Re: [PATCH v36 14/24] x86/sgx: Add SGX_IOC_ENCLAVE_INIT

[Darren Kenny]

On Thursday, 2020-07-16 at 16:52:53 +03, Jarkko Sakkinen wrote:
> Add an ioctl that performs ENCLS[EINIT], which locks down the measurement
> and initializes the enclave for entrance. After this, new pages can no
> longer be added.
>
> 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>
> ---
>  arch/x86/include/uapi/asm/sgx.h |  11 ++
>  arch/x86/kernel/cpu/sgx/ioctl.c | 188 ++++++++++++++++++++++++++++++++
>  2 files changed, 199 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/sgx.h b/arch/x86/include/uapi/asm/sgx.h
> index c8f199b3fb6f..5edb08ab8fd0 100644
> --- a/arch/x86/include/uapi/asm/sgx.h
> +++ b/arch/x86/include/uapi/asm/sgx.h
> @@ -23,6 +23,8 @@ enum sgx_page_flags {
>  	_IOW(SGX_MAGIC, 0x00, struct sgx_enclave_create)
>  #define SGX_IOC_ENCLAVE_ADD_PAGES \
>  	_IOWR(SGX_MAGIC, 0x01, struct sgx_enclave_add_pages)
> +#define SGX_IOC_ENCLAVE_INIT \
> +	_IOW(SGX_MAGIC, 0x02, struct sgx_enclave_init)
>  
>  /**
>   * struct sgx_enclave_create - parameter structure for the
> @@ -52,4 +54,13 @@ struct sgx_enclave_add_pages {
>  	__u64	count;
>  };
>  
> +/**
> + * struct sgx_enclave_init - parameter structure for the
> + *                           %SGX_IOC_ENCLAVE_INIT ioctl
> + * @sigstruct:	address for the SIGSTRUCT data
> + */
> +struct sgx_enclave_init {
> +	__u64 sigstruct;
> +};
> +
>  #endif /* _UAPI_ASM_X86_SGX_H */
> diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
> index c63a51362d14..3444de955191 100644
> --- a/arch/x86/kernel/cpu/sgx/ioctl.c
> +++ b/arch/x86/kernel/cpu/sgx/ioctl.c
> @@ -16,6 +16,9 @@
>  #include "encl.h"
>  #include "encls.h"
>  
> +/* A per-cpu cache for the last known values of IA32_SGXLEPUBKEYHASHx MSRs. */
> +static DEFINE_PER_CPU(u64 [4], sgx_lepubkeyhash_cache);
> +
>  static u32 sgx_calc_ssa_frame_size(u32 miscselect, u64 xfrm)
>  {
>  	u32 size_max = PAGE_SIZE;
> @@ -485,6 +488,188 @@ static long sgx_ioc_enclave_add_pages(struct sgx_encl *encl, void __user *arg)
>  	return ret;
>  }
>  
> +static int __sgx_get_key_hash(struct crypto_shash *tfm, const void *modulus,
> +			      void *hash)
> +{
> +	SHASH_DESC_ON_STACK(shash, tfm);
> +
> +	shash->tfm = tfm;
> +
> +	return crypto_shash_digest(shash, modulus, SGX_MODULUS_SIZE, hash);
> +}
> +
> +static int sgx_get_key_hash(const void *modulus, void *hash)
> +{
> +	struct crypto_shash *tfm;
> +	int ret;
> +
> +	tfm = crypto_alloc_shash("sha256", 0, CRYPTO_ALG_ASYNC);
> +	if (IS_ERR(tfm))
> +		return PTR_ERR(tfm);
> +
> +	ret = __sgx_get_key_hash(tfm, modulus, hash);
> +
> +	crypto_free_shash(tfm);
> +	return ret;
> +}
> +
> +static void sgx_update_lepubkeyhash_msrs(u64 *lepubkeyhash, bool enforce)
> +{
> +	u64 *cache;
> +	int i;
> +
> +	cache = per_cpu(sgx_lepubkeyhash_cache, smp_processor_id());
> +	for (i = 0; i < 4; i++) {
> +		if (enforce || (lepubkeyhash[i] != cache[i])) {
> +			wrmsrl(MSR_IA32_SGXLEPUBKEYHASH0 + i, lepubkeyhash[i]);
> +			cache[i] = lepubkeyhash[i];
> +		}
> +	}
> +}
> +
> +static int sgx_einit(struct sgx_sigstruct *sigstruct, void *token,
> +		     struct sgx_epc_page *secs, u64 *lepubkeyhash)
> +{
> +	int ret;
> +
> +	preempt_disable();
> +	sgx_update_lepubkeyhash_msrs(lepubkeyhash, false);
> +	ret = __einit(sigstruct, token, sgx_get_epc_addr(secs));
> +	if (ret == SGX_INVALID_EINITTOKEN) {
> +		sgx_update_lepubkeyhash_msrs(lepubkeyhash, true);
> +		ret = __einit(sigstruct, token, sgx_get_epc_addr(secs));
> +	}
> +	preempt_enable();
> +	return ret;
> +}
> +
> +static int sgx_encl_init(struct sgx_encl *encl, struct sgx_sigstruct *sigstruct,
> +			 void *token)
> +{
> +	u64 mrsigner[4];
> +	int ret;
> +	int i;
> +	int j;
> +
> +	/* Check that the required attributes have been authorized. */
> +	if (encl->secs_attributes & ~encl->allowed_attributes)
> +		return -EACCES;
> +
> +	ret = sgx_get_key_hash(sigstruct->modulus, mrsigner);
> +	if (ret)
> +		return ret;
> +
> +	mutex_lock(&encl->lock);
> +
> +	/*
> +	 * Periodically, EINIT polls for certain asynchronous events. If such an
> +	 * event is detected, it completes with SGX_UNMSKED_EVENT.
