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 <[email protected]>
---
drivers/crypto/chelsio/chtls/chtls_main.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/crypto/chelsio/chtls/chtls_main.c b/drivers/crypto/chelsio/chtls/chtls_main.c
index 007c45c..39aab05 100644
--- a/drivers/crypto/chelsio/chtls/chtls_main.c
+++ b/drivers/crypto/chelsio/chtls/chtls_main.c
@@ -491,9 +491,13 @@ static int do_chtls_setsockopt(struct sock *sk, int optname,
switch (tmp_crypto_info.cipher_type) {
case TLS_CIPHER_AES_GCM_128: {
- rc = copy_from_user(crypto_info, optval,
- sizeof(struct
- tls12_crypto_info_aes_gcm_128));
+ /* Obtain version and type from previous copy */
+ crypto_info[0] = tmp_crypto_info;
+ /* Now copy the following data */
+ rc = copy_from_user((char *)crypto_info + sizeof(*crypto_info),
+ optval + sizeof(*crypto_info),
+ sizeof(struct tls12_crypto_info_aes_gcm_128)
+ - sizeof(*crypto_info));
if (rc) {
rc = -EFAULT;
--
2.7.4
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 <[email protected]>
Patch applied. Thanks.
--
Email: Herbert Xu <[email protected]>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt