crypto: chtls - fix a missing-check bug

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@umn.edu>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/drivers/crypto/chelsio/chtls/chtls_main.c b/drivers/crypto/chelsio/chtls/chtls_main.c
index 5b9dd58..53ffb00 100644 (file)
--- a/drivers/crypto/chelsio/chtls/chtls_main.c
+++ b/drivers/crypto/chelsio/chtls/chtls_main.c
@@ -490,9 +490,13 @@ 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;