Section delimiters injected into an application can be used to
compromise a system.
Extended Description
As data is parsed, an injected/absent/malformed delimiter may cause the
process to take unexpected actions that result in an attack. One example of
a section delimiter is the boundary string in a multipart MIME message. In
many cases, doubled line delimiters can serve as a section delimiter.
Time of Introduction
Implementation
Applicable Platforms
Languages
All
Potential Mitigations
Phase
Description
Developers should anticipate that section delimiters will be
injected/removed/manipulated in the input vectors of their software
system. Use an appropriate combination of black lists and white lists to
ensure only valid, expected and appropriate input is processed by the
system.
Architecture and Design
Assume all input is malicious. Use a standard input validation
mechanism to validate all input for length, type, syntax, and business
rules before accepting the data to be displayed or stored. Use an
"accept known good" validation strategy.
Use and specify a strong output encoding (such as ISO 8859-1 or UTF
8).
Do not rely exclusively on blacklist validation to detect malicious
input or to encode output. There are too many variants to encode a
character; you're likely to miss some variants.
Inputs should be decoded and canonicalized to the application's
current internal representation before being validated. Make sure that
your application does not decode the same input twice. Such errors could
be used to bypass whitelist schemes by introducing dangerous inputs
after they have been checked.
Description
