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dns: consistency; performance on malicious input #20445

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dns: consistency; performance on malicious input #20445

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cd73836
dns: make invalid setServers yield uniform error
davisjam May 1, 2018
fc93b59
dns: revise quadratic regex in setServers
davisjam May 31, 2018
03451b4
address review comments
davisjam Jun 1, 2018
ae34731
add missing semicolon caught by linter
davisjam Jun 2, 2018
260ee07
Update test-dns.js
Trott Jun 7, 2018
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15 changes: 10 additions & 5 deletions lib/dns.js
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Original file line number Diff line number Diff line change
Expand Up @@ -289,7 +289,7 @@ function setServers(servers) {
// servers cares won't have any servers available for resolution
const orig = this._handle.getServers();
const newSet = [];
const IPv6RE = /\[(.*)\]/;
const IPv6RE = /^\[([^[\]]*)\]/;
const addrSplitRE = /(^.+?)(?::(\d+))?$/;

servers.forEach((serv) => {
Expand All @@ -309,11 +309,16 @@ function setServers(servers) {
}
}

const [, s, p] = serv.match(addrSplitRE);
ipVersion = isIP(s);
// addr::port
const addrSplitMatch = serv.match(addrSplitRE);
if (addrSplitMatch) {
const hostIP = addrSplitMatch[1];
const port = addrSplitMatch[2] || IANA_DNS_PORT;
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Can you explain the default value here? That is something unexpected for me.

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addrSplitMatch[2] might be undefined (see #20441), in which case I figured the port should be 53 (DNS port).

I think this is consistent with existing cases where a default port is selected, e.g. here and here.

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@bnoordhuis @apapirovski PTAL

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I think it should be fine. parseInt('') works out to 0 when coerced to int32 and c-ares uses the default port in that case. IOW, there should be no observable change in behavior, it'll use port 53 either way.


if (ipVersion !== 0) {
return newSet.push([ipVersion, s, parseInt(p)]);
ipVersion = isIP(hostIP);
if (ipVersion !== 0) {
return newSet.push([ipVersion, hostIP, parseInt(port)]);
}
}

throw new ERR_INVALID_IP_ADDRESS(serv);
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25 changes: 25 additions & 0 deletions test/parallel/test-dns.js
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Expand Up @@ -62,6 +62,31 @@ assert(existing.length > 0);
]);
}

{
// Various invalidities, all of which should throw a clean error.
const invalidServers = [
' ',
'\n',
'\0',
'1'.repeat(3 * 4),
// Check for REDOS issues.
':'.repeat(100000),
'['.repeat(100000),
'['.repeat(100000) + ']'.repeat(100000) + 'a'
];
invalidServers.forEach((serv) => {
assert.throws(
() => {
dns.setServers([serv]);
},
{
name: 'TypeError [ERR_INVALID_IP_ADDRESS]',
code: 'ERR_INVALID_IP_ADDRESS'
}
);
});
}

const goog = [
'8.8.8.8',
'8.8.4.4',
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