Re: [PATCH v38 12/24] x86/sgx: Add SGX_IOC_ENCLAVE_CREATE

[Jarkko Sakkinen]

On Fri, Oct 02, 2020 at 07:23:55PM -0500, Haitao Huang wrote:
> On Tue, 15 Sep 2020 06:28:30 -0500, Jarkko Sakkinen
> <jarkko.sakkinen@xxxxxxxxxxxxxxx> wrote:
> 
> > Add an ioctl that performs ENCLS[ECREATE], which creates SGX Enclave
> > Control Structure for the enclave. SECS contains attributes about the
> > enclave that are used by the hardware and cannot be directly accessed by
> > software, as SECS resides in the EPC.
> > 
> > One essential field in SECS is a field that stores the SHA256 of the
> > measured enclave pages. This field, MRENCLAVE, is initialized by the
> > ECREATE instruction and updated by every EADD and EEXTEND operation.
> > Finally, EINIT locks down the value.
> > 
> > Acked-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> > Tested-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> > Tested-by: Haitao Huang <haitao.huang@xxxxxxxxxxxxxxx>
> > Tested-by: Chunyang Hui <sanqian.hcy@xxxxxxxxxx>
> > Tested-by: Jordan Hand <jorhand@xxxxxxxxxxxxxxxxxxx>
> > Tested-by: Nathaniel McCallum <npmccallum@xxxxxxxxxx>
> > Tested-by: Seth Moore <sethmo@xxxxxxxxxx>
> > Tested-by: Darren Kenny <darren.kenny@xxxxxxxxxx>
> > Reviewed-by: Darren Kenny <darren.kenny@xxxxxxxxxx>
> > Co-developed-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
> > Co-developed-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
> > Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx>
> > Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> > ---
> >  .../userspace-api/ioctl/ioctl-number.rst      |   1 +
> >  arch/x86/include/uapi/asm/sgx.h               |  25 ++
> >  arch/x86/kernel/cpu/sgx/Makefile              |   1 +
> >  arch/x86/kernel/cpu/sgx/driver.c              |  12 +
> >  arch/x86/kernel/cpu/sgx/driver.h              |   1 +
> >  arch/x86/kernel/cpu/sgx/ioctl.c               | 220 ++++++++++++++++++
> >  6 files changed, 260 insertions(+)
> >  create mode 100644 arch/x86/include/uapi/asm/sgx.h
> >  create mode 100644 arch/x86/kernel/cpu/sgx/ioctl.c
> > 
> > diff --git a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > index 2a198838fca9..a89e1c46a25a 100644
> > --- a/Documentation/userspace-api/ioctl/ioctl-number.rst
> > +++ b/Documentation/userspace-api/ioctl/ioctl-number.rst
> > @@ -323,6 +323,7 @@ Code  Seq#    Include File
> > Comments
> >                                                                       <mailto:tlewis@xxxxxxxxxxxxxx>
> >  0xA3  90-9F  linux/dtlk.h
> >  0xA4  00-1F  uapi/linux/tee.h
> > Generic TEE subsystem
> > +0xA4  00-1F  uapi/asm/sgx.h
> > <mailto:linux-sgx@xxxxxxxxxxxxxxx>
> >  0xAA  00-3F  linux/uapi/linux/userfaultfd.h
> >  0xAB  00-1F  linux/nbd.h
> >  0xAC  00-1F  linux/raw.h
> > diff --git a/arch/x86/include/uapi/asm/sgx.h
> > b/arch/x86/include/uapi/asm/sgx.h
> > new file mode 100644
> > index 000000000000..c75b375f3770
> > --- /dev/null
> > +++ b/arch/x86/include/uapi/asm/sgx.h
> > @@ -0,0 +1,25 @@
> > +/* SPDX-License-Identifier: ((GPL-2.0+ WITH Linux-syscall-note) OR
> > BSD-3-Clause) */
> > +/*
> > + * Copyright(c) 2016-19 Intel Corporation.
> > + */
> > +#ifndef _UAPI_ASM_X86_SGX_H
> > +#define _UAPI_ASM_X86_SGX_H
> > +
> > +#include <linux/types.h>
> > +#include <linux/ioctl.h>
> > +
> > +#define SGX_MAGIC 0xA4
> > +
> > +#define SGX_IOC_ENCLAVE_CREATE \
> > +	_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
> > +
> > +/**
> > + * struct sgx_enclave_create - parameter structure for the
> > + *                             %SGX_IOC_ENCLAVE_CREATE ioctl
> > + * @src:	address for the SECS page data
> > + */
> > +struct sgx_enclave_create  {
> > +	__u64	src;
> > +};
> > +
> > +#endif /* _UAPI_ASM_X86_SGX_H */
> > diff --git a/arch/x86/kernel/cpu/sgx/Makefile
> > b/arch/x86/kernel/cpu/sgx/Makefile
> > index 3fc451120735..91d3dc784a29 100644
> > --- a/arch/x86/kernel/cpu/sgx/Makefile
> > +++ b/arch/x86/kernel/cpu/sgx/Makefile
> > @@ -1,4 +1,5 @@
> >  obj-y += \
> >  	driver.o \
> >  	encl.o \
> > +	ioctl.o \
> >  	main.o
> > diff --git a/arch/x86/kernel/cpu/sgx/driver.c
> > b/arch/x86/kernel/cpu/sgx/driver.c
> > index f54da5f19c2b..7bdb49dfcca6 100644
> > --- a/arch/x86/kernel/cpu/sgx/driver.c
> > +++ b/arch/x86/kernel/cpu/sgx/driver.c
> > @@ -114,10 +114,22 @@ static unsigned long sgx_get_unmapped_area(struct
> > file *file,
> >  	return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
