Integrity Service API and dummy provider
RFC PATCH 2/8 Integrity Service API and dummy provider
This patch provides a framework and dummy provider for an integrity service. The three integrity functions provided are:
integrity_verify_metadata
integrity_verity_data
integrity_measure
(Details on the calls and their exact arguments are in linux/integrity.h, included in the patch.)
Normally these functions would be called by an LSM module during d_instantiate. The first function is used to retrieve a requested dentry's label (xattr, such as security.selinux, or security.slim.level), along with the result of integrity verification of the label.
Based on the result of this call, the LSM module may also choose to use integrity_verify_data to request a verification of the file's data, and integrity_measure, to commit the file's measurement to some form of logging/attestation service, such as a TPM.
The latter two functions are separate calls, so that the LSM module can optimize performance by using them only as needed. For example, if the integrity_verify_metadata call shows that the label is not trustworthy, it is probably not necessary to hash and measure the file, as the current LSM check will likely be denied anyway.
Updated to use more standard error returning per comments.
--- include/linux/integrity.h | 90 +++++++++++++++++++++++++++++++++++ security/Makefile | 1 security/integrity.c | 45 +++++++++++++++++ security/integrity_dummy.c | 77 +++++++++++++++++++++++++++++ security/integrity_dummy.h | 12 ++++ 5 files changed, 225 insertions(+)
security/integrity.c +45 -0
@@ -0,0 +1,45 @@ +/* +* integrity.c +* +* register integrity subsystem +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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/config.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/sched.h> +#include <linux/integrity.h> + +#include "integrity_dummy.h" + +struct integrity_operations *integrity_ops = &dummy_integrity_ops; + +int register_integrity (struct integrity_operations *ops) +{ +if (integrity_ops != &dummy_integrity_ops) +return -EAGAIN ; + + integrity_ops = ops; +return 0 ; +} + +int unregister_integrity (struct integrity_operations *ops) +{ +if (ops != integrity_ops) +return -EINVAL ; + + integrity_ops = &dummy_integrity_ops; +return 0 ; +} + +EXPORT_SYMBOL_GPL (register_integrity); +EXPORT_SYMBOL_GPL (unregister_integrity); +EXPORT_SYMBOL_GPL (integrity_ops);
security/integrity_dummy.c +77 -0
77 lines not on this page · raw message
include/linux/integrity.h +90 -0
90 lines not on this page · raw message
security/Makefile +1 -0
@@ -12,6 +13,7 @@ endif # Object file lists obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o +obj-$(CONFIG_SECURITY) += integrity.o integrity_dummy.o # Must precede capability.o in order to stack properly. obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
security/integrity_dummy.h +12 -0
@@ -0,0 +1,12 @@ +/* +* integrity_dummy.h +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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. +*/ + +extern struct integrity_operations dummy_integrity_ops;
Quoted 51 lines · Kylene Jo Hall
security/integrity_dummy.c +48
-0@@ -0,0 +1,77 @@ +/* +* integrity_dummy.c +* +* Instantiate integrity subsystem +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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/config.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/integrity.h> + +/* +* Return the extended attribute +*/ +static int dummy_verify_metadata (struct dentry *dentry,char *xattr_name, +char **xattr_value,int *xattr_value_len, +int *status) +{ +char *value; +int size; +int error; + +if (!xattr_value || !xattr_value_len || !status) +return -EINVAL ; + +if (!dentry || !dentry->d_inode || !dentry->d_inode->i_op + || !dentry->d_inode->i_op->getxattr) { +return -EOPNOTSUPP ; + } + + size = dentry->d_inode->i_op->getxattr (dentry, xattr_name,NULL ,0 ); +if (size <0 ) { +if (size == -ENODATA ) { + *status =INTEGRITY_NOLABEL ; +return 0 ; + } +return size; + } + + value =kzalloc (size +1 ,GFP_KERNEL );
security/integrity_dummy.c line 58
Quoted 10 lines
security/integrity_dummy.c +10
-0+if (!value) +return -ENOMEM ; + + error = dentry->d_inode->i_op->getxattr (dentry, xattr_name, + value, size); + *xattr_value_len = size; + *xattr_value = value; + *status =INTEGRITY_PASS ; +return error; +}
If the second call to ->getxattr returns an error, is it a good idea to overwrite the values in xattr_value_len and *xattr_value? Does the integrity really "pass" if there is an error?
