Message-ID: <20110519060543.GA10320@mail.hallyn.com>
Date:	Thu, 19 May 2011 01:05:43 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc:	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	James Morris <jmorris@...ei.org>,
	David Safford <safford@...son.ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Greg KH <greg@...ah.com>,
	Dmitry Kasatkin <dmitry.kasatkin@...ia.com>,
	Mimi Zohar <zohar@...ibm.com>
Subject: Re: [PATCH v5 03/21] evm: re-release

Quoting Mimi Zohar (zohar@...ux.vnet.ibm.com):
> EVM protects a file's security extended attributes(xattrs) against integrity
> attacks.  This patchset provides the framework and an initial method.  The
> initial method maintains an HMAC-sha1 value across the security extended
> attributes, storing the HMAC value as the extended attribute 'security.evm'.
> Other methods of validating the integrity of a file's metadata will be posted
> separately (eg. EVM-digital-signatures).
> 
> While this patchset does authenticate the security xattrs, and
> cryptographically binds them to the inode, coming extensions will bind other
> directory and inode metadata for more complete protection.  To help simplify
> the review and upstreaming process, each extension will be posted separately
> (eg. IMA-appraisal, IMA-appraisal-directory).  For a general overview of the
> proposed Linux integrity subsystem, refer to Dave Safford's whitepaper:
> http://downloads.sf.net/project/linux-ima/linux-ima/Integrity_overview.pdf.
> 
> EVM depends on the Kernel Key Retention System to provide it with a
> trusted/encrypted key for the HMAC-sha1 operation. The key is loaded onto the
> root's keyring using keyctl.  Until EVM receives notification that the key has
> been successfully loaded onto the keyring (echo 1 > <securityfs>/evm), EVM can
> not create or validate the 'security.evm' xattr, but returns INTEGRITY_UNKNOWN.
> Loading the key and signaling EVM should be done as early as possible. Normally
> this is done in the initramfs, which has already been measured as part of the
> trusted boot.  For more information on creating and loading existing
> trusted/encrypted keys, refer to Documentation/keys-trusted-encrypted.txt.  A
> sample dracut patch, which loads the trusted/encrypted key and enables EVM, is
> available from http://linu-ima.sourceforge.net/#EVM.

That should read http://linux-ima.sourceforge.net/#EVM.

