| Message ID | 1696457386-3010-4-git-send-email-wufan@linux.microsoft.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Delegated to: | Paul Moore |
| Headers | show |
| Series | Integrity Policy Enforcement LSM (IPE) | expand |
On Oct 4, 2023 Fan Wu <wufan@linux.microsoft.com> wrote: > > IPE must have a centralized function to evaluate incoming callers > against IPE's policy. This iteration of the policy for against the rules > for that specific caller is known as the evaluation loop. > > Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> > Signed-off-by: Fan Wu <wufan@linux.microsoft.com> > --- > v2: > + Split evaluation loop, access control hooks, and evaluation loop from policy parser and userspace interface to pass mailing list character limit > > v3: > + Move ipe_load_properties to patch 04. > + Remove useless 0-initializations Prefix extern variables with ipe_ > + Remove kernel module parameters, as these are exposed through sysctls. > + Add more prose to the IPE base config option help text. > + Use GFP_KERNEL for audit_log_start. > + Remove unnecessary caching system. > + Remove comments from headers > + Use rcu_access_pointer for rcu-pointer null check > + Remove usage of reqprot; use prot only. > +Move policy load and activation audit event to 03/12 > > v4: > + Remove sysctls in favor of securityfs nodes > + Re-add kernel module parameters, as these are now exposed through securityfs. > + Refactor property audit loop to a separate function. > > v5: > + fix minor grammatical errors > + do not group rule by curly-brace in audit record, > + reconstruct the exact rule. > > v6: > + No changes > > v7: > + Further split lsm creation into a separate commit from the evaluation loop and audit system, for easier review. > + Propagating changes to support the new ipe_context structure in the evaluation loop. > > v8: > + Remove ipe_hook enumeration; hooks can be correlated via syscall record. > > v9: > + Remove ipe_context related code and simplify the evaluation loop. > > v10: > + Split eval part and boot_verified part > > v11: > + Fix code style issues > --- > security/ipe/Makefile | 1 + > security/ipe/eval.c | 96 +++++++++++++++++++++++++++++++++++++++++++ > security/ipe/eval.h | 24 +++++++++++ > 3 files changed, 121 insertions(+) > create mode 100644 security/ipe/eval.c > create mode 100644 security/ipe/eval.h ... > diff --git a/security/ipe/eval.c b/security/ipe/eval.c > new file mode 100644 > index 000000000000..5533c359bbeb > --- /dev/null > +++ b/security/ipe/eval.c > @@ -0,0 +1,96 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (C) Microsoft Corporation. All rights reserved. > + */ > + > +#include <linux/fs.h> > +#include <linux/types.h> > +#include <linux/slab.h> > +#include <linux/file.h> > +#include <linux/sched.h> > +#include <linux/rcupdate.h> > + > +#include "ipe.h" > +#include "eval.h" > +#include "policy.h" > + > +struct ipe_policy __rcu *ipe_active_policy; > + > +/** > + * evaluate_property - Analyze @ctx against a property. > + * @ctx: Supplies a pointer to the context to be evaluated. > + * @p: Supplies a pointer to the property to be evaluated. > + * > + * Return: > + * * true - The current @ctx match the @p > + * * false - The current @ctx doesn't match the @p > + */ > +static bool evaluate_property(const struct ipe_eval_ctx *const ctx, > + struct ipe_prop *p) > +{ > + return false; > +} > + > +/** > + * ipe_evaluate_event - Analyze @ctx against the current active policy. > + * @ctx: Supplies a pointer to the context to be evaluated. > + * > + * This is the loop where all policy evaluation happens against IPE policy. > + * > + * Return: > + * * 0 - OK > + * * -EACCES - @ctx did not pass evaluation. > + * * !0 - Error > + */ > +int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) > +{ > + bool match = false; > + enum ipe_action_type action; > + struct ipe_policy *pol = NULL; > + const struct ipe_rule *rule = NULL; > + const struct ipe_op_table *rules = NULL; > + struct ipe_prop *prop = NULL; > + > + rcu_read_lock(); > + > + pol = rcu_dereference(ipe_active_policy); > + if (!pol) { > + rcu_read_unlock(); > + return 0; > + } > + > + if (ctx->op == IPE_OP_INVALID) { > + rcu_read_unlock(); > + if (pol->parsed->global_default_action == IPE_ACTION_DENY) > + return -EACCES; Assuming that the RCU lock protects @pol, shouldn't it be held until after the global_default_action comparison? > + return 0; > + } > + > + rules = &pol->parsed->rules[ctx->op]; > + > + list_for_each_entry(rule, &rules->rules, next) { > + match = true; > + > + list_for_each_entry(prop, &rule->props, next) { > + match = match && evaluate_property(ctx, prop); The @match variable will always be true on the right side above, or am I missing something? > + if (!match) > + break; > + } > + > + if (match) > + break; > + } > + > + if (match) > + action = rule->action; > + else if (rules->default_action != IPE_ACTION_INVALID) > + action = rules->default_action; > + else > + action = pol->parsed->global_default_action; > + > + rcu_read_unlock(); > + if (action == IPE_ACTION_DENY) > + return -EACCES; > + > + return 0; > +} -- paul-moore.com
On 10/23/2023 8:52 PM, Paul Moore wrote: > On Oct 4, 2023 Fan Wu <wufan@linux.microsoft.com> wrote: >> >> IPE must have a centralized function to evaluate incoming callers >> against IPE's policy. This iteration of the policy for against the rules >> for that specific caller is known as the evaluation loop. >> >> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com> >> Signed-off-by: Fan Wu <wufan@linux.microsoft.com> ... >> --- >> security/ipe/Makefile | 1 + >> security/ipe/eval.c | 96 +++++++++++++++++++++++++++++++++++++++++++ >> security/ipe/eval.h | 24 +++++++++++ >> 3 files changed, 121 insertions(+) >> create mode 100644 security/ipe/eval.c >> create mode 100644 security/ipe/eval.h > > ... > >> diff --git a/security/ipe/eval.c b/security/ipe/eval.c >> new file mode 100644 >> index 000000000000..5533c359bbeb >> --- /dev/null >> +++ b/security/ipe/eval.c >> @@ -0,0 +1,96 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +/* >> + * Copyright (C) Microsoft Corporation. All rights reserved. >> + */ >> + >> +#include <linux/fs.h> >> +#include <linux/types.h> >> +#include <linux/slab.h> >> +#include <linux/file.h> >> +#include <linux/sched.h> >> +#include <linux/rcupdate.h> >> + >> +#include "ipe.h" >> +#include "eval.h" >> +#include "policy.h" >> + >> +struct ipe_policy __rcu *ipe_active_policy; >> + >> +/** >> + * evaluate_property - Analyze @ctx against a property. >> + * @ctx: Supplies a pointer to the context to be evaluated. >> + * @p: Supplies a pointer to the property to be evaluated. >> + * >> + * Return: >> + * * true - The current @ctx match the @p >> + * * false - The current @ctx doesn't match the @p >> + */ >> +static bool evaluate_property(const struct ipe_eval_ctx *const ctx, >> + struct ipe_prop *p) >> +{ >> + return false; >> +} >> + >> +/** >> + * ipe_evaluate_event - Analyze @ctx against the current active policy. >> + * @ctx: Supplies a pointer to the context to be evaluated. >> + * >> + * This is the loop where all policy evaluation happens against IPE policy. >> + * >> + * Return: >> + * * 0 - OK >> + * * -EACCES - @ctx did not pass evaluation. >> + * * !0 - Error >> + */ >> +int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) >> +{ >> + bool match = false; >> + enum ipe_action_type action; >> + struct ipe_policy *pol = NULL; >> + const struct ipe_rule *rule = NULL; >> + const struct ipe_op_table *rules = NULL; >> + struct ipe_prop *prop = NULL; >> + >> + rcu_read_lock(); >> + >> + pol = rcu_dereference(ipe_active_policy); >> + if (!pol) { >> + rcu_read_unlock(); >> + return 0; >> + } >> + >> + if (ctx->op == IPE_OP_INVALID) { >> + rcu_read_unlock(); >> + if (pol->parsed->global_default_action == IPE_ACTION_DENY) >> + return -EACCES; > > Assuming that the RCU lock protects @pol, shouldn't it be held until > after the global_default_action comparison? > Yes for this part the