Messages in this thread | | | Subject | Re: [RFC][PATCH 4/5]integrity: Linux Integrity Module(LIM) | From | Mimi Zohar <> | Date | Wed, 28 May 2008 22:46:02 -0400 |
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On Wed, 2008-05-28 at 00:46 -0700, Andrew Morton wrote: > On Fri, 23 May 2008 11:05:33 -0400 Mimi Zohar <zohar@linux.vnet.ibm.com> wrote: > > > This is a request for comments for a redesign of the integrity patches. > > > > ... > > > > +int register_template(char *template_name, > > + struct template_operations *template_ops) > > +{ > > + int template_len; > > + struct template_list_entry *entry; > > + > > + if (!template_initialized++) { > > + INIT_LIST_HEAD(&integrity_templates); > > + mutex_init(&integrity_templates_mutex); > > + } > > + > > + entry = kmalloc(sizeof(*entry), GFP_ATOMIC); > > + INIT_LIST_HEAD(&entry->template); > > + > > + template_len = strlen(template_name); > > + if (template_len > TEMPLATE_NAME_LEN_MAX) > > + template_len = TEMPLATE_NAME_LEN_MAX; > > + memcpy(entry->template_name, template_name, template_len); > > + entry->template_name[template_len] = '\0'; > > + entry->template_ops = template_ops; > > + > > + mutex_lock(&integrity_templates_mutex); > > + list_add_rcu(&entry->template, &integrity_templates); > > + mutex_unlock(&integrity_templates_mutex); > > + synchronize_rcu(); > > + > > + return 0; > > +} > > +EXPORT_SYMBOL_GPL(register_template); > > Should be integrity_register_template()?
yes, definitely.
> > +/** > > + * unregister_template > > + * @template_name: a pointer to a string containing the template name. > > + * > > + * Unregister the template functions > > + */ > > +int unregister_template(char *template_name) > > +{ > > + struct template_list_entry *entry; > > + > > + mutex_lock(&integrity_templates_mutex); > > + list_for_each_entry(entry, &integrity_templates, template) { > > + if (strncmp(entry->template_name, template_name, > > + strlen(entry->template_name)) == 0) { > > + list_del_rcu(&entry->template); > > + mutex_unlock(&integrity_templates_mutex); > > + synchronize_rcu(); > > + kfree(entry); > > + return 0; > > + } > > + } > > + mutex_unlock(&integrity_templates_mutex); > > + return -EINVAL; > > +} > > +EXPORT_SYMBOL_GPL(unregister_template); > > Similarly.
Ok
> > +/** > > + * integrity_find_template > > + * @template_name: a pointer to a string containing the template name. > > + * @template_ops: a pointer to the template functions > > + * > > + * Find the template functions based on the template name. > > + */ > > +int integrity_find_template(char *template_name, > > + struct template_operations **template_ops) > > +{ > > + struct template_list_entry *entry; > > + > > + rcu_read_lock(); > > + list_for_each_entry_rcu(entry, &integrity_templates, template) { > > + if (strncmp(entry->template_name, template_name, > > + strlen(entry->template_name)) == 0) { > > + *template_ops = entry->template_ops; > > + rcu_read_unlock(); > > + return 0; > > + } > > + } > > + rcu_read_unlock(); > > + return 1; > > +} > > +EXPORT_SYMBOL_GPL(integrity_find_template); > > Strange locking. We take the rcu_read_lock then locate a pointer to an > object then drop the lock, returning that pointer while doing nothing > to ensure the stability of the returned object?
yep, I messed up the locking here. Will fix it.
> > > > ... > > > > +#define set_to_dummy_if_null(ops, function) \ > > + do { \ > > + if (!ops->function) { \ > > + ops->function = dummy_##function; \ > > + printk(KERN_INFO "Had to override the " #function \ > > + " integrity operation with the dummy one.\n");\ > > + } \ > > + } while (0) > > hrm. > > Probably the message should identify where it came from? "integrity: > had to override ..."
Ok.
