tpm2: add SWTPM fallback test, fixes and hardening (#42722)

src/shared/swtpm-util.c

@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <fcntl.h>
 #include <unistd.h>
 
 #include "sd-json.h"
@@ -8,6 +9,7 @@
 #include "escape.h"
 #include "fd-util.h"
 #include "fileio.h"
+#include "fs-util.h"
 #include "json-util.h"
 #include "log.h"
 #include "memfd-util.h"
@@ -17,6 +19,7 @@
 #include "string-util.h"
 #include "strv.h"
 #include "swtpm-util.h"
+#include "sync-util.h"
 
 static int swtpm_find_best_profile(const char *swtpm_setup, char **ret) {
         int r;
@@ -135,6 +138,10 @@ int manufacture_swtpm(const char *state_dir, const char *secret) {
 
         assert(state_dir);
 
+        _cleanup_close_ int state_dir_fd = open(state_dir, O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+        if (state_dir_fd < 0)
+                return log_error_errno(errno, "Failed to open TPM state directory '%s': %m", state_dir);
+
         _cleanup_free_ char *swtpm_setup = NULL;
         r = find_executable("swtpm_setup", &swtpm_setup);
         if (r < 0)
@@ -151,9 +158,9 @@ int manufacture_swtpm(const char *state_dir, const char *secret) {
         if (!localca_conf)
                 return log_oom();
 
-        r = write_string_filef(
-                        localca_conf,
-                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_TRUNCATE|WRITE_STRING_FILE_MKDIR_0755,
+        r = write_string_filef_at(
+                        state_dir_fd, "swtpm-localca.conf",
+                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC,
                         "statedir = %1$s\n"
                         "signingkey = %1$s/signing-private-key.pem\n"
                         "issuercert = %1$s/issuer-certificate.pem\n"
@@ -166,12 +173,12 @@ int manufacture_swtpm(const char *state_dir, const char *secret) {
         if (!localca_options)
                 return log_oom();
 
-        r = write_string_file(
-                        localca_options,
+        r = write_string_file_at(
+                        state_dir_fd, "swtpm-localca.options",
                         "--platform-manufacturer systemd\n"
                         "--platform-version 2.1\n"
                         "--platform-model swtpm\n",
-                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_TRUNCATE|WRITE_STRING_FILE_MKDIR_0755);
+                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
         if (r < 0)
                 return log_error_errno(r, "Failed to write swtpm-localca.options: %m");
 
@@ -184,9 +191,9 @@ int manufacture_swtpm(const char *state_dir, const char *secret) {
         if (!setup_conf)
                 return log_oom();
 
-        r = write_string_filef(
-                        setup_conf,
-                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_TRUNCATE|WRITE_STRING_FILE_MKDIR_0755,
+        r = write_string_filef_at(
+                        state_dir_fd, "swtpm_setup.conf",
+                        WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC,
                         "create_certs_tool = %1$s\n"
                         "create_certs_tool_config = %2$s\n"
                         "create_certs_tool_options = %3$s\n",
@@ -234,5 +241,15 @@ int manufacture_swtpm(const char *state_dir, const char *secret) {
                 _exit(EXIT_FAILURE);
         }
 
+        /* Persist swtpm_setup's freshly created TPM state before writing the completion marker. */
+        r = syncfs_path(state_dir_fd, NULL);
+        if (r < 0)
+                return log_error_errno(r, "Failed to sync TPM state directory: %m");
+
+        /* Marker, written last, signals that manufacturing completed successfully. */
+        _cleanup_close_ int marker_fd = xopenat(state_dir_fd, SWTPM_MANUFACTURED_MARKER, O_WRONLY|O_CREAT|O_CLOEXEC|O_NOFOLLOW);
+        if (marker_fd < 0)
+                return log_error_errno(marker_fd, "Failed to write '%s' marker: %m", SWTPM_MANUFACTURED_MARKER);
+
         return 0;
 }

src/shared/swtpm-util.h

@@ -1,4 +1,9 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 #pragma once
 
+/* Marker file written into the TPM state directory once swtpm_setup has successfully created the TPM state.
+ * It is written last, so its presence reliably means a complete TPM was manufactured, rather than a manufacture
+ * that was interrupted halfway through. */
+#define SWTPM_MANUFACTURED_MARKER ".manufactured"
+
 int manufacture_swtpm(const char *state_dir, const char *secret);