> Based on the LSMs enabled, the set of EVM protected security xattrs is defined
> at compile.  EVM adds the following three calls to the existing security hooks:
> evm_inode_setxattr(), evm_inode_post_setxattr(), and evm_inode_removexattr.  To
> initialize and update the 'security.evm' extended attribute, EVM defines three
> calls: evm_inode_post_init(), evm_inode_post_setattr() and
> evm_inode_post_removexattr() hooks.  To verify the integrity of a security
> xattr, EVM exports evm_verifyxattr().
> 
> Changelog:
> - locking based on i_mutex, remove evm_mutex
> - using trusted/encrypted keys for storing the EVM key used in the HMAC-sha1
>   operation.
> - replaced crypto hash with shash (Dmitry Kasatkin)
> - support for additional methods of verifying the security xattrs
>   (Dmitry Kasatkin)
> - iint not allocated for all regular files, but only for those appraised
> - Use cap_sys_admin in lieu of cap_mac_admin
> - Use __vfs_setxattr_noperm(), without permission checks, from EVM
> 
> Signed-off-by: Mimi Zohar <zohar@...ibm.com>
> ---
>  Documentation/ABI/testing/evm       |   23 +++
>  include/linux/integrity.h           |    7 +
>  include/linux/xattr.h               |    3 +
>  security/integrity/Kconfig          |    3 +-
>  security/integrity/Makefile         |    2 +
>  security/integrity/evm/Kconfig      |   12 ++
>  security/integrity/evm/Makefile     |    6 +
>  security/integrity/evm/evm.h        |   34 ++++
>  security/integrity/evm/evm_crypto.c |  177 ++++++++++++++++++++++
>  security/integrity/evm/evm_main.c   |  283 +++++++++++++++++++++++++++++++++++
>  security/integrity/evm/evm_secfs.c  |  108 +++++++++++++
>  security/integrity/iint.c           |    1 +
>  security/integrity/integrity.h      |    1 +
>  13 files changed, 659 insertions(+), 1 deletions(-)
>  create mode 100644 Documentation/ABI/testing/evm
>  create mode 100644 security/integrity/evm/Kconfig
>  create mode 100644 security/integrity/evm/Makefile
>  create mode 100644 security/integrity/evm/evm.h
>  create mode 100644 security/integrity/evm/evm_crypto.c
>  create mode 100644 security/integrity/evm/evm_main.c
>  create mode 100644 security/integrity/evm/evm_secfs.c
> 
> diff --git a/Documentation/ABI/testing/evm b/Documentation/ABI/testing/evm
> new file mode 100644
> index 0000000..37c4e02
> --- /dev/null
> +++ b/Documentation/ABI/testing/evm
> @@ -0,0 +1,23 @@
> +What:		security/evm
> +Date:		March 2011
> +Contact:	Mimi Zohar <zohar@...ibm.com>
> +Description:
> +		EVM protects a file's security extended attributes(xattrs)
> +		against integrity attacks. The initial method maintains an
> +		HMAC-sha1 value across the extended attributes, storing the
> +		value as the extended attribute 'security.evm'.
> +
> +		EVM depends on the Kernel Key Retention System to provide it
> +		with a trusted/encrypted key for the HMAC-sha1 operation.
> +		The key is loaded onto the root's keyring using keyctl.  Until
> +		EVM receives notification that the key has been successfully
> +		loaded onto the keyring (echo 1 > <securityfs>/evm), EVM
> +		can not create or validate the 'security.evm' xattr, but
> +		returns INTEGRITY_UNKNOWN.  Loading the key and signaling EVM
> +		should be done as early as possible.  Normally this is done
> +		in the initramfs, which has already been measured as part
> +		of the trusted boot.  For more information on creating and
> +		loading existing trusted/encrypted keys, refer to:
> +		Documentation/keys-trusted-encrypted.txt.  (A sample dracut
> +		patch, which loads the trusted/encrypted key and enables
> +		EVM, is available from http://linu-ima.sourceforge.net/#EVM.)
> diff --git a/include/linux/integrity.h b/include/linux/integrity.h
> index 9059812..e715a2a 100644
> --- a/include/linux/integrity.h
> +++ b/include/linux/integrity.h
> @@ -12,6 +12,13 @@
>  
>  #include <linux/fs.h>
>  
> +enum integrity_status {
> +	INTEGRITY_PASS = 0,
> +	INTEGRITY_FAIL,
> +	INTEGRITY_NOLABEL,
> +	INTEGRITY_UNKNOWN,
> +};
> +
>  #ifdef CONFIG_INTEGRITY