> > > > ... > > > > @@ -1036,6 +1038,7 @@ struct dentry *d_instantiate_unique(stru > > spin_unlock(&dcache_lock); > > > > if (!result) { > > + integrity_d_instantiate(entry, inode); > > security_d_instantiate(entry, inode); > > return NULL; > > } > > @@ -1173,6 +1176,7 @@ struct dentry *d_splice_alias(struct ino > > BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED)); > > fsnotify_d_instantiate(new, inode); > > spin_unlock(&dcache_lock); > > + integrity_d_instantiate(new, inode); > > security_d_instantiate(new, inode); > > d_rehash(dentry); > > d_move(new, dentry); > > @@ -1183,6 +1187,7 @@ struct dentry *d_splice_alias(struct ino > > dentry->d_inode = inode; > > fsnotify_d_instantiate(dentry, inode); > > spin_unlock(&dcache_lock); > > + integrity_d_instantiate(dentry, inode); > > security_d_instantiate(dentry, inode); > > d_rehash(dentry); > > } > > @@ -1733,6 +1738,7 @@ found: > > spin_unlock(&dcache_lock); > > out_nolock: > > if (actual == dentry) { > > + integrity_d_instantiate(dentry, inode); > > security_d_instantiate(dentry, inode); > > return NULL; > > } > > I'm trying to find a non-trivial ->d_instantiate() implementation to > see how much overhead is being added to these performance-critical > codepaths, but afaict this patchset doesn't add one?
The current IMA, as a stand alone integrity provider, does not use integrity_d_instantiate. It was used by EVM to verify the integrity of the hash and store the results in i_integrity. (Refer to 2.6.22-rc1-mm1-broken-out.tar.bz2)
We could defer this discussion by removing it for now, as it is not being used by the IMA.
> > Index: linux-2.6.26-rc3-git2/fs/ext3/xattr_security.c > > =================================================================== > > --- linux-2.6.26-rc3-git2.orig/fs/ext3/xattr_security.c > > +++ linux-2.6.26-rc3-git2/fs/ext3/xattr_security.c > > @@ -9,6 +9,7 @@ > > #include <linux/ext3_jbd.h> > > #include <linux/ext3_fs.h> > > #include <linux/security.h> > > +#include <linux/integrity.h> > > #include "xattr.h" > > > > static size_t > > @@ -57,12 +58,19 @@ ext3_init_security(handle_t *handle, str > > > > err = security_inode_init_security(inode, dir, &name, &value, &len); > > if (err) { > > + /* Even if creation of the security xattr fails, must > > + * indicate this is a new inode. */ > > + integrity_inode_init_integrity(inode, dir, NULL, NULL, NULL); > > if (err == -EOPNOTSUPP) > > return 0; > > return err; > > } > > err = ext3_xattr_set_handle(handle, inode, EXT3_XATTR_INDEX_SECURITY, > > name, value, len, 0); > > + > > + integrity_inode_init_integrity(inode, dir, &name, &value, &len); > > + err = ext3_xattr_set_handle(handle, inode, EXT3_XATTR_INDEX_SECURITY, > > + name, value, len, 0); > > Can we put the integrity_inode_init_integrity() call into > security_inode_init_security() thus avoiding having to change lots of > filesystems?
That is fine by me, not sure how others feel.
> > kfree(name); > > kfree(value); > > return err; > > > > ... > > > > @@ -17,6 +17,7 @@ > > #include <linux/hash.h> > > #include <linux/swap.h> > > #include <linux/security.h> > > +#include <linux/integrity.h> > > #include <linux/pagemap.h> > > #include <linux/cdev.h> > > #include <linux/bootmem.h> > > @@ -160,6 +161,14 @@ static struct inode *alloc_inode(struct > > init_rwsem(&inode->i_alloc_sem); > > lockdep_set_class(&inode->i_alloc_sem, &sb->s_type->i_alloc_sem_key); > > > > + if (integrity_inode_alloc(inode)) { > > + if (inode->i_sb->s_op->destroy_inode) > > + inode->i_sb->s_op->destroy_inode(inode); > > + else > > + kmem_cache_free(inode_cachep, (inode)); > > + return NULL; > > + } > > This code is uncommented and integrity_inode_alloc() also is > uncommented. People will want to know what's going on, please.
integrity_inode_alloc() is the wrapper which calls inode_alloc_integrity(). It is commented in integrity.h. I'll comment the code here as well.
> Again, where do we go to see how much overhead is being added to these > codepaths?
