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

[Deven Bowers <deven.desai@linux.microsoft.com>]

On 10/25/2021 5:22 AM, Roberto Sassu wrote:
>> From:deven.desai@linux.microsoft.com
>> [mailto:deven.desai@linux.microsoft.com]
>> 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;
> Possible problem here. If someone (like me) adds a new file type
> and forgets to add a case, there will be an out of bound access
> in evaluate():
>
>          rules = &pol->parsed->rules[ctx->op];
>
> due to the static definition of the rules array in the ipe_parsed_policy
> structure (array length: ipe_operation_max).

Yeah, that's a problem. I can fix this down in the eval loop by matching
the global default and emitting a WARN here.

> Roberto
>
> HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063
> Managing Director: Li Peng, Zhong Ronghua
>
>> +	}
>> +
>> +	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),
>>   };
>>
>>   /**
>> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
>> index b766824cc08f..048500229365 100644
>> --- a/security/ipe/policy.c
>> +++ b/security/ipe/policy.c
>> @@ -483,6 +483,14 @@ int ipe_parse_op(const struct ipe_policy_token *tok,
>>   {
>>   	substring_t match[MAX_OPT_ARGS] = { 0 };
>>   	const match_table_t ops = {
>> +		{ ipe_operation_exec,		 "EXECUTE" },
>> +		{ ipe_operation_firmware,	 "FIRMWARE" },
>> +		{ ipe_operation_kernel_module,	 "KMODULE" },
>> +		{ ipe_operation_kexec_image,	 "KEXEC_IMAGE" },
>> +		{ ipe_operation_kexec_initramfs, "KEXEC_INITRAMFS"},
>> +		{ ipe_operation_ima_policy,	 "IMA_POLICY" },
>> +		{ ipe_operation_ima_x509,	 "IMA_X509_CERT" },
>> +		{ ipe_op_alias_kernel_read,	 "KERNEL_READ" },
>>   		{ ipe_op_alias_max, NULL },
>>   	};
>>
>> @@ -838,6 +846,15 @@ static int parse_policy(struct ipe_policy *p)
>>   	return rc;
>>   }
>>
>> +static const enum ipe_operation alias_kread[] = {
>> +	ipe_operation_firmware,
>> +	ipe_operation_kernel_module,
>> +	ipe_operation_ima_policy,
>> +	ipe_operation_ima_x509,
>> +	ipe_operation_kexec_image,
>> +	ipe_operation_kexec_initramfs,
>> +};
>> +
>>   /**
>>    * ipe_is_op_alias: Determine if @op is an alias for one or more operations
>>    * @op: Supplies the operation to check. Should be either ipe_operation or
>> @@ -852,9 +869,15 @@ static int parse_policy(struct ipe_policy *p)
>>   bool ipe_is_op_alias(int op, const enum ipe_operation **map, size_t *size)
>>   {
>>   	switch (op) {
>> +	case ipe_op_alias_kernel_read:
>> +		*map = alias_kread;
>> +		*size = ARRAY_SIZE(alias_kread);
>> +		break;
>>   	default:
>>   		return false;
>>   	}
>> +
>> +	return true;
>>   }
>>
>>   /**
>> diff --git a/security/ipe/policy.h b/security/ipe/policy.h
>> index 6818f6405dd0..ca37af46e5af 100644
>> --- a/security/ipe/policy.h
>> +++ b/security/ipe/policy.h
>> @@ -26,7 +26,14 @@ struct ipe_policy_line {
>>   struct ipe_module;
>>
>>   enum ipe_operation {
>> -	ipe_operation_max = 0,
>> +	ipe_operation_exec = 0,
>> +	ipe_operation_firmware,
>> +	ipe_operation_kernel_module,
>> +	ipe_operation_kexec_image,
>> +	ipe_operation_kexec_initramfs,
>> +	ipe_operation_ima_policy,
>> +	ipe_operation_ima_x509,
>> +	ipe_operation_max
>>   };
>>
>>   /*
>> @@ -34,7 +41,8 @@ enum ipe_operation {
>>    * that are just one or more operations under the hood
>>    */
>>   enum ipe_op_alias {
>> -	ipe_op_alias_max = ipe_operation_max,
>> +	ipe_op_alias_kernel_read = ipe_operation_max,
>> +	ipe_op_alias_max,
>>   };
>>
>>   enum ipe_action {
>> --
>> 2.33.0

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