Currently, there is no privilege separation of the SEV command; you can
run them all or none of them. This is less than ideal because it means
that a compromise of the code which launches VMs could make permanent
change to the SEV certifcate chain which will affect others.
These commands are required to attest the VM environment:
- SEV_PDH_CERT_EXPORT
- SEV_PLATFORM_STATUS
- SEV_GET_{ID,ID2}
These commands manage the SEV certificate chain:
- SEV_PEK_CERR_IMPORT
- SEV_FACTORY_RESET
- SEV_PEK_GEN
- SEV_PEK_CSR
- SEV_PDH_GEN
Lets add the CAP_SYS_ADMIN check for the group of the commands which alters
the SEV certificate chain to provide some level of privilege separation.
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Gary Hook <gary.hook@xxxxxxx>
Cc: Erdem Aktas <erdemaktas@xxxxxxxxxx>
Cc: Tom Lendacky <Thomas.Lendacky@xxxxxxx>
Tested-by: David Rientjes <rientjes@xxxxxxxxxx>
Co-developed-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
---
drivers/crypto/ccp/psp-dev.c | 29 ++++++++++++++++++++++-------
drivers/crypto/ccp/psp-dev.h | 1 +
2 files changed, 23 insertions(+), 7 deletions(-)
diff --git a/drivers/crypto/ccp/psp-dev.c b/drivers/crypto/ccp/psp-dev.c
index c4da8d1a9abc..5ff842c03a70 100644
--- a/drivers/crypto/ccp/psp-dev.c
+++ b/drivers/crypto/ccp/psp-dev.c
@@ -294,6 +294,9 @@ static int sev_ioctl_do_reset(struct sev_issue_cmd *argp)
{
int state, rc;
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
/*
* The SEV spec requires that FACTORY_RESET must be issued in
* UNINIT state. Before we go further lets check if any guest is
@@ -338,6 +341,9 @@ static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp)
{
int rc;
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
if (psp_master->sev_state == SEV_STATE_UNINIT) {
rc = __sev_platform_init_locked(&argp->error);
if (rc)
@@ -354,6 +360,9 @@ static int sev_ioctl_do_pek_csr(struct sev_issue_cmd *argp)
void *blob = NULL;
int ret;
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
return -EFAULT;
@@ -540,6 +549,9 @@ static int sev_ioctl_do_pek_import(struct sev_issue_cmd *argp)
void *pek_blob, *oca_blob;
int ret;
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
return -EFAULT;
@@ -695,6 +707,16 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp)
struct sev_data_pdh_cert_export *data;
int ret;
+ /* If platform is not in INIT state then transition it to INIT. */
+ if (psp_master->sev_state != SEV_STATE_INIT) {
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ ret = __sev_platform_init_locked(&argp->error);
+ if (ret)
+ return ret;
+ }
+
if (copy_from_user(&input, (void __user *)argp->data, sizeof(input)))
return -EFAULT;
@@ -741,13 +763,6 @@ static int sev_ioctl_do_pdh_export(struct sev_issue_cmd *argp)
data->cert_chain_len = input.cert_chain_len;
cmd:
- /* If platform is not in INIT state then transition it to INIT. */
- if (psp_master->sev_state != SEV_STATE_INIT) {
- ret = __sev_platform_init_locked(&argp->error);
- if (ret)
- goto e_free_cert;
- }
-
ret = __sev_do_cmd_locked(SEV_CMD_PDH_CERT_EXPORT, data, &argp->error);
/* If we query the length, FW responded with expected data. */
diff --git a/drivers/crypto/ccp/psp-dev.h b/drivers/crypto/ccp/psp-dev.h
index 82a084f02990..dd516b35ba86 100644
--- a/drivers/crypto/ccp/psp-dev.h
+++ b/drivers/crypto/ccp/psp-dev.h
@@ -23,6 +23,7 @@
#include <linux/dmaengine.h>
#include <linux/psp-sev.h>
#include <linux/miscdevice.h>
+#include <linux/capability.h>
#include "sp-dev.h"
--
2.17.1