>  extern int integrity_inode_alloc(struct inode *inode);
>  extern void integrity_inode_free(struct inode *inode);
> diff --git a/include/linux/xattr.h b/include/linux/xattr.h
> index 953a0d5..61a9a349 100644
> --- a/include/linux/xattr.h
> +++ b/include/linux/xattr.h
> @@ -34,6 +34,9 @@
>  #define XATTR_USER_PREFIX_LEN (sizeof (XATTR_USER_PREFIX) - 1)
>  
>  /* Security namespace */
> +#define XATTR_EVM_SUFFIX "evm"
> +#define XATTR_NAME_EVM XATTR_SECURITY_PREFIX XATTR_EVM_SUFFIX
> +
>  #define XATTR_SELINUX_SUFFIX "selinux"
>  #define XATTR_NAME_SELINUX XATTR_SECURITY_PREFIX XATTR_SELINUX_SUFFIX
>  
> diff --git a/security/integrity/Kconfig b/security/integrity/Kconfig
> index 2704691..4bf00ac 100644
> --- a/security/integrity/Kconfig
> +++ b/security/integrity/Kconfig
> @@ -1,6 +1,7 @@
>  #
>  config INTEGRITY
>  	def_bool y
> -	depends on IMA
> +	depends on IMA || EVM
>  
>  source security/integrity/ima/Kconfig
> +source security/integrity/evm/Kconfig
> diff --git a/security/integrity/Makefile b/security/integrity/Makefile
> index 6eddd61..0ae44ae 100644
> --- a/security/integrity/Makefile
> +++ b/security/integrity/Makefile
> @@ -8,3 +8,5 @@ integrity-y := iint.o
>  
>  subdir-$(CONFIG_IMA)			+= ima
>  obj-$(CONFIG_IMA)			+= ima/built-in.o
> +subdir-$(CONFIG_EVM)			+= evm
> +obj-$(CONFIG_EVM)			+= evm/built-in.o
> diff --git a/security/integrity/evm/Kconfig b/security/integrity/evm/Kconfig
> new file mode 100644
> index 0000000..73f6540
> --- /dev/null
> +++ b/security/integrity/evm/Kconfig
> @@ -0,0 +1,12 @@
> +config EVM
> +	boolean "EVM support"
> +	depends on SECURITY && KEYS && ENCRYPTED_KEYS
> +	select CRYPTO_HMAC
> +	select CRYPTO_MD5
> +	select CRYPTO_SHA1
> +	default n
> +	help
> +	  EVM protects a file's security extended attributes against
> +	  integrity attacks.
> +
> +	  If you are unsure how to answer this question, answer N.
> diff --git a/security/integrity/evm/Makefile b/security/integrity/evm/Makefile
> new file mode 100644
> index 0000000..0787d26
> --- /dev/null
> +++ b/security/integrity/evm/Makefile
> @@ -0,0 +1,6 @@
> +#
> +# Makefile for building the Extended Verification Module(EVM)
> +#
> +obj-$(CONFIG_EVM) += evm.o
> +
> +evm-y := evm_main.o evm_crypto.o evm_secfs.o
> diff --git a/security/integrity/evm/evm.h b/security/integrity/evm/evm.h
> new file mode 100644
> index 0000000..f2bbe43
> --- /dev/null
> +++ b/security/integrity/evm/evm.h
> @@ -0,0 +1,34 @@
> +/*
> + * Copyright (C) 2005-2010 IBM Corporation
> + *
> + * Authors:
> + * Mimi Zohar <zohar@...ibm.com>
> + * Kylene Hall <kjhall@...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.
> + *
> + * File: evm.h
> + *
> + */
> +#include <linux/security.h>
> +#include "../integrity.h"
> +
> +extern int evm_initialized;
> +extern char *evm_hmac;
> +extern int evm_hmac_size;
> +
> +/* List of EVM protected security xattrs */
> +extern char *evm_config_xattrnames[];
> +
> +extern int evm_init_key(void);
> +extern int evm_update_evmxattr(struct dentry *dentry,
> +			       const char *req_xattr_name,
> +			       const char *req_xattr_value,
> +			       size_t req_xattr_value_len);
> +extern int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
> +			 const char *req_xattr_value,
> +			 size_t req_xattr_value_len, char *digest);
> +extern int evm_init_secfs(void);
> +extern void evm_cleanup_secfs(void);
> diff --git a/security/integrity/evm/evm_crypto.c b/security/integrity/evm/evm_crypto.c
> new file mode 100644
> index 0000000..c43be5a
> --- /dev/null
> +++ b/security/integrity/evm/evm_crypto.c
> @@ -0,0 +1,177 @@
> +/*
> + * Copyright (C) 2005-2010 IBM Corporation
> + *
> + * Authors:
> + * Mimi Zohar <zohar@...ibm.com>
> + * Kylene Hall <kjhall@...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.
> + *
> + * File: evm_crypto.c
> + *	 Using root's kernel master key (kmk), calculate the HMAC
> + */
> +
> +#include <linux/module.h>
> +#include <linux/crypto.h>
> +#include <linux/xattr.h>
> +#include <keys/encrypted-type.h>