(Or is the point of the 'dummy' verification that .. well .. no verification is done?)
Quoted 59 lines
security/integrity_dummy.c +18
-0+static int dummy_verify_data (struct dentry *dentry,int *status) +{ +if (status) + *status =INTEGRITY_PASS ; +return 0 ; +} + +static void dummy_measure (struct dentry *dentry, +const unsigned char *filename,int mask) +{ +return ; +} + +struct integrity_operations dummy_integrity_ops = { + .verify_metadata = dummy_verify_metadata, + .verify_data = dummy_verify_data, + .measure = dummy_measure +};include/linux/integrity.h +38
-0@@ -0,0 +1,90 @@ +/* +* integrity.h +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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. +*/ + +#ifndef _LINUX_INTEGRITY_H +#define _LINUX_INTEGRITY_H + +#include <linux/fs.h> + +/* +* struct integrity_operations - main integrity structure +* +* @verify_data: +* Verify the integrity of a dentry. +* @dentry contains the dentry structure to be verified. +* @status contains INTEGRITY_PASS, INTEGRITY_FAIL, or +* INTEGRITY_NOLABEL +* Return 0 on success or errno values +* +* @verify_metadata: +* Verify the integrity of a dentry's metadata; return the value +* of the requested xattr_name and the verification result of the +* dentry's metadata. +* @dentry contains the dentry structure of the metadata to be verified. +* @xattr_name, if not null, contains the name of the xattr +* being requested. +* @xattr_value, if not null, is a pointer for the xattr value. +* @xattr_val_len will be set to the length of the xattr value. +* @status contains INTEGRITY_PASS, INTEGRITY_FAIL, or +* INTEGRITY_NOLABEL +* Return 0 on success or errno values
include/linux/integrity.h line 48
Quoted 10 lines
include/linux/integrity.h +10
-0+* +* @measure: +* Update an aggregate integrity value with the inode's measurement. +* The aggregate integrity value is maintained in secure storage such +* as in a TPM PCR. +* @dentry contains the dentry structure of the inode to be measured. +* @filename either contains the full pathname/short file name. +* @mask contains the filename permission status(i.e. read, write, append). +* +*/
I wouldn't normally expect a function named 'measure' to update a datastructure, especially not one potentially stored in hardware. Is this just my unfamiliarity with TPM nomenclature?
What is the proper use of the filename?
Quoted 44 lines
include/linux/integrity.h +41
-0+#define PASS_STR "INTEGRITY_PASS" +#define FAIL_STR "INTEGRITY_FAIL" +#define NOLABEL_STR "INTEGRITY_NOLABEL" + +struct integrity_operations { +int (*verify_metadata) (struct dentry *dentry,char *xattr_name, +char **xattr_value,int *xattr_val_len,int *status); +int (*verify_data) (struct dentry *dentry,int *status); +void (*measure) (struct dentry *dentry, +const unsigned char *filename,int mask); +}; +extern int register_integrity (struct integrity_operations *ops); +extern int unregister_integrity (struct integrity_operations *ops); + +/* global variables */ +extern struct integrity_operations *integrity_ops; +enum integrity_verify_status { +INTEGRITY_PASS =0 ,INTEGRITY_FAIL =-1 ,INTEGRITY_NOLABEL =-2 +}; + +/* inline stuff */ +static inline int integrity_verify_metadata (struct dentry *dentry, +char *xattr_name,char **xattr_value, +int *xattr_val_len,int *status) +{ +return integrity_ops->verify_metadata (dentry, xattr_name, + xattr_value, xattr_val_len, status); +} + +static inline int integrity_verify_data (struct dentry *dentry, +int *status) +{ +return integrity_ops->verify_data (dentry, status); +} + +static inline void integrity_measure (struct dentry *dentry, +const unsigned char *filename,int mask) +{ +return integrity_ops->measure (dentry, filename, mask); +} +#endif
security/Makefile endif · line 16
Quoted 4 lines
security/Makefile +1
-0@@ -12,6 +13,7 @@ endif # Object file lists obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o +obj-$(CONFIG_SECURITY) += integrity.o integrity_dummy.o
Not CONFIG_SECURITY_INTEGRITY or similar?
security/Makefile endif · line 19
Quoted 3 lines
security/Makefile +0
-0# Must precede capability.o in order to stack properly. obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o
Thanks
Comments inline below.
