From: Dov Murik <dovmurik@linux.ibm.com>
To: Eduardo Habkost <ehabkost@redhat.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
Ashish Kalra <ashish.kalra@amd.com>,
Brijesh Singh <brijesh.singh@amd.com>,
"Michael S . Tsirkin" <mst@redhat.com>,
Tobin Feldman-Fitzthum <tobin@ibm.com>,
James Bottomley <jejb@linux.ibm.com>,
Richard Henderson <richard.henderson@linaro.org>,
qemu-devel@nongnu.org, Hubertus Franke <frankeh@us.ibm.com>,
Tobin Feldman-Fitzthum <tobin@linux.ibm.com>,
Jim Cadden <jcadden@ibm.com>, Paolo Bonzini <pbonzini@redhat.com>,
Laszlo Ersek <lersek@redhat.com>
Subject: Re: [PATCH] x86: add SEV hashing to fw_cfg for kernel/initrd/cmdline
Date: Wed, 16 Jun 2021 15:04:24 +0300 [thread overview]
Message-ID: <19ca38d7-7779-9707-b195-d608f3200951@linux.ibm.com> (raw)
In-Reply-To: <20210615152033.czhsaz44yxtc5ext@habkost.net>
Hi Eduardo,
On 15/06/2021 18:20, Eduardo Habkost wrote:
> On Tue, May 25, 2021 at 06:59:31AM +0000, Dov Murik wrote:
>> From: James Bottomley <jejb@linux.ibm.com>
>>
>> If the VM is using memory encryption and also specifies a kernel/initrd
>> or appended command line, calculate the hashes and add them to the
>> encrypted data. For this to work, OVMF must support an encrypted area
>> to place the data which is advertised via a special GUID in the OVMF
>> reset table (if the GUID doesn't exist, the user isn't allowed to pass
>> in the kernel/initrd/cmdline via the fw_cfg interface).
>>
>> The hashes of each of the files is calculated (or the string in the case
>> of the cmdline with trailing '\0' included). Each entry in the hashes
>> table is GUID identified and since they're passed through the memcrypt
>> interface, the hash of the encrypted data will be accumulated by the
>> PSP.
>>
>> Signed-off-by: James Bottomley <jejb@linux.ibm.com>
>> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
>> [dovmurik@linux.ibm.com: use machine->cgs, remove parsing of GUID
>> strings, remove GCC pragma, fix checkpatch errors]
>> ---
>>
>> OVMF support for handling the table of hashes (verifying that the
>> kernel/initrd/cmdline passed via the fw_cfg interface indeed correspond
>> to the measured hashes in the table) will be posted soon to edk2-devel.
>>
>> ---
>> hw/i386/x86.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++++-
>> 1 file changed, 119 insertions(+), 1 deletion(-)
>>
>
> This is not an objection to the patch itself, but: can we do
> something to move all sev-related code to sev.c? It would make
> the process of assigning a maintainer and reviewing/merging
> future patches much simpler.
>
I'll look into this following Philippe's suggestions.
> I am not familiar with SEV internals, so my only question is
> about configurations where SEV is disabled:
>
> [...]
>> diff --git a/hw/i386/x86.c b/hw/i386/x86.c
>> @@ -778,6 +818,11 @@ void x86_load_linux(X86MachineState *x86ms,
>> const char *initrd_filename = machine->initrd_filename;
>> const char *dtb_filename = machine->dtb;
>> const char *kernel_cmdline = machine->kernel_cmdline;
>> + uint8_t buf[HASH_SIZE];
>> + uint8_t *hash = buf;
>> + size_t hash_len = sizeof(buf);
>> + struct sev_hash_table *sev_ht = NULL;
>> + int sev_ht_index = 0;
>>
>> /* Align to 16 bytes as a paranoia measure */
>> cmdline_size = (strlen(kernel_cmdline) + 16) & ~15;
>> @@ -799,6 +844,22 @@ void x86_load_linux(X86MachineState *x86ms,
>> exit(1);
>> }
>>
>> + if (machine->cgs && machine->cgs->ready) {
>
> machine->cgs doesn't seem to be a SEV-specific field.
> What if machine->cgs->ready is set but SEV is disabled?
>
You're right; I'll change this to sev_enabled() like in
hw/i386/pc_sysfw.c .
-Dov
>> + uint8_t *data;
>> + struct sev_hash_table_descriptor *area;
>> +
>> + if (!pc_system_ovmf_table_find(SEV_HASH_TABLE_RV_GUID, &data, NULL)) {
>> + fprintf(stderr, "qemu: kernel command line specified but OVMF has "
>> + "no hash table guid\n");
>> + exit(1);
>> + }
>> + area = (struct sev_hash_table_descriptor *)data;
>> +
>> + sev_ht = qemu_map_ram_ptr(NULL, area->base);
>> + memcpy(sev_ht->guid, sev_hash_table_header_guid, sizeof(sev_ht->guid));
>> + sev_ht->len = sizeof(*sev_ht);
>> + }
>> +
>> /* kernel protocol version */
>> if (ldl_p(header + 0x202) == 0x53726448) {
>> protocol = lduw_p(header + 0x206);
> [...]
>
next prev parent reply other threads:[~2021-06-16 12:06 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 6:59 [PATCH] x86: add SEV hashing to fw_cfg for kernel/initrd/cmdline Dov Murik
2021-05-25 13:10 ` Dov Murik
2021-06-14 7:08 ` Dov Murik
2021-06-15 15:20 ` Eduardo Habkost
2021-06-15 19:53 ` Philippe Mathieu-Daudé
2021-06-17 12:48 ` Dov Murik
2021-06-17 15:48 ` Philippe Mathieu-Daudé
2021-06-21 8:44 ` Thomas Huth
2021-06-21 9:15 ` Philippe Mathieu-Daudé
2021-06-21 9:42 ` Philippe Mathieu-Daudé
2021-06-17 17:22 ` Eduardo Habkost
2021-06-17 19:16 ` Dov Murik
2021-06-17 20:35 ` Eduardo Habkost
2021-06-16 12:04 ` Dov Murik [this message]
2021-07-03 16:42 ` Michael S. Tsirkin
2021-07-04 6:16 ` Dov Murik
2021-07-04 6:29 ` Michael S. Tsirkin
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