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tls: add minDHSize option to tls.connect()
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Add a new option to specifiy a minimum size of an ephemeral DH
parameter to accept a tls connection. Default is 1024 bit.

PR-URL: #1831
Reviewed-By: indutny - Fedor Indutny <[email protected]>
Reviewed-By: bnoordhuis - Ben Noordhuis <[email protected]>
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Shigeki Ohtsu committed Oct 16, 2015
1 parent 6d92eba commit f72e178
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Showing 3 changed files with 104 additions and 1 deletion.
5 changes: 5 additions & 0 deletions doc/api/tls.markdown
Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,11 @@ Creates a new client connection to the given `port` and `host` (old API) or

- `session`: A `Buffer` instance, containing TLS session.

- `minDHSize`: Minimum size of DH parameter in bits to accept a TLS
connection. When a server offers DH parameter with a size less
than this, the TLS connection is destroyed and throws an
error. Default: 1024.

The `callback` parameter will be added as a listener for the
['secureConnect'][] event.

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19 changes: 18 additions & 1 deletion lib/_tls_wrap.js
Original file line number Diff line number Diff line change
Expand Up @@ -945,14 +945,20 @@ exports.connect = function(/* [port, host], options, cb */) {
var defaults = {
rejectUnauthorized: '0' !== process.env.NODE_TLS_REJECT_UNAUTHORIZED,
ciphers: tls.DEFAULT_CIPHERS,
checkServerIdentity: tls.checkServerIdentity
checkServerIdentity: tls.checkServerIdentity,
minDHSize: 1024
};

options = util._extend(defaults, options || {});
if (!options.keepAlive)
options.singleUse = true;

assert(typeof options.checkServerIdentity === 'function');
assert(typeof options.minDHSize === 'number',
'options.minDHSize is not a number: ' + options.minDHSize);
assert(options.minDHSize > 0,
'options.minDHSize is not a posivie number: ' +
options.minDHSize);

var hostname = options.servername ||
options.host ||
Expand Down Expand Up @@ -1004,6 +1010,17 @@ exports.connect = function(/* [port, host], options, cb */) {
socket._start();

socket.on('secure', function() {
// Check the size of DHE parameter above minimum requirement
// specified in options.
var ekeyinfo = socket.getEphemeralKeyInfo();
if (ekeyinfo.type === 'DH' && ekeyinfo.size < options.minDHSize) {
var err = new Error('DH parameter size ' + ekeyinfo.size +
' is less than ' + options.minDHSize);
socket.emit('error', err);
socket.destroy();
return;
}

var verifyError = socket._handle.verifyError();

// Verify that server's identity matches it's certificate's names
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81 changes: 81 additions & 0 deletions test/parallel/test-tls-client-mindhsize.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,81 @@
'use strict';
var common = require('../common');
var assert = require('assert');

if (!common.hasCrypto) {
console.log('1..0 # Skipped: missing crypto');
process.exit();
}
var tls = require('tls');

var fs = require('fs');
var key = fs.readFileSync(common.fixturesDir + '/keys/agent2-key.pem');
var cert = fs.readFileSync(common.fixturesDir + '/keys/agent2-cert.pem');

var nsuccess = 0;
var nerror = 0;

function loadDHParam(n) {
var path = common.fixturesDir;
if (n !== 'error') path += '/keys';
return fs.readFileSync(path + '/dh' + n + '.pem');
}

function test(size, err, next) {
var options = {
key: key,
cert: cert,
dhparam: loadDHParam(size),
ciphers: 'DHE-RSA-AES128-GCM-SHA256'
};

var server = tls.createServer(options, function(conn) {
conn.end();
});

server.on('close', function(isException) {
assert(!isException);
if (next) next();
});

server.listen(common.PORT, '127.0.0.1', function() {
// client set minimum DH parameter size to 2048 bits so that
// it fails when it make a connection to the tls server where
// dhparams is 1024 bits
var client = tls.connect({
minDHSize: 2048,
port: common.PORT,
rejectUnauthorized: false
}, function() {
nsuccess++;
server.close();
});
if (err) {
client.on('error', function(e) {
nerror++;
assert.strictEqual(e.message, 'DH parameter size 1024 is less'
+ ' than 2048');
server.close();
});
}
});
}

// A client connection fails with an error when a client has an
// 2048 bits minDHSize option and a server has 1024 bits dhparam
function testDHE1024() {
test(1024, true, testDHE2048);
}

// A client connection successes when a client has an
// 2048 bits minDHSize option and a server has 2048 bits dhparam
function testDHE2048() {
test(2048, false, null);
}

testDHE1024();

process.on('exit', function() {
assert.equal(nsuccess, 1);
assert.equal(nerror, 1);
});

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