[RFC,v7,07/16] ipe: add auditing support

Message ID	1634151995-16266-8-git-send-email-deven.desai@linux.microsoft.com (mailing list archive)
State	Not Applicable
Headers	show Return-Path: <linux-fscrypt-owner@kernel.org> From: deven.desai@linux.microsoft.com To: corbet@lwn.net, axboe@kernel.dk, agk@redhat.com, snitzer@redhat.com, ebiggers@kernel.org, tytso@mit.edu, paul@paul-moore.com, eparis@redhat.com, jmorris@namei.org, serge@hallyn.com Cc: jannh@google.com, dm-devel@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-fscrypt@vger.kernel.org, linux-audit@redhat.com, linux-security-module@vger.kernel.org Subject: [RFC PATCH v7 07/16] ipe: add auditing support Date: Wed, 13 Oct 2021 12:06:26 -0700 Message-Id: <1634151995-16266-8-git-send-email-deven.desai@linux.microsoft.com> In-Reply-To: <1634151995-16266-1-git-send-email-deven.desai@linux.microsoft.com> References: <1634151995-16266-1-git-send-email-deven.desai@linux.microsoft.com> Precedence: bulk
Series	Integrity Policy Enforcement (IPE) \| expand [RFC,v7,00/16] Integrity Policy Enforcement (IPE) [RFC,v7,01/16] security: add ipe lsm & initial context creation [RFC,v7,02/16] ipe: add policy parser [RFC,v7,03/16] ipe: add evaluation loop [RFC,v7,04/16] ipe: add userspace interface [RFC,v7,05/16] ipe: add LSM hooks on execution and kernel read [RFC,v7,06/16] uapi\|audit: add trust audit message definitions [RFC,v7,07/16] ipe: add auditing support [RFC,v7,08/16] ipe: add permissive toggle [RFC,v7,09/16] ipe: introduce 'boot_verified' as a trust provider [RFC,v7,10/16] fs\|dm-verity: add block_dev LSM blob and submit dm-verity data [RFC,v7,11/16] ipe: add support for dm-verity as a trust provider [RFC,v7,12/16] fsverity\|security: add security hooks to fsverity digest and signature [RFC,v7,13/16] ipe: enable support for fs-verity as a trust provider [RFC,v7,14/16] scripts: add boot policy generation program [RFC,v7,15/16] ipe: kunit tests [RFC,v7,16/16] documentation: add ipe documentation

diff --git a/security/ipe/Kconfig b/security/ipe/Kconfig index c4503083e92d..ef556b66e674 100644 --- a/security/ipe/Kconfig +++ b/security/ipe/Kconfig @@ -17,3 +17,55 @@ menuconfig SECURITY_IPE requirements on the fly. If unsure, answer N. + +if SECURITY_IPE + +choice + prompt "Hash algorithm used in auditing policies" + default IPE_AUDIT_HASH_SHA1 + depends on AUDIT + help + Specify the hash algorithm used when auditing policies. + The hash is used to uniquely identify a policy from other + policies on the system. + + If unsure, leave default. + + config IPE_AUDIT_HASH_SHA1 + bool "sha1" + depends on CRYPTO_SHA1 + help + Use the SHA128 algorithm to hash policies + in the audit records. + + config IPE_AUDIT_HASH_SHA256 + bool "sha256" + depends on CRYPTO_SHA256 + help + Use the SHA256 algorithm to hash policies + in the audit records. + + config IPE_AUDIT_HASH_SHA384 + bool "sha384" + depends on CRYPTO_SHA512 + help + Use the SHA384 algorithm to hash policies + in the audit records + + config IPE_AUDIT_HASH_SHA512 + bool "sha512" + depends on CRYPTO_SHA512 + help + Use the SHA512 algorithm to hash policies + in the audit records +endchoice + +config IPE_AUDIT_HASH_ALG + string + depends on AUDIT + default "sha1" if IPE_AUDIT_HASH_SHA1 + default "sha256" if IPE_AUDIT_HASH_SHA256 + default "sha384" if IPE_AUDIT_HASH_SHA384 + default "sha512" if IPE_AUDIT_HASH_SHA512 + +endif diff --git a/security/ipe/Makefile b/security/ipe/Makefile index d5660a17364c..6d9ac818e8c6 100644 --- a/security/ipe/Makefile +++ b/security/ipe/Makefile @@ -18,3 +18,5 @@ obj-$(CONFIG_SECURITY_IPE) += \ parsers.o \ policy.o \ policyfs.o \ + +obj-$(CONFIG_AUDIT) += audit.o diff --git a/security/ipe/audit.c b/security/ipe/audit.c new file mode 100644 index 000000000000..5f6c0a52b0cb --- /dev/null +++ b/security/ipe/audit.c @@ -0,0 +1,264 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#include "ipe.h" +#include "eval.h" +#include "hooks.h" +#include "policy.h" +#include "audit.h" +#include "modules/ipe_module.h" + +#include <linux/slab.h> +#include <linux/audit.h> +#include <linux/types.h> +#include <crypto/hash.h> + +#define NULLSTR(x) ((x) == NULL ? "NULL" : "!NULL") +#define ACTSTR(x) ((x) == ipe_action_allow ? "ALLOW" : "DENY") + +#define POLICY_LOAD_FMT "IPE policy_name=%s policy_version=%hu.%hu.%hu "\ + CONFIG_IPE_AUDIT_HASH_ALG "=" + +static const char *const audit_hook_names[ipe_hook_max] = { + "EXECVE", + "MMAP", + "MPROTECT", + "KERNEL_READ", + "KERNEL_LOAD", +}; + +static const char *const audit_op_names[ipe_operation_max] = { + "EXECUTE", + "FIRMWARE", + "KMODULE", + "KEXEC_IMAGE", + "KEXEC_INITRAMFS", + "IMA_X509_CERT", + "IMA_POLICY", +}; + +/** + * audit_pathname: retrieve the absoute path to a file being evaluated. + * @f: File to retrieve the absolute path for. + * + * This function walks past symlinks and mounts. + * + * Return: + * !IS_ERR - OK + */ +static char *audit_pathname(const struct file *f) +{ + int rc = 0; + char *pos = NULL; + char *pathbuf = NULL; + char *temp_path = NULL; + + if (IS_ERR_OR_NULL(f)) + return ERR_PTR(-ENOENT); + + pathbuf = __getname(); + if (!pathbuf) + return ERR_PTR(-ENOMEM); + + pos = d_absolute_path(&f->f_path, pathbuf, PATH_MAX); + if (IS_ERR(pos)) { + rc = PTR_ERR(pos); + goto err; + } + + temp_path = __getname(); + if (!temp_path) { + rc = -ENOMEM; + goto err; + } + + strscpy(temp_path, pos, PATH_MAX); + __putname(pathbuf); + + return temp_path; +err: + __putname(pathbuf); + return ERR_PTR(rc); +} + +/** + * audit_eval_ctx: audit an evaluation context structure. + * @ab: Supplies a poniter to the audit_buffer to append to. + * @ctx: Supplies a pointer to the evaluation context to audit + * @enforce: Supplies a boolean representing the enforcement state + */ +static void audit_eval_ctx(struct audit_buffer *ab, + const struct ipe_eval_ctx *const ctx, bool enforce) +{ + char *abspath = NULL; + + audit_log_format(ab, "ctx_pid=%d ", task_tgid_nr(current)); + audit_log_format(ab, "ctx_op=%s ", audit_op_names[ctx->op]); + audit_log_format(ab, "ctx_hook=%s ", audit_hook_names[ctx->hook]); + audit_log_format(ab, "ctx_ns_enforce=%d ", enforce); + audit_log_format(ab, "ctx_comm="); + audit_log_n_untrustedstring(ab, current->comm, ARRAY_SIZE(current->comm)); + audit_log_format(ab, " "); + + /* best effort */ + if (ctx->file) { + abspath = audit_pathname(ctx->file); + if (!IS_ERR(abspath)) { + audit_log_format(ab, "ctx_pathname="); + audit_log_n_untrustedstring(ab, abspath, PATH_MAX); + __putname(abspath); + } + + audit_log_format(ab, " ctx_ino=%ld ctx_dev=%s", + ctx->file->f_inode->i_ino, + ctx->file->f_inode->i_sb->s_id); + } +} + +/** + * audit_rule: audit an IPE policy rule approximation. + * @ab: Supplies a poniter to the audit_buffer to append to. + * @r: Supplies a pointer to the ipe_rule to approximate a string form for. + * + * This is an approximation because aliases like "KERNEL_READ" will be + * emitted in their expanded form. + */ +static void audit_rule(struct audit_buffer *ab, const struct ipe_rule *r) +{ + const struct ipe_policy_mod *ptr; + + audit_log_format(ab, "rule=\"op=%s ", audit_op_names[r->op]); + + list_for_each_entry(ptr, &r->modules, next) { + audit_log_format(ab, "%s=", ptr->mod->name); + + ptr->mod->audit(ab, ptr->mod_value); + + audit_log_format(ab, " "); + } + + audit_log_format(ab, "action=%s\"", ACTSTR(r->action)); +} + +/** + * ipe_audit_match: audit a match for IPE policy. + * @ctx: Supplies a poniter to the evaluation context that was used in the + * evaluation. + * @match_type: Supplies the scope of the match: rule, operation default, + * global default. + * @act: Supplies the IPE's evaluation decision, deny or allow. + * @r: Supplies a pointer to the rule that was matched, if possible. + * @enforce: Supplies the enforcement/permissive state at the point + * the enforcement decision was made. + */ +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce) +{ + struct audit_buffer *ab; + bool success_audit; + + rcu_read_lock(); + success_audit = READ_ONCE(ctx->ci_ctx->success_audit); + rcu_read_unlock(); + + if (act != ipe_action_deny && !success_audit) + return; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_RESULT); + if (!ab) + return; + + audit_log_format(ab, "IPE "); + audit_eval_ctx(ab, ctx, enforce); + audit_log_format(ab, " "); + + if (match_type == ipe_match_rule) + audit_rule(ab, r); + else if (match_type == ipe_match_table) + audit_log_format(ab, "rule=\"DEFAULT op=%s action=%s\"", + audit_op_names[ctx->op], ACTSTR(act)); + else + audit_log_format(ab, "rule=\"DEFAULT action=%s\"", + ACTSTR(act)); + + audit_log_end(ab); +} + +/** + * audit_policy: Audit a policy's name, version and thumprint to @ab + * @ab: Supplies a pointer to the audit buffer to append to. + * @p: Supplies a pointer to the policy to audit + */ +static void audit_policy(struct audit_buffer *ab, + const struct ipe_policy *const p) +{ + u8 *digest = NULL; + struct crypto_shash *tfm; + SHASH_DESC_ON_STACK(desc, tfm); + + tfm = crypto_alloc_shash(CONFIG_IPE_AUDIT_HASH_ALG, 0, 0); + if (IS_ERR(tfm)) + return; + + desc->tfm = tfm; + + digest = kzalloc(crypto_shash_digestsize(tfm), GFP_KERNEL); + if (!digest) + goto out; + + if (crypto_shash_init(desc)) + goto out; + + if (crypto_shash_update(desc, p->pkcs7, p->pkcs7len)) + goto out; + + if (crypto_shash_final(desc, digest)) + goto out; + + audit_log_format(ab, POLICY_LOAD_FMT, p->parsed->name, + p->parsed->version.major, p->parsed->version.minor, + p->parsed->version.rev); + audit_log_n_hex(ab, digest, crypto_shash_digestsize(tfm)); + +out: + kfree(digest); + crypto_free_shash(tfm); +} + +/** + * ipe_audit_policy_activation: Audit a policy being made the active policy. + * @p: Supplies a pointer to the policy to audit + */ +void ipe_audit_policy_activation(const struct ipe_policy *const p) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_POLICY_ACTIVATE); + if (!ab) + return; + + audit_policy(ab, p); + + audit_log_end(ab); +} + +/** + * ipe_audit_policy_load: Audit a policy being loaded into the kernel. + * @p: Supplies a pointer to the policy to audit + */ +void ipe_audit_policy_load(const struct ipe_policy *const p) +{ + struct audit_buffer *ab; + + ab = audit_log_start(audit_context(), GFP_KERNEL, AUDIT_TRUST_POLICY_LOAD); + if (!ab) + return; + + audit_policy(ab, p); + + audit_log_end(ab); +} diff --git a/security/ipe/audit.h b/security/ipe/audit.h new file mode 100644 index 000000000000..6b6880f6e8e7 --- /dev/null +++ b/security/ipe/audit.h @@ -0,0 +1,36 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) Microsoft Corporation. All rights reserved. + */ + +#ifndef IPE_AUDIT_H +#define IPE_AUDIT_H + +#include "ipe.h" +#include "eval.h" + +#ifdef CONFIG_AUDIT +void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce); +void