> >  }
> > +#ifdef CONFIG_COMPAT
> > +static long sgx_compat_ioctl(struct file *filep, unsigned int cmd,
> > +			      unsigned long arg)
> > +{
> > +	return sgx_ioctl(filep, cmd, arg);
> > +}
> > +#endif
> > +
> >  static const struct file_operations sgx_encl_fops = {
> >  	.owner			= THIS_MODULE,
> >  	.open			= sgx_open,
> >  	.release		= sgx_release,
> > +	.unlocked_ioctl		= sgx_ioctl,
> > +#ifdef CONFIG_COMPAT
> > +	.compat_ioctl		= sgx_compat_ioctl,
> > +#endif
> >  	.mmap			= sgx_mmap,
> >  	.get_unmapped_area	= sgx_get_unmapped_area,
> >  };
> > diff --git a/arch/x86/kernel/cpu/sgx/driver.h
> > b/arch/x86/kernel/cpu/sgx/driver.h
> > index f7ce40dedc91..e4063923115b 100644
> > --- a/arch/x86/kernel/cpu/sgx/driver.h
> > +++ b/arch/x86/kernel/cpu/sgx/driver.h
> > @@ -9,6 +9,7 @@
> >  #include <linux/rwsem.h>
> >  #include <linux/sched.h>
> >  #include <linux/workqueue.h>
> > +#include <uapi/asm/sgx.h>
> >  #include "sgx.h"
> > #define SGX_EINIT_SPIN_COUNT	20
> > diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c
> > b/arch/x86/kernel/cpu/sgx/ioctl.c
> > new file mode 100644
> > index 000000000000..352a3c461812
> > --- /dev/null
> > +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> > @@ -0,0 +1,220 @@
> > +// SPDX-License-Identifier: (GPL-2.0 OR BSD-3-Clause)
> > +// Copyright(c) 2016-19 Intel Corporation.
> > +
> > +#include <asm/mman.h>
> > +#include <linux/mman.h>
> > +#include <linux/delay.h>
> > +#include <linux/file.h>
> > +#include <linux/hashtable.h>
> > +#include <linux/highmem.h>
> > +#include <linux/ratelimit.h>
> > +#include <linux/sched/signal.h>
> > +#include <linux/shmem_fs.h>
> > +#include <linux/slab.h>
> > +#include <linux/suspend.h>
> > +#include "driver.h"
> > +#include "encl.h"
> > +#include "encls.h"
> > +
> > +static u32 sgx_calc_ssa_frame_size(u32 miscselect, u64 xfrm)
> > +{
> > +	u32 size_max = PAGE_SIZE;
> > +	u32 size;
> > +	int i;
> > +
> > +	for (i = 2; i < 64; i++) {
> > +		if (!((1 << i) & xfrm))
> > +			continue;
> > +
> > +		size = SGX_SSA_GPRS_SIZE + sgx_xsave_size_tbl[i];
> > +
> > +		if (miscselect & SGX_MISC_EXINFO)
> > +			size += SGX_SSA_MISC_EXINFO_SIZE;
> > +
> > +		if (size > size_max)
> > +			size_max = size;
> > +	}
> > +
> > +	return PFN_UP(size_max);
> > +}
> > +
> > +static int sgx_validate_secs(const struct sgx_secs *secs)
> > +{
> > +	u64 max_size = (secs->attributes & SGX_ATTR_MODE64BIT) ?
> > +		       sgx_encl_size_max_64 : sgx_encl_size_max_32;
> > +
> > +	if (secs->size < (2 * PAGE_SIZE) || !is_power_of_2(secs->size))
> > +		return -EINVAL;
> > +
> > +	if (secs->base & (secs->size - 1))
> > +		return -EINVAL;
> > +
> > +	if (secs->miscselect & sgx_misc_reserved_mask ||
> > +	    secs->attributes & sgx_attributes_reserved_mask ||
> > +	    secs->xfrm & sgx_xfrm_reserved_mask)
> > +		return -EINVAL;
> > +
> 
> Attributes should not be enforced against what's available on platform but
> checked and enforced against the mask for enforcement in sigstruct. For
> example an enclave could opt to sign with AVX bit in xfrm, but still be
> loadable on a platform without it if the sigstruct->body.attributes_mask
> does not turn that bit on.
> 
> Suggest to remove the above check,and do following during EINIt in
> sgx_encl_init:
> 
> -       /* Check that the required attributes have been authorized. */
> +       /* Check that the requested attributes have been authorized. */

This is as bad and useless comment as the existing was. In the paragraph
you wrote above you state the things that are useful.

So: I'll take the code change and put the response above here instead
because it is says the right things :-) (maybe with very minor edit)

>         if (encl->secs_attributes & ~encl->allowed_attributes)
>                 return -EACCES;
> 
> +       /* Check that mandatory features are supported. */
> +       if (sigstruct->body.attributes & sigstruct->body.attributes_mask &
> +           sgx_attributes_reserved_mask)
> +               return -EINVAL;
> +       if (sigstruct->body.miscselect & sigstruct->body.misc_mask &
> +           sgx_misc_reserved_mask)
> +               return -EINVAL;
> +       if (sigstruct->body.xfrm & sigstruct->body.xfrm_mask &
> +           sgx_xfrm_reserved_mask)
> +               return -EINVAL;
> +
>         ret = sgx_get_key_hash(sigstruct->modulus, mrsigner);
> 
> Haitao

Thanks a lot!

/Jarkko