[RFC PATCH v1 0/1] ipe: added script enforcement with BPRM check

[RFC PATCH v1 0/1] ipe: added script enforcement with BPRM check

[Jasjiv Singh]

From: jasjivsingh_microsoft <jasjivsingh@linux.microsoft.com>

Currently, IPE only enforces the policy operations for direct
file execution (e.g. ./script.sh). However, indirect file execution
(e.g. sh script.sh) needs to be enforced by IPE based on the rules.

Overview
--------

This patch introduces the `ipe_bprm_creds_for_exec` LSM hook. This hook
specifically targets the `AT_EXECVE_CHECK` scenario [1], allowing IPE to
evaluate the `EXECUTE` operation policy for the script file during the
check phase itself.

[1] https://lore.kernel.org/linux-security-module/20241212174223.389435-1-mic@digikod.net/

Example
--------

ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1 pid=18571 comm="inc" 
path="/tmp/script/hello.inc" dev="tmpfs" ino=24 rule="DEFAULT action=DENY"

the log message when the IPE policy denies the indirect script execution 
via the 'inc' test interpreter.

The IPE test suite has been updated to include script enforcement tests:
https://github.com/microsoft/ipe/tree/test-suite

jasjivsingh_microsoft (1):
  ipe: add script enforcement with BPRM check

 security/ipe/hooks.c | 23 +++++++++++++++++++++++
 security/ipe/hooks.h |  2 ++
 security/ipe/ipe.c   |  1 +
 3 files changed, 26 insertions(+)

-- 
2.34.1

[RFC PATCH v1 1/1] ipe: add script enforcement with BPRM check

[Jasjiv Singh]

From: jasjivsingh_microsoft <jasjivsingh@linux.microsoft.com>

Like direct file execution (e.g. ./script.sh), indirect file execution
(e.g. sh script.sh) needs to be enforce by IPE based on the rules.  
Added a new security_bprm_creds_for_exec() hook to verify the indirect 
file's integrity.

Signed-off-by: Jasjiv Singh <jasjivsingh@linux.microsoft.com>
---
 security/ipe/hooks.c | 23 +++++++++++++++++++++++
 security/ipe/hooks.h |  2 ++
 security/ipe/ipe.c   |  1 +
 3 files changed, 26 insertions(+)

diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
index d0323b81cd8f..12713a0495cf 100644
--- a/security/ipe/hooks.c
+++ b/security/ipe/hooks.c
@@ -35,6 +35,29 @@ int ipe_bprm_check_security(struct linux_binprm *bprm)
 	return ipe_evaluate_event(&ctx);
 }
 
+/**
+ * ipe_bprm_creds_for_exec() - ipe security hook function for bprm creds check.
+ * @bprm: Supplies a pointer to a linux_binprm structure to source the file
+ *	  being evaluated.
+ *
+ * This LSM hook is called when a script is checked for execution through the
+ * execveat syscall with the AT_EXECVE_CHECK flag.
+ *
+ * Return:
+ * * %0		- Success
+ * * %-EACCES	- Did not pass IPE policy
+ */
+int ipe_bprm_creds_for_exec(struct linux_binprm *bprm)
+{
+	struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
+
+	if (!bprm->is_check)
+		return 0;
+
+	ipe_build_eval_ctx(&ctx, bprm->file, IPE_OP_EXEC, IPE_HOOK_BPRM_CHECK);
+	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.
diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
index 38d4a387d039..1c16a25d806e 100644
--- a/security/ipe/hooks.h
+++ b/security/ipe/hooks.h
@@ -24,6 +24,8 @@ enum ipe_hook_type {
 
 int ipe_bprm_check_security(struct linux_binprm *bprm);
 
+int ipe_bprm_creds_for_exec(struct linux_binprm *bprm);
+
 int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
 		  unsigned long flags);
 
diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
index 4317134cb0da..845e3fd7a345 100644
--- a/security/ipe/ipe.c
+++ b/security/ipe/ipe.c
@@ -47,6 +47,7 @@ struct ipe_inode *ipe_inode(const struct inode *inode)
 
 static struct security_hook_list ipe_hooks[] __ro_after_init = {
 	LSM_HOOK_INIT(bprm_check_security, ipe_bprm_check_security),
+	LSM_HOOK_INIT(bprm_creds_for_exec, ipe_bprm_creds_for_exec),
 	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),
-- 
2.34.1

Re: [RFC PATCH v1 0/1] ipe: added script enforcement with BPRM check

[Fan Wu]