Quoted 67 lines · Seth Arnold
Quoted 51 lines · Kylene Jo Hall
security/integrity_dummy.c +48
-0@@ -0,0 +1,77 @@ +/* +* integrity_dummy.c +* +* Instantiate integrity subsystem +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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/config.h> +#include <linux/module.h> +#include <linux/init.h> +#include <linux/kernel.h> +#include <linux/integrity.h> + +/* +* Return the extended attribute +*/ +static int dummy_verify_metadata (struct dentry *dentry,char *xattr_name, +char **xattr_value,int *xattr_value_len, +int *status) +{ +char *value; +int size; +int error; + +if (!xattr_value || !xattr_value_len || !status) +return -EINVAL ; + +if (!dentry || !dentry->d_inode || !dentry->d_inode->i_op + || !dentry->d_inode->i_op->getxattr) { +return -EOPNOTSUPP ; + } + + size = dentry->d_inode->i_op->getxattr (dentry, xattr_name,NULL ,0 ); +if (size <0 ) { +if (size == -ENODATA ) { + *status =INTEGRITY_NOLABEL ; +return 0 ; + } +return size; + } + + value =kzalloc (size +1 ,GFP_KERNEL );security/integrity_dummy.c line 58
Quoted 10 lines
security/integrity_dummy.c +10
-0+if (!value) +return -ENOMEM ; + + error = dentry->d_inode->i_op->getxattr (dentry, xattr_name, + value, size); + *xattr_value_len = size; + *xattr_value = value; + *status =INTEGRITY_PASS ; +return error; +}If the second call to ->getxattr returns an error, is it a good idea to overwrite the values in
xattr_value_lenand*xattr_value? Does the integrity really "pass" if there is an error?
Quoted 2 lines
(Or is the point of the 'dummy' verification that .. well .. no verification is done?)
Yes that is the point of the dummy.
Quoted 67 lines
Quoted 67 lines
security/integrity_dummy.c +18
-0+static int dummy_verify_data (struct dentry *dentry,int *status) +{ +if (status) + *status =INTEGRITY_PASS ; +return 0 ; +} + +static void dummy_measure (struct dentry *dentry, +const unsigned char *filename,int mask) +{ +return ; +} + +struct integrity_operations dummy_integrity_ops = { + .verify_metadata = dummy_verify_metadata, + .verify_data = dummy_verify_data, + .measure = dummy_measure +};include/linux/integrity.h +45
-0@@ -0,0 +1,90 @@ +/* +* integrity.h +* +* Copyright (C) 2005,2006 IBM Corporation +* Author: Mimi Zohar <[email protected]> +* +* 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. +*/ + +#ifndef _LINUX_INTEGRITY_H +#define _LINUX_INTEGRITY_H + +#include <linux/fs.h> + +/* +* struct integrity_operations - main integrity structure +* +* @verify_data: +* Verify the integrity of a dentry. +* @dentry contains the dentry structure to be verified. +* @status contains INTEGRITY_PASS, INTEGRITY_FAIL, or +* INTEGRITY_NOLABEL +* Return 0 on success or errno values +* +* @verify_metadata: +* Verify the integrity of a dentry's metadata; return the value +* of the requested xattr_name and the verification result of the +* dentry's metadata. +* @dentry contains the dentry structure of the metadata to be verified. +* @xattr_name, if not null, contains the name of the xattr +* being requested. +* @xattr_value, if not null, is a pointer for the xattr value. +* @xattr_val_len will be set to the length of the xattr value. +* @status contains INTEGRITY_PASS, INTEGRITY_FAIL, or +* INTEGRITY_NOLABEL +* Return 0 on success or errno values +* +* @measure: +* Update an aggregate integrity value with the inode's measurement. +* The aggregate integrity value is maintained in secure storage such +* as in a TPM PCR. +* @dentry contains the dentry structure of the inode to be measured. +* @filename either contains the full pathname/short file name.
