> 1; + tmp |= tmp >> 2; + tmp |= tmp >> 4; + correct |= (tmp & 1) - 1; + } + + /* + * Make sure the padding ends with a 0 byte. + */ + correct |= encoded[encoded.length - (pLen +1)]; + + /* + * Return 0 or 1, depending on the result. + */ + correct |= correct >> 1; + correct |= correct >> 2; + correct |= correct >> 4; + return ~((correct & 1) - 1); + } + + + /** + * Decode PKCS#1.5 encoding, and return a random value if the padding is not correct. + * + * @param in The encrypted block. + * @param inOff Offset in the encrypted block. + * @param inLen Length of the encrypted block. + * //@param pLen Length of the desired output. + * @return The plaintext without padding, or a random value if the padding was incorrect. + * + * @throws InvalidCipherTextException + */ + private byte[] decodeBlockOrRandom(byte[] in, int inOff, int inLen) + throws InvalidCipherTextException + { + if (!forPrivateKey) + { + throw new InvalidCipherTextException("sorry, this method is only for decryption, not for signing"); + } + + byte[] block = engine.processBlock(in, inOff, inLen); + byte[] random = null; + if (this.fallback == null) + { + random = new byte[this.pLen]; + this.random.nextBytes(random); + } + else + { + random = fallback; + } + + /* + * TODO: This is a potential dangerous side channel. However, you can + * fix this by changing the RSA engine in a way, that it will always + * return blocks of the same length and prepend them with 0 bytes if + * needed. + */ + if (block.length < getOutputBlockSize()) + { + throw new InvalidCipherTextException("block truncated"); + } + + /* + * TODO: Potential side channel. Fix it by making the engine always + * return blocks of the correct length. + */ + if (useStrictLength && block.length != engine.getOutputBlockSize()) + { + throw new InvalidCipherTextException("block incorrect size"); + } + + /* + * Check the padding. + */ + int correct = PKCS1Encoding.checkPkcs1Encoding(block, this.pLen); + + /* + * Now, to a constant time constant memory copy of the decrypted value + * or the random value, depending on the validity of the padding. + */ + byte[] result = new byte[this.pLen]; + for (int i = 0; i < this.pLen; i++) + { + result[i] = (byte)((block[i + (block.length - pLen)] & (~correct)) | (random[i] & correct)); + } + + return result; + } + + /** + * @exception InvalidCipherTextException if the decrypted block is not in PKCS1 format. + */ + private byte[] decodeBlock( + byte[] in, + int inOff, + int inLen) + throws InvalidCipherTextException + { + /* + * If the length of the expected plaintext is known, we use a constant-time decryption. + * If the decryption fails, we return a random value. + */ + if (this.pLen != -1) { + return this.decodeBlockOrRandom(in, inOff, inLen); + } + + byte[] block = engine.processBlock(in, inOff, inLen); + + if (block.length < getOutputBlockSize()) + { + throw new InvalidCipherTextException("block truncated"); + } + + byte type = block[0]; + + if (forPrivateKey) + { + if (type != 2) + { + throw new InvalidCipherTextException("unknown block type"); + } + } + else + { + if (type != 1) + { + throw new InvalidCipherTextException("unknown block type"); + } + } + + if (useStrictLength && block.length != engine.getOutputBlockSize()) + { + throw new InvalidCipherTextException("block incorrect size"); + } + + // + // find and extract the message block. + // + int start; + + for (start = 1; start != block.length; start++) + { + byte pad = block[start]; + + if (pad == 0) + { + break; + } + if (type == 1 && pad != (byte)0xff) + { + throw new InvalidCipherTextException("block padding incorrect"); + } + } + + start++; // data should start at the next byte + + if (start > block.length || start < HEADER_LENGTH) + { + throw new InvalidCipherTextException("no data in block"); + } + + byte[] result = new byte[block.length - start]; + + System.arraycopy(block, start, result, 0, result.length); + + return result; + } +} |