Re: [RFC PATCH v7 05/16] ipe: add LSM hooks on execution and kernel read

Deven Bowers
2021-10-15T19:26:10Z

On 10/13/2021 1:04 PM, Casey Schaufler wrote:
> On 10/13/2021 12:06 PM, deven.desai@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 execve,
>> mprotect, mmap, kernel_load_data and kernel_read_data.
>>
>> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
>> ---
>>
>> Relevant changes since v6:
>> * Split up patch 02/12 into four parts:
>> 1. context creation [01/16]
>> 2. audit [07/16]
>> 3. evaluation loop [03/16]
>> 4. access control hooks [05/16] (this patch)
>>
>> ---
>> security/ipe/hooks.c | 149 ++++++++++++++++++++++++++++++++++++++++++
>> security/ipe/hooks.h | 23 ++++++-
>> security/ipe/ipe.c | 5 ++
>> security/ipe/policy.c | 23 +++++++
>> security/ipe/policy.h | 12 +++-
>> 5 files changed, 209 insertions(+), 3 deletions(-)
>>
>> diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
>> index ed0c886eaa5a..216242408a80 100644
>> --- a/security/ipe/hooks.c
>> +++ b/security/ipe/hooks.c
>> @@ -6,11 +6,15 @@
>> #include "ipe.h"
>> #include "ctx.h"
>> #include "hooks.h"
>> +#include "eval.h"
>>
>> +#include <linux/fs.h>
>> #include <linux/sched.h>
>> #include <linux/types.h>
>> #include <linux/refcount.h>
>> #include <linux/rcupdate.h>
>> +#include <linux/binfmts.h>
>> +#include <linux/mman.h>
>>
>> /**
>> * ipe_task_alloc: Assign a new context for an associated task structure.
>> @@ -56,3 +60,148 @@ void ipe_task_free(struct task_struct *task)
>> ipe_put_ctx(ctx);
>> rcu_read_unlock();
>> }
>> +
>> +/**
>> + * ipe_on_exec: LSM hook called when a process is loaded through the exec
>> + * family of system calls.
>> + * @bprm: Supplies a pointer to a linux_binprm structure to source the file
>> + * being evaluated.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +int ipe_on_exec(struct linux_binprm *bprm)
>> +{
>> + return ipe_process_event(bprm->file, ipe_operation_exec, ipe_hook_exec);
>> +}
>> +
>> +/**
>> + * ipe_on_mmap: LSM hook called when a file is loaded through the mmap
>> + * family of system calls.
>> + * @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.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +int ipe_on_mmap(struct file *f, unsigned long reqprot, unsigned long prot,
>> + unsigned long flags)
>> +{
>> + if (prot & PROT_EXEC || reqprot & PROT_EXEC)
>> + return ipe_process_event(f, ipe_operation_exec, ipe_hook_mmap);
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * ipe_on_mprotect: LSM hook called when a mmap'd region of memory is changing
>> + * its protections via mprotect.
>> + * @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.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +int ipe_on_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
>> + unsigned long prot)
>> +{
>> + /* Already Executable */
>> + if (vma->vm_flags & VM_EXEC)
>> + return 0;
>> +
>> + if (((prot & PROT_EXEC) || reqprot & PROT_EXEC))
>> + return ipe_process_event(vma->vm_file, ipe_operation_exec,
>> + ipe_hook_mprotect);
>> +
>> + return 0;
>> +}
>> +
>> +/**
>> + * ipe_on_kernel_read: LSM hook called when a file is being read in from
>> + * disk.
>> + * @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.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +int ipe_on_kernel_read(struct file *file, enum kernel_read_file_id id,
>> + bool contents)
>> +{
>> + enum ipe_operation op;
>> +
>> + switch (id) {
>> + case READING_FIRMWARE:
>> + op = ipe_operation_firmware;
>> + break;
>> + case READING_MODULE:
>> + op = ipe_operation_kernel_module;
>> + break;
