When multiple sockets are allowed to bind to the same port, other services on that port may be stolen or spoofed.
On most systems, a combination of setting the SO_REUSEADDR socket option, and a call to bind() allows any process to bind to a port to which a previous process has bound with INADDR_ANY. This allows a user to bind to the specific address of a server bound to INADDR_ANY on an unprivileged port, and steal its UDP packets/TCP connection.
Threat Mapped score: 0.0
Industry: Finiancial
Threat priority: Unclassified
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| Phase | Note |
|---|---|
| Implementation | N/A |
| Operation | N/A |
Intro: This code binds a server socket to port 21, allowing the server to listen for traffic on that port.
Body: This code may result in two servers binding a socket to same port, thus receiving each other's traffic. This could be used by an attacker to steal packets meant for another process, such as a secure FTP server.
void bind_socket(void) { int server_sockfd; int server_len; struct sockaddr_in server_address; /*unlink the socket if already bound to avoid an error when bind() is called*/ unlink("server_socket"); server_sockfd = socket(AF_INET, SOCK_STREAM, 0); server_address.sin_family = AF_INET; server_address.sin_port = 21; server_address.sin_addr.s_addr = htonl(INADDR_ANY); server_len = sizeof(struct sockaddr_in); bind(server_sockfd, (struct sockaddr *) &s1, server_len); }