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authorMimi Zohar <zohar@linux.vnet.ibm.com>2011-08-18 18:07:44 -0400
committerMimi Zohar <zohar@linux.vnet.ibm.com>2011-09-14 15:24:51 -0400
commitbf6d0f5dcda17df3cc5577e203d0f8ea1c2ad6aa (patch)
treec6c5f39d43fe0d27bc1d3aedbd2f9b3ba2f8f537 /security
parenta924ce0b35875ef9512135b46a32f4150fd700b2 (diff)
downloadlinux-stericsson-bf6d0f5dcda17df3cc5577e203d0f8ea1c2ad6aa.tar.gz
evm: posix acls modify i_mode
The posix xattr acls are 'system' prefixed, which normally would not affect security.evm. An interesting side affect of writing posix xattr acls is their modifying of the i_mode, which is included in security.evm. This patch updates security.evm when posix xattr acls are written. Signed-off-by: Mimi Zohar <zohar@us.ibm.com>
Diffstat (limited to 'security')
-rw-r--r--security/integrity/evm/Makefile1
-rw-r--r--security/integrity/evm/evm_main.c24
-rw-r--r--security/integrity/evm/evm_posix_acl.c26
3 files changed, 46 insertions, 5 deletions
diff --git a/security/integrity/evm/Makefile b/security/integrity/evm/Makefile
index 0787d262b9e3..7393c415a066 100644
--- a/security/integrity/evm/Makefile
+++ b/security/integrity/evm/Makefile
@@ -4,3 +4,4 @@
obj-$(CONFIG_EVM) += evm.o
evm-y := evm_main.o evm_crypto.o evm_secfs.o
+evm-$(CONFIG_FS_POSIX_ACL) += evm_posix_acl.o
diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
index 7d4247535f9e..73c008d047c7 100644
--- a/security/integrity/evm/evm_main.c
+++ b/security/integrity/evm/evm_main.c
@@ -177,7 +177,14 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
/*
* evm_protect_xattr - protect the EVM extended attribute
*
- * Prevent security.evm from being modified or removed.
+ * Prevent security.evm from being modified or removed without the
+ * necessary permissions or when the existing value is invalid.
+ *
+ * The posix xattr acls are 'system' prefixed, which normally would not
+ * affect security.evm. An interesting side affect of writing posix xattr
+ * acls is their modifying of the i_mode, which is included in security.evm.
+ * For posix xattr acls only, permit security.evm, even if it currently
+ * doesn't exist, to be updated.
*/
static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
@@ -187,9 +194,15 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
if (!capable(CAP_SYS_ADMIN))
return -EPERM;
- } else if (!evm_protected_xattr(xattr_name))
- return 0;
-
+ } else if (!evm_protected_xattr(xattr_name)) {
+ if (!posix_xattr_acl(xattr_name))
+ return 0;
+ evm_status = evm_verify_current_integrity(dentry);
+ if ((evm_status == INTEGRITY_PASS) ||
+ (evm_status == INTEGRITY_NOLABEL))
+ return 0;
+ return -EPERM;
+ }
evm_status = evm_verify_current_integrity(dentry);
return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
}
@@ -240,7 +253,8 @@ int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
const void *xattr_value, size_t xattr_value_len)
{
- if (!evm_initialized || !evm_protected_xattr(xattr_name))
+ if (!evm_initialized || (!evm_protected_xattr(xattr_name)
+ && !posix_xattr_acl(xattr_name)))
return;
evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
diff --git a/security/integrity/evm/evm_posix_acl.c b/security/integrity/evm/evm_posix_acl.c
new file mode 100644
index 000000000000..b1753e98bf9a
--- /dev/null
+++ b/security/integrity/evm/evm_posix_acl.c
@@ -0,0 +1,26 @@
+/*
+ * Copyright (C) 2011 IBM Corporation
+ *
+ * Author:
+ * Mimi Zohar <zohar@us.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 2 of the License.
+ */
+
+#include <linux/module.h>
+#include <linux/xattr.h>
+
+int posix_xattr_acl(char *xattr)
+{
+ int xattr_len = strlen(xattr);
+
+ if ((strlen(XATTR_NAME_POSIX_ACL_ACCESS) == xattr_len)
+ && (strncmp(XATTR_NAME_POSIX_ACL_ACCESS, xattr, xattr_len) == 0))
+ return 1;
+ if ((strlen(XATTR_NAME_POSIX_ACL_DEFAULT) == xattr_len)
+ && (strncmp(XATTR_NAME_POSIX_ACL_DEFAULT, xattr, xattr_len) == 0))
+ return 1;
+ return 0;
+}