ipe: add LSM hooks on execution and kernel read

IPE's initial goal is to control both execution and the loading of
kernel modules based on the system's definition of trust. It
accomplishes this by plugging into the security hooks for
bprm_check_security, file_mprotect, mmap_file, kernel_load_data,
and kernel_read_data.
Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/ipe/Makefile

@@ -7,6 +7,7 @@
 
 obj-$(CONFIG_SECURITY_IPE) += \
 	eval.o \
+	hooks.o \
 	ipe.o \
 	policy.o \
 	policy_parser.o \

security/ipe/eval.c

@@ -16,6 +16,20 @@
 
 struct ipe_policy __rcu *ipe_active_policy;
 
+/**
+ * ipe_build_eval_ctx() - Build an ipe evaluation context.
+ * @ctx: Supplies a pointer to the context to be populated.
+ * @file: Supplies a pointer to the file to associated with the evaluation.
+ * @op: Supplies the IPE policy operation associated with the evaluation.
+ */
+void ipe_build_eval_ctx(struct ipe_eval_ctx *ctx,
+			const struct file *file,
+			enum ipe_op_type op)
+{
+	ctx->file = file;
+	ctx->op = op;
+}
+
 /**
  * evaluate_property() - Analyze @ctx against a rule property.
  * @ctx: Supplies a pointer to the context to be evaluated.

security/ipe/eval.h

@@ -11,6 +11,8 @@
 
 #include "policy.h"
 
+#define IPE_EVAL_CTX_INIT ((struct ipe_eval_ctx){ 0 })
+
 extern struct ipe_policy __rcu *ipe_active_policy;
 
 struct ipe_eval_ctx {
@@ -19,6 +21,9 @@ struct ipe_eval_ctx {
 	const struct file *file;
 };
 
+void ipe_build_eval_ctx(struct ipe_eval_ctx *ctx,
+			const struct file *file,
+			enum ipe_op_type op);
 int ipe_evaluate_event(const struct ipe_eval_ctx *const ctx);
 
