| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 005/196] EVM: Use crypto_memneq() for digest comparisons | Date | Tue, 8 Mar 2016 16:27:43 -0800 |
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3.19.8-ckt16 -stable review patch. If anyone has any objections, please let me know.
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From: Ryan Ware <ware@linux.intel.com>
commit 613317bd212c585c20796c10afe5daaa95d4b0a1 upstream.
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@intel.com> Signed-off-by: Ryan Ware <ware@linux.intel.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> Signed-off-by: James Morris <james.l.morris@oracle.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- security/integrity/evm/evm_main.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 02c6e4d..6c9c11d 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; -- 2.7.0
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