joel16/android_kernel_sony_msm8994_rework
1
0
Fork 0
mirror of https://github.com/joel16/android_kernel_sony_msm8994_rework.git synced 2024-11-23 20:09:51 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

evm: prohibit userspace writing 'security.evm' HMAC value

Browse Source 
commit 2fb1c9a4f2dbc2f0bd2431c7fa64d0b5483864e4 upstream.

Calculating the 'security.evm' HMAC value requires access to the
EVM encrypted key.  Only the kernel should have access to it.  This
patch prevents userspace tools(eg. setfattr, cp --preserve=xattr)
from setting/modifying the 'security.evm' HMAC value directly.

Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Mimi Zohar 2014-05-11 00:05:23 -04:00 committed by Greg Kroah-Hartman
parent 8b46db3abb
commit bb7f9e5c38
1 changed files with 10 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
security/integrity/evm/evm_main.c
View File

@ -275,12 +275,20 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
* @xattr_value: pointer to the new extended attribute value * @xattr_value: pointer to the new extended attribute value
* @xattr_value_len: pointer to the new extended attribute value length * @xattr_value_len: pointer to the new extended attribute value length
* *
* Updating 'security.evm' requires CAP_SYS_ADMIN privileges and that * Before allowing the 'security.evm' protected xattr to be updated,
* the current value is valid. * verify the existing value is valid. As only the kernel should have
* access to the EVM encrypted key needed to calculate the HMAC, prevent
* userspace from writing HMAC value. Writing 'security.evm' requires
* requires CAP_SYS_ADMIN privileges.
*/ */
int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name, int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len) const void *xattr_value, size_t xattr_value_len)
{ {
const struct evm_ima_xattr_data *xattr_data = xattr_value;
if ((strcmp(xattr_name, XATTR_NAME_EVM) == 0)
&& (xattr_data->type == EVM_XATTR_HMAC))
return -EPERM;
return evm_protect_xattr(dentry, xattr_name, xattr_value, return evm_protect_xattr(dentry, xattr_name, xattr_value,
xattr_value_len); xattr_value_len);
} }