Quoted 9 lines
include/linux/integrity.h line 48
Quoted 3 lines
include/linux/integrity.h +3
-0+* @mask contains the filename permission status(i.e. read, write, append). +* +*/ I wouldn't normally expect a function named 'measure' to update a datastructure, especially not one potentially stored in hardware. Is this just my unfamiliarity with TPM nomenclature?
What is the proper use of the filename?
measure is standard TCG nomenclature refering to calculating the hash of a file and extending that value into the TPM to be able to verify what has run on the system. Here are a couple of references for sample term
use: [1]
http://domino.research.ibm.com/comm/research_projects.nsf/pages/ssd_ima.index.html
[2] https://www.trustedcomputinggroup.org/news/articles/rc23363.pdf
The filename can be either and is used for logging such that the TPM PCR aggregate of the measurements can be verified later. Which is needed would be implementation specific with full pathname probably preferable when available.
Quoted 45 lines
Quoted 45 lines
include/linux/integrity.h +41
-0+#define PASS_STR "INTEGRITY_PASS" +#define FAIL_STR "INTEGRITY_FAIL" +#define NOLABEL_STR "INTEGRITY_NOLABEL" + +struct integrity_operations { +int (*verify_metadata) (struct dentry *dentry,char *xattr_name, +char **xattr_value,int *xattr_val_len,int *status); +int (*verify_data) (struct dentry *dentry,int *status); +void (*measure) (struct dentry *dentry, +const unsigned char *filename,int mask); +}; +extern int register_integrity (struct integrity_operations *ops); +extern int unregister_integrity (struct integrity_operations *ops); + +/* global variables */ +extern struct integrity_operations *integrity_ops; +enum integrity_verify_status { +INTEGRITY_PASS =0 ,INTEGRITY_FAIL =-1 ,INTEGRITY_NOLABEL =-2 +}; + +/* inline stuff */ +static inline int integrity_verify_metadata (struct dentry *dentry, +char *xattr_name,char **xattr_value, +int *xattr_val_len,int *status) +{ +return integrity_ops->verify_metadata (dentry, xattr_name, + xattr_value, xattr_val_len, status); +} + +static inline int integrity_verify_data (struct dentry *dentry, +int *status) +{ +return integrity_ops->verify_data (dentry, status); +} + +static inline void integrity_measure (struct dentry *dentry, +const unsigned char *filename,int mask) +{ +return integrity_ops->measure (dentry, filename, mask); +} +#endif security/Makefile +0
-0@@ -12,6 +13,7 @@ endif
Quoted 6 lines
security/Makefile endif · line 16
Quoted 3 lines
security/Makefile +1
-0# Object file lists obj-$(CONFIG_SECURITY) += security.o dummy.o inode.o +obj-$(CONFIG_SECURITY) += integrity.o integrity_dummy.oNot
CONFIG_SECURITY_INTEGRITYor similar?
This is probably a good idea. I'll incorporate.
Quoted 5 lines
security/Makefile endif · line 19
Quoted 3 lines
security/Makefile +0
-0# Must precede capability.o in order to stack properly. obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.oThanks
Quoted 6 lines · Kylene Jo Hall
measure is standard TCG nomenclature refering to calculating the hash of a file and extending that value into the TPM to be able to verify what has run on the system. Here are a couple of references for sample term
use: [1]
http://domino.research.ibm.com/comm/research_projects.nsf/pages/ssd_ima.index.html
[2] https://www.trustedcomputinggroup.org/news/articles/rc23363.pdf
Thanks for the pointers. Much appreciated.
And thanks for the detailed responses to my various questions. Always nice to learn. :)