Known security limitations¶
Secure memory wiping¶
Memory wiping is used to protect secret data or key material from attackers with access to deallocated memory. This is a defense-in-depth measure against vulnerabilities that leak application memory.
cryptography APIs which accept
bytes also accept types which
implement the buffer interface. Thus, users wishing to do so can pass
memoryview or another mutable type to
cryptography APIs, and overwrite
the contents once the data is no longer needed.
cryptography does not clear memory by default, as there is no way
to clear immutable structures such as
bytes. As a result,
like almost all software in Python is potentially vulnerable to this attack. The
CERT secure coding guidelines assesses this issue as “Severity: medium,
Likelihood: unlikely, Remediation Cost: expensive to repair” and we do not
consider this a high risk for most users.