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24 lines
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ReStructuredText
24 lines
1.2 KiB
ReStructuredText
Known security limitations
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==========================
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Secure memory wiping
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--------------------
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`Memory wiping`_ is used to protect secret data or key material from attackers
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with access to deallocated memory. This is a defense-in-depth measure against
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vulnerabilities that leak application memory.
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Many ``cryptography`` APIs which accept ``bytes`` also accept types which
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implement the buffer interface. Thus, users wishing to do so can pass
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``memoryview`` or another mutable type to ``cryptography`` APIs, and overwrite
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the contents once the data is no longer needed.
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However, ``cryptography`` does not clear memory by default, as there is no way
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to clear immutable structures such as ``bytes``. As a result, ``cryptography``,
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like almost all software in Python is potentially vulnerable to this attack. The
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`CERT secure coding guidelines`_ assesses this issue as "Severity: medium,
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Likelihood: unlikely, Remediation Cost: expensive to repair" and we do not
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consider this a high risk for most users.
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.. _`Memory wiping`: https://devblogs.microsoft.com/oldnewthing/?p=4223
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.. _`CERT secure coding guidelines`: https://wiki.sei.cmu.edu/confluence/display/c/MEM03-C.+Clear+sensitive+information+stored+in+reusable+resources
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