id = 2946
title = "crypto/aes.c (used for emulating aes instructions) has a timing side-channel"
state = "opened"
created_at = "2025-05-02T07:29:06.756Z"
closed_at = "n/a"
labels = ["Build System", "Cryptography"]
url = "https://gitlab.com/qemu-project/qemu/-/issues/2946"
host-os = "any"
host-arch = "any"
qemu-version = "a9cd5bc6399a80fcf233ed0fffe6067b731227d8"
guest-os = "n/a"
guest-arch = "x86 or arm, maybe more..."
description = """https://gitlab.com/qemu-project/qemu/-/blob/a9cd5bc6399a80fcf233ed0fffe6067b731227d8/crypto/aes.c#L1021

much of the code in crypto/aes.c accesses memory arrays where the array index is based on the secret data being encrypted/decrypted. because of cpu caches and other things that can delay memory accesses based on their address, this is a timing side-channel, potentially allowing leaking secrets over a network based on timing how long cryptography operations take.

compare to openssl which uses an algorithm where its execution time doesn't depend on the data being processed:
https://github.com/openssl/openssl/commit/0051746e03c65f5970d8ca424579d50f58a877e0

I initially reported this as a security issue, but was told that since it's only used by TCG, it isn't a security issue, since TCG isn't considered secure."""
reproduce = "n/a"
additional = "n/a"