stub: handle random seed like sd-boot does

sd-stub has an opportunity to handle the seed the same way sd-boot does,
which would have benefits for UKIs when sd-boot is not in use. This
commit wires that up.

It refactors the XBOOTLDR partition discovery to also find the ESP
partition, so that it access the random seed there.

7 files changed, 42 insertions, 24 deletions

diff --git a/src/boot/bootctl.c b/src/boot/bootctl.c
index 1e862018d4..0df456827c 100644
--- a/src/boot/bootctl.c
+++ b/src/boot/bootctl.c
@@ -1808,6 +1808,7 @@ static int verb_status(int argc, char *argv[], void *userdata) {
                         { EFI_STUB_FEATURE_PICK_UP_CREDENTIALS,       "Picks up credentials from boot partition"             },
                         { EFI_STUB_FEATURE_PICK_UP_SYSEXTS,           "Picks up system extension images from boot partition" },
                         { EFI_STUB_FEATURE_THREE_PCRS,                "Measures kernel+command line+sysexts"                 },
+                        { EFI_STUB_FEATURE_RANDOM_SEED,               "Support for passing random seed to OS"                },
                 };
                 _cleanup_free_ char *fw_type = NULL, *fw_info = NULL, *loader = NULL, *loader_path = NULL, *stub = NULL;
                 sd_id128_t loader_part_uuid = SD_ID128_NULL;
diff --git a/src/boot/efi/boot.c b/src/boot/efi/boot.c
index caa2a69a6f..85e936b866 100644
--- a/src/boot/efi/boot.c
+++ b/src/boot/efi/boot.c
@@ -15,6 +15,7 @@
 #include "initrd.h"
 #include "linux.h"
 #include "measure.h"
+#include "part-discovery.h"
 #include "pe.h"
 #include "vmm.h"
 #include "random-seed.h"
@@ -22,7 +23,6 @@
 #include "shim.h"
 #include "ticks.h"
 #include "util.h"
-#include "xbootldr.h"
 
 #ifndef GNU_EFI_USE_MS_ABI
         /* We do not use uefi_call_wrapper() in systemd-boot. As such, we rely on the
@@ -2241,7 +2241,7 @@ static void config_load_xbootldr(
         assert(config);
         assert(device);
 
-        err = xbootldr_open(device, &new_device, &root_dir);
+        err = partition_open(XBOOTLDR_GUID, device, &new_device, &root_dir);
         if (err != EFI_SUCCESS)
                 return;
 
diff --git a/src/boot/efi/meson.build b/src/boot/efi/meson.build
index 0de43993a4..2a7e457df3 100644
--- a/src/boot/efi/meson.build
+++ b/src/boot/efi/meson.build
@@ -360,6 +360,7 @@ efi_headers = files(
         'linux.h',
         'measure.h',
         'missing_efi.h',
+        'part-discovery.h',
         'pe.h',
         'random-seed.h',
         'secure-boot.h',
@@ -367,7 +368,6 @@ efi_headers = files(
         'splash.h',
         'ticks.h',
         'util.h',
-        'xbootldr.h',
 )
 
 common_sources = files(
@@ -379,7 +379,9 @@ common_sources = files(
         'graphics.c',
         'initrd.c',
         'measure.c',
+        'part-discovery.c',
         'pe.c',
+        'random-seed.c',
         'secure-boot.c',
         'ticks.c',
         'util.c',
@@ -388,10 +390,8 @@ common_sources = files(
 systemd_boot_sources = files(
         'boot.c',
         'drivers.c',
-        'random-seed.c',
-        'vmm.c',
         'shim.c',
-        'xbootldr.c',
+        'vmm.c',
 )
 
 stub_sources = files(
diff --git a/src/boot/efi/xbootldr.c b/src/boot/efi/part-discovery.c
index e5b9ca7268..de6d6112a1 100644
--- a/src/boot/efi/xbootldr.c
+++ b/src/boot/efi/part-discovery.c
@@ -4,8 +4,8 @@
 #include <efigpt.h>
 #include <efilib.h>
 