The rule historically has been linux/ includes come first.  I could
be wrong but suspect that's still the case here.

> +#include <linux/scatterlist.h>
> +#include "evm.h"
> +
> +#define EVMKEY "evm-key"
> +#define MAX_KEY_SIZE 128
> +static unsigned char evmkey[MAX_KEY_SIZE];
> +static int evmkey_len = MAX_KEY_SIZE;
> +
> +static int init_desc(struct hash_desc *desc)
> +{
> +	int rc;
> +
> +	desc->tfm = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
> +	if (IS_ERR(desc->tfm)) {
> +		pr_info("Can not allocate %s (reason: %ld)\n",
> +			evm_hmac, PTR_ERR(desc->tfm));
> +		rc = PTR_ERR(desc->tfm);
> +		return rc;
> +	}
> +	desc->flags = 0;
> +	crypto_hash_setkey(desc->tfm, evmkey, evmkey_len);

crypto_hash_setkey() can fail, right?

> +	rc = crypto_hash_init(desc);
> +	if (rc)
> +		crypto_free_hash(desc->tfm);
> +	return rc;
> +}
> +
> +/* Protect against 'cutting & pasting' security.evm xattr, include inode
> + * specific info.
> + *
> + * (Additional directory/file metadata needs to be added for more complete
> + * protection.)
> + */
> +static void hmac_add_misc(struct hash_desc *desc, struct inode *inode,
> +			  char *digest)
> +{
> +	struct h_misc {
> +		unsigned long ino;
> +		__u32 generation;
> +		uid_t uid;
> +		gid_t gid;
> +		umode_t mode;
> +	} hmac_misc;
> +	struct scatterlist sg[1];
> +
> +	memset(&hmac_misc, 0, sizeof hmac_misc);
> +	hmac_misc.ino = inode->i_ino;
> +	hmac_misc.generation = inode->i_generation;
> +	hmac_misc.uid = inode->i_uid;
> +	hmac_misc.gid = inode->i_gid;
> +	hmac_misc.mode = inode->i_mode;
> +	sg_init_one(sg, &hmac_misc, sizeof hmac_misc);
> +	crypto_hash_update(desc, sg, sizeof hmac_misc);
> +	crypto_hash_final(desc, digest);
> +}
> +
> +/*
> + * Calculate the HMAC value across the set of protected security xattrs.
> + *
> + * Instead of retrieving the requested xattr, for performance, calculate
> + * the hmac using the requested xattr value. Don't alloc/free memory for
> + * each xattr, but attempt to re-use the previously allocated memory.
> + */
> +int evm_calc_hmac(struct dentry *dentry, const char *req_xattr_name,
> +		  const char *req_xattr_value, size_t req_xattr_value_len,
> +		  char *digest)
> +{
> +	struct inode *inode = dentry->d_inode;
> +	struct hash_desc desc;
> +	struct scatterlist sg[1];
> +	char **xattrname;
> +	size_t xattr_size = 0;
> +	char *xattr_value = NULL;
> +	int error;
> +	int size;
> +
> +	if (!inode->i_op || !inode->i_op->getxattr)
> +		return -EOPNOTSUPP;
> +	error = init_desc(&desc);
> +	if (error)
> +		return error;
> +
> +	error = -ENODATA;
> +	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
> +		if ((req_xattr_name && req_xattr_value)
> +		    && !strcmp(*xattrname, req_xattr_name)) {

Is this special case only here to avoid one vfs_getxattr_alloc(),
or is there another reason for it?

