From: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx> If EVM is not supported or enabled, evm_verify_hmac() returns INTEGRITY_UNKNOWN, which ima_appraise_measurement() ignores and sets the appraisal status based solely on the security.ima verification. evm_verify_hmac() also returns INTEGRITY_UNKNOWN for other failures, such as temporary failures like -ENOMEM, resulting in possible attack vectors. This patch changes the default return code for temporary/unexpected failures, like -ENOMEM, from INTEGRITY_UNKNOWN to INTEGRITY_FAIL, making evm_verify_hmac() fail safe. As a result, failures need to be re-evaluated in order to catch both temporary errors, such as the -ENOMEM, as well as errors that have been resolved in fix mode. Signed-off-by: Dmitry Kasatkin <dmitry.kasatkin@xxxxxxxxx> Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxx> --- security/integrity/evm/evm_main.c | 11 +++++------ 1 files changed, 5 insertions(+), 6 deletions(-) diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c index 944783c..245ef23 100644 --- a/security/integrity/evm/evm_main.c +++ b/security/integrity/evm/evm_main.c @@ -57,14 +57,16 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry, char hmac_val[MAX_DIGEST_SIZE + 1]; int rc; - if (iint->hmac_status != INTEGRITY_UNKNOWN) + if (iint->hmac_status == INTEGRITY_PASS) return iint->hmac_status; + /* if status is not PASS, try to check again - against -ENOMEM */ + memset(hmac_val, 0, sizeof hmac_val); rc = evm_calc_hmac(dentry, xattr_name, xattr_value, xattr_value_len, hmac_val + 1); if (rc < 0) - return INTEGRITY_UNKNOWN; + goto err_out; hmac_val[0] = EVM_XATTR_HMAC; rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, hmac_val, sizeof hmac_val, @@ -79,11 +81,8 @@ err_out: case -ENODATA: /* file not labelled */ iint->hmac_status = INTEGRITY_NOLABEL; break; - case -EINVAL: - iint->hmac_status = INTEGRITY_FAIL; - break; default: - iint->hmac_status = INTEGRITY_UNKNOWN; + iint->hmac_status = INTEGRITY_FAIL; } return iint->hmac_status; } -- 1.7.3.4 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
