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Authentication bypass by spoofing

ID: cpp/user-controlled-bypass Kind: path-problem Security severity: 8.1 Severity: warning Precision: medium Tags: - security - external/cwe/cwe-290 Query suites: - cpp-security-extended.qls - cpp-security-and-quality.qls

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Code which relies on an IP address or domain name for authentication can be exploited by an attacker who spoofs their address.

Recommendation

IP address verification can be a useful part of an authentication scheme, but it should not be the single factor required for authentication. Make sure that other authentication methods are also in place.

Example

In this example (taken from CWE-290: Authentication Bypass by Spoofing), the client is authenticated by checking that its IP address is 127.0.0.1. An attacker might be able to bypass this authentication by spoofing their IP address.

#define BUFFER_SIZE (4 * 1024)voidreceiveData(){intsock;sockaddr_inaddr,addr_from;charbuffer[BUFFER_SIZE];intmsg_size;socklen_taddr_from_len;// configure addrmemset(&addr,0,sizeof(addr));addr.sin_family=AF_INET;addr.sin_port=htons(1234);addr.sin_addr.s_addr=INADDR_ANY;// create and bind the socketsock=socket(AF_INET,SOCK_DGRAM,0);bind(sock,(sockaddr*)&addr,sizeof(addr));// receive messageaddr_from_len=sizeof(addr_from);msg_size=recvfrom(sock,buffer,BUFFER_SIZE,0,(sockaddr*)&addr_from,&addr_from_len);// BAD: the address is controllable by the user, so it// could be spoofed to bypass the security check below.if((msg_size>0)&&(strcmp("127.0.0.1",inet_ntoa(addr_from.sin_addr))==0)){// ...}}

References

  • Common Weakness Enumeration: CWE-290.

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