From: Ryan Ware <[email protected]> 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 <[email protected]> Signed-off-by: Ryan Ware <[email protected]> Cc: [email protected] Signed-off-by: Mimi Zohar <[email protected]> Signed-off-by: James Morris <[email protected]> Cc: Jason A. Donenfeld <[email protected]> Signed-off-by: Willy Tarreau <[email protected]> --- 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 b980a6c..3db2bf1 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -20,6 +20,7 @@ #include <linux/integrity.h> #include <linux/evm.h> #include <crypto/hash.h> +#include <crypto/algapi.h> #include "evm.h" int evm_initialized; @@ -128,7 +129,7 @@ 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; -- 2.8.0.rc2.1.gbe9624a
