CWE-350: Reliance on Reverse DNS Resolution for a Security-Critical Action

Description

The product performs reverse DNS resolution on an IP address to obtain the hostname and make a security decision, but it does not properly ensure that the IP address is truly associated with the hostname.

Since DNS names can be easily spoofed or misreported, and it may be difficult for the product to detect if a trusted DNS server has been compromised, DNS names do not constitute a valid authentication mechanism. When the product performs a reverse DNS resolution for an IP address, if an attacker controls the DNS server for that IP address, then the attacker can cause the server to return an arbitrary hostname. As a result, the attacker may be able to bypass authentication, cause the wrong hostname to be recorded in log files to hide activities, or perform other attacks. Attackers can spoof DNS names by either (1) compromising a DNS server and modifying its records (sometimes called DNS cache poisoning), or (2) having legitimate control over a DNS server associated with their IP address.

Potential Impact

Demonstrative Examples

struct hostent *hp;struct in_addr myaddr;char* tHost = "trustme.example.com";myaddr.s_addr=inet_addr(ip_addr_string);
                     hp = gethostbyaddr((char *) &myaddr, sizeof(struct in_addr), AF_INET);if (hp && !strncmp(hp->h_name, tHost, sizeof(tHost))) {trusted = true;} else {trusted = false;}

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;}

sd = socket(AF_INET, SOCK_DGRAM, 0);serv.sin_family = AF_INET;serv.sin_addr.s_addr = htonl(INADDR_ANY);servr.sin_port = htons(1008);bind(sd, (struct sockaddr *) & serv, sizeof(serv));while (1) {
                        
                           memset(msg, 0x0, MAX_MSG);clilen = sizeof(cli);h=gethostbyname(inet_ntoa(cliAddr.sin_addr));if (h->h_name==...) n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *) & cli, &clilen);
                     }

while(true) {
                        DatagramPacket rp=new DatagramPacket(rData,rData.length);outSock.receive(rp);String in = new String(p.getData(),0, rp.getLength());InetAddress IPAddress = rp.getAddress();int port = rp.getPort();if ((rp.getHostName()==...) & (in==...)) {
                              
                                 out = secret.getBytes();DatagramPacket sp =new DatagramPacket(out,out.length, IPAddress, port);outSock.send(sp);
                           }
                     }

Mitigations & Prevention

Detection Methods

• Automated Static Analysis High — Automated static analysis, commonly referred to as Static Application Security Testing (SAST), can find some instances of this weakness by analyzing source code (or binary/compiled code) without having to execute it. Typically, this is done by building a model of data flow and control flow, then sea

Real-World CVE Examples

Related Weaknesses

Taxonomy Mappings

• PLOVER: — Improperly Trusted Reverse DNS
• CLASP: — Trusting self-reported DNS name
• Software Fault Patterns: SFP29 — Faulty endpoint authentication