diff -r 000000000000 -r 6474c204b198 mobile/android/base/sync/jpake/JPakeCrypto.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mobile/android/base/sync/jpake/JPakeCrypto.java Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,264 @@ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +package org.mozilla.gecko.sync.jpake; + +import java.io.UnsupportedEncodingException; +import java.math.BigInteger; +import java.security.GeneralSecurityException; +import java.security.InvalidKeyException; +import java.security.MessageDigest; +import java.security.NoSuchAlgorithmException; + +import javax.crypto.Mac; +import javax.crypto.spec.SecretKeySpec; + +import org.mozilla.gecko.background.common.log.Logger; +import org.mozilla.gecko.sync.crypto.HKDF; +import org.mozilla.gecko.sync.crypto.KeyBundle; + +public class JPakeCrypto { + private static final String LOG_TAG = "JPakeCrypto"; + + /* + * Primes P and Q, and generator G - from original Mozilla J-PAKE + * implementation. + */ + public static final BigInteger P = new BigInteger( + "90066455B5CFC38F9CAA4A48B4281F292C260FEEF01FD61037E56258A7795A1C" + + "7AD46076982CE6BB956936C6AB4DCFE05E6784586940CA544B9B2140E1EB523F" + + "009D20A7E7880E4E5BFA690F1B9004A27811CD9904AF70420EEFD6EA11EF7DA1" + + "29F58835FF56B89FAA637BC9AC2EFAAB903402229F491D8D3485261CD068699B" + + "6BA58A1DDBBEF6DB51E8FE34E8A78E542D7BA351C21EA8D8F1D29F5D5D159394" + + "87E27F4416B0CA632C59EFD1B1EB66511A5A0FBF615B766C5862D0BD8A3FE7A0" + + "E0DA0FB2FE1FCB19E8F9996A8EA0FCCDE538175238FC8B0EE6F29AF7F642773E" + + "BE8CD5402415A01451A840476B2FCEB0E388D30D4B376C37FE401C2A2C2F941D" + + "AD179C540C1C8CE030D460C4D983BE9AB0B20F69144C1AE13F9383EA1C08504F" + + "B0BF321503EFE43488310DD8DC77EC5B8349B8BFE97C2C560EA878DE87C11E3D" + + "597F1FEA742D73EEC7F37BE43949EF1A0D15C3F3E3FC0A8335617055AC91328E" + + "C22B50FC15B941D3D1624CD88BC25F3E941FDDC6200689581BFEC416B4B2CB73", + 16); + + public static final BigInteger Q = new BigInteger( + "CFA0478A54717B08CE64805B76E5B14249A77A4838469DF7F7DC987EFCCFB11D", + 16); + + public static final BigInteger G = new BigInteger( + "5E5CBA992E0A680D885EB903AEA78E4A45A469103D448EDE3B7ACCC54D521E37" + + "F84A4BDD5B06B0970CC2D2BBB715F7B82846F9A0C393914C792E6A923E2117AB" + + "805276A975AADB5261D91673EA9AAFFEECBFA6183DFCB5D3B7332AA19275AFA1" + + "F8EC0B60FB6F66CC23AE4870791D5982AAD1AA9485FD8F4A60126FEB2CF05DB8" + + "A7F0F09B3397F3937F2E90B9E5B9C9B6EFEF642BC48351C46FB171B9BFA9EF17" + + "A961CE96C7E7A7CC3D3D03DFAD1078BA21DA425198F07D2481622BCE45969D9C" + + "4D6063D72AB7A0F08B2F49A7CC6AF335E08C4720E31476B67299E231F8BD90B3" + + "9AC3AE3BE0C6B6CACEF8289A2E2873D58E51E029CAFBD55E6841489AB66B5B4B" + + "9BA6E2F784660896AFF387D92844CCB8B69475496DE19DA2E58259B090489AC8" + + "E62363CDF82CFD8EF2A427ABCD65750B506F56DDE3B988567A88126B914D7828" + + "E2B63A6D7ED0747EC59E0E0A23CE7D8A74C1D2C2A7AFB6A29799620F00E11C33" + + "787F7DED3B30E1A22D09F1FBDA1ABBBFBF25CAE05A13F812E34563F99410E73B", + 16); + + /** + * + * Round 1 of J-PAKE protocol. + * Generate x1, x2, and ZKP for other party. + */ + public static void round1(JPakeParty jp, JPakeNumGenerator gen) throws NoSuchAlgorithmException, UnsupportedEncodingException { + // Randomly select x1 from [0,q), x2 from [1,q). + BigInteger x1 = gen.generateFromRange(Q); // [0, q) + BigInteger x2 = jp.x2 = BigInteger.ONE.add(gen.generateFromRange(Q + .subtract(BigInteger.ONE))); // [1, q) + + BigInteger gx1 = G.modPow(x1, P); + BigInteger gx2 = G.modPow(x2, P); + + jp.gx1 = gx1; + jp.gx2 = gx2; + + // Generate and store zero knowledge proofs. + jp.zkp1 = createZkp(G, x1, gx1, jp.signerId, gen); + jp.zkp2 = createZkp(G, x2, gx2, jp.signerId, gen); + } + + /** + * Round 2 of J-PAKE protocol. + * Generate A and ZKP for A. + * Verify ZKP from other party. Does not check for replay ZKP. + */ + public static void round2(BigInteger secretValue, JPakeParty jp, JPakeNumGenerator gen) + throws IncorrectZkpException, NoSuchAlgorithmException, + Gx3OrGx4IsZeroOrOneException, UnsupportedEncodingException { + + Logger.debug(LOG_TAG, "round2 started."); + + // checkZkp does some additional checks, but we can throw a more informative exception here. + if (BigInteger.ZERO.compareTo(jp.gx3) == 0 || BigInteger.ONE.compareTo(jp.gx3) == 0 || + BigInteger.ZERO.compareTo(jp.gx4) == 0 || BigInteger.ONE.compareTo(jp.gx4) == 0) { + throw new Gx3OrGx4IsZeroOrOneException(); + } + + // Check ZKP. + checkZkp(G, jp.gx3, jp.zkp3); + checkZkp(G, jp.gx4, jp.zkp4); + + // Compute a = g^[(x1+x3+x4)*(x2*secret)]. + BigInteger y1 = jp.gx3.multiply(jp.gx4).mod(P).multiply(jp.gx1).mod(P); + BigInteger y2 = jp.x2.multiply(secretValue).mod(P); + + BigInteger a = y1.modPow(y2, P); + jp.thisZkpA = createZkp(y1, y2, a, jp.signerId, gen); + jp.thisA = a; + + Logger.debug(LOG_TAG, "round2 finished."); + } + + /** + * Final round of J-PAKE protocol. + */ + public static KeyBundle finalRound(BigInteger secretValue, JPakeParty jp) + throws IncorrectZkpException, NoSuchAlgorithmException, InvalidKeyException, UnsupportedEncodingException { + Logger.debug(LOG_TAG, "Final round started."); + BigInteger gb = jp.gx1.multiply(jp.gx2).mod(P).multiply(jp.gx3) + .mod(P); + checkZkp(gb, jp.otherA, jp.otherZkpA); + + // Calculate shared key g^(x1+x3)*x2*x4*secret, which is equivalent to + // (B/g^(x2*x4*s))^x2 = (B*(g^x4)^x2^s^-1)^2. + BigInteger k = jp.gx4.modPow(jp.x2.multiply(secretValue).negate().mod(Q), P).multiply(jp.otherA) + .modPow(jp.x2, P); + + byte[] enc = new byte[32]; + byte[] hmac = new byte[32]; + generateKeyAndHmac(k, enc, hmac); + + Logger.debug(LOG_TAG, "Final round finished; returning key."); + return new KeyBundle(enc, hmac); + } + + // TODO Replace this function with the one in the crypto library + private static byte[] HMACSHA256(byte[] data, byte[] key) { + byte[] result = null; + try { + Mac hmacSha256; + hmacSha256 = Mac.getInstance("HmacSHA256"); + SecretKeySpec secret_key = new SecretKeySpec(key, "HmacSHA256"); + hmacSha256.init(secret_key); + result = hmacSha256.doFinal(data); + } catch (GeneralSecurityException e) { + Logger.error(LOG_TAG, "Got exception calculating HMAC.", e); + } + return result; + } + + /* Helper Methods */ + + /* + * Generate the ZKP b = r - x*h, and g^r, where h = hash(g, g^r, g^x, id). (We + * pass in gx to save on an exponentiation of g^x) + */ + private static Zkp createZkp(BigInteger g, BigInteger x, BigInteger gx, + String id, JPakeNumGenerator gen) throws NoSuchAlgorithmException, UnsupportedEncodingException { + // Generate random r for exponent. + BigInteger r = gen.generateFromRange(Q); + + // Calculate g^r for ZKP. + BigInteger gr = g.modPow(r, P); + + // Calculate the ZKP b value = (r-x*h) % q. + BigInteger h = computeBHash(g, gr, gx, id); + Logger.debug(LOG_TAG, "myhash: " + h.toString(16)); + + // ZKP value = b = r-x*h + BigInteger b = r.subtract(x.multiply(h)).mod(Q); + + return new Zkp(gr, b, id); + } + + /* + * Verify ZKP. + */ + private static void checkZkp(BigInteger g, BigInteger gx, Zkp zkp) + throws IncorrectZkpException, NoSuchAlgorithmException, UnsupportedEncodingException { + + BigInteger h = computeBHash(g, zkp.gr, gx, zkp.id); + + // Check parameters of zkp, and compare to computed hash. These shouldn't + // fail. + if (gx.compareTo(BigInteger.ONE) < 1) { // g^x > 1. + Logger.error(LOG_TAG, "g^x > 1 fails."); + throw new IncorrectZkpException(); + } + if (gx.compareTo(P.subtract(BigInteger.ONE)) > -1) { // g^x < p-1 + Logger.error(LOG_TAG, "g^x < p-1 fails."); + throw new IncorrectZkpException(); + } + if (gx.modPow(Q, P).compareTo(BigInteger.ONE) != 0) { + Logger.error(LOG_TAG, "g^x^q % p = 1 fails."); + throw new IncorrectZkpException(); + } + if (zkp.gr.compareTo(g.modPow(zkp.b, P).multiply(gx.modPow(h, P)).mod(P)) != 0) { + // b = r-h*x ==> g^r = g^b*g^x^(h) + Logger.debug(LOG_TAG, "gb*g(xh) = " + g.modPow(zkp.b, P).multiply(gx.modPow(h, P)).mod(P).toString(16)); + Logger.debug(LOG_TAG, "gr = " + zkp.gr.toString(16)); + Logger.debug(LOG_TAG, "b = " + zkp.b.toString(16)); + Logger.debug(LOG_TAG, "g^b = " + g.modPow(zkp.b, P).toString(16)); + Logger.debug(LOG_TAG, "g^(xh) = " + gx.modPow(h, P).toString(16)); + Logger.debug(LOG_TAG, "gx = " + gx.toString(16)); + Logger.debug(LOG_TAG, "h = " + h.toString(16)); + Logger.error(LOG_TAG, "zkp calculation incorrect."); + throw new IncorrectZkpException(); + } + Logger.debug(LOG_TAG, "*** ZKP SUCCESS ***"); + } + + /* + * Use SHA-256 to compute a BigInteger hash of g, gr, gx values with + * mySignerId to prevent replay. Does not make a twos-complement BigInteger + * form hash. + */ + private static BigInteger computeBHash(BigInteger g, BigInteger gr, BigInteger gx, + String id) throws NoSuchAlgorithmException, UnsupportedEncodingException { + MessageDigest sha = MessageDigest.getInstance("SHA-256"); + sha.reset(); + + /* + * Note: you should ensure the items in H(...) have clear boundaries. It + * is simple if the other party knows sizes of g, gr, gx and signerID and + * hence the boundary is unambiguous. If not, you'd better prepend each + * item with its byte length, but I've omitted that here. + */ + + hashByteArrayWithLength(sha, BigIntegerHelper.BigIntegerToByteArrayWithoutSign(g)); + hashByteArrayWithLength(sha, BigIntegerHelper.BigIntegerToByteArrayWithoutSign(gr)); + hashByteArrayWithLength(sha, BigIntegerHelper.BigIntegerToByteArrayWithoutSign(gx)); + hashByteArrayWithLength(sha, id.getBytes("UTF-8")); + + byte[] hash = sha.digest(); + + return BigIntegerHelper.ByteArrayToBigIntegerWithoutSign(hash); + } + + /* + * Update a hash with a byte array's length and the byte array. + */ + private static void hashByteArrayWithLength(MessageDigest sha, byte[] data) { + int length = data.length; + byte[] b = new byte[] { (byte) (length >>> 8), (byte) (length & 0xff) }; + sha.update(b); + sha.update(data); + } + + /* + * Helper function to generate encryption key and HMAC from a byte array. + */ + public static void generateKeyAndHmac(BigInteger k, byte[] encOut, byte[] hmacOut) throws NoSuchAlgorithmException, InvalidKeyException { + // Generate HMAC and Encryption keys from synckey. + byte[] zerokey = new byte[32]; + byte[] prk = HMACSHA256(BigIntegerHelper.BigIntegerToByteArrayWithoutSign(k), zerokey); + + byte[] okm = HKDF.hkdfExpand(prk, HKDF.HMAC_INPUT, 32 * 2); + System.arraycopy(okm, 0, encOut, 0, 32); + System.arraycopy(okm, 32, hmacOut, 0, 32); + } +}