Re: [PATCH v5 03/21] evm: re-release

Mimi Zohar
2011-05-19T22:49:15Z

On Thu, 2011-05-19 at 01:05 -0500, Serge E. Hallyn wrote:
> Quoting Mimi Zohar (zohar@linux.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.

Thanks for catching that.

> > 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@us.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@us.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@us.ibm.com>
> > + * Kylene Hall <kjhall@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.
> > + *
> > + * 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@us.ibm.com>
> > + * Kylene Hall <kjhall@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.
> > + *
> > + * 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.

No, you're correct.

> > +#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?

Yes, will add the check.

> > + 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?

Right, it's to avoid making an unecessary vfs_getxattr_alloc() call.

> > + 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?

Yes, it's probably a good idea to return something meaningful, rather
than letting it fail latter on use. :-)

> > + 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.

Right, it should be: memset(ekp->decrypted_data, 0, ekp->decrypted_datalen);

> > + 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@us.ibm.com>
> > + * Kylene Hall <kjhall@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.
> > + *
> > + * 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)

yes, length checking is necessary.

> > + 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@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.
> > + *
> > + * 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