On Apple hosts we can read AppleSMC OSK key directly from host's
SMC and forward this value to QEMU Guest.

New 'hostosk' property is added:
* `-device isa-applesmc,hostosk=on`
The property is set to 'on' by default for machine version > 6.2

Apple licence allows use and run up to two additional copies
or instances of macOS operating system within virtual operating system
environments on each Apple-branded computer that is already running
the Apple Software, for purposes of:
 * software development
 * testing during software development
 * using macOS Server
 * personal, non-commercial use

Guest macOS requires AppleSMC with correct OSK. The most legal
way to pass it to the Guest is to forward the key from host SMC
without any value exposion.

Based on https://web.archive.org/web/20200103161737/osxbook.com/book/bonus/chapter7/tpmdrmmyth/

Signed-off-by: Vladislav Yaroshchuk <yaroshchuk2000@gmail.com>
---
 hw/core/machine.c  |   4 +-
 hw/misc/applesmc.c | 127 +++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 126 insertions(+), 5 deletions(-)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index cb9bbc844d..7f4a27406a 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -37,7 +37,9 @@
 #include "hw/virtio/virtio.h"
 #include "hw/virtio/virtio-pci.h"
 
-GlobalProperty hw_compat_7_0[] = {};
+GlobalProperty hw_compat_7_0[] = {
+    { "isa-applesmc", "hostosk", "off" }
+};
 const size_t hw_compat_7_0_len = G_N_ELEMENTS(hw_compat_7_0);
 
 GlobalProperty hw_compat_6_2[] = {
diff --git a/hw/misc/applesmc.c b/hw/misc/applesmc.c
index 81cd6b6423..99bcc937f9 100644
--- a/hw/misc/applesmc.c
+++ b/hw/misc/applesmc.c
@@ -37,6 +37,11 @@
 #include "qemu/module.h"
 #include "qemu/timer.h"
 #include "qom/object.h"
+#include "qapi/error.h"
+
+#if defined(__APPLE__) && defined(__MACH__)
+#include <IOKit/IOKitLib.h>
+#endif
 
 /* #define DEBUG_SMC */
 
@@ -80,7 +85,7 @@ enum {
 #define smc_debug(...) do { } while (0)
 #endif
 
-static char default_osk[64] = "This is a dummy key. Enter the real key "
+static char default_osk[65] = "This is a dummy key. Enter the real key "
                               "using the -osk parameter";
 
 struct AppleSMCData {
@@ -109,6 +114,7 @@ struct AppleSMCState {
     uint8_t data_pos;
     uint8_t data[255];
     char *osk;
+    bool hostosk;
     QLIST_HEAD(, AppleSMCData) data_def;
 };
 
@@ -253,7 +259,7 @@ static void applesmc_add_key(AppleSMCState *s, const char *key,
 {
     struct AppleSMCData *def;
 
-    def = g_new0(struct AppleSMCData, 1);
+    def = g_malloc0(sizeof(struct AppleSMCData));
     def->key = key;
     def->len = len;
     def->data = data;
@@ -312,6 +318,101 @@ static const MemoryRegionOps applesmc_err_io_ops = {
     },
 };
 