+#include "part-discovery.h"
 #include "util.h"
-#include "xbootldr.h"
 
 union GptHeaderBuffer {
         EFI_PARTITION_TABLE_HEADER gpt_header;
@@ -81,6 +81,7 @@ static bool verify_gpt(union GptHeaderBuffer *gpt_header_buffer, EFI_LBA lba_exp
 }
 
 static EFI_STATUS try_gpt(
+                const EFI_GUID *type,
                 EFI_BLOCK_IO_PROTOCOL *block_io,
                 EFI_LBA lba,
                 EFI_LBA *ret_backup_lba, /* May be changed even on error! */
@@ -133,7 +134,7 @@ static EFI_STATUS try_gpt(
                 EFI_PARTITION_ENTRY *entry =
                                 (EFI_PARTITION_ENTRY *) ((uint8_t *) entries + gpt.gpt_header.SizeOfPartitionEntry * i);
 
-                if (memcmp(&entry->PartitionTypeGUID, XBOOTLDR_GUID, sizeof(entry->PartitionTypeGUID)) != 0)
+                if (memcmp(&entry->PartitionTypeGUID, type, sizeof(entry->PartitionTypeGUID)) != 0)
                         continue;
 
                 if (entry->EndingLBA < entry->StartingLBA) /* Bogus? */
@@ -165,7 +166,7 @@ static EFI_STATUS try_gpt(
         return EFI_NOT_FOUND;
 }
 
-static EFI_STATUS find_device(EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_path) {
+static EFI_STATUS find_device(const EFI_GUID *type, EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_path) {
         EFI_STATUS err;
 
         assert(device);
@@ -231,8 +232,7 @@ static EFI_STATUS find_device(EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_p
                         continue;
 
                 HARDDRIVE_DEVICE_PATH hd;
-                err = try_gpt(
-                        block_io, lba,
+                err = try_gpt(type, block_io, lba,
                         nr == 0 ? &backup_lba : NULL, /* Only get backup LBA location from first GPT header. */
                         &hd);
                 if (err != EFI_SUCCESS) {
@@ -252,17 +252,18 @@ static EFI_STATUS find_device(EFI_HANDLE *device, EFI_DEVICE_PATH **ret_device_p
         return EFI_NOT_FOUND;
 }
 
-EFI_STATUS xbootldr_open(EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **ret_root_dir) {
+EFI_STATUS partition_open(const EFI_GUID *type, EFI_HANDLE *device, EFI_HANDLE *ret_device,
+                          EFI_FILE **ret_root_dir) {
         _cleanup_free_ EFI_DEVICE_PATH *partition_path = NULL;
         EFI_HANDLE new_device;
         EFI_FILE *root_dir;
         EFI_STATUS err;
 
+        assert(type);
         assert(device);
-        assert(ret_device);
         assert(ret_root_dir);
 
-        err = find_device(device, &partition_path);
+        err = find_device(type, device, &partition_path);
         if (err != EFI_SUCCESS)
                 return err;
 
@@ -275,7 +276,8 @@ EFI_STATUS xbootldr_open(EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **
         if (err != EFI_SUCCESS)
                 return err;
 