The IMA patch(5/5) instantiates the inode_alloc_integrity hook. .inode_alloc_integrity = ima_inode_alloc_integrity,
> > mapping->a_ops = &empty_aops; > > mapping->host = inode; > > mapping->flags = 0; > > @@ -190,6 +199,7 @@ void destroy_inode(struct inode *inode) > > { > > BUG_ON(inode_has_buffers(inode)); > > security_inode_free(inode); > > + integrity_inode_free(inode); > > if (inode->i_sb->s_op->destroy_inode) > > inode->i_sb->s_op->destroy_inode(inode); > > else > > > > ... > > > > --- linux-2.6.26-rc3-git2.orig/include/linux/fs.h > > +++ linux-2.6.26-rc3-git2/include/linux/fs.h > > @@ -653,6 +653,9 @@ struct inode { > > #ifdef CONFIG_SECURITY > > void *i_security; > > #endif > > +#ifdef CONFIG_INTEGRITY > > + void *i_integrity; > > +#endif > > Does this _have_ to be a void*? Something typesafe would be far > preferable.
Different integrity providers will define it differently, using their specific data structure.
> > void *i_private; /* fs or device private pointer */ > > }; > > > > ... > > > > @@ -521,6 +528,7 @@ extern int audit_signals; > > #define audit_get_loginuid(t) (-1) > > #define audit_get_sessionid(t) (-1) > > #define audit_log_task_context(b) do { ; } while (0) > > +#define audit_log_inode_context(b, a) do { ; } while (0) > > static inline C functions are preferable. > > The ";" inside the {} is unneeded.
Ok
> > #define audit_ipc_obj(i) ({ 0; }) > > #define audit_ipc_set_perm(q,u,g,m) ({ 0; }) > > #define audit_bprm(p) ({ 0; }) > > Index: linux-2.6.26-rc3-git2/security/integrity/integrity_audit.c > > =================================================================== > > --- /dev/null > > +++ linux-2.6.26-rc3-git2/security/integrity/integrity_audit.c > > @@ -0,0 +1,73 @@ > > +/* > > + * Copyright (C) 2008 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. > > + * > > + * File: integrity_audit.c > > + * Audit calls for the integrity subsystem > > + */ > > + > > +#include <linux/audit.h> > > +#include <linux/fs.h> > > +#include <linux/integrity.h> > > + > > +#ifdef CONFIG_INTEGRITY_AUDIT > > +static int integrity_audit = 1; > > + > > +static int __init integrity_audit_setup(char *str) > > +{ > > + char *op; > > + > > + integrity_audit = simple_strtol(str, NULL, 0); > > This will treat "42foo" as valid input. strict_strtoul() fixes that.
Thank you for pointing this out.
> > + op = integrity_audit ? "integrity_audit_enabled" : > > + "integrity_audit_not_enabled"; > > + integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL, NULL, op, 0); > > + return 1; > > +} > > + > > +__setup("integrity_audit=", integrity_audit_setup); > > +#else > > +static int integrity_audit = 1; > > This could be outside the ifdef. If it is correct?
Yes, will fix it.
> > +#endif > > + > > +void integrity_audit_msg(int audit_msgno, struct inode *inode, > > + const unsigned char *fname, char *op, > > + char *cause, int result) > > +{ > > + struct audit_buffer *ab; > > + if (!integrity_audit && result == 1) > > + return; > > A newline between end-of-declarations and start-of-code is conventional.
Of course, don't know how I missed it.
> > + ab = audit_log_start(current->audit_context, GFP_ATOMIC, audit_msgno); > > + audit_log_format(ab, "integrity: pid=%d uid=%u auid=%u", > > + current->pid, current->uid, > > + audit_get_loginuid(current)); > > + audit_log_task_context(ab); > > + switch (audit_msgno) { > > + case AUDIT_INTEGRITY_DATA: > > + case AUDIT_INTEGRITY_METADATA: > > + case AUDIT_INTEGRITY_PCR: > > + audit_log_format(ab, " op=%s cause=%s", op, cause); > > + break; > > + case AUDIT_INTEGRITY_HASH: > > + audit_log_format(ab, " op=%s hash=%s", op, cause); > > + break; > > + case AUDIT_INTEGRITY_STATUS: > > + default: > > + audit_log_format(ab, " op=%s", op); > > + } > > + audit_log_format(ab, " comm="); > > + audit_log_untrustedstring(ab, current->comm); > > + if (fname) { > > + audit_log_format(ab, " name="); > > + audit_log_untrustedstring(ab, fname); > > + } > > + if (inode) > > + audit_log_format(ab, " dev=%s ino=%lu", > > + inode->i_sb->s_id, inode->i_ino); > > + audit_log_format(ab, " res=%d", result); > > + audit_log_end(ab); > > +} > > > > ... > > > > +static struct integrity_measure_rule_entry default_rules[] = { > > + {{NULL, NULL}, NULL, NULL, FILE_MMAP, MAY_EXEC}, > > + {{NULL, NULL}, NULL, NULL, BPRM_CHECK, MAY_EXEC}, > > + {{NULL, NULL}, NULL, NULL, INODE_PERMISSION, MAY_READ}, > > +}; > > Can we use the > > .field = value, > > format here please? That will permit the omission of all the NULLs.
