CVE-2024-26789

In the Linux kernel, the following vulnerability has been resolved:

crypto: arm64/neonbs - fix out-of-bounds access on short input

The bit-sliced implementation of AES-CTR operates on blocks of 128 bytes, and will fall back to the plain NEON version for tail blocks or inputs that are shorter than 128 bytes to begin with.

It will call straight into the plain NEON asm helper, which performs all memory accesses in granules of 16 bytes (the size of a NEON register). For this reason, the associated plain NEON glue code will copy inputs shorter than 16 bytes into a temporary buffer, given that this is a rare occurrence and it is not worth the effort to work around this in the asm code.

The fallback from the bit-sliced NEON version fails to take this into account, potentially resulting in out-of-bounds accesses. So clone the same workaround, and use a temp buffer for short in/outputs.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://git.kernel.org/stable/c/034e2d70b5c7f578200ad09955aeb2aa65d1164a
• https://git.kernel.org/stable/c/1291d278b5574819a7266568ce4c28bce9438705
• https://git.kernel.org/stable/c/1c0cf6d19690141002889d72622b90fc01562ce4
• https://git.kernel.org/stable/c/9e8ecd4908b53941ab6f0f51584ab80c6c6606c4
• https://git.kernel.org/stable/c/034e2d70b5c7f578200ad09955aeb2aa65d1164a
• https://git.kernel.org/stable/c/1291d278b5574819a7266568ce4c28bce9438705
• https://git.kernel.org/stable/c/1c0cf6d19690141002889d72622b90fc01562ce4
• https://git.kernel.org/stable/c/9e8ecd4908b53941ab6f0f51584ab80c6c6606c4