From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-lf1-f51.google.com (mail-lf1-f51.google.com [209.85.167.51]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 337AD2C82 for ; Thu, 18 Nov 2021 16:43:20 +0000 (UTC) Received: by mail-lf1-f51.google.com with SMTP id b1so28694619lfs.13 for ; Thu, 18 Nov 2021 08:43:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=A7D/BeXVr7wzzWFs8SKVTpLA5OK3s6ikrHABb23KOco=; b=CqP/wh5rSorV/TnAQxzdgsZz00pJ5cWLtZd6e3yhJ0X2NfcSIeOGNa4K1m8IOgAuZ/ IhTPa0XJNMCiP+pgVih/Bi3fq+TwkhnPnoUretxdR/GVsXAbwudVYOECqRPhHYqKXLFQ IWNRqYT+ZOi+IcKyGcxDtm9HuylzUxlZ8WwILX5upefDxs8JGP6Q2BmfWBsc3yHywHAX 9tg08Uy5hehL2b/S0KNhF2j1aITHPZTiUW1kXHrP4cuqQJJCU2ydhZs6+YN1zZ0LvLXR xNfmFuA0sXeU3wxMPjanG//zwdlWx6bTfDU1DGAk3gOII5FKYLJHJgajYOYiOX31wQsP LAww== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=A7D/BeXVr7wzzWFs8SKVTpLA5OK3s6ikrHABb23KOco=; b=THW5zj1ljlMP8DA+KFNCgbDqzP91HVRrmSzKRlOMa76011oVYNvwz9yKSA1ZAKK95Y alJnn/dgebGaWNWQcgZ93Gi8rj9ibXQwSUPVHpMtud4z6F9JzPGjcX0umZiRXsw6/tYG d59ZaXZTJBtynOx/XynIzOZEF0yp18UAbN9xhdNxkCcpWqEpiJGDlyTNxvQZzr3KmrKk GDGlC4HUmwN9FfJ8GRD5Z73F1svjADVEjK7dcXm6kTYizddIwNN9xK19rwLvAQcI2L7W 0LW1ndTmXrD7XDfHFq6FVsL/jHMUxgRCJJc9rdi4GfaF7z/ka4A41Axm87ZI2KjddgXx HOBw== X-Gm-Message-State: AOAM532lowTlHsUokR2qXr/MeS98Az4pN3u6z7ukxazwt2xRX7dmqlaP 3kFVqA/qbq2zCvqjwF1WSxb4eN6nroHKA0Y1ole80Q== X-Google-Smtp-Source: ABdhPJxW6myjWm6lja6OnE0jaItEXzM/1vqY0/QtkI9jvuFbZMxUM+NzZUA0oYBmrWBnvhOYOZf0hJ2GBlFtQttYCpA= X-Received: by 2002:a05:6512:2804:: with SMTP id cf4mr1847789lfb.644.1637253797827; Thu, 18 Nov 2021 08:43:17 -0800 (PST) Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20211110220731.2396491-1-brijesh.singh@amd.com> <20211110220731.2396491-45-brijesh.singh@amd.com> In-Reply-To: <20211110220731.2396491-45-brijesh.singh@amd.com> From: Peter Gonda Date: Thu, 18 Nov 2021 09:43:06 -0700 Message-ID: Subject: Re: [PATCH v7 44/45] virt: sevguest: Add support to derive key To: Brijesh Singh Cc: x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org, linux-coco@lists.linux.dev, linux-mm@kvack.org, Thomas Gleixner , Ingo Molnar , Joerg Roedel , Tom Lendacky , "H. Peter Anvin" , Ard Biesheuvel , Paolo Bonzini , Sean Christopherson , Vitaly Kuznetsov , Jim Mattson , Andy Lutomirski , Dave Hansen , Sergio Lopez , Peter Zijlstra , Srinivas Pandruvada , David Rientjes , Dov Murik , Tobin Feldman-Fitzthum , Borislav Petkov , Michael Roth , Vlastimil Babka , "Kirill A . Shutemov" , Andi Kleen , "Dr . David Alan Gilbert" , tony.luck@intel.com, marcorr@google.com, sathyanarayanan.kuppuswamy@linux.intel.com Content-Type: text/plain; charset="UTF-8" On Wed, Nov 10, 2021 at 3:09 PM Brijesh Singh wrote: > > The SNP_GET_DERIVED_KEY ioctl interface can be used by the SNP guest to > ask the firmware to provide a key derived from a root key. The derived > key may be used by the guest for any purposes it choose, such as a > sealing key or communicating with the external entities. > > See SEV-SNP firmware spec for more information. > > Signed-off-by: Brijesh Singh > --- > Documentation/virt/coco/sevguest.rst | 19 ++++++++++- > drivers/virt/coco/sevguest/sevguest.c | 49 +++++++++++++++++++++++++++ > include/uapi/linux/sev-guest.h | 24 +++++++++++++ > 3 files changed, 91 insertions(+), 1 deletion(-) > > diff --git a/Documentation/virt/coco/sevguest.rst b/Documentation/virt/coco/sevguest.rst > index 002c90946b8a..0bd9a65e0370 100644 > --- a/Documentation/virt/coco/sevguest.rst > +++ b/Documentation/virt/coco/sevguest.rst > @@ -64,10 +64,27 @@ The SNP_GET_REPORT ioctl can be used to query the attestation report from the > SEV-SNP firmware. The ioctl uses the SNP_GUEST_REQUEST (MSG_REPORT_REQ) command > provided by the SEV-SNP firmware to query the attestation report. > > -On success, the snp_report_resp.data will contains the report. The report > +On success, the snp_report_resp.data will contain the report. The report > will contain the format described in the SEV-SNP specification. See the SEV-SNP > specification for further details. > > +2.2 SNP_GET_DERIVED_KEY > +----------------------- > +:Technology: sev-snp > +:Type: guest ioctl > +:Parameters (in): struct snp_derived_key_req > +:Returns (out): struct snp_derived_key_req on