Re: [RFC PATCH v9 06/16] ipe: add LSM hooks on execution and kernel read

[Fan Wu <wufan@linux.microsoft.com>]

On Thu, Mar 02, 2023 at 02:05:20PM -0500, Paul Moore wrote:
> On Mon, Jan 30, 2023 at 5:59???PM Fan Wu <wufan@linux.microsoft.com> wrote:
> >
> > From: Deven Bowers <deven.desai@linux.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@linux.microsoft.com>
> > Signed-off-by: Fan Wu <wufan@linux.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.
> 

Yes I double checked and found that's not necessary, I will remove that.

-Fan

> > +               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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