Bug Classes/Format string injection

Details

When an attacker supplied string is accidentally passed to format string parsing, the attacker can manipulate the resulting output. The write primitive available is through the use of the %n specifier, which writes to memory. All the other formats lead to information leaks.

Examples

• injection via block layer

Mitigations

• Eliminate the use of %n
• detect non-const format strings at compile time (e.g. gcc's -Wformat-security)
• detect non-const format strings at run time (e.g. memory location checking done with glibc's -D_FORITY_SOURCE=2)