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Improve compatibility with application bundlers #20

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2157a2f
Avoid using `return` outside of a function
skozin Mar 24, 2018
2bb889b
Use ".node" extension when importing native module
skozin Mar 25, 2018
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196 changes: 3 additions & 193 deletions index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -5,203 +5,13 @@

"use strict";

var promise = typeof Promise === "undefined" ?
require("es6-promise").Promise :
Promise;
var crypto = require("crypto");
// try to use secp256k1, fallback to browser implementation
// try to use Node.js-specific dependencies, fallback to browser implementation
try {
var secp256k1 = require("secp256k1");
var ecdh = require("./build/Release/ecdh");
module.exports = require("./node");
} catch (e) {
if (process.env.ECCRYPTO_NO_FALLBACK) {
throw e;
} else {
return (module.exports = require("./browser"));
module.exports = require("./browser");
}
}

function assert(condition, message) {
if (!condition) {
throw new Error(message || "Assertion failed");
}
}

function sha512(msg) {
return crypto.createHash("sha512").update(msg).digest();
}

function aes256CbcEncrypt(iv, key, plaintext) {
var cipher = crypto.createCipheriv("aes-256-cbc", key, iv);
var firstChunk = cipher.update(plaintext);
var secondChunk = cipher.final();
return Buffer.concat([firstChunk, secondChunk]);
}

function aes256CbcDecrypt(iv, key, ciphertext) {
var cipher = crypto.createDecipheriv("aes-256-cbc", key, iv);
var firstChunk = cipher.update(ciphertext);
var secondChunk = cipher.final();
return Buffer.concat([firstChunk, secondChunk]);
}

function hmacSha256(key, msg) {
return crypto.createHmac("sha256", key).update(msg).digest();
}

// Compare two buffers in constant time to prevent timing attacks.
function equalConstTime(b1, b2) {
if (b1.length !== b2.length) {
return false;
}
var res = 0;
for (var i = 0; i < b1.length; i++) {
res |= b1[i] ^ b2[i]; // jshint ignore:line
}
return res === 0;
}

function pad32(msg){
var buf;
if (msg.length < 32) {
buf = new Buffer(32);
buf.fill(0);
msg.copy(buf, 32 - msg.length);
return buf;
} else {
return msg;
}
}

/**
* Compute the public key for a given private key.
* @param {Buffer} privateKey - A 32-byte private key
* @return {Buffer} A 65-byte public key.
* @function
*/
var getPublic = exports.getPublic = function(privateKey) {
assert(privateKey.length === 32, "Bad private key");
// See https://github.com/wanderer/secp256k1-node/issues/46
var compressed = secp256k1.publicKeyCreate(privateKey);
return secp256k1.publicKeyConvert(compressed, false);
};

/**
* Create an ECDSA signature.
* @param {Buffer} privateKey - A 32-byte private key
* @param {Buffer} msg - The message being signed
* @return {Promise.<Buffer>} A promise that resolves with the
* signature and rejects on bad key or message.
*/
exports.sign = function(privateKey, msg) {
return new promise(function(resolve) {
assert(msg.length > 0, "Message should not be empty");
assert(msg.length <= 32, "Message is too long");
msg = pad32(msg);
var sig = secp256k1.signSync(msg, privateKey).signature;
resolve(secp256k1.signatureExport(sig));
});
};

/**
* Verify an ECDSA signature.
* @param {Buffer} publicKey - A 65-byte public key
* @param {Buffer} msg - The message being verified
* @param {Buffer} sig - The signature
* @return {Promise.<null>} A promise that resolves on correct signature
* and rejects on bad key or signature.
*/
exports.verify = function(publicKey, msg, sig) {
return new promise(function(resolve, reject) {
assert(msg.length > 0, "Message should not be empty");
assert(msg.length <= 32, "Message is too long");
msg = pad32(msg);
sig = secp256k1.signatureImport(sig);
if (secp256k1.verifySync(msg, sig, publicKey)) {
resolve(null);
} else {
reject(new Error("Bad signature"));
}
});
};

/**
* Derive shared secret for given private and public keys.
* @param {Buffer} privateKeyA - Sender's private key (32 bytes)
* @param {Buffer} publicKeyB - Recipient's public key (65 bytes)
* @return {Promise.<Buffer>} A promise that resolves with the derived
* shared secret (Px, 32 bytes) and rejects on bad key.
*/
var derive = exports.derive = function(privateKeyA, publicKeyB) {
return new promise(function(resolve) {
resolve(ecdh.derive(privateKeyA, publicKeyB));
});
};

/**
* Input/output structure for ECIES operations.
* @typedef {Object} Ecies
* @property {Buffer} iv - Initialization vector (16 bytes)
* @property {Buffer} ephemPublicKey - Ephemeral public key (65 bytes)
* @property {Buffer} ciphertext - The result of encryption (variable size)
* @property {Buffer} mac - Message authentication code (32 bytes)
*/

/**
* Encrypt message for given recepient's public key.
* @param {Buffer} publicKeyTo - Recipient's public key (65 bytes)
* @param {Buffer} msg - The message being encrypted
* @param {?{?iv: Buffer, ?ephemPrivateKey: Buffer}} opts - You may also
* specify initialization vector (16 bytes) and ephemeral private key
* (32 bytes) to get deterministic results.
* @return {Promise.<Ecies>} - A promise that resolves with the ECIES
* structure on successful encryption and rejects on failure.
*/
exports.encrypt = function(publicKeyTo, msg, opts) {
opts = opts || {};
// Tmp variable to save context from flat promises;
var ephemPublicKey;
return new promise(function(resolve) {
var ephemPrivateKey = opts.ephemPrivateKey || crypto.randomBytes(32);
ephemPublicKey = getPublic(ephemPrivateKey);
resolve(derive(ephemPrivateKey, publicKeyTo));
}).then(function(Px) {
var hash = sha512(Px);
var iv = opts.iv || crypto.randomBytes(16);
var encryptionKey = hash.slice(0, 32);
var macKey = hash.slice(32);
var ciphertext = aes256CbcEncrypt(iv, encryptionKey, msg);
var dataToMac = Buffer.concat([iv, ephemPublicKey, ciphertext]);
var mac = hmacSha256(macKey, dataToMac);
return {
iv: iv,
ephemPublicKey: ephemPublicKey,
ciphertext: ciphertext,
mac: mac,
};
});
};

/**
* Decrypt message using given private key.
* @param {Buffer} privateKey - A 32-byte private key of recepient of
* the mesage
* @param {Ecies} opts - ECIES structure (result of ECIES encryption)
* @return {Promise.<Buffer>} - A promise that resolves with the
* plaintext on successful decryption and rejects on failure.
*/
exports.decrypt = function(privateKey, opts) {
return derive(privateKey, opts.ephemPublicKey).then(function(Px) {
var hash = sha512(Px);
var encryptionKey = hash.slice(0, 32);
var macKey = hash.slice(32);
var dataToMac = Buffer.concat([
opts.iv,
opts.ephemPublicKey,
opts.ciphertext
]);
var realMac = hmacSha256(macKey, dataToMac);
assert(equalConstTime(opts.mac, realMac), "Bad MAC");
return aes256CbcDecrypt(opts.iv, encryptionKey, opts.ciphertext);
});
};
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