> +			error = 0;
> +			sg_init_one(sg, req_xattr_value, req_xattr_value_len);
> +			crypto_hash_update(&desc, sg, req_xattr_value_len);
> +			continue;
> +		}
> +		size = vfs_getxattr_alloc(dentry, *xattrname,
> +					  &xattr_value, xattr_size, GFP_NOFS);
> +		if (size == -ENOMEM) {
> +			error = -ENOMEM;
> +			goto out;
> +		}
> +		if (size < 0)
> +			continue;
> +
> +		error = 0;
> +		xattr_size = size;
> +		sg_init_one(sg, xattr_value, xattr_size);
> +		crypto_hash_update(&desc, sg, xattr_size);
> +	}
> +	hmac_add_misc(&desc, inode, digest);
> +	kfree(xattr_value);
> +out:
> +	crypto_free_hash(desc.tfm);
> +	return error;
> +}
> +
> +/*
> + * Calculate the hmac and update security.evm xattr
> + *
> + * Expects to be called with i_mutex locked.
> + */
> +int evm_update_evmxattr(struct dentry *dentry, const char *xattr_name,
> +			const char *xattr_value, size_t xattr_value_len)
> +{
> +	struct inode *inode = dentry->d_inode;
> +	u8 hmac[MAX_DIGEST_SIZE];
> +	int rc = 0;
> +
> +	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
> +			   xattr_value_len, hmac);
> +	if (rc == 0)
> +		rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_EVM,
> +					   hmac, evm_hmac_size, 0);
> +	else if (rc == -ENODATA)
> +		rc = inode->i_op->removexattr(dentry, XATTR_NAME_EVM);
> +	return rc;
> +}
> +
> +/*
> + * Get the key from the TPM for the SHA1-HMAC
> + */
> +int evm_init_key(void)
> +{
> +	struct key *evm_key;
> +	struct encrypted_key_payload *ekp;
> +
> +	evm_key = request_key(&key_type_encrypted, EVMKEY, NULL);
> +	if (IS_ERR(evm_key))
> +		return -ENOENT;
> +
> +	down_read(&evm_key->sem);
> +	ekp = evm_key->payload.data;
> +	evmkey_len = ekp->decrypted_datalen > MAX_KEY_SIZE ? MAX_KEY_SIZE :

If decrypted_datalen > MAX_KEY_SIZE, shouldn't you assume something went
wrong and return an error?

> +			ekp->decrypted_datalen;
> +	memcpy(evmkey, ekp->decrypted_data, evmkey_len);
> +
> +	/* burn the original key contents */
> +	memset(ekp->decrypted_data, 0, evmkey_len);

You're potentially leaving akp->decrypted_datalen - evmkey_len bits
unburned.

> +	up_read(&evm_key->sem);
> +	key_put(evm_key);
> +	return 0;
> +}
> diff --git a/security/integrity/evm/evm_main.c b/security/integrity/evm/evm_main.c
> new file mode 100644
> index 0000000..66d7544
> --- /dev/null
> +++ b/security/integrity/evm/evm_main.c
> @@ -0,0 +1,283 @@
> +/*
> + * Copyright (C) 2005-2010 IBM Corporation
> + *
> + * Author:
> + * Mimi Zohar <zohar@...ibm.com>
> + * Kylene Hall <kjhall@...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.
> + *
> + * File: evm_main.c
> + *	implements evm_inode_setxattr, evm_inode_post_setxattr,
> + *	evm_inode_removexattr, and evm_verifyxattr
> + */
> +
> +#include <linux/module.h>
> +#include <linux/crypto.h>
> +#include <linux/xattr.h>
> +#include <linux/integrity.h>
> +#include "evm.h"
> +
> +int evm_initialized;
> +
> +char *evm_hmac = "hmac(sha1)";
> +int evm_hmac_size = SHA1_DIGEST_SIZE;
> +
> +char *evm_config_xattrnames[] = {
> +#ifdef CONFIG_SECURITY_SELINUX
> +	XATTR_NAME_SELINUX,
> +#endif
> +#ifdef CONFIG_SECURITY_SMACK
> +	XATTR_NAME_SMACK,
> +#endif
> +	XATTR_NAME_CAPS,
> +	NULL
> +};
> +
> +/*
> + * evm_verify_hmac - calculate and compare the HMAC with the EVM xattr
> + *
> + * Compute the HMAC on the dentry's protected set of extended attributes
> + * and compare it against the stored security.evm xattr. (For performance,
> + * use the previoulsy retrieved xattr value and length to calculate the
> + * HMAC.)
> + *
> + * Returns integrity status
> + */
> +static enum integrity_status evm_verify_hmac(struct dentry *dentry,
> +					     const char *xattr_name,
> +					     char *xattr_value,
> +					     size_t xattr_value_len,
> +					     struct integrity_iint_cache *iint)
> +{
> +	char hmac_val[MAX_DIGEST_SIZE];
> +	int rc;
> +
> +	if (iint->hmac_status != INTEGRITY_UNKNOWN)
> +		return iint->hmac_status;
> +
> +	memset(hmac_val, 0, sizeof hmac_val);
> +	rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
> +			   xattr_value_len, hmac_val);
> +	if (rc < 0)
> +		return INTEGRITY_UNKNOWN;
> +
> +	rc = vfs_xattr_cmp(dentry, XATTR_NAME_EVM, hmac_val, sizeof hmac_val,
> +			   GFP_NOFS);
> +	if (rc < 0)
> +		goto err_out;
> +	iint->hmac_status = INTEGRITY_PASS;
> +	return iint->hmac_status;
> +
> +err_out:
> +	switch (rc) {
> +	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;
> +	}
> +	return iint->hmac_status;
> +}
> +
> +static int evm_protected_xattr(const char *req_xattr_name)
> +{
> +	char **xattrname;
> +	int found = 0;
> +
> +	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++) {
> +		if (strncmp(req_xattr_name, *xattrname,
> +			    strlen(req_xattr_name)) == 0) {