ipe_audit_policy_load(const struct ipe_policy *const p); +void ipe_audit_policy_activation(const struct ipe_policy *const p); +#else +static inline void ipe_audit_match(const struct ipe_eval_ctx *const ctx, + enum ipe_match match_type, + enum ipe_action act, const struct ipe_rule *const r, + bool enforce) +{ +} + +static inline void ipe_audit_policy_load(const struct ipe_policy *const p) +{ +} + +static inline void ipe_audit_policy_activation(const struct ipe_policy *const p) +{ +} +#endif /* CONFIG_AUDIT */ + +#endif /* IPE_AUDIT_H */ diff --git a/security/ipe/ctx.c b/security/ipe/ctx.c index 664c671a4f9c..77475aedbfe9 100644 --- a/security/ipe/ctx.c +++ b/security/ipe/ctx.c @@ -6,12 +6,16 @@ #include "ipe.h" #include "ctx.h" #include "policy.h" +#include "audit.h" #include <linux/slab.h> #include <linux/types.h> #include <linux/parser.h> #include <linux/refcount.h> #include <linux/spinlock.h> +#include <linux/moduleparam.h> + +static bool success_audit; /** * ver_to_u64: convert an internal ipe_policy_version to a u64 @@ -265,6 +269,7 @@ int ipe_set_active_pol(const struct ipe_policy *p) spin_unlock(&ctx->lock); synchronize_rcu(); + ipe_audit_policy_activation(p); out: ipe_put_policy(ap); ipe_put_ctx(ctx); @@ -330,6 +335,10 @@ int __init ipe_init_ctx(void) goto err; } + spin_lock(&lns->lock); + WRITE_ONCE(lns->success_audit, success_audit); + spin_unlock(&lns->lock); + rcu_assign_pointer(*ipe_tsk_ctx(current), lns); return 0; @@ -337,3 +346,12 @@ int __init ipe_init_ctx(void) ipe_put_ctx(lns); return rc; } + +/* Set the right module name */ +#ifdef KBUILD_MODNAME +#undef KBUILD_MODNAME +#define KBUILD_MODNAME "ipe" +#endif + +module_param(success_audit, bool, 0400); +MODULE_PARM_DESC(success_audit, "Start IPE with success auditing enabled"); diff --git a/security/ipe/ctx.h b/security/ipe/ctx.h index fe11fb767788..31aea2fb9e49 100644 --- a/security/ipe/ctx.h +++ b/security/ipe/ctx.h @@ -15,6 +15,8 @@ struct ipe_context { struct ipe_policy __rcu *active_policy; + bool __rcu success_audit; + refcount_t refcount; /* Protects concurrent writers */ spinlock_t lock; diff --git a/security/ipe/eval.c b/security/ipe/eval.c index b732f76cfd05..dcb62179e4bf 100644 --- a/security/ipe/eval.c +++ b/security/ipe/eval.c @@ -9,6 +9,7 @@ #include "hooks.h" #include "policy.h" #include "modules/ipe_module.h" +#include "audit.h" #include <linux/slab.h> #include <linux/file.h> @@ -73,7 +74,9 @@ static int evaluate(const struct ipe_eval_ctx *const ctx) { int rc = 0; bool match = false; + bool enforcing = true; enum ipe_action action; + enum ipe_match match_type; struct ipe_policy *pol = NULL; const struct ipe_rule *rule = NULL; const struct ipe_policy_mod *module = NULL; @@ -97,12 +100,17 @@ static int evaluate(const struct ipe_eval_ctx *const ctx) if (match) { action = rule->action; + match_type = ipe_match_rule; } else if (rules->default_action != ipe_action_max) { action = rules->default_action; + match_type = ipe_match_table; } else { action = pol->parsed->global_default; + match_type = ipe_match_global; } + ipe_audit_match(ctx, match_type, action, rule, enforcing); + if (action == ipe_action_deny) rc = -EACCES; diff --git a/security/ipe/eval.h b/security/ipe/eval.h index db6da2998a20..8c08eed5af2b 100644 --- a/security/ipe/eval.h +++ b/security/ipe/eval.h @@ -20,6 +20,13 @@ struct ipe_eval_ctx { struct ipe_context *ci_ctx; }; +enum ipe_match { + ipe_match_rule = 0, + ipe_match_table, + ipe_match_global, + ipe_match_max +}; + int ipe_process_event(const struct file *file, enum ipe_operation op, enum ipe_hook hook); diff --git a/security/ipe/fs.c