[GIT] EVM hmac security fix

[James Morris]

Please pull this patch for the EVM code, which fixes CVE-2016-2085.


The following changes since commit c05235d50f681bf685e7290cae05ab3b4fa493f3:

  Merge tag 'gpio-v4.5-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio (2016-02-11 11:25:55 -0800)

are available in the git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security.git for-linus

Ryan Ware (1):
      EVM: Use crypto_memneq() for digest comparisons

 security/integrity/evm/evm_main.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

---

commit 613317bd212c585c20796c10afe5daaa95d4b0a1
Author: Ryan Ware <ware@xxxxxxxxxxxxxxx>
Date:   Thu Feb 11 15:58:44 2016 -0800

    EVM: Use crypto_memneq() for digest comparisons
    
    This patch fixes vulnerability CVE-2016-2085.  The problem exists
    because the vm_verify_hmac() function includes a use of memcmp().
    Unfortunately, this allows timing side channel attacks; specifically
    a MAC forgery complexity drop from 2^128 to 2^12.  This patch changes
    the memcmp() to the cryptographically safe crypto_memneq().
    
    Reported-by: Xiaofei Rex Guo <xiaofei.rex.guo@xxxxxxxxx>
    Signed-off-by: Ryan Ware <ware@xxxxxxxxxxxxxxx>
    Cc: stable@xxxxxxxxxxxxxxx
    Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxxxxxxx>
    Signed-off-by: James Morris <james.l.morris@xxxxxxxxxx>

diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index f716025..e6ea9d4 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -23,6 +23,7 @@
 #include <linux/integrity.h>
 #include <linux/evm.h>
 #include <crypto/hash.h>
+#include <crypto/algapi.h>
 #include "evm.h"
 
 int evm_initialized;
@@ -148,7 +149,7 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 				   xattr_value_len, calc.digest);
 		if (rc)
 			break;
-		rc = memcmp(xattr_data->digest, calc.digest,
+		rc = crypto_memneq(xattr_data->digest, calc.digest,
 			    sizeof(calc.digest));
 		if (rc)
 			rc = -EINVAL;