forked from Minki/linux
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>
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@ -33,6 +33,14 @@ extern void evm_inode_post_removexattr(struct dentry *dentry,
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extern int evm_inode_init_security(struct inode *inode,
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const struct xattr *xattr_array,
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struct xattr *evm);
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#ifdef CONFIG_FS_POSIX_ACL
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extern int posix_xattr_acl(const char *xattrname);
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#else
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static inline int posix_xattr_acl(const char *xattrname)
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{
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return 0;
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}
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#endif
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#else
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#ifdef CONFIG_INTEGRITY
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static inline enum integrity_status evm_verifyxattr(struct dentry *dentry,
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@ -52,6 +52,11 @@
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#define XATTR_CAPS_SUFFIX "capability"
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#define XATTR_NAME_CAPS XATTR_SECURITY_PREFIX XATTR_CAPS_SUFFIX
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#define XATTR_POSIX_ACL_ACCESS "posix_acl_access"
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#define XATTR_NAME_POSIX_ACL_ACCESS XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_ACCESS
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#define XATTR_POSIX_ACL_DEFAULT "posix_acl_default"
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#define XATTR_NAME_POSIX_ACL_DEFAULT XATTR_SYSTEM_PREFIX XATTR_POSIX_ACL_DEFAULT
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#ifdef __KERNEL__
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#include <linux/types.h>
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@ -4,3 +4,4 @@
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obj-$(CONFIG_EVM) += evm.o
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evm-y := evm_main.o evm_crypto.o evm_secfs.o
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evm-$(CONFIG_FS_POSIX_ACL) += evm_posix_acl.o
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@ -177,7 +177,14 @@ static enum integrity_status evm_verify_current_integrity(struct dentry *dentry)
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/*
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* evm_protect_xattr - protect the EVM extended attribute
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*
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* Prevent security.evm from being modified or removed.
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* Prevent security.evm from being modified or removed without the
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* necessary permissions or when the existing value is invalid.
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*
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* The posix xattr acls are 'system' prefixed, which normally would not
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* affect security.evm. An interesting side affect of writing posix xattr
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* acls is their modifying of the i_mode, which is included in security.evm.
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* For posix xattr acls only, permit security.evm, even if it currently
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* doesn't exist, to be updated.
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*/
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static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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@ -187,9 +194,15 @@ static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
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if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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} else if (!evm_protected_xattr(xattr_name))
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return 0;
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} else if (!evm_protected_xattr(xattr_name)) {
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if (!posix_xattr_acl(xattr_name))
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return 0;
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evm_status = evm_verify_current_integrity(dentry);
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if ((evm_status == INTEGRITY_PASS) ||
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(evm_status == INTEGRITY_NOLABEL))
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return 0;
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return -EPERM;
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}
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evm_status = evm_verify_current_integrity(dentry);
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return evm_status == INTEGRITY_PASS ? 0 : -EPERM;
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}
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@ -240,7 +253,8 @@ int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
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void evm_inode_post_setxattr(struct dentry *dentry, const char *xattr_name,
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const void *xattr_value, size_t xattr_value_len)
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{
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if (!evm_initialized || !evm_protected_xattr(xattr_name))
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if (!evm_initialized || (!evm_protected_xattr(xattr_name)
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&& !posix_xattr_acl(xattr_name)))
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return;
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evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
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26
security/integrity/evm/evm_posix_acl.c
Normal file
26
security/integrity/evm/evm_posix_acl.c
Normal file
@ -0,0 +1,26 @@
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/*
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* Copyright (C) 2011 IBM Corporation
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*
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* Author:
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* Mimi Zohar <zohar@us.ibm.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, version 2 of the License.
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*/
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#include <linux/module.h>
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#include <linux/xattr.h>
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int posix_xattr_acl(char *xattr)
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{
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int xattr_len = strlen(xattr);
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if ((strlen(XATTR_NAME_POSIX_ACL_ACCESS) == xattr_len)
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&& (strncmp(XATTR_NAME_POSIX_ACL_ACCESS, xattr, xattr_len) == 0))
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return 1;
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if ((strlen(XATTR_NAME_POSIX_ACL_DEFAULT) == xattr_len)
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&& (strncmp(XATTR_NAME_POSIX_ACL_DEFAULT, xattr, xattr_len) == 0))
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return 1;
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return 0;
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}
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