Can you put a comment here as to why currently checking the lengths is
unnecessary due to the xattrs which exist?  (Or add a length comparison)

> +			found = 1;
> +			break;
> +		}
> +	}
> +	return found;
> +}
> +
> +/**
> + * evm_verifyxattr - verify the integrity of the requested xattr
> + * @dentry: object of the verify xattr
> + * @xattr_name: requested xattr
> + * @xattr_value: requested xattr value
> + * @xattr_value_len: requested xattr value length
> + *
> + * Calculate the HMAC for the given dentry and verify it against the stored
> + * security.evm xattr. For performance, use the xattr value and length
> + * previously retrieved to calculate the HMAC.
> + *
> + * Returns the xattr integrity status.
> + *
> + * This function requires the caller to lock the inode's i_mutex before it
> + * is executed.
> + */
> +enum integrity_status evm_verifyxattr(struct dentry *dentry,
> +				      const char *xattr_name,
> +				      void *xattr_value, size_t xattr_value_len)
> +{
> +	struct inode *inode = dentry->d_inode;
> +	struct integrity_iint_cache *iint;
> +	enum integrity_status status;
> +
> +	if (!evm_initialized || !evm_protected_xattr(xattr_name))
> +		return INTEGRITY_UNKNOWN;
> +
> +	iint = integrity_iint_find(inode);
> +	if (!iint)
> +		return INTEGRITY_UNKNOWN;
> +	status = evm_verify_hmac(dentry, xattr_name, xattr_value,
> +				 xattr_value_len, iint);
> +	return status;
> +}
> +EXPORT_SYMBOL_GPL(evm_verifyxattr);
> +
> +/*
> + * evm_protect_xattr - protect the EVM extended attribute
> + *
> + * Prevent security.evm from being modified or removed.
> + */
> +static int evm_protect_xattr(struct dentry *dentry, const char *xattr_name,
> +			     const void *xattr_value, size_t xattr_value_len)
> +{
> +	if (strcmp(xattr_name, XATTR_NAME_EVM) == 0) {
> +		if (!capable(CAP_SYS_ADMIN))
> +			return -EPERM;
> +	}
> +	return 0;
> +}
> +
> +/**
> + * evm_inode_setxattr - protect the EVM extended attribute
> + * @dentry: pointer to the affected dentry
> + * @xattr_name: pointer to the affected extended attribute name
> + * @xattr_value: pointer to the new extended attribute value
> + * @xattr_value_len: pointer to the new extended attribute value length
> + *
> + * Prevent 'security.evm' from being modified
> + */
> +int evm_inode_setxattr(struct dentry *dentry, const char *xattr_name,
> +		       const void *xattr_value, size_t xattr_value_len)
> +{
> +	return evm_protect_xattr(dentry, xattr_name, xattr_value,
> +				 xattr_value_len);
> +}
> +
> +/**
> + * evm_inode_removexattr - protect the EVM extended attribute
> + * @dentry: pointer to the affected dentry
> + * @xattr_name: pointer to the affected extended attribute name
> + *
> + * Prevent 'security.evm' from being removed.
> + */
> +int evm_inode_removexattr(struct dentry *dentry, const char *xattr_name)
> +{
> +	return evm_protect_xattr(dentry, xattr_name, NULL, 0);
> +}
> +
> +/**
> + * evm_inode_post_setxattr - update 'security.evm' to reflect the changes
> + * @dentry: pointer to the affected dentry
> + * @xattr_name: pointer to the affected extended attribute name
> + * @xattr_value: pointer to the new extended attribute value
> + * @xattr_value_len: pointer to the new extended attribute value length
