1 files changed, 117 insertions, 0 deletions
diff --git a/src/shared/base-filesystem.c b/src/shared/base-filesystem.c
new file mode 100644
index 0000000..89d7a7d
--- /dev/null
+++ b/src/shared/base-filesystem.c
@@ -0,0 +1,117 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "base-filesystem.h"
+#include "fd-util.h"
+#include "log.h"
+#include "macro.h"
+#include "string-util.h"
+#include "umask-util.h"
+#include "user-util.h"
+#include "util.h"
+
+typedef struct BaseFilesystem {
+        const char *dir;
+        mode_t mode;
+        const char *target;
+        const char *exists;
+        bool ignore_failure;
+} BaseFilesystem;
+
+static const BaseFilesystem table[] = {
+        { "bin",      0, "usr/bin\0",                  NULL },
+        { "lib",      0, "usr/lib\0",                  NULL },
+        { "root",  0755, NULL,                         NULL, true },
+        { "sbin",     0, "usr/sbin\0",                 NULL },
+        { "usr",   0755, NULL,                         NULL },
+        { "var",   0755, NULL,                         NULL },
+        { "etc",   0755, NULL,                         NULL },
+        { "proc",  0755, NULL,                         NULL, true },
+        { "sys",   0755, NULL,                         NULL, true },
+        { "dev",   0755, NULL,                         NULL, true },
+#if defined(__i386__) || defined(__x86_64__)
+        { "lib64",    0, "usr/lib/x86_64-linux-gnu\0"
+                         "usr/lib64\0",                "ld-linux-x86-64.so.2" },
+#endif
+};
+
+int base_filesystem_create(const char *root, uid_t uid, gid_t gid) {
+        _cleanup_close_ int fd = -1;
+        int r = 0;
+        size_t i;
+
+        fd = open(root, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW);
+        if (fd < 0)
+                return log_error_errno(errno, "Failed to open root file system: %m");
+
+        for (i = 0; i < ELEMENTSOF(table); i ++) {
+                if (faccessat(fd, table[i].dir, F_OK, AT_SYMLINK_NOFOLLOW) >= 0)
+                        continue;
+
+                if (table[i].target) {
+                        const char *target = NULL, *s;
+
+                        /* check if one of the targets exists */
+                        NULSTR_FOREACH(s, table[i].target) {
+                                if (faccessat(fd, s, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
+                                        continue;
+
+                                /* check if a specific file exists at the target path */
+                                if (table[i].exists) {
+                                        _cleanup_free_ char *p = NULL;
+
+                                        p = strjoin(s, "/", table[i].exists);
+                                        if (!p)
+                                                return log_oom();
+
+                                        if (faccessat(fd, p, F_OK, AT_SYMLINK_NOFOLLOW) < 0)
+                                                continue;
+                                }
+
+                                target = s;
+                                break;
+                        }
+
+                        if (!target)
+                                continue;
+
+                        r = symlinkat(target, fd, table[i].dir);
+                        if (r < 0 && errno != EEXIST)
+                                return log_error_errno(errno, "Failed to create symlink at %s/%s: %m", root, table[i].dir);
+
+                        if (uid_is_valid(uid) || gid_is_valid(gid)) {
+                                if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
+                                        return log_error_errno(errno, "Failed to chown symlink at %s/%s: %m", root, table[i].dir);
+                        }
+
+                        continue;
+                }
+
+                RUN_WITH_UMASK(0000)
+                        r = mkdirat(fd, table[i].dir, table[i].mode);
+                if (r < 0 && errno != EEXIST) {
+                        log_full_errno(table[i].ignore_failure ? LOG_DEBUG : LOG_ERR, errno,
+                                       "Failed to create directory at %s/%s: %m", root, table[i].dir);
+
+                        if (!table[i].ignore_failure)
+                                return -errno;
+
+                        continue;
+                }
+
+                if (uid != UID_INVALID || gid != UID_INVALID) {
+                        if (fchownat(fd, table[i].dir, uid, gid, AT_SYMLINK_NOFOLLOW) < 0)
+                                return log_error_errno(errno, "Failed to chown directory at %s/%s: %m", root, table[i].dir);
+                }
+        }
+
+        return 0;
+}