b/security/ipe/fs.c index 10ad23f8bf92..c202c0753755 100644 --- a/security/ipe/fs.c +++ b/security/ipe/fs.c @@ -5,6 +5,7 @@ #include "ipe.h" #include "fs.h" #include "policy.h" +#include "audit.h" #include <linux/dcache.h> #include <linux/security.h> @@ -12,6 +13,70 @@ static struct dentry *np __ro_after_init; static struct dentry *root __ro_after_init; static struct dentry *config __ro_after_init; +static struct dentry *success_audit __ro_after_init; + +/** + * setaudit: Write handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the write syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t setaudit(struct file *f, const char __user *data, + size_t len, loff_t *offset) +{ + int rc = 0; + bool value; + struct ipe_context *ctx; + + if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN)) + return -EPERM; + + rc = kstrtobool_from_user(data, len, &value); + if (rc) + return rc; + + ctx = ipe_current_ctx(); + + spin_lock(&ctx->lock); + WRITE_ONCE(ctx->success_audit, value); + spin_unlock(&ctx->lock); + synchronize_rcu(); + + ipe_put_ctx(ctx); + return len; +} + +/** + * getaudit: Read handler for the securityfs node, "ipe/success_audit" + * @f: Supplies a file structure representing the securityfs node. + * @data: Supplies a buffer passed to the read syscall + * @len: Supplies the length of @data + * @offset: unused. + * + * Return: + * >0 - Success, Length of buffer written + * <0 - Error + */ +static ssize_t getaudit(struct file *f, char __user *data, + size_t len, loff_t *offset) +{ + const char *result; + struct ipe_context *ctx; + + ctx = ipe_current_ctx(); + + rcu_read_lock(); + result = ((READ_ONCE(ctx->success_audit)) ? "1" : "0"); + rcu_read_unlock(); + + ipe_put_ctx(ctx); + return simple_read_from_buffer(data, len, offset, result, 2); +} /** * new_policy: Write handler for the securityfs node, "ipe/new_policy" @@ -54,6 +119,7 @@ static ssize_t new_policy(struct file *f, const char __user *data, goto err; ipe_add_policy(ctx, p); + ipe_audit_policy_load(p); err: ipe_put_policy(p); ipe_put_ctx(ctx); @@ -119,6 +185,11 @@ static const struct file_operations np_fops = { .write = new_policy, }; +static const struct file_operations audit_fops = { + .write = setaudit, + .read = getaudit, +}; + /** * ipe_init_securityfs: Initialize IPE's securityfs tree at fsinit * @@ -152,6 +223,13 @@ static int __init ipe_init_securityfs(void) goto err; } + success_audit = securityfs_create_file("success_audit", 0600, root, + NULL, &audit_fops); + if (IS_ERR(success_audit)) { + rc = PTR_ERR(success_audit); + goto err; + } + ctx->policy_root = securityfs_create_dir("policies", root); if (IS_ERR(ctx->policy_root)) { rc = PTR_ERR(ctx->policy_root); @@ -163,6 +241,7 @@ static int __init ipe_init_securityfs(void) securityfs_remove(np); securityfs_remove(root); securityfs_remove(config); + securityfs_remove(success_audit); securityfs_remove(ctx->policy_root); return rc; } diff --git a/security/ipe/modules/ipe_module.h b/security/ipe/modules/ipe_module.h index b4f975e9218a..6855815d72da 100644 --- a/security/ipe/modules/ipe_module.h +++ b/security/ipe/modules/ipe_module.h @@ -6,6 +6,7 @@ #define IPE_MODULE_H #include <linux/types.h> +#include <linux/audit.h> #include "../eval.h" /** @@ -26,6 +27,7 @@ struct ipe_module { int (*free)(void **value); /* optional */ bool (*eval)(const struct ipe_eval_ctx *ctx, /* required */ const void *val); + void (*audit)(struct audit_buffer *ab, const void *val); /* required */ }; #define IPE_MODULE(parser) \

[RFC,v7,07/16] ipe: add auditing support

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