unlock should be moved after the comparison. Thanks for spotting this. >> + return 0; >> + } >> + >> + rules = &pol->parsed->rules[ctx->op]; >> + >> + list_for_each_entry(rule, &rules->rules, next) { >> + match = true; >> + >> + list_for_each_entry(prop, &rule->props, next) { >> + match = match && evaluate_property(ctx, prop); > > The @match variable will always be true on the right side above, or am > I missing something? > Yes the "match &&" are completely unnecessary. I will remove them. -Fan >> + if (!match) >> + break; >> + } >> + >> + if (match) >> + break; >> + } >> + >> + if (match) >> + action = rule->action; >> + else if (rules->default_action != IPE_ACTION_INVALID) >> + action = rules->default_action; >> + else >> + action = pol->parsed->global_default_action; >> + >> + rcu_read_unlock(); >> + if (action == IPE_ACTION_DENY) >> + return -EACCES; >> + >> + return 0; >> +} > > -- > paul-moore.com
diff --git a/security/ipe/Makefile b/security/ipe/Makefile index c09aec4904f2..57fe922cf1fc 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -6,6 +6,7 @@ # obj-$(CONFIG_SECURITY_IPE) += \ + eval.o \ ipe.o \ policy.o \ policy_parser.o \ diff --git a/security/ipe/eval.c b/security/ipe/eval.c new file mode 100644 index 000000000000..5533c359bbeb --- /dev/null +++ b/security/ipe/eval.c @@ -0,0 +1,96 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include <linux/fs.h> +#include <linux/types.h> +#include <linux/slab.h> +#include <linux/file.h> +#include <linux/sched.h> +#include <linux/rcupdate.h> + +#include "ipe.h" +#include "eval.h" +#include "policy.h" + +struct ipe_policy __rcu *ipe_active_policy; + +/** + * evaluate_property - Analyze @ctx against a property. + * @ctx: Supplies a pointer to the context to be evaluated. + * @p: Supplies a pointer to the property to be evaluated. + * + * Return: + * * true - The current @ctx match the @p + * * false - The current @ctx doesn't match the @p + */ +static bool evaluate_property(const struct ipe_eval_ctx *const ctx, + struct ipe_prop *p) +{ + return false; +} + +/** + * ipe_evaluate_event - Analyze @ctx against the current active policy. + * @ctx: Supplies a pointer to the context to be evaluated. + * + * This is the loop where all policy evaluation happens against IPE policy. + * + * Return: + * * 0 - OK + * * -EACCES - @ctx did not pass evaluation. + * * !0 - Error + */ +int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx) +{ + bool match = false; + enum ipe_action_type action; + struct ipe_policy *pol = NULL; + const struct ipe_rule *rule = NULL; + const struct ipe_op_table *rules = NULL; + struct ipe_prop *prop = NULL; + + rcu_read_lock(); + + pol = rcu_dereference(ipe_active_policy); + if (!pol) { + rcu_read_unlock(); + return 0; + } + + if (ctx->op == IPE_OP_INVALID) { + rcu_read_unlock(); + if (pol->parsed->global_default_action == IPE_ACTION_DENY) + return -EACCES; + return 0; + } + + rules = &pol->parsed->rules[ctx->op]; + + list_for_each_entry(rule, &rules->rules, next) { + match = true; + + list_for_each_entry(prop, &rule->props, next) { + match = match && evaluate_property(ctx, prop); + if (!match) + break; + } + + if (match) + break; + } + + if (match) + action = rule->action; + else if (rules->default_action != IPE_ACTION_INVALID) + action = rules->default_action; + else + action = pol->parsed->global_default_action; + + rcu_read_unlock(); + if (action == IPE_ACTION_DENY) + return -EACCES; + + return 0; +} diff --git a/security/ipe/eval.h b/security/ipe/eval.h new file mode 100644 index 000000000000..6b434515968f --- /dev/null +++ b/security/ipe/eval.h @@ -0,0 +1,24 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef _IPE_EVAL_H +#define _IPE_EVAL_H + +#include <linux/file.h> +#include <linux/types.h> + +#include "policy.h" + +extern struct ipe_policy __rcu *ipe_active_policy; + +struct ipe_eval_ctx { + enum ipe_op_type op; + + const struct file *file; +}; + +int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx); + +#endif /* _IPE_EVAL_H */