-        *ret_device = new_device;
+        if (ret_device)
+                *ret_device = new_device;
         *ret_root_dir = root_dir;
         return EFI_SUCCESS;
 }
diff --git a/src/boot/efi/part-discovery.h b/src/boot/efi/part-discovery.h
new file mode 100644
index 0000000000..5cc17f6b3b
--- /dev/null
+++ b/src/boot/efi/part-discovery.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <efi.h>
+
+#define XBOOTLDR_GUID \
+        &(const EFI_GUID) { 0xbc13c2ff, 0x59e6, 0x4262, { 0xa3, 0x52, 0xb2, 0x75, 0xfd, 0x6f, 0x71, 0x72 } }
+#define ESP_GUID \
+        &(const EFI_GUID) { 0xc12a7328, 0xf81f, 0x11d2, { 0xba, 0x4b, 0x00, 0xa0, 0xc9, 0x3e, 0xc9, 0x3b } }
+
+EFI_STATUS partition_open(const EFI_GUID *type, EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **ret_root_dir);
diff --git a/src/boot/efi/stub.c b/src/boot/efi/stub.c
index a842c5c679..6ece3cf733 100644
--- a/src/boot/efi/stub.c
+++ b/src/boot/efi/stub.c
@@ -9,7 +9,9 @@
 #include "graphics.h"
 #include "linux.h"
 #include "measure.h"
+#include "part-discovery.h"
 #include "pe.h"
+#include "random-seed.h"
 #include "secure-boot.h"
 #include "splash.h"
 #include "tpm-pcr.h"
@@ -84,6 +86,7 @@ static void export_variables(EFI_LOADED_IMAGE_PROTOCOL *loaded_image) {
                 EFI_STUB_FEATURE_PICK_UP_CREDENTIALS |      /* We pick up credentials from the boot partition */
                 EFI_STUB_FEATURE_PICK_UP_SYSEXTS |          /* We pick up system extensions from the boot partition */
                 EFI_STUB_FEATURE_THREE_PCRS |               /* We can measure kernel image, parameters and sysext */
+                EFI_STUB_FEATURE_RANDOM_SEED |              /* We pass a random seed to the kernel */
                 0;
 
         char16_t uuid[37];
@@ -142,6 +145,7 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
         _cleanup_free_ char *cmdline_owned = NULL;
         int sections_measured = -1, parameters_measured = -1;
         bool sysext_measured = false, m;
+        uint64_t loader_features = 0;
         EFI_STATUS err;
 
         InitializeLib(image, sys_table);
@@ -159,6 +163,15 @@ EFI_STATUS efi_main(EFI_HANDLE image, EFI_SYSTEM_TABLE *sys_table) {
         if (err != EFI_SUCCESS)
                 return log_error_status_stall(err, L"Error getting a LoadedImageProtocol handle: %r", err);
 
+        if (efivar_get_uint64_le(LOADER_GUID, L"LoaderFeatures", &loader_features) != EFI_SUCCESS ||
+            !FLAGS_SET(loader_features, EFI_LOADER_FEATURE_RANDOM_SEED)) {
+                _cleanup_(file_closep) EFI_FILE *esp_dir = NULL;
+
+                err = partition_open(ESP_GUID, loaded_image->DeviceHandle, NULL, &esp_dir);
+                if (err == EFI_SUCCESS) /* Non-fatal on failure, so that we still boot without it. */
+                        (void) process_random_seed(esp_dir);
+        }
+
         err = pe_memory_locate_sections(loaded_image->ImageBase, unified_sections, addrs, szs);
         if (err != EFI_SUCCESS || szs[UNIFIED_SECTION_LINUX] == 0) {
                 if (err == EFI_SUCCESS)
diff --git a/src/boot/efi/xbootldr.h b/src/boot/efi/xbootldr.h
deleted file mode 100644
index 205ce71edf..0000000000
--- a/src/boot/efi/xbootldr.h
+++ /dev/null
@@ -1,9 +0,0 @@
-/* SPDX-License-Identifier: LGPL-2.1-or-later */
-#pragma once
-
-#include <efi.h>
-
-#define XBOOTLDR_GUID \
-        &(const EFI_GUID) { 0xbc13c2ff, 0x59e6, 0x4262, { 0xa3, 0x52, 0xb2, 0x75, 0xfd, 0x6f, 0x71, 0x72 } }
-
-EFI_STATUS xbootldr_open(EFI_HANDLE *device, EFI_HANDLE *ret_device, EFI_FILE **ret_root_dir);