linux-kernel - Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for SNP_{GET, GET_EXT}

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <064cdef7-d90b-9fa6-fc04-30637c992f60@amd.com>
Date:   Tue, 15 Aug 2023 15:50:18 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Dan Williams <dan.j.williams@...el.com>, linux-coco@...ts.linux.dev
Cc:     Borislav Petkov <bp@...en8.de>,
        Dionna Glaze <dionnaglaze@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>, peterz@...radead.org,
        x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 5/5] virt: sevguest: Add TSM_REPORTS support for
 SNP_{GET, GET_EXT}_REPORT

On 8/14/23 02:43, Dan Williams wrote:
> The sevguest driver was a first mover in the confidential computing
> space. As a first mover that afforded some leeway to build the driver
> without concern for common infrastructure.
> 
> Now that sevguest is no longer a singleton [1] the common operation of
> building and transmitting attestation report blobs can / should be made
> common. In this model the so called "TSM-provider" implementations can
> share a common envelope ABI even if the contents of that envelope remain
> vendor-specific. When / if the industry agrees on an attestation record
> format, that definition can also fit in the same ABI. In the meantime
> the kernel's maintenance burden is reduced and collaboration on the
> commons is increased.
> 
> Convert sevguest to use CONFIG_TSM_REPORTS to retrieve the blobs that
> the SNP_{GET,GET_EXT}_REPORT ioctls produce. An example flow for
> retrieving the SNP_GET_REPORT blob via the TSM interface utility,
> assuming no nonce and VMPL==2:
> 
>      echo 2 > /sys/class/tsm/tsm0/privlevel
>      dd if=/dev/urandom bs=64 count=1 | xxd -p -c 0 > /sys/class/tsm/tsm0/inhex
>      hexdump -C /sys/class/tsm/tsm0/outblob
> 
> ...while the SNP_GET_EXT_REPORT flow needs to additionally set the
> format to "extended":
> 
>      echo 2 > /sys/class/tsm/tsm0/privlevel
>      echo extended > /sys/class/tsm/tsm0/format
>      dd if=/dev/urandom bs=64 count=1 | xxd -p -c 0 > /sys/class/tsm/tsm0/inhex
>      hexdump -C /sys/class/tsm/tsm0/outblob
> 
> The old ioctls can be lazily deprecated, the main motivation of this
> effort is to stop the proliferation of new ioctls, and to increase
> cross-vendor colloboration.
> 
> Note, only compile-tested.

I just got back from vacation, so I'll apply and test as soon as I get a 
chance.

> 
> Link: http://lore.kernel.org/r/64961c3baf8ce_142af829436@dwillia2-xfh.jf.intel.com.notmuch [1]
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Dionna Glaze <dionnaglaze@...gle.com>
> Cc: Brijesh Singh <brijesh.singh@....com>
> Signed-off-by: Dan Williams <dan.j.williams@...el.com>
> ---
>   drivers/virt/coco/sev-guest/Kconfig     |    1
>   drivers/virt/coco/sev-guest/sev-guest.c |   81 +++++++++++++++++++++++++++++++
>   2 files changed, 82 insertions(+)
> 
> diff --git a/drivers/virt/coco/sev-guest/Kconfig b/drivers/virt/coco/sev-guest/Kconfig
> index da2d7ca531f0..1cffc72c41cb 100644
> --- a/drivers/virt/coco/sev-guest/Kconfig
> +++ b/drivers/virt/coco/sev-guest/Kconfig
> @@ -5,6 +5,7 @@ config SEV_GUEST
>   	select CRYPTO
>   	select CRYPTO_AEAD2
>   	select CRYPTO_GCM
> +	select TSM_REPORTS
>   	help
>   	  SEV-SNP firmware provides the guest a mechanism to communicate with
>   	  the PSP without risk from a malicious hypervisor who wishes to read,
> diff --git a/drivers/virt/coco/sev-guest/sev-guest.c b/drivers/virt/coco/sev-guest/sev-guest.c
> index f48c4764a7a2..5941081502e8 100644
> --- a/drivers/virt/coco/sev-guest/sev-guest.c
> +++ b/drivers/virt/coco/sev-guest/sev-guest.c
> @@ -16,6 +16,7 @@
>   #include <linux/miscdevice.h>
>   #include <linux/set_memory.h>
>   #include <linux/fs.h>
> +#include <linux/tsm.h>
>   #include <crypto/aead.h>
>   #include <linux/scatterlist.h>
>   #include <linux/psp-sev.h>
> @@ -769,6 +770,78 @@ static u8 *get_vmpck(int id, struct snp_secrets_page_layout *layout, u32 **seqno
>   	return key;
>   }
>   
> +static u8 *sev_report_new(struct device *dev, const struct tsm_desc *desc,
> +			  size_t *outblob_len)
> +{
> +	struct snp_guest_dev *snp_dev = dev_get_drvdata(dev);
> +	const int report_size = SZ_16K;