np
> > +static struct list_head measure_default_rules; > > +static struct list_head measure_policy_rules; > > +static struct list_head *integrity_measure; > > + > > +static DEFINE_MUTEX(integrity_measure_mutex); > > + > > +/** > > + * integrity_measure_rules - determine whether an inode matches the given rule. > > + * @rule - a pointer to a rule > > + * @inode - a pointer to an inode > > + * @func - LIM hook identifier > > + * @mask - requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) > > + * > > + * Returns 1 on rule match, 0 on failure. > > + */ > > What a strange name. integrity_match_rules()
The match decision, here, is deciding whether or not to measure a file.
The functions below are called: integrity_measure_policy_init(), integrity_measure_policy_complete(), integrity_measure_policy_add(). To parallel the rest of the names, then the function here would be integrity_measure_rules_match(). Or I could remove 'measure' from all of the function names, as you're suggesting.
choice 2: integrity_policy_init, integrity_policy_add, integrity_policy_complete/end, integrity_policy_match, integrity_rules_match
choice 3: integrity_init_policy, integrity_add_policy, integrity_complete/end_policy, integrity_match_policy, integrity_match_rules
> Could return a bool type, if you like that sort of thing. > > > +static int integrity_measure_rules(struct integrity_measure_rule_entry *rule, > > + struct inode *inode, enum lim_hooks func, > > + int mask) > > +{ > > + int result = 1; > > + > > + if (result && (rule->func != 0)) { > > The test of the known-to-be-non-zero `result' is a bit weird, btu I > guess it makes sense in context, and the compiler should elide it OK. > > > + if (rule->func != func) > > + result = 0; > > + } > > + if (result && (rule->mask != 0)) { > > + if (rule->mask != mask) > > + result = 0; > > + } > > + if (result && rule->lsm_subj_rule) { > > + struct task_struct *tsk = current; > > + u32 sid; > > + > > + security_task_getsecid(tsk, &sid); > > + result = security_filter_rule_match(sid, AUDIT_SUBJ_USER, > > + AUDIT_EQUAL, > > + rule->lsm_subj_rule, NULL); > > + } > > + if (result && rule->lsm_obj_rule) { > > + u32 osid; > > + > > + security_inode_getsecid(inode, &osid); > > + result = security_filter_rule_match(osid, AUDIT_OBJ_USER, > > + AUDIT_EQUAL, > > + rule->lsm_obj_rule, NULL); > > + } > > + return result; > > +} > > However the shole function could be simplified and sped up (depending > on how smart the compiler is) via: > > if (rule->func && rule->func != func) > return 0; > if (rule->mask && rule->mask != mask) > return 0; > ... > return 1; > } > > or similar.
yes, of course. thanks!
> > +/** > > + * integrity_measure_policy - base measure decision on: subj, obj, LIM hook, > > + * and mask > > + * @inode - pointer to an inode > > + * @func - LIM hook identifier > > + * @mask - requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) > > + * > > + * Returns 1 on rule match, 0 on failure. > > + */ > > +int integrity_measure_policy(struct inode *inode, enum lim_hooks func, int mask) > > +{ > > + struct integrity_measure_rule_entry *entry; > > + int rc = 0; > > + > > + rcu_read_lock(); > > + list_for_each_entry_rcu(entry, integrity_measure, list) { > > + rc = integrity_measure_rules(entry, inode, func, mask); > > + if (rc) { > > + rcu_read_unlock(); > > + return rc; > > + } > > + } > > + rcu_read_unlock(); > > + return rc; > > +} > > "measure"? Or "match"?
discussion above.
