persist_timestamp: use open directory fd to check and work with timestamp files

diff --git a/persist_timestamp.c b/persist_timestamp.c
index ac16c8f727e916fdef2eb738b85748a8966ff143..1ca1e140141afbc70db461d3252529eeacdeda22 100644 (file)
--- a/persist_timestamp.c
+++ b/persist_timestamp.c
@@ -101,9 +101,9 @@ ttynr()
 #endif
 
 static const char *
-tspath()
+tsname()
 {
-       static char pathbuf[PATH_MAX];
+       static char buf[128];
        int tty;
        pid_t ppid, sid;
        if ((tty = ttynr()) == -1)
@@ -111,55 +111,85 @@ tspath()
        ppid = getppid();
        if ((sid = getsid(0)) == -1)
                err(1, "getsid");
-       if (snprintf(pathbuf, sizeof pathbuf, "%s/.%d_%d_%d",
-               TIMESTAMP_DIR, tty, ppid, sid) == -1)
+       if (snprintf(buf, sizeof buf, ".%d_%d_%d", tty, ppid, sid) == -1)
                return NULL;
-       return pathbuf;
+       return buf;
 }
 
 static int
-checktsdir(const char *path)
+checktsdir(int fd)
 {
-       char *dir, *buf;
        struct stat st;
+
+       if (fstat(fd, &st) == -1)
+               err(1, "fstatat");
+
+       if ((st.st_mode & S_IFMT) != S_IFDIR)
+               errx(0, "timestamp directory is not a directory");
+       if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
+               errx(1, "timestamp directory permissions wrong");
+       if (st.st_uid != 0 || st.st_gid != 0)
+               errx(1, "timestamp directory is not owned by root");
+
+#if defined(TIMESTAMP_TMPFS) && defined(__linux__)
        struct statfs sf;
-       gid_t gid;
+       if (fstatfs(fd, &sf) == -1)
+               err(1, "statfs");
 
-       if (!(buf = strdup(path)))
-               err(1, "strdup");
-       dir = dirname(buf);
+       if (sf.f_type != TMPFS_MAGIC)
+               errx(1, "timestamp directory not on tmpfs");
+#endif
 
-check:
-       if (lstat(dir, &st) == -1) {
+       return 0;
+}
+
+static int
+opentsdir()
+{
+       gid_t gid;
+       int fd;
+
+reopen:
+       if ((fd = open(TIMESTAMP_DIR, O_RDONLY | O_DIRECTORY)) == -1) {
                if (errno == ENOENT) {
                        gid = getegid();
                        if (setegid(0) != 0)
                                err(1, "setegid");
-                       if (mkdir(dir, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0)
+                       if (mkdir(TIMESTAMP_DIR, (S_IRUSR|S_IWUSR|S_IXUSR)) != 0)
                                err(1, "mkdir");
                        if (setegid(gid) != 0)
                                err(1, "setegid");
-                       goto check;
+                       goto reopen;
                } else {
-                       err(1, "stat");
+                       err(1, "failed to open timestamp directory: %s", TIMESTAMP_DIR);
                }
        }
 
-       if ((st.st_mode & S_IFMT) != S_IFDIR)
-               errx(1, "timestamp directory is not a directory");
+       if (checktsdir(fd) != 0)
+               return -1;
+
+       return fd;
+}
+
+static int
+checktsfile(int fd, size_t *tssize)
+{
+       struct stat st;
+       gid_t gid;
+
+       if (fstat(fd, &st) == -1)
+               err(1, "stat");
+       if ((st.st_mode & S_IFMT) != S_IFREG)
+               errx(1, "timestamp is not a file");
        if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
-               errx(1, "timestamp directory permissions wrong");
-       if (st.st_uid != 0 || st.st_gid != 0)
-               errx(1, "timestamp directory is not owned by root");
-       if (statfs(dir, &sf) == -1)
-               err(1, "statfs");
+               errx(1, "timestamp permissions wrong");
 
-#if defined(TIMESTAMP_TMPFS) && defined(__linux__)
-       if (sf.f_type != TMPFS_MAGIC)
-               errx(1, "timestamp directory not on tmpfs");
-#endif
+       gid = getegid();
+       if (st.st_uid != 0 || st.st_gid != gid)
+               errx(1, "timestamp has wrong owner");
+
+       *tssize = st.st_size;
 
-       free(buf);
        return 0;
 }
 
@@ -220,58 +250,54 @@ persist_set(int fd, int secs)
 int
 persist_open(int *valid, int secs)
 {
-       struct stat st;
-       int fd;
-       gid_t gid;
-       const char *path;
+       int dirfd, fd;
+       const char *name;
 
-       if ((path = tspath()) == NULL)
-               errx(1, "failed to get timestamp path");
-       if (checktsdir(path))
-               errx(1, "checktsdir");
+       if ((name = tsname()) == NULL)
+               errx(1, "failed to get timestamp name");
+       if ((dirfd = opentsdir()) == -1)
+               errx(1, "opentsdir");
 
-       if ((fd = open(path, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1)
+       if ((fd = openat(dirfd, name, (O_RDWR), (S_IRUSR|S_IWUSR))) == -1)
                if (errno != ENOENT)
-                       err(1, "open: %s", path);
+                       err(1, "open: %s", name);
 
        if (fd == -1) {
-               if ((fd = open(path, (O_RDWR|O_CREAT|O_EXCL), (S_IRUSR|S_IWUSR))) == -1)
-                       err(1, "open: %s", path);
+               if ((fd = openat(dirfd, name, (O_RDWR|O_CREAT|O_EXCL), (S_IRUSR|S_IWUSR))) == -1)
+                       err(1, "open: %s", name);
                *valid = 0;
-               return fd;
+               goto ret;
        }
 
-       if (fstat(fd, &st) == -1)
-               err(1, "stat");
-       if ((st.st_mode & S_IFMT) != S_IFREG)
-               errx(1, "timestamp is not a file");
-       if ((st.st_mode & (S_IWGRP|S_IRGRP|S_IXGRP|S_IWOTH|S_IROTH|S_IXOTH)) != 0)
-               errx(1, "timestamp permissions wrong");
-
-       gid = getegid();
-       if (st.st_uid != 0 || st.st_gid != gid)
-               errx(1, "timestamp has wrong owner");
+       size_t tssize;
+       if (checktsfile(fd, &tssize) == -1)
+               err(1, "checktsfile");
 
-       if (st.st_size == 0) {
+       if (tssize == 0) {
                *valid = 0;
-               return fd;
+               goto ret;
        }
 
-       if (st.st_size != sizeof(struct timespec) * 2)
+       if (tssize != sizeof(struct timespec) * 2)
                errx(1, "corrupt timestamp file");
 
        *valid = persist_check(fd, secs) == 0;
-
+ret:
+       close(dirfd);
        return fd;
 }
 
 int
 persist_clear()
 {
-       const char *path;
-       if ((path = tspath()) == NULL)
-               errx(1, "failed to get timestamp path");
-       if (unlink(path) == -1 && errno != ENOENT)
+       const char *name;
+       int dirfd;
+       if ((name = tsname()) == NULL)
+               errx(1, "failed to get timestamp name");
+       if ((dirfd = opentsdir()) == -1)
+               errx(1, "opentsdir");
+       if (unlinkat(dirfd, name, 0) == -1 && errno != ENOENT)
                return -1;
+       close(dirfd);
        return 0;
 }