Improving Web Application Security: Threats and - CGISecurity

322 Part III: Building Secure Web ApplicationsParameter ManipulationParameter manipulation refers to the unauthorized modification of data sent betweenthe Web service consumer and the Web service. For example, an attacker can intercepta Web service message, perhaps as it passes through an intermediate node en route toits destination; and can then modify it before sending it on to its intended endpoint.VulnerabilitiesVulnerabilities that can make parameter manipulation possible include:● Messages that are not digitally signed to provide tamperproofing● Messages that are not encrypted to provide privacy and tamperproofingCountermeasuresYou can use the following countermeasures to prevent parameter manipulation:●●Digitally sign the message. The digital signature is used at the recipient end toverify that the message has not been tampered with while it was in transit.Encrypt the message payload to provide privacy and tamperproofing.Network EavesdroppingWith network eavesdropping, an attacker is able to view Web service messages asthey flow across the network. For example, an attacker can use network monitoringsoftware to retrieve sensitive data contained in a SOAP message. This might includesensitive application level data or credential information.VulnerabilitiesVulnerabilities that can enable successful network eavesdropping include:● Credentials passed in plaintext in SOAP headers● No message level encryption used● No transport level encryption usedCountermeasuresYou can use the following countermeasures to protect sensitive SOAP messages asthey flow across the network:● Use transport level encryption such as SSL or IPSec. This is applicable only if youcontrol both endpoints.● Encrypt the message payload to provide privacy. This approach works inscenarios where your message travels through intermediary nodes route to thefinal destination.