success, -negative on error > + > +The SNP_GET_DERIVED_KEY ioctl can be used to get a key derive from a root key. derived > +The derived key can be used by the guest for any purpose, such as sealing keys > +or communicating with external entities. > + > +The ioctl uses the SNP_GUEST_REQUEST (MSG_KEY_REQ) command provided by the > +SEV-SNP firmware to derive the key. See SEV-SNP specification for further details > +on the various fields passed in the key derivation request. > + > +On success, the snp_derived_key_resp.data will contains the derived key value. See ".data will contain the..." or ".data contains the derived key..." > +the SEV-SNP specification for further details. > > Reference > --------- > diff --git a/drivers/virt/coco/sevguest/sevguest.c b/drivers/virt/coco/sevguest/sevguest.c > index 982714c1b4ca..bece6856573e 100644 > --- a/drivers/virt/coco/sevguest/sevguest.c > +++ b/drivers/virt/coco/sevguest/sevguest.c > @@ -392,6 +392,52 @@ static int get_report(struct snp_guest_dev *snp_dev, struct snp_guest_request_io > return rc; > } > > +static int get_derived_key(struct snp_guest_dev *snp_dev, struct snp_guest_request_ioctl *arg) > +{ > + struct snp_guest_crypto *crypto = snp_dev->crypto; > + struct snp_derived_key_resp resp = {0}; > + struct snp_derived_key_req req; > + int rc, resp_len; > + u8 buf[89]; Could we document this magic number? > + > + if (!arg->req_data || !arg->resp_data) > + return -EINVAL; > + > + /* Copy the request payload from userspace */ > + if (copy_from_user(&req, (void __user *)arg->req_data, sizeof(req))) > + return -EFAULT; > + > + /* Message version must be non-zero */ > + if (!req.msg_version) > + return -EINVAL; > + > + /* > + * The intermediate response buffer is used while decrypting the > + * response payload. Make sure that it has enough space to cover the > + * authtag. > + */ > + resp_len = sizeof(resp.data) + crypto->a_len; > + if (sizeof(buf) < resp_len) > + return -ENOMEM; > + > + /* Issue the command to get the attestation report */ > + rc = handle_guest_request(snp_dev, SVM_VMGEXIT_GUEST_REQUEST, req.msg_version, > + SNP_MSG_KEY_REQ, &req.data, sizeof(req.data), buf, resp_len, > + &arg->fw_err); > + if (rc) > + goto e_free; Should we check the first 32 bits of |data| here since that is a status field? If we see 16h here we could return -EINVAL, or better to let userspace deal with that error handling? > + > + /* Copy the response payload to userspace */ > + memcpy(resp.data, buf, sizeof(resp.data)); > + if (copy_to_user((void __user *)arg->resp_data, &resp, sizeof(resp))) > + rc = -EFAULT; > + > +e_free: > + memzero_explicit(buf, sizeof(buf)); > + memzero_explicit(&resp, sizeof(resp)); > + return rc; > +} > + > static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long arg) > { > struct snp_guest_dev *snp_dev = to_snp_dev(file); > @@ -417,6 +463,9 @@ static long snp_guest_ioctl(struct file *file, unsigned int ioctl, unsigned long > case SNP_GET_REPORT: > ret = get_report(snp_dev, &input); > break; > + case SNP_GET_DERIVED_KEY: > + ret = get_derived_key(snp_dev, &input); > + break; > default: > break; > } > diff --git a/include/uapi/linux/sev-guest.h b/include/uapi/linux/sev-guest.h > index eda7edcffda8..f6d9c136ff4d 100644 > --- a/include/uapi/linux/sev-guest.h > +++ b/include/uapi/linux/sev-guest.h > @@ -36,9 +36,33 @@ struct snp_guest_request_ioctl { > __u64 fw_err; > }; > > +struct __snp_derived_key_req { > + __u32 root_key_select; > + __u32 rsvd; > + __u64 guest_field_select; > + __u32 vmpl; > + __u32 guest_svn; > + __u64 tcb_version; > +}; > + > +struct snp_derived_key_req { > + /* message version number (must be non-zero) */ > + __u8 msg_version; > + > + struct __snp_derived_key_req data; > +}; > + > +struct snp_derived_key_resp { > + /* response data, see SEV-SNP spec for the format */ > + __u8 data[64]; > +}; > + > #define SNP_GUEST_REQ_IOC_TYPE 'S' > > /* Get SNP attestation report */ > #define SNP_GET_REPORT _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x0, struct snp_guest_request_ioctl) > > +/* Get a derived key from the root */ > +#define SNP_GET_DERIVED_KEY _IOWR(SNP_GUEST_REQ_IOC_TYPE, 0x1, struct snp_guest_request_ioctl) > + > #endif /* __UAPI_LINUX_SEV_GUEST_H_ */ > -- > 2.25.1 >