> + *
> + * Update the HMAC stored in 'security.evm' to reflect the change.
> + *
> + * No need to take the i_mutex lock here, as this function is called from
> + * __vfs_setxattr_noperm().  The caller of which has taken the inode's
> + * i_mutex lock.
> + */
> +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))
> +		return;
> +
> +	evm_update_evmxattr(dentry, xattr_name, xattr_value, xattr_value_len);
> +	return;
> +}
> +
> +/**
> + * evm_inode_post_removexattr - update 'security.evm' after removing the xattr
> + * @dentry: pointer to the affected dentry
> + * @xattr_name: pointer to the affected extended attribute name
> + *
> + * Update the HMAC stored in 'security.evm' to reflect removal of the xattr.
> + */
> +void evm_inode_post_removexattr(struct dentry *dentry, const char *xattr_name)
> +{
> +	struct inode *inode = dentry->d_inode;
> +
> +	if (!evm_initialized || !evm_protected_xattr(xattr_name))
> +		return;
> +
> +	mutex_lock(&inode->i_mutex);
> +	evm_update_evmxattr(dentry, xattr_name, NULL, 0);
> +	mutex_unlock(&inode->i_mutex);
> +	return;
> +}
> +
> +/**
> + * evm_inode_post_setattr - update 'security.evm' after modifying metadata
> + * @dentry: pointer to the affected dentry
> + * @ia_valid: for the UID and GID status
> + *
> + * For now, update the HMAC stored in 'security.evm' to reflect UID/GID
> + * changes.
> + *
> + * This function is called from notify_change(), which expects the caller
> + * to lock the inode's i_mutex.
> + */
> +void evm_inode_post_setattr(struct dentry *dentry, int ia_valid)
> +{
> +	if (!evm_initialized)
> +		return;
> +
> +	if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID))
> +		evm_update_evmxattr(dentry, NULL, NULL, 0);
> +	return;
> +}
> +
> +static struct crypto_hash *tfm_hmac;	/* preload crypto alg */
> +static int __init init_evm(void)
> +{
> +	int error;
> +
> +	tfm_hmac = crypto_alloc_hash(evm_hmac, 0, CRYPTO_ALG_ASYNC);
> +	error = evm_init_secfs();
> +	if (error < 0) {
> +		printk(KERN_INFO "EVM: Error registering secfs\n");
> +		goto err;
> +	}
> +err:
> +	return error;
> +}
> +
> +static void __exit cleanup_evm(void)
> +{
> +	evm_cleanup_secfs();
> +	crypto_free_hash(tfm_hmac);
> +}
> +
> +/*
> + * evm_display_config - list the EVM protected security extended attributes
> + */
> +static int __init evm_display_config(void)
> +{
> +	char **xattrname;
> +
> +	for (xattrname = evm_config_xattrnames; *xattrname != NULL; xattrname++)
> +		printk(KERN_INFO "EVM: %s\n", *xattrname);
> +	return 0;
> +}
> +
> +pure_initcall(evm_display_config);
> +late_initcall(init_evm);
> +
> +MODULE_DESCRIPTION("Extended Verification Module");
> +MODULE_LICENSE("GPL");
> diff --git a/security/integrity/evm/evm_secfs.c b/security/integrity/evm/evm_secfs.c
> new file mode 100644
> index 0000000..ac76299
> --- /dev/null
> +++ b/security/integrity/evm/evm_secfs.c
> @@ -0,0 +1,108 @@
> +/*
> + * Copyright (C) 2010 IBM Corporation
> + *
> + * Authors:
> + * Mimi Zohar <zohar@...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.
> + *
> + * File: evm_secfs.c
> + *	- Used to signal when key is on keyring
> + *	- Get the key and enable EVM
> + */
> +
> +#include <linux/uaccess.h>
> +#include <linux/module.h>
> +#include "evm.h"