The response buffer from the PSP is limited to 4K, so the report size can 
be SZ_4K.

> +	const int ext_size = SZ_16K;
> +	int ret, size;
> +
> +	if (desc->inblob_len != 64)
> +		return ERR_PTR(-EINVAL);
> +
> +	if (desc->outblob_format == TSM_FORMAT_EXTENDED)
> +		size = report_size + ext_size;
> +	else
> +		size = report_size;
> +
> +	u8 *buf __free(kvfree) = kvzalloc(size, GFP_KERNEL);
> +
> +	if (desc->outblob_format == TSM_FORMAT_EXTENDED) {
> +		struct snp_ext_report_req ext_req = {
> +			.data = { .vmpl = desc->privlevel },
> +			.certs_address = (__u64)buf + report_size,
> +			.certs_len = ext_size,
> +		};
> +		memcpy(&ext_req.data.user_data, desc->inblob, desc->inblob_len);
> +
> +		struct snp_guest_request_ioctl input = {
> +			.msg_version = 1,
> +			.req_data = (__u64)&ext_req,
> +			.resp_data = (__u64)buf,
> +		};

Won't the compiler complain about this declaration being after the memcpy()?

> +
> +		ret = get_ext_report(snp_dev, &input, SNP_KARG);
> +	} else {
> +		struct snp_report_req req = {
> +			.vmpl = desc->privlevel,
> +		};
> +		memcpy(&req.user_data, desc->inblob, desc->inblob_len);
> +
> +		struct snp_guest_request_ioctl input = {
> +			.msg_version = 1,
> +			.req_data = (__u64) &req,
> +			.resp_data = (__u64) buf,
> +		};

Ditto here.

Thanks,
Tom

> +
> +		ret = get_report(snp_dev, &input, SNP_KARG);
> +	}
> +
> +	if (ret)
> +		return ERR_PTR(ret);
> +
> +	*outblob_len = size;
> +	no_free_ptr(buf);
> +	return buf;
> +}
> +
> +static const struct tsm_ops sev_tsm_ops = {
> +	.name = KBUILD_MODNAME,
> +	.report_new = sev_report_new,
> +};
> +
> +static const struct attribute_group *sev_tsm_attribute_groups[] = {
> +	&tsm_default_attribute_group,
> +	&tsm_extra_attribute_group,
> +	NULL,
> +};
> +
> +static void unregister_sev_tsm(void *data)
> +{
> +	unregister_tsm(&sev_tsm_ops);
> +}
> +
>   static int __init sev_guest_probe(struct platform_device *pdev)
>   {
>   	struct snp_secrets_page_layout *layout;
> @@ -842,6 +915,14 @@ static int __init sev_guest_probe(struct platform_device *pdev)
>   	snp_dev->input.resp_gpa = __pa(snp_dev->response);
>   	snp_dev->input.data_gpa = __pa(snp_dev->certs_data);
>   
> +	ret = register_tsm(&sev_tsm_ops, &pdev->dev, sev_tsm_attribute_groups);
> +	if (ret)
> +		goto e_free_cert_data;
> +
> +	ret = devm_add_action_or_reset(&pdev->dev, unregister_sev_tsm, NULL);
> +	if (ret)
> +		goto e_free_cert_data;
> +
>   	ret =  misc_register(misc);
>   	if (ret)
>   		goto e_free_cert_data;
>