Re: [PATCH] crypto: chtls - fix a missing-check bug

[Herbert Xu]

On Fri, May 18, 2018 at 02:55:35PM -0500, Wenwen Wang wrote:
> In do_chtls_setsockopt(), the tls crypto info is first copied from the
> poiner 'optval' in userspace and saved to 'tmp_crypto_info'. Then the
> 'version' of the crypto info is checked. If the version is not as expected,
> i.e., TLS_1_2_VERSION, error code -ENOTSUPP is returned to indicate that
> the provided crypto info is not supported yet. Then, the 'cipher_type'
> field of the 'tmp_crypto_info' is also checked to see if it is
> TLS_CIPHER_AES_GCM_128. If it is, the whole struct of
> tls12_crypto_info_aes_gcm_128 is copied from the pointer 'optval' and then
> the function chtls_setkey() is invoked to set the key.
> 
> Given that the 'optval' pointer resides in userspace, a malicious userspace
> process can race to change the data pointed by 'optval' between the two
> copies. For example, a user can provide a crypto info with TLS_1_2_VERSION
> and TLS_CIPHER_AES_GCM_128. After the first copy, the user can modify the
> 'version' and the 'cipher_type' fields to any versions and/or cipher types
> that are not allowed. This way, the user can bypass the checks, inject
> bad data to the kernel, cause chtls_setkey() to set a wrong key or other
> issues.
> 
> This patch reuses the data copied in the first try so as to ensure these
> checks will not be bypassed.
> 
> Signed-off-by: Wenwen Wang <wang6495@xxxxxxx>

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
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