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evm: evm_verify_hmac must not return INTEGRITY_UNKNOWN
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@nokia.com> Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
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parent
2960e6cb5f
commit
6d38ca01c0
1 changed files with 5 additions and 6 deletions
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@ -56,13 +56,15 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
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struct evm_ima_xattr_data xattr_data;
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struct evm_ima_xattr_data xattr_data;
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int rc;
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int rc;
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if (iint->hmac_status != INTEGRITY_UNKNOWN)
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if (iint->hmac_status == INTEGRITY_PASS)
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return iint->hmac_status;
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return iint->hmac_status;
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/* if status is not PASS, try to check again - against -ENOMEM */
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rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
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rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
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xattr_value_len, xattr_data.digest);
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xattr_value_len, xattr_data.digest);
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if (rc < 0)
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if (rc < 0)
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return INTEGRITY_UNKNOWN;
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goto err_out;
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xattr_data.type = EVM_XATTR_HMAC;
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xattr_data.type = EVM_XATTR_HMAC;
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rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
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rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, (u8 *)&xattr_data,
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@ -77,11 +79,8 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
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case -ENODATA: /* file not labelled */
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case -ENODATA: /* file not labelled */
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iint->hmac_status = INTEGRITY_NOLABEL;
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iint->hmac_status = INTEGRITY_NOLABEL;
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break;
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break;
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case -EINVAL:
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iint->hmac_status = INTEGRITY_FAIL;
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break;
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default:
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default:
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iint->hmac_status = INTEGRITY_UNKNOWN;
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iint->hmac_status = INTEGRITY_FAIL;
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}
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}
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return iint->hmac_status;
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return iint->hmac_status;
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}
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}
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