> +
> +static struct dentry *evm_init_tpm;
> +
> +/**
> + * evm_read_key - read() for <securityfs>/evm
> + *
> + * @filp: file pointer, not actually used
> + * @buf: where to put the result
> + * @count: maximum to send along
> + * @ppos: where to start
> + *
> + * Returns number of bytes read or error code, as appropriate
> + */
> +static ssize_t evm_read_key(struct file *filp, char __user *buf,
> +			    size_t count, loff_t *ppos)
> +{
> +	char temp[80];
> +	ssize_t rc;
> +
> +	if (*ppos != 0)
> +		return 0;
> +
> +	sprintf(temp, "%d", evm_initialized);
> +	rc = simple_read_from_buffer(buf, count, ppos, temp, strlen(temp));
> +
> +	return rc;
> +}
> +
> +/**
> + * evm_write_key - write() for <securityfs>/evm
> + * @file: file pointer, not actually used
> + * @buf: where to get the data from
> + * @count: bytes sent
> + * @ppos: where to start
> + *
> + * Used to signal that key is on the kernel key ring.
> + * - get the integrity hmac key from the kernel key ring
> + * - create list of hmac protected extended attributes
> + * Returns number of bytes written or error code, as appropriate
> + */
> +static ssize_t evm_write_key(struct file *file, const char __user *buf,
> +			     size_t count, loff_t *ppos)
> +{
> +	char temp[80];
> +	int i, error;
> +
> +	if (!capable(CAP_SYS_ADMIN) || evm_initialized)
> +		return -EPERM;
> +
> +	if (count >= sizeof(temp) || count == 0)
> +		return -EINVAL;
> +
> +	if (copy_from_user(temp, buf, count) != 0)
> +		return -EFAULT;
> +
> +	temp[count] = '\0';
> +
> +	if ((sscanf(temp, "%d", &i) != 1) || (i != 1))
> +		return -EINVAL;
> +
> +	error = evm_init_key();
> +	if (!error) {
> +		evm_initialized = 1;
> +		pr_info("EVM: initialized\n");
> +	} else
> +		pr_err("EVM: initialization failed\n");
> +	return count;
> +}
> +
> +static const struct file_operations evm_key_ops = {
> +	.read		= evm_read_key,
> +	.write		= evm_write_key,
> +};
> +
> +int __init evm_init_secfs(void)
> +{
> +	int error = 0;
> +
> +	evm_init_tpm = securityfs_create_file("evm", S_IRUSR | S_IRGRP,
> +					      NULL, NULL, &evm_key_ops);
> +	if (!evm_init_tpm || IS_ERR(evm_init_tpm))
> +		error = -EFAULT;
> +	return error;
> +}
> +
> +void __exit evm_cleanup_secfs(void)
> +{
> +	if (evm_init_tpm)
> +		securityfs_remove(evm_init_tpm);
> +}
> diff --git a/security/integrity/iint.c b/security/integrity/iint.c
> index d17de48..991df20 100644
> --- a/security/integrity/iint.c
> +++ b/security/integrity/iint.c
> @@ -157,6 +157,7 @@ static void init_once(void *foo)
>  	iint->version = 0;
>  	iint->flags = 0UL;
>  	mutex_init(&iint->mutex);
> +	iint->hmac_status = INTEGRITY_UNKNOWN;
>  }
>  
>  static int __init integrity_iintcache_init(void)
> diff --git a/security/integrity/integrity.h b/security/integrity/integrity.h
> index 2217a28..2232cd1 100644
> --- a/security/integrity/integrity.h
> +++ b/security/integrity/integrity.h
> @@ -28,6 +28,7 @@ struct integrity_iint_cache {
>  	unsigned char flags;
>  	u8 digest[MAX_DIGEST_SIZE];
>  	struct mutex mutex;	/* protects: version, flags, digest */
> +	enum integrity_status hmac_status;
>  };
>  
>  /* rbtree tree calls to lookup, insert, delete
> -- 
> 1.7.3.4
> 
> --
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