>> + case READING_KEXEC_INITRAMFS:
>> + op = ipe_operation_kexec_initramfs;
>> + break;
>> + case READING_KEXEC_IMAGE:
>> + op = ipe_operation_kexec_image;
>> + break;
>> + case READING_POLICY:
>> + op = ipe_operation_ima_policy;
>> + break;
>> + case READING_X509_CERTIFICATE:
>> + op = ipe_operation_ima_x509;
>> + break;
>> + default:
>> + op = ipe_operation_max;
>> + }
>> +
>> + return ipe_process_event(file, op, ipe_hook_kernel_read);
>> +}
>> +
>> +/**
>> + * ipe_on_kernel_load_data: LSM hook called when a buffer is being read in from
>> + * disk.
>> + * @id: Supplies the enumeration identifying the purpose of the read.
>> + * @contents: Unused.
>> + *
>> + * Return:
>> + * 0 - OK
>> + * !0 - Error
>> + */
>> +int ipe_on_kernel_load_data(enum kernel_load_data_id id, bool contents)
>> +{
>> + enum ipe_operation op;
>> +
>> + switch (id) {
>> + case LOADING_FIRMWARE:
>> + op = ipe_operation_firmware;
>> + break;
>> + case LOADING_MODULE:
>> + op = ipe_operation_kernel_module;
>> + break;
>> + case LOADING_KEXEC_INITRAMFS:
>> + op = ipe_operation_kexec_initramfs;
>> + break;
>> + case LOADING_KEXEC_IMAGE:
>> + op = ipe_operation_kexec_image;
>> + break;
>> + case LOADING_POLICY:
>> + op = ipe_operation_ima_policy;
>> + break;
>> + case LOADING_X509_CERTIFICATE:
>> + op = ipe_operation_ima_x509;
>> + break;
>> + default:
>> + op = ipe_operation_max;
>> + }
>> +
>> + return ipe_process_event(NULL, op, ipe_hook_kernel_load);
>> +}
>> diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
>> index 58ed4a612e26..c99a0b7f45f7 100644
>> --- a/security/ipe/hooks.h
>> +++ b/security/ipe/hooks.h
>> @@ -5,11 +5,19 @@
>> #ifndef IPE_HOOKS_H
>> #define IPE_HOOKS_H
>>
>> +#include <linux/fs.h>
>> #include <linux/types.h>
>> #include <linux/sched.h>
>> +#include <linux/binfmts.h>
>> +#include <linux/security.h>
>>
>> enum ipe_hook {
>> - ipe_hook_max = 0
>> + ipe_hook_exec = 0,
>> + ipe_hook_mmap,
>> + ipe_hook_mprotect,
>> + ipe_hook_kernel_read,
>> + ipe_hook_kernel_load,
>> + ipe_hook_max
>> };
>>
>> int ipe_task_alloc(struct task_struct *task,
>> @@ -17,4 +25,17 @@ int ipe_task_alloc(struct task_struct *task,
>>
>> void ipe_task_free(struct task_struct *task);
>>
>> +int ipe_on_exec(struct linux_binprm *bprm);
>> +
>> +int ipe_on_mmap(struct file *f, unsigned long reqprot, unsigned long prot,
>> + unsigned long flags);
>> +
>> +int ipe_on_mprotect(struct vm_area_struct *vma, unsigned long reqprot,
>> + unsigned long prot);
>> +
>> +int ipe_on_kernel_read(struct file *file, enum kernel_read_file_id id,
>> + bool contents);
>> +
>> +int ipe_on_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 b58b372327a1..3f9d43783293 100644
>> --- a/security/ipe/ipe.c
>> +++ b/security/ipe/ipe.c
>> @@ -25,6 +25,11 @@ struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = {
>> static struct security_hook_list ipe_hooks[] __lsm_ro_after_init = {
>> LSM_HOOK_INIT(task_alloc, ipe_task_alloc),
>> LSM_HOOK_INIT(task_free, ipe_task_free),
>> + LSM_HOOK_INIT(bprm_check_security, ipe_on_exec),
>> + LSM_HOOK_INIT(mmap_file, ipe_on_mmap),
>> + LSM_HOOK_INIT(file_mprotect, ipe_on_mprotect),
>> + LSM_HOOK_INIT(kernel_read_file, ipe_on_kernel_read),
>> + LSM_HOOK_INIT(kernel_load_data, ipe_on_kernel_load_data),
> Please stick with the lsmname_hook_name convention, as you did
> with ipe_task_alloc and ipe_task_free. Anyone who is looking at
> more than one LSM is going to have a much harder time working
> with your code the way you have it. Think
>
> % find security | xargs grep '_bprm_check_security('

Sure. I'll make this change with the v8 series.