CWE-291: Reliance on IP Address for Authentication
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IP addresses can be easily spoofed. Attackers can 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.
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Example 1 Both of these examples check if a request is from a trusted address before responding to the request. (bad code)
Example Language: C
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); if (inet_ntoa(cli.sin_addr)==getTrustedAddress()) { n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *) & cli, &clilen); }(bad code)
Example Language: Java
while(true) {
DatagramPacket rp=new DatagramPacket(rData,rData.length);
outSock.receive(rp); String in = new String(p.getData(),0, rp.getLength()); InetAddress clientIPAddress = rp.getAddress(); int port = rp.getPort(); if (isTrustedAddress(clientIPAddress) & secretKey.equals(in)) { out = secret.getBytes(); }DatagramPacket sp =new DatagramPacket(out,out.length, IPAddress, port); outSock.send(sp); The code only verifies the address as stored in the request packet. An attacker can spoof this address, thus impersonating a trusted client. Note: this is a curated list of examples for users to understand the variety of ways in which this weakness can be introduced. It is not a complete list of all CVEs that are related to this CWE entry.
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