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Message-ID: <CAHC9VhRX4-=SSAkb0f2722dJ9JGudTyT-B=t8uoRqA8efwcoSg@mail.gmail.com>
Date: Thu, 2 Mar 2023 14:05:20 -0500
From: Paul Moore <paul@...l-moore.com>
To: Fan Wu <wufan@...ux.microsoft.com>
Cc: corbet@....net, zohar@...ux.ibm.com, jmorris@...ei.org,
serge@...lyn.com, tytso@....edu, ebiggers@...nel.org,
axboe@...nel.dk, agk@...hat.com, snitzer@...nel.org,
eparis@...hat.com, linux-doc@...r.kernel.org,
linux-integrity@...r.kernel.org,
linux-security-module@...r.kernel.org,
linux-fscrypt@...r.kernel.org, linux-block@...r.kernel.org,
dm-devel@...hat.com, linux-audit@...hat.com,
roberto.sassu@...wei.com, linux-kernel@...r.kernel.org,
Deven Bowers <deven.desai@...ux.microsoft.com>
Subject: Re: [RFC PATCH v9 06/16] ipe: add LSM hooks on execution and kernel read
On Mon, Jan 30, 2023 at 5:59 PM Fan Wu <wufan@...ux.microsoft.com> wrote:
>
> From: Deven Bowers <deven.desai@...ux.microsoft.com>
>
> 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@...ux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@...ux.microsoft.com>
...
> ---
> security/ipe/hooks.c | 169 +++++++++++++++++++++++++++++++++++++++++++
> security/ipe/hooks.h | 13 ++++
> security/ipe/ipe.c | 6 ++
> 3 files changed, 188 insertions(+)
>
> diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
> index 335b773c7ae1..fd5109e29c76 100644
> --- a/security/ipe/hooks.c
> +++ b/security/ipe/hooks.c
> @@ -23,3 +23,172 @@ void ipe_sb_free_security(struct super_block *mnt_sb)
> {
> ipe_invalidate_pinned_sb(mnt_sb);
> }
> +
> +/**
> + * 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 - OK
> + * *!0 - Error
> + */
> +int ipe_bprm_check_security(struct linux_binprm *bprm)
> +{
> + struct ipe_eval_ctx ctx = { 0 };
> +
> + 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 - OK
> + * * !0 - Error
> + */
> +int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
> + unsigned long flags)
> +{
> + struct ipe_eval_ctx ctx = { 0 };
> +
> + if (prot & PROT_EXEC || reqprot & PROT_EXEC) {
Is there a reason why you care about @reqprot? It seems like IPE
would only be interested in the protection flags that the kernel is
actually using.
I notice that in the `ipe_file_mprotect()` hook you ignore @reqprot,
which I believe is the right thing to do.
> + 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 - OK
> + * * !0 - Error
> + */
> +int ipe_file_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
> + unsigned long prot)
> +{
> + struct ipe_eval_ctx ctx = { 0 };
> +
> + /* Already Executable */
> + if (vma->vm_flags & VM_EXEC)
> + return 0;
> +
> + if (prot & PROT_EXEC) {
> + 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 being read in from disk from
> + * the kernel.
> + *
> + * Return:
> + * 0 - OK
> + * !0 - Error
> + */
> +int ipe_kernel_read_file(struct file *file, enum kernel_read_file_id id,
> + bool contents)
> +{
> + enum ipe_op_type op;
> + struct ipe_eval_ctx ctx;
> +
> + 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_ima_policy;
> + break;
> + case READING_X509_CERTIFICATE:
> + op = ipe_op_ima_x509;
> + break;
> + default:
> + op = ipe_op_max;
> + WARN(op == ipe_op_max, "no rule setup for enum %d", id);
> + }
> +
> + 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 read.
> + * @contents: Unused.
> + *
> + * This LSM hook is called when a buffer is being read in from disk.
> + *
> + * Return:
> + * * 0 - OK
> + * * !0 - Error
> + */
> +int ipe_kernel_load_data(enum kernel_load_data_id id, bool contents)
> +{
> + enum ipe_op_type op;
> + struct ipe_eval_ctx ctx = { 0 };
> +
> + 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_ima_policy;
> + break;
> + case LOADING_X509_CERTIFICATE:
> + op = ipe_op_ima_x509;
> + break;
> + default:
> + op = ipe_op_max;
> + WARN(op == ipe_op_max, "no rule setup for enum %d", id);
> + }
> +
> + build_eval_ctx(&ctx, NULL, op);
> + return ipe_evaluate_event(&ctx);
> +}
> diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
> index 30fe455389bf..857cae69678c 100644
> --- a/security/ipe/hooks.h
> +++ b/security/ipe/hooks.h
> @@ -11,4 +11,17 @@
>
> void ipe_sb_free_security(struct super_block *mnt_sb);
>
> +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 */
> diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
> index bef923026b50..7af2f942decd 100644
> --- a/security/ipe/ipe.c
> +++ b/security/ipe/ipe.c
> @@ -4,6 +4,7 @@
> */
>
> #include "ipe.h"
> +#include "hooks.h"
>
> bool ipe_enabled;
>
> @@ -12,6 +13,11 @@ static struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = {
>
> static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = {
> LSM_HOOK_INIT(sb_free_security, ipe_sb_free_security),
> + 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),
> };
>
> /**
> --
> 2.39.0
--
paul-moore.com
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