On Tue, Apr 29, 2025 at 2:23 PM Jasjiv Singh
<jasjivsingh@linux.microsoft.com> wrote:
>
> From: jasjivsingh_microsoft <jasjivsingh@linux.microsoft.com>
>
> Currently, IPE only enforces the policy operations for direct
> file execution (e.g. ./script.sh). However, indirect file execution
> (e.g. sh script.sh) needs to be enforced by IPE based on the rules.
>
> Overview
> --------
>
> This patch introduces the `ipe_bprm_creds_for_exec` LSM hook. This hook
> specifically targets the `AT_EXECVE_CHECK` scenario [1], allowing IPE to
> evaluate the `EXECUTE` operation policy for the script file during the
> check phase itself.
>
> [1] https://lore.kernel.org/linux-security-module/20241212174223.389435-1-mic@digikod.net/
>
> Example
> --------
>
> ipe_op=EXECUTE ipe_hook=BPRM_CHECK enforcing=1 pid=18571 comm="inc"
> path="/tmp/script/hello.inc" dev="tmpfs" ino=24 rule="DEFAULT action=DENY"
>
> the log message when the IPE policy denies the indirect script execution
> via the 'inc' test interpreter.
>
> The IPE test suite has been updated to include script enforcement tests:
> https://github.com/microsoft/ipe/tree/test-suite

Please use the PR link instead of the repo link.

-Fan

Re: [RFC PATCH v1 1/1] ipe: add script enforcement with BPRM check

[Fan Wu]

On Tue, Apr 29, 2025 at 2:23 PM Jasjiv Singh
<jasjivsingh@linux.microsoft.com> wrote:
>
> From: jasjivsingh_microsoft <jasjivsingh@linux.microsoft.com>
>
> Like direct file execution (e.g. ./script.sh), indirect file execution
> (e.g. sh script.sh) needs to be enforce by IPE based on the rules.
> Added a new security_bprm_creds_for_exec() hook to verify the indirect
> file's integrity.
>
> Signed-off-by: Jasjiv Singh <jasjivsingh@linux.microsoft.com>
> ---
>  security/ipe/hooks.c | 23 +++++++++++++++++++++++
>  security/ipe/hooks.h |  2 ++
>  security/ipe/ipe.c   |  1 +
>  3 files changed, 26 insertions(+)
>
> diff --git a/security/ipe/hooks.c b/security/ipe/hooks.c
> index d0323b81cd8f..12713a0495cf 100644
> --- a/security/ipe/hooks.c
> +++ b/security/ipe/hooks.c
> @@ -35,6 +35,29 @@ int ipe_bprm_check_security(struct linux_binprm *bprm)
>         return ipe_evaluate_event(&ctx);
>  }
>
> +/**
> + * ipe_bprm_creds_for_exec() - ipe security hook function for bprm creds check.
> + * @bprm: Supplies a pointer to a linux_binprm structure to source the file
> + *       being evaluated.
> + *
> + * This LSM hook is called when a script is checked for execution through the
> + * execveat syscall with the AT_EXECVE_CHECK flag.

I remember the script is only one case, user space can add this flag
for other cases.

> + *
> + * Return:
> + * * %0                - Success
> + * * %-EACCES  - Did not pass IPE policy
> + */
> +int ipe_bprm_creds_for_exec(struct linux_binprm *bprm)
> +{
> +       struct ipe_eval_ctx ctx = IPE_EVAL_CTX_INIT;
> +
> +       if (!bprm->is_check)
> +               return 0;
> +
> +       ipe_build_eval_ctx(&ctx, bprm->file, IPE_OP_EXEC, IPE_HOOK_BPRM_CHECK);

A new enum needs to be added to audit this new hook in the audit
event. Please create something like IPE_HOOK_BPRM_CREDS_FOR_EXEC.

-Fan

> +       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.
> diff --git a/security/ipe/hooks.h b/security/ipe/hooks.h
> index 38d4a387d039..1c16a25d806e 100644
> --- a/security/ipe/hooks.h
> +++ b/security/ipe/hooks.h
> @@ -24,6 +24,8 @@ enum ipe_hook_type {
>
>  int ipe_bprm_check_security(struct linux_binprm *bprm);
>
> +int ipe_bprm_creds_for_exec(struct linux_binprm *bprm);
> +
>  int ipe_mmap_file(struct file *f, unsigned long reqprot, unsigned long prot,
>                   unsigned long flags);
>
> diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
> index 4317134cb0da..845e3fd7a345 100644
> --- a/security/ipe/ipe.c
> +++ b/security/ipe/ipe.c
> @@ -47,6 +47,7 @@ struct ipe_inode *ipe_inode(const struct inode *inode)
>
>  static struct security_hook_list ipe_hooks[] __ro_after_init = {
>         LSM_HOOK_INIT(bprm_check_security, ipe_bprm_check_security),
> +       LSM_HOOK_INIT(bprm_creds_for_exec, ipe_bprm_creds_for_exec),
>         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),
> --
> 2.34.1
>