Am Samstag, 17. Januar 2015, 17:37:06 schrieb Tadeusz Struk: Hi Tadeusz,
> Hi Stephan, > > On 01/17/2015 10:23 AM, Stephan Mueller wrote: > > during testing of my algif_aead patch with the different GCM > > implementations I am able to trigger a kernel crash from user space using > > __driver-gcm-aes- aesni. > > > > As I hope that algif_aead is going to be included, unprivileged userspace > > would then reliably crash the kernel -- with the current kernel code, > > userspace has no interface to trigger the issue. > > Yes, that's a problem. > > > As I am not sure what the purpose of __driver-gcm-aes-aesni is (only a > > backend for RFC4106 GCM or a regular cipher), I did not yet create a > > patch. IMHO there are two solutions: > > > > - either create a valid setkey callback so that a key is set > > > > - or create a noop setkey that returns -EOPNOTSUPP which effectively > > disables that cipher for regular consumption. > > __driver-gcm-aes-aesni is only a helper for rfc4106-gcm-aesni and it > never supposed to be used on it's own. I think implementing a setkey > function that only returns an error would be a good solution for this. Ok, I will send a patch shortly. > Another question is what if someone will ignore the error or skip the > setsockopt(ALG_SET_KEY) altogether and still call the sendmsg() and > read() to trigger encrypt()? Using my libkcapi [1] test bench, I disabled key and IV submission for symmetric ciphers (tested cbc(aes) which invokes your AESNI code path on my box -- and gcm(aes) and ccm(aes) which again both use the AESNI core and the C implementation of GCM and CCM). All tests with missing keys and IVs: - showed a successful encryption / decryption with the CBC mode - returned the error code of either ENOKEY or EINVAL for GCM / CCM encryption/decryption There is no crash/BUG/WARN observed. > > > Note, if it is only a backend for the RFC4106 implementation, may I ask > > why > > __driver-gcm-aes-aesni is implemented as a separate cipher that is > > registered with the kernel crypto API? > > This is because we need to have one instance of the helper tfm with its > context per each of the rfc4106-gcm-aesni tfm instance and that was one > convenient way to do this. Then I concur with you that having a setkey function returning an error is the right way. > > Tadeusz > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Ciao Stephan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
