CWE-602: Client-Side Enforcement of Server-Side Security

Description

The product is composed of a server that relies on the client to implement a mechanism that is intended to protect the server.

When the server relies on protection mechanisms placed on the client side, an attacker can modify the client-side behavior to bypass the protection mechanisms, resulting in potentially unexpected interactions between the client and server. The consequences will vary, depending on what the mechanisms are trying to protect.

Potential Impact

Demonstrative Examples

$server = "server.example.com";$username = AskForUserName();$password = AskForPassword();$address = AskForAddress();$sock = OpenSocket($server, 1234);writeSocket($sock, "AUTH $username $password\n");$resp = readSocket($sock);if ($resp eq "success") {
                        
                           
                           # username/pass is valid, go ahead and update the info!
                           writeSocket($sock, "CHANGE-ADDRESS $username $address\n";
                     }else {print "ERROR: Invalid Authentication!\n";}

$sock = acceptSocket(1234);($cmd, $args) = ParseClientRequest($sock);if ($cmd eq "AUTH") {
                        ($username, $pass) = split(/\s+/, $args, 2);$result = AuthenticateUser($username, $pass);writeSocket($sock, "$result\n");
                           # does not close the socket on failure; assumes the
                           
                           
                           # user will try again
                           
                        
                     }elsif ($cmd eq "CHANGE-ADDRESS") {if (validateAddress($args)) {$res = UpdateDatabaseRecord($username, "address", $args);writeSocket($sock, "SUCCESS\n");}else {writeSocket($sock, "FAILURE -- address is malformed\n");}}

Mitigations & Prevention

Detection Methods

• Fuzzing — Use dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The software's operation may slow down, but it should not become unstable, crash,
• Manual Analysis — Use tools and techniques that require manual (human) analysis, such as penetration testing, threat modeling, and interactive tools that allow the tester to record and modify an active session. These may be more effective than strictly automated techniques. This is especially the case with weaknesses

Real-World CVE Examples

Related Weaknesses

Taxonomy Mappings

• OWASP Top Ten 2004: A1 — Unvalidated Input