> +	 */
> +	for (i = 0; i < SGX_EINIT_SLEEP_COUNT; i++) {
> +		for (j = 0; j < SGX_EINIT_SPIN_COUNT; j++) {
> +			ret = sgx_einit(sigstruct, token, encl->secs.epc_page,
> +					mrsigner);
> +			if (ret == SGX_UNMASKED_EVENT)
> +				continue;
> +			else
> +				break;
> +		}
> +
> +		if (ret != SGX_UNMASKED_EVENT)
> +			break;
> +
> +		msleep_interruptible(SGX_EINIT_SLEEP_TIME);
> +
> +		if (signal_pending(current)) {
> +			ret = -ERESTARTSYS;
> +			goto err_out;
> +		}
> +	}
> +
> +	if (ret & ENCLS_FAULT_FLAG) {
> +		if (encls_failed(ret))
> +			ENCLS_WARN(ret, "EINIT");
> +
> +		sgx_encl_destroy(encl);
> +		ret = -EFAULT;
> +	} else if (ret) {
> +		pr_debug("EINIT returned %d\n", ret);
> +		ret = -EPERM;
> +	} else {
> +		atomic_or(SGX_ENCL_INITIALIZED, &encl->flags);
> +	}
> +
> +err_out:
> +	mutex_unlock(&encl->lock);
> +	return ret;
> +}
> +
> +/**
> + * sgx_ioc_enclave_init - handler for %SGX_IOC_ENCLAVE_INIT
> + *
> + * @filep:	open file to /dev/sgx
> + * @arg:	userspace pointer to a struct sgx_enclave_init instance
> + *
> + * Flush any outstanding enqueued EADD operations and perform EINIT.  The
> + * Launch Enclave Public Key Hash MSRs are rewritten as necessary to match
> + * the enclave's MRSIGNER, which is caculated from the provided sigstruct.
> + *
> + * Return:
> + *   0 on success,
> + *   SGX error code on EINIT failure,
> + *   -errno otherwise
> + */
> +static long sgx_ioc_enclave_init(struct sgx_encl *encl, void __user *arg)
> +{
> +	struct sgx_sigstruct *sigstruct;
> +	struct sgx_enclave_init einit;
> +	struct page *initp_page;
> +	void *token;
> +	int ret;
> +
> +	if ((atomic_read(&encl->flags) & SGX_ENCL_INITIALIZED) ||
> +	    !(atomic_read(&encl->flags) & SGX_ENCL_CREATED))
> +		return -EINVAL;
> +
> +	if (copy_from_user(&einit, arg, sizeof(einit)))
> +		return -EFAULT;
> +
> +	initp_page = alloc_page(GFP_KERNEL);
> +	if (!initp_page)
> +		return -ENOMEM;
> +
> +	sigstruct = kmap(initp_page);
> +	token = (void *)((unsigned long)sigstruct + PAGE_SIZE / 2);
> +	memset(token, 0, SGX_LAUNCH_TOKEN_SIZE);
> +
> +	if (copy_from_user(sigstruct, (void __user *)einit.sigstruct,
> +			   sizeof(*sigstruct))) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	/*
> +	 * A legacy field used with Intel signed enclaves. These used to mean
> +	 * regular and architectural enclaves. The CPU only accepts these values
> +	 * but they do not have any other meaning.
> +	 *
> +	 * Thus, reject any other values.
> +	 */
> +	if (sigstruct->header.vendor != 0x0000 &&
> +	    sigstruct->header.vendor != 0x8086) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
> +	ret = sgx_encl_init(encl, sigstruct, token);
> +
> +out:
> +	kunmap(initp_page);
> +	__free_page(initp_page);
> +	return ret;
> +}
> +
> +
>  long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  {
>  	struct sgx_encl *encl = filep->private_data;
> @@ -506,6 +691,9 @@ long sgx_ioctl(struct file *filep, unsigned int cmd, unsigned long arg)
>  	case SGX_IOC_ENCLAVE_ADD_PAGES:
>  		ret = sgx_ioc_enclave_add_pages(encl, (void __user *)arg);
>  		break;
> +	case SGX_IOC_ENCLAVE_INIT:
> +		ret = sgx_ioc_enclave_init(encl, (void __user *)arg);
> +		break;
>  	default:
>  		ret = -ENOIOCTLCMD;
>  		break;
> -- 
> 2.25.1