[PATCH v5 17/25] powerpc/pseries: Implement signed update for PLPKS objects

Andrew Donnellan
2023-01-31T06:41:25Z

From: Nayna Jain <nayna@linux.ibm.com>

The Platform Keystore provides a signed update interface which can be used
to create, replace or append to certain variables in the PKS in a secure
fashion, with the hypervisor requiring that the update be signed using the
Platform Key.

Implement an interface to the H_PKS_SIGNED_UPDATE hcall in the plpks
driver to allow signed updates to PKS objects.

(The plpks driver doesn't need to do any cryptography or otherwise handle
the actual signed variable contents - that will be handled by userspace
tooling.)

Signed-off-by: Nayna Jain <nayna@linux.ibm.com>
[ajd: split patch, add timeout handling and misc cleanups]
Co-developed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Russell Currey <ruscur@russell.cc>

---

v3: Merge plpks fixes and signed update series with secvar series

Fix error code handling in plpks_confirm_object_flushed() (ruscur)

Pass plpks_var struct to plpks_signed_update_var() by reference (mpe)

Consistent constant naming scheme (ruscur)

v4: Fix MAX_HCALL_OPCODE rebasing issue (npiggin)

v5: Drop the EXPORT_SYMBOL since we don't need it (npiggin)

Return an error if plpks_signed_update_var() is called with non-NULL
component (npiggin)
---
arch/powerpc/include/asm/hvcall.h | 1 +
arch/powerpc/include/asm/plpks.h | 5 ++
arch/powerpc/platforms/pseries/plpks.c | 74 ++++++++++++++++++++++++--
3 files changed, 75 insertions(+), 5 deletions(-)

diff --git a/arch/powerpc/include/asm/hvcall.h b/arch/powerpc/include/asm/hvcall.h
index 95fd7f9485d5..c099780385dd 100644
--- a/arch/powerpc/include/asm/hvcall.h
+++ b/arch/powerpc/include/asm/hvcall.h
@@ -335,6 +335,7 @@
#define H_RPT_INVALIDATE 0x448
#define H_SCM_FLUSH 0x44C
#define H_GET_ENERGY_SCALE_INFO 0x450
+#define H_PKS_SIGNED_UPDATE 0x454
#define H_WATCHDOG 0x45C
#define MAX_HCALL_OPCODE H_WATCHDOG

diff --git a/arch/powerpc/include/asm/plpks.h b/arch/powerpc/include/asm/plpks.h
index 7c5f51a9af7c..e7204e6c0ca4 100644
--- a/arch/powerpc/include/asm/plpks.h
+++ b/arch/powerpc/include/asm/plpks.h
@@ -68,6 +68,11 @@ struct plpks_var_name_list {
struct plpks_var_name varlist[];
};

+/**
+ * Updates the authenticated variable. It expects NULL as the component.
+ */
+int plpks_signed_update_var(struct plpks_var *var, u64 flags);
+
/**
* Writes the specified var and its data to PKS.
* Any caller of PKS driver should present a valid component type for
diff --git a/arch/powerpc/platforms/pseries/plpks.c b/arch/powerpc/platforms/pseries/plpks.c
index 1189246b03dc..cee06fb9a370 100644
--- a/arch/powerpc/platforms/pseries/plpks.c
+++ b/arch/powerpc/platforms/pseries/plpks.c
@@ -81,6 +81,12 @@ static int pseries_status_to_err(int rc)
err = -ENOENT;
break;
case H_BUSY:
+ case H_LONG_BUSY_ORDER_1_MSEC:
+ case H_LONG_BUSY_ORDER_10_MSEC:
+ case H_LONG_BUSY_ORDER_100_MSEC:
+ case H_LONG_BUSY_ORDER_1_SEC:
+ case H_LONG_BUSY_ORDER_10_SEC:
+ case H_LONG_BUSY_ORDER_100_SEC:
err = -EBUSY;
break;
case H_AUTHORITY:
@@ -184,14 +190,17 @@ static struct label *construct_label(char *component, u8 varos, u8 *name,
u16 namelen)
{
struct label *label;
- size_t slen;
+ size_t slen = 0;

if (!name || namelen > PLPKS_MAX_NAME_SIZE)
return ERR_PTR(-EINVAL);

- slen = strlen(component);
- if (component && slen > sizeof(label->attr.prefix))
- return ERR_PTR(-EINVAL);
+ // Support NULL component for signed updates
+ if (component) {
+ slen = strlen(component);
+ if (slen > sizeof(label->attr.prefix))
+ return ERR_PTR(-EINVAL);
+ }

// The label structure must not cross a page boundary, so we align to the next power of 2
label = kzalloc(roundup_pow_of_two(sizeof(*label)), GFP_KERNEL);
@@ -397,6 +406,61 @@ static int plpks_confirm_object_flushed(struct label *label,
return pseries_status_to_err(rc);
}

+int plpks_signed_update_var(struct plpks_var *var, u64 flags)
+{
+ unsigned long retbuf[PLPAR_HCALL9_BUFSIZE] = {0};
+ int rc;
+ struct label *label;
+ struct plpks_auth *auth;
+ u64 continuetoken = 0;
+ u64 timeout = 0;
+
+ if (!var->data || var->datalen <= 0 || var->namelen > PLPKS_MAX_NAME_SIZE)
+ return -EINVAL;
+
+ if (!(var->policy & PLPKS_SIGNEDUPDATE))
+ return -EINVAL;
+
+ // Signed updates need the component to be NULL.
+ if (var->component)
+ return -EINVAL;
+
+ auth = construct_auth(PLPKS_OS_OWNER);
+ if (IS_ERR(auth))
+ return PTR_ERR(auth);
+
+ label = construct_label(var->component, var->os, var->name, var->namelen);
+ if (IS_ERR(label)) {
+ rc = PTR_ERR(label);
+ goto out;
+ }
+
+ do {
+ rc = plpar_hcall9(H_PKS_SIGNED_UPDATE, retbuf,
+ virt_to_phys(auth), virt_to_phys(label),
+ label->size, var->policy, flags,
+ virt_to_phys(var->data), var->datalen,
+ continuetoken);
+
+ continuetoken = retbuf[0];
+ if (pseries_status_to_err(rc) == -EBUSY) {
+ int delay_ms = get_longbusy_msecs(rc);
+ mdelay(delay_ms);
+ timeout += delay_ms;
+ }
+ rc = pseries_status_to_err(rc);
+ } while (rc == -EBUSY && timeout < PLPKS_MAX_TIMEOUT);
+
+ if (!rc)
+ rc = plpks_confirm_object_flushed(label, auth);
+
+ kfree(label);
+out:
+ kfree(auth);
+
+ return rc;
+}
+
int plpks_write_var(struct plpks_var var)
{
unsigned long retbuf[PLPAR_HCALL_BUFSIZE] = { 0 };
@@ -443,7 +507,7 @@ int plpks_remove_var(char *component, u8 varos, struct plpks_var_name vname)
struct label *label;
int rc;

- if (!component || vname.namelen > PLPKS_MAX_NAME_SIZE)
+ if (vname.namelen > PLPKS_MAX_NAME_SIZE)
return -EINVAL;

auth = construct_auth(PLPKS_OS_OWNER);
--
2.39.1