Reliance on DNS Lookups in a Security Decision
Weakness ID: 247 (Weakness Variant)Status: Incomplete
+ Description

Description Summary

Attackers can spoof DNS entries. Do not rely on DNS names for security.
+ Time of Introduction
  • Implementation
  • Architecture and Design
+ Applicable Platforms

Languages

All

+ Demonstrative Examples

Example 1

The following code sample uses a DNS lookup in order to decide whether or not an inbound request is from a trusted host. If an attacker can poison the DNS cache, they can gain trusted status.

(Bad Code)
Example Language: Java 
String ip = request.getRemoteAddr();
InetAddress addr = InetAddress.getByName(ip);
if (addr.getCanonicalHostName().endsWith("trustme.com")) {
trusted = true;
}
IPAddress hostIPAddress = IPAddress.Parse(RemoteIpAddress);
IPHostEntry hostInfo = Dns.GetHostByAddress(hostIPAddress);
if (hostInfo.HostName.EndsWith("trustme.com")) {
trusted = true;
}

IP addresses are more reliable than DNS names, but they can also be spoofed. Attackers can easily forge the source IP address of the packets they send, but response packets will return to the forged IP address. To see the response packets, the attacker has to sniff the traffic between the victim machine and the forged IP address. In order to accomplish the required sniffing, attackers typically attempt to locate themselves on the same subnet as the victim machine. Attackers may be able to circumvent this requirement by using source routing, but source routing is disabled across much of the Internet today. In summary, IP address verification can be a useful part of an authentication scheme, but it should not be the single factor required for authentication.

+ Other Notes

Many DNS servers are susceptible to spoofing attacks, so you should assume that your software will someday run in an environment with a compromised DNS server. If attackers are allowed to make DNS updates (sometimes called DNS cache poisoning), they can route your network traffic through their machines or make it appear as if their IP addresses are part of your domain. Do not base the security of your system on DNS names.

+ Relationships
NatureTypeIDNameView(s) this relationship pertains toView(s)
ChildOfWeakness ClassWeakness Class227Failure to Fulfill API Contract ('API Abuse')
Development Concepts (primary)699
ChildOfWeakness ClassWeakness Class345Insufficient Verification of Data Authenticity
Research Concepts1000
ChildOfWeakness BaseWeakness Base807Reliance on Untrusted Inputs in a Security Decision
Research Concepts (primary)1000
PeerOfWeakness BaseWeakness Base290Authentication Bypass by Spoofing
Research Concepts1000
+ Related Attack Patterns
CAPEC-IDAttack Pattern Name
(CAPEC Version: 1.4)
89Pharming
+ Content History
Submissions
Submission DateSubmitterOrganizationSource
7 Pernicious KingdomsExternally Mined
Modifications
Modification DateModifierOrganizationSource
2008-07-01Eric DalciCigitalExternal
updated Time of Introduction
2008-09-08CWE Content TeamMITREInternal
updated Relationships, Other Notes, Taxonomy Mappings
2009-05-27CWE Content TeamMITREInternal
updated Relationships, Taxonomy Mappings
2009-07-27CWE Content TeamMITREInternal
updated Demonstrative Examples
Previous Entry Names
Change DatePrevious Entry Name
2008-04-11Often Misused: Authentication
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