util: add creds-util.[ch] with helpers for dealing with credentials

src/basic/creds-util.c

@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "creds-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "path-util.h"
+
+bool credential_name_valid(const char *s) {
+        /* We want that credential names are both valid in filenames (since that's our primary way to pass
+         * them around) and as fdnames (which is how we might want to pass them around eventually) */
+        return filename_is_valid(s) && fdname_is_valid(s);
+}
+
+int get_credentials_dir(const char **ret) {
+        const char *e;
+
+        assert(ret);
+
+        e = secure_getenv("CREDENTIALS_DIRECTORY");
+        if (!e)
+                return -ENXIO;
+
+        if (!path_is_absolute(e) || !path_is_normalized(e))
+                return -EINVAL;
+
+        *ret = e;
+        return 0;
+}
+
+int read_credential(const char *name, void **ret, size_t *ret_size) {
+        _cleanup_free_ char *fn = NULL;
+        const char *d;
+        int r;
+
+        assert(ret);
+
+        if (!credential_name_valid(name))
+                return -EINVAL;
+
+        r = get_credentials_dir(&d);
+        if (r < 0)
+                return r;
+
+        fn = path_join(d, name);
+        if (!fn)
+                return -ENOMEM;
+
+        return read_full_file_full(
+                        AT_FDCWD, fn,
+                        UINT64_MAX, SIZE_MAX,
+                        READ_FULL_FILE_SECURE,
+                        NULL,
+                        (char**) ret, ret_size);
+}

src/basic/creds-util.h

@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <sys/types.h>
+
+bool credential_name_valid(const char *s);
+
+int get_credentials_dir(const char **ret);
+
+int read_credential(const char *name, void **ret, size_t *ret_size);

src/basic/meson.build

@@ -35,6 +35,8 @@ basic_sources = files('''
         conf-files.h
         copy.c
         copy.h
+        creds-util.c
+        creds-util.h
         def.h
         device-nodes.c
         device-nodes.h

src/basic/path-util.c

@@ -1190,9 +1190,3 @@ bool prefixed_path_strv_contains(char **l, const char *path) {
 
         return false;
 }
-
-bool credential_name_valid(const char *s) {
-        /* We want that credential names are both valid in filenames (since that's our primary way to pass
-         * them around) and as fdnames (which is how we might want to pass them around eventually) */
-        return filename_is_valid(s) && fdname_is_valid(s);
-}

src/basic/path-util.h

@@ -183,5 +183,3 @@ static inline const char *empty_to_root(const char *path) {
 
 bool path_strv_contains(char **l, const char *path);
 bool prefixed_path_strv_contains(char **l, const char *path);
-
-bool credential_name_valid(const char *s);

src/core/dbus-execute.c

@@ -13,6 +13,7 @@
 #include "cap-list.h"
 #include "capability-util.h"
 #include "cpu-set-util.h"
+#include "creds-util.h"
 #include "dbus-execute.h"
 #include "dbus-util.h"
 #include "env-util.h"

src/core/load-fragment.c

@@ -16,8 +16,8 @@
 #include "sd-messages.h"
 
 #include "af-list.h"
-#include "alloc-util.h"
 #include "all-units.h"
+#include "alloc-util.h"
 #include "bpf-firewall.h"
 #include "bus-error.h"
 #include "bus-internal.h"
@@ -28,6 +28,7 @@
 #include "conf-parser.h"
 #include "core-varlink.h"
 #include "cpu-set-util.h"
+#include "creds-util.h"
 #include "env-util.h"
 #include "errno-list.h"
 #include "escape.h"

src/core/manager.c

@@ -30,6 +30,7 @@
 #include "clean-ipc.h"
 #include "clock-util.h"
 #include "core-varlink.h"
+#include "creds-util.h"
 #include "dbus-job.h"
 #include "dbus-manager.h"
 #include "dbus-unit.h"
@@ -49,8 +50,8 @@
 #include "install.h"
 #include "io-util.h"
 #include "label.h"
-#include "locale-setup.h"
 #include "load-fragment.h"
+#include "locale-setup.h"
 #include "log.h"
 #include "macro.h"
 #include "manager.h"
@@ -852,8 +853,8 @@ int manager_new(UnitFileScope scope, ManagerTestRunFlags test_run_flags, Manager
         if (r < 0)
                 return r;
 
-        e = secure_getenv("CREDENTIALS_DIRECTORY");
-        if (e) {
+        r = get_credentials_dir(&e);
+        if (r >= 0) {
                 m->received_credentials = strdup(e);
                 if (!m->received_credentials)
                         return -ENOMEM;

src/nspawn/nspawn.c

@@ -35,6 +35,7 @@
 #include "cgroup-util.h"
 #include "copy.h"
 #include "cpu-set-util.h"
+#include "creds-util.h"
 #include "dev-setup.h"
 #include "discover-image.h"
 #include "dissect-image.h"
@@ -1592,9 +1593,9 @@ static int parse_argv(int argc, char *argv[]) {
                         else {
                                 const char *e;
 
-                                e = getenv("CREDENTIALS_DIRECTORY");
-                                if (!e)
-                                        return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Credential not available (no credentials passed at all): %s", word);
+                                r = get_credentials_dir(&e);
+                                if (r < 0)
+                                        return log_error_errno(r, "Credential not available (no credentials passed at all): %s", word);
 
                                 j = path_join(e, p);
                                 if (!j)