+#if defined(__APPLE__) && defined(__MACH__)
+/*
+ * Based on
+ * https://web.archive.org/web/20200103161737/osxbook.com/book/bonus/chapter7/tpmdrmmyth/
+ */
+enum {
+    SMC_HANDLE_EVENT     = 2,
+    SMC_READ_KEY         = 5
+};
+
+struct AppleSMCParam {
+    uint32_t key;
+    uint8_t pad0[22];
+    IOByteCount data_size;
+    uint8_t pad1[10];
+    uint8_t command;
+    uint32_t pad2;
+    uint8_t bytes[32];
+};
+
+static bool applesmc_read_host_osk(char *host_osk, Error **errp)
+{
+    assert(host_osk != NULL);
+
+    io_service_t hostsmc_service = IO_OBJECT_NULL;
+    io_connect_t hostsmc_connect = IO_OBJECT_NULL;
+    size_t smc_param_size = sizeof(struct AppleSMCParam);
+    IOReturn status = kIOReturnError;
+    int i;
+
+    struct AppleSMCParam smc_param[2] = {
+         {
+             .key = ('OSK0'),
+             .data_size = sizeof(smc_param[0].bytes),
+             .command = SMC_READ_KEY,
+         }, {
+             .key = ('OSK1'),
+             .data_size = sizeof(smc_param[0].bytes),
+             .command = SMC_READ_KEY,
+         },
+    };
+
+    hostsmc_service = IOServiceGetMatchingService(
+        kIOMasterPortDefault,
+        IOServiceMatching("AppleSMC"));
+    if (hostsmc_service == IO_OBJECT_NULL) {
+        error_setg(errp, "Unable to get host-AppleSMC service");
+        goto error;
+    }
+
+    status = IOServiceOpen(hostsmc_service,
+                           mach_task_self(),
+                           0,
+                           &hostsmc_connect);
+    if (status != kIOReturnSuccess || hostsmc_connect == IO_OBJECT_NULL) {
+        error_setg(errp, "Unable to open host-AppleSMC service");
+        goto error;
+    }
+
+    for (i = 0; i < ARRAY_SIZE(smc_param); ++i) {
+        status = IOConnectCallStructMethod(
+                hostsmc_connect,
+                SMC_HANDLE_EVENT,
+                &smc_param[i],
+                sizeof(struct AppleSMCParam),
+                &smc_param[i],
+                &smc_param_size
+            );
+
+        if (status != kIOReturnSuccess) {
+            error_setg(errp, "Unable to read OSK from host-AppleSMC");
+            goto error;
+        }
+    }
+
+    memcpy(host_osk, smc_param[0].bytes, 32);
+    memcpy(host_osk + 32, smc_param[1].bytes, 32);
+
+    IOServiceClose(hostsmc_connect);
+    IOObjectRelease(hostsmc_service);
+    return true;
+
+error:
+    IOServiceClose(hostsmc_connect);
+    IOObjectRelease(hostsmc_service);
+    return false;
+}
+#else
+static bool applesmc_read_host_osk(char *host_osk, Error **errp)
+{
+    error_setg(errp, "OSK read is not supported on this host");
+    return false;
+}
+#endif
+
 static void applesmc_isa_realize(DeviceState *dev, Error **errp)
 {
     AppleSMCState *s = APPLE_SMC(dev);
@@ -331,9 +432,26 @@ static void applesmc_isa_realize(DeviceState *dev, Error **errp)
     isa_register_ioport(&s->parent_obj, &s->io_err,
                         s->iobase + APPLESMC_ERR_PORT);
 
-    if (!s->osk || (strlen(s->osk) != 64)) {
-        warn_report("Using AppleSMC with invalid key");
+    if (s->osk && s->hostosk) {
+        error_setg(errp, "-osk property cannot be used with -hostosk=on");
+    }
+
+    if (!s->osk && !s->hostosk) {
         s->osk = default_osk;
+        warn_report("Using AppleSMC with default (dummy) OSK");
+    }
+
+    if (s->hostosk) {
+        s->osk = g_malloc0(65);
+        /* Fail hard if we cannot read requested host OSK */
+        if (!applesmc_read_host_osk(s->osk, errp)) {
+            g_assert_not_reached();
+        }
+    }
+
+    if (s->osk && strlen(s->osk) != 64) {
+        /* Only valid OSK is accepted within 'osk' property */
+        error_setg(errp, "Using AppleSMC with key of invalid length");
     }
 
     QLIST_INIT(&s->data_def);
@@ -344,6 +462,7 @@ static Property applesmc_isa_properties[] = {
     DEFINE_PROP_UINT32(APPLESMC_PROP_IO_BASE, AppleSMCState, iobase,
                        APPLESMC_DEFAULT_IOBASE),
     DEFINE_PROP_STRING("osk", AppleSMCState, osk),
+    DEFINE_PROP_BOOL("hostosk", AppleSMCState, hostosk, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.34.1.vfs.0.0