Trusting Self Reported IP Address

Description

The use of IP addresses as authentication is flawed and can easily be spoofed by malicious users.

Applies To

• Languages: All
• Operating platforms: All

Example

The following code connects to a remote host and then checks its IP address to make a trust decision:

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);
  //Make a trust decision based on IP
  if (inet_ntoa(cli.sin_addr)==...)
     n = recvfrom(sd, msg, MAX_MSG, 0, (struct sockaddr *) & cli, &clilen);
}

Since IP address may be spoofed by the remote host, a valid trust decision cannot be made with this information

Impact

• Authentication: Malicious users can fake authentication information, impersonating any IP address.

Vulnerabilities

• Use of IP address to make a trust decision about a remote host.

Countermeasures

• Design: Use other means of identity verification that cannot be simply spoofed.

Vulnerability Patterns

• Trusting Self Reported IP Address Vulnerability Pattern

How Tos

• How To Recognize Trusting Self Reported IP Address Vulnerabilities
• How To Protect from Trusting Self Reported IP Address
• How To Perform an Attack Based On Trusting Self Reported IP Address