Re: [PATCH v32 12/21] x86/sgx: Add provisioning

[Darren Kenny]

Hi Jarkko,

Just a couple of nits below...

On Monday, 2020-06-01 at 10:52:09 +03, Jarkko Sakkinen wrote:
> In order to provide a mechanism for devilering provisoning rights:

TYPO: s/devilering/delivering/?

>
> 1. Add a new device file /dev/sgx/provision that works as a token for
>    allowing an enclave to have the provisioning privileges.
> 2. Add a new ioctl called SGX_IOC_ENCLAVE_SET_ATTRIBUTE that accepts the
>    following data structure:
>
>    struct sgx_enclave_set_attribute {
>            __u64 addr;
>            __u64 attribute_fd;
>    };
>
> A daemon could sit on top of /dev/sgx/provision and send a file
> descriptor of this file to a process that needs to be able to provision
> enclaves.
>
> The way this API is used is straight-forward. Lets assume that dev_fd is
> a handle to /dev/sgx/enclave and prov_fd is a handle to
> /dev/sgx/provision.  You would allow SGX_IOC_ENCLAVE_CREATE to
> initialize an enclave with the PROVISIONKEY attribute by
>
> params.addr = <enclave address>;
> params.token_fd = prov_fd;
>
> ioctl(dev_fd, SGX_IOC_ENCLAVE_SET_ATTRIBUTE, &params);
>
> Cc: linux-security-module@xxxxxxxxxxxxxxx
> Acked-by: Jethro Beekman <jethro@xxxxxxxxxxxx>
> Suggested-by: Andy Lutomirski <luto@xxxxxxxxxx>
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
> ---
>  arch/x86/include/uapi/asm/sgx.h  | 11 ++++++++
>  arch/x86/kernel/cpu/sgx/driver.c | 14 ++++++++++
>  arch/x86/kernel/cpu/sgx/driver.h |  2 ++
>  arch/x86/kernel/cpu/sgx/ioctl.c  | 47 ++++++++++++++++++++++++++++++++
>  4 files changed, 74 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
> index 5edb08ab8fd0..57d0d30c79b3 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -25,6 +25,8 @@ enum sgx_page_flags {
>  	_IOWR(SGX_MAGIC, 0x01, struct sgx_enclave_add_pages)
>  #define SGX_IOC_ENCLAVE_INIT \
>  	_IOW(SGX_MAGIC, 0x02, struct sgx_enclave_init)
> +#define SGX_IOC_ENCLAVE_SET_ATTRIBUTE \
> +	_IOW(SGX_MAGIC, 0x03, struct sgx_enclave_set_attribute)
>  
>  /**
>   * struct sgx_enclave_create - parameter structure for the
> @@ -63,4 +65,13 @@ struct sgx_enclave_init {
>  	__u64 sigstruct;
>  };
>  
> +/**
> + * struct sgx_enclave_set_attribute - parameter structure for the
> + *				      %SGX_IOC_ENCLAVE_SET_ATTRIBUTE ioctl
> + * @attribute_fd:	file handle of the attribute file in the securityfs
> + */
> +struct sgx_enclave_set_attribute {
> +	__u64 attribute_fd;
> +};
> +
>  #endif /* _UAPI_ASM_X86_SGX_H */
> diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
> index b4aa7b9f8376..d90114cec1c3 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.c
> +++ b/arch/x86/kernel/cpu/sgx/driver.c
> @@ -150,6 +150,13 @@ static struct miscdevice sgx_dev_enclave = {
>  	.fops = &sgx_encl_fops,
>  };
>  
> +static struct miscdevice sgx_dev_provision = {
> +	.minor = MISC_DYNAMIC_MINOR,
> +	.name = "provision",
> +	.nodename = "sgx/provision",
> +	.fops = &sgx_provision_fops,
> +};
> +
>  int __init sgx_drv_init(void)
>  {
>  	unsigned int eax, ebx, ecx, edx;
> @@ -190,5 +197,12 @@ int __init sgx_drv_init(void)
>  		return ret;
>  	}
>  
> +	ret = misc_register(&sgx_dev_provision);
> +	if (ret) {
> +		pr_err("Creating /dev/sgx/provision failed with %d.\n", ret);
> +		misc_deregister(&sgx_dev_enclave);
> +		return ret;
> +	}
> +
>  	return 0;
>  }
> diff --git a/arch/x86/kernel/cpu/sgx/driver.h b/arch/x86/kernel/cpu/sgx/driver.h
> index e4063923115b..72747d01c046 100644
> --- a/arch/x86/kernel/cpu/sgx/driver.h
> +++ b/arch/x86/kernel/cpu/sgx/driver.h
> @@ -23,6 +23,8 @@ extern u64 sgx_attributes_reserved_mask;
>  extern u64 sgx_xfrm_reserved_mask;
>  extern u32 sgx_xsave_size_tbl[64];
>  
> +extern const struct file_operations sgx_provision_fops;
> +
>  long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg);
>  
>  int sgx_drv_init(void);
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index 757cb9a4ae70..713bce437659 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -669,6 +669,50 @@ static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
>  	return ret;
>  }
>  
> +/**
> + * sgx_ioc_enclave_set_attribute - handler for %SGX_IOC_ENCLAVE_SET_ATTRIBUTE
> + * @filep:	open file to /dev/sgx
> + * @arg:	userspace pointer to a struct sgx_enclave_set_attribute instance
> + *
> + * Mark the enclave as being allowed to access a restricted attribute bit.
> + * The requested attribute is specified via the attribute_fd field in the
> + * provided struct sgx_enclave_set_attribute.  The attribute_fd must be a
> + * handle to an SGX attribute file, e.g. ?/dev/sgx/provision".

Maybe this should be simply a double-quote rather than the Unicode left
quote?

Thanks,

Darren.

> + *
> + * Failure to explicitly request access to a restricted attribute will cause
> + * sgx_ioc_enclave_init() to fail.  Currently, the only restricted attribute
> + * is access to the PROVISION_KEY.
> + *
> + * Note, access to the EINITTOKEN_KEY is disallowed entirely.
> + *
> + * Return: 0 on success, -errno otherwise
> + */
> +static long sgx_ioc_enclave_set_attribute(struct sgx_encl *encl,
> +					  void __user *arg)
> +{
> +	struct sgx_enclave_set_attribute params;
> +	struct file *attribute_file;
> +	int ret;
> +
> +	if (copy_from_user(&params, arg, sizeof(params)))
> +		return -EFAULT;
> +
> +	attribute_file = fget(params.attribute_fd);
> +	if (!attribute_file)
> +		return -EINVAL;
> +
> +	if (attribute_file->f_op != &sgx_provision_fops) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	encl->allowed_attributes |= SGX_ATTR_PROVISIONKEY;
> +	ret = 0;
> +
> +out:
> +	fput(attribute_file);
> +	return ret;
> +}
>  
>  long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  {
> @@ -694,6 +738,9 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  	case SGX_IOC_ENCLAVE_INIT:
>  		ret = sgx_ioc_enclave_init(encl, (void __user *)arg);
>  		break;
> +	case SGX_IOC_ENCLAVE_SET_ATTRIBUTE:
> +		ret = sgx_ioc_enclave_set_attribute(encl, (void __user *)arg);
> +		break;
>  	default:
>  		ret = -ENOIOCTLCMD;
>  		break;