 #endif /* _IPE_EVAL_H */

security/ipe/hooks.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
+ */
+
+#include <linux/fs.h>
+#include <linux/types.h>
+#include <linux/binfmts.h>
+#include <linux/mman.h>
+
+#include "ipe.h"
+#include "hooks.h"
+#include "eval.h"
+
+/**
+ * ipe_bprm_check_security() - ipe security hook function for bprm check.
+ * @bprm: Supplies a pointer to a linux_binprm structure to source the file
+ *	  being evaluated.
+ *
+ * This LSM hook is called when a binary is loaded through the exec
+ * family of system calls.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_bprm_check_security(struct linux_binprm *bprm)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+
+	ipe_build_eval_ctx(&ctx, bprm->file, IPE_OP_EXEC);
+	return ipe_evaluate_event(&ctx);
+}
+
+/**
+ * ipe_mmap_file() - ipe security hook function for mmap check.
+ * @f: File being mmap'd. Can be NULL in the case of anonymous memory.
+ * @reqprot: The requested protection on the mmap, passed from usermode.
+ * @prot: The effective protection on the mmap, resolved from reqprot and
+ *	  system configuration.
+ * @flags: Unused.
+ *
+ * This hook is called when a file is loaded through the mmap
+ * family of system calls.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_mmap_file(struct file *f, unsigned long reqprot __always_unused,
+		  unsigned long prot, unsigned long flags)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+
+	if (prot & PROT_EXEC) {
+		ipe_build_eval_ctx(&ctx, f, IPE_OP_EXEC);
+		return ipe_evaluate_event(&ctx);
+	}
+
+	return 0;
+}
+
+/**
+ * ipe_file_mprotect() - ipe security hook function for mprotect check.
+ * @vma: Existing virtual memory area created by mmap or similar.
+ * @reqprot: The requested protection on the mmap, passed from usermode.
+ * @prot: The effective protection on the mmap, resolved from reqprot and
+ *	  system configuration.
+ *
+ * This LSM hook is called when a mmap'd region of memory is changing
+ * its protections via mprotect.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_file_mprotect(struct vm_area_struct *vma,
+		      unsigned long reqprot __always_unused,
+		      unsigned long prot)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+
+	/* Already Executable */
+	if (vma->vm_flags & VM_EXEC)
+		return 0;
+
+	if (prot & PROT_EXEC) {
+		ipe_build_eval_ctx(&ctx, vma->vm_file, IPE_OP_EXEC);
+		return ipe_evaluate_event(&ctx);
+	}
+
+	return 0;
+}
+
+/**
+ * ipe_kernel_read_file() - ipe security hook function for kernel read.
+ * @file: Supplies a pointer to the file structure being read in from disk.
+ * @id: Supplies the enumeration identifying the purpose of the read.
+ * @contents: Unused.
+ *
+ * This LSM hook is called when a file is read from disk in the kernel.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
+			 bool contents)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+	enum ipe_op_type op;
+
+	switch (id) {
+	case READING_FIRMWARE:
+		op = IPE_OP_FIRMWARE;
+		break;
+	case READING_MODULE:
+		op = IPE_OP_KERNEL_MODULE;
+		break;
+	case READING_KEXEC_INITRAMFS:
+		op = IPE_OP_KEXEC_INITRAMFS;
+		break;
+	case READING_KEXEC_IMAGE:
+		op = IPE_OP_KEXEC_IMAGE;
+		break;
+	case READING_POLICY:
+		op = IPE_OP_POLICY;
+		break;
+	case READING_X509_CERTIFICATE:
+		op = IPE_OP_X509;
+		break;
+	default:
+		op = IPE_OP_INVALID;
+		WARN(1, "no rule setup for kernel_read_file enum %d", id);
+	}
+
+	ipe_build_eval_ctx(&ctx, file, op);
+	return ipe_evaluate_event(&ctx);
+}
+
+/**
+ * ipe_kernel_load_data() - ipe security hook function for kernel load data.
+ * @id: Supplies the enumeration identifying the purpose of the load.
+ * @contents: Unused.
+ *
+ * This LSM hook is called when a data buffer provided by userspace is loading
+ * into the kernel.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+	enum ipe_op_type op;
+
+	switch (id) {
+	case LOADING_FIRMWARE:
+		op = IPE_OP_FIRMWARE;
+		break;
+	case LOADING_MODULE:
+		op = IPE_OP_KERNEL_MODULE;
+		break;
+	case LOADING_KEXEC_INITRAMFS:
+		op = IPE_OP_KEXEC_INITRAMFS;
+		break;
+	case LOADING_KEXEC_IMAGE:
+		op = IPE_OP_KEXEC_IMAGE;
+		break;
+	case LOADING_POLICY:
+		op = IPE_OP_POLICY;
+		break;
+	case LOADING_X509_CERTIFICATE:
+		op = IPE_OP_X509;
+		break;
+	default:
+		op = IPE_OP_INVALID;
+		WARN(1, "no rule setup for kernel_load_data enum %d", id);
+	}
+
+	ipe_build_eval_ctx(&ctx, NULL, op);
+	return ipe_evaluate_event(&ctx);
+}

security/ipe/hooks.h

+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
+ */
+#ifndef _IPE_HOOKS_H
+#define _IPE_HOOKS_H
+
+#include <linux/fs.h>
+#include <linux/binfmts.h>
+#include <linux/security.h>
+
+int ipe_bprm_check_security(struct linux_binprm *bprm);
+
+int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
+		  unsigned long flags);
+
+int ipe_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
+		      unsigned long prot);
+
+int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
+			 bool contents);
+
+int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents);
+
+#endif /* _IPE_HOOKS_H */

security/ipe/ipe.c

@@ -5,6 +5,7 @@
 #include <uapi/linux/lsm.h>
 
 #include "ipe.h"
+#include "hooks.h"
 
 static struct lsm_blob_sizes ipe_blobs __ro_after_init = {
 };
@@ -15,6 +16,11 @@ static const struct lsm_id ipe_lsmid = {
 };
 
 static struct security_hook_list ipe_hooks[] __ro_after_init = {
+	LSM_HOOK_INIT(bprm_check_security, ipe_bprm_check_security),
+	LSM_HOOK_INIT(mmap_file, ipe_mmap_file),
+	LSM_HOOK_INIT(file_mprotect, ipe_file_mprotect),
+	LSM_HOOK_INIT(kernel_read_file, ipe_kernel_read_file),
+	LSM_HOOK_INIT(kernel_load_data, ipe_kernel_load_data),
 };
 
 /**