> > +/** > > + * integrity_measure_policy_init - initialize the default and policy rules. > > + */ > > +void integrity_measure_policy_init(void) > > +{ > > + int i; > > + > > + INIT_LIST_HEAD(&measure_default_rules); > > + for (i = 0; i < ARRAY_SIZE(default_rules); i++) > > + list_add(&default_rules[i].list, &measure_default_rules); > > + integrity_measure = &measure_default_rules; > > + mutex_init(&integrity_measure_mutex); > > The mutex_init() is unneeded.
Ok
> > + INIT_LIST_HEAD(&measure_policy_rules); > > +} > > + > > +/** > > + * integrity_measure_policy_complete - wait to replace default_rules with > > + * a complete policy ruleset. > > + */ > > +void integrity_measure_policy_complete(void) > > +{ > > + char *op = "policy_update"; > > + char *cause = "already exists"; > > + int result = 1; > > + > > + if (integrity_measure == &measure_default_rules) { > > + integrity_measure = &measure_policy_rules; > > + cause = "complete"; > > + result = 0; > > + } > > + integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, > > + NULL, op, cause, result); > > +} > > Does it actually "wait"?
No, it doesn't wait. The function is called when the file closes, meaning that all of the rules have been added. Refer to ima_release_policy() in the IMA patch (5/5). Only after this function is called, are the new set of rules used.
> The name again doesn't seem to match the behaviour. "foo_complete" > would mean "tell listeners that foo has completed". What you have here > is a "foo_wait".
Juxtaposed to the function below called integrity_measure_policy_add(), how about integrity_measure_policy_end()?
> > +/** > > + * integrity_measure_rule_add - add integrity measure rules > > + * @subj - pointer to an LSM subject value > > + * @obj - pointer to an LSM object value > > + * @func - LIM hook identifier > > + * @mask - requested action (MAY_READ | MAY_WRITE | MAY_APPEND | MAY_EXEC) > > + * > > + * Returns 0 on success, an error code on failure. > > + */ > > +int integrity_measure_rule_add(char *subj, char *obj, char *func, char *mask) > > +{ > > + struct integrity_measure_rule_entry *entry; > > + int result = 0; > > + > > + /* Prevent installed policy from changing */ > > + if (integrity_measure != &measure_default_rules) { > > + integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, > > + NULL, "policy_update", "already exists", 1); > > + return -EACCES; > > + } > > + > > + entry = kzalloc(sizeof(*entry), GFP_ATOMIC); > > GFP_ATOMIC is unreliable. GFP_KERNEL is much much preferable, and I > suspect that it can be used here?
Probably. Will look into it.
> > + INIT_LIST_HEAD(&entry->list); > > + if (!result && subj) > > + result = security_filter_rule_init(AUDIT_SUBJ_USER, AUDIT_EQUAL, > > + subj, &entry->lsm_subj_rule); > > + if (!result && obj) > > + result = security_filter_rule_init(AUDIT_OBJ_USER, AUDIT_EQUAL, > > + obj, &entry->lsm_obj_rule); > > + if (!result && func) { > > + if (strcmp(func, "INODE_PERMISSION") == 0) > > + entry->func = INODE_PERMISSION; > > + else if (strcmp(func, "FILE_MMAP") == 0) > > + entry->func = FILE_MMAP; > > + else if (strcmp(func, "BPRM_CHECK") == 0) > > + entry->func = BPRM_CHECK; > > + else > > + result = -EINVAL; > > + } > > + if (!result && mask) { > > + if (strcmp(mask, "MAY_EXEC") == 0) > > + entry->mask = MAY_EXEC; > > + else if (strcmp(mask, "MAY_WRITE") == 0) > > + entry->mask = MAY_WRITE; > > + else if (strcmp(mask, "MAY_READ") == 0) > > + entry->mask = MAY_READ; > > + else if (strcmp(mask, "MAY_APPEND") == 0) > > + entry->mask = MAY_APPEND; > > + else > > + result = -EINVAL; > > + } > > + if (!result) { > > + mutex_lock(&integrity_measure_mutex); > > + list_add_tail(&entry->list, &measure_policy_rules); > > + mutex_unlock(&integrity_measure_mutex); > > + } > > + return result; > > +} > > > > ...
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