sandbox: use sane access rights for files

When writing an executable, allowing other users to modify it introduces
a security issue.

Generally we should avoid giving other users write access to our files by
default.

Replace chmod(777) by chmod(755) and chmod(644).

Fixes: 47f5fcfb4169 ("sandbox: Add os_jump_to_image() to run another executable")
Fixes: d9165153caea ("sandbox: add flags for open() call")
Fixes: 5c2859cdc302 ("sandbox: Allow reading/writing of RAM buffer")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>

diff --git a/arch/sandbox/cpu/os.c b/arch/sandbox/cpu/os.c
index 154a5d77490c3132be9f1df4a722d132f203d020..d7869b2e368152c801d7acb6f2f563c113da367a 100644 (file)
--- a/arch/sandbox/cpu/os.c
+++ b/arch/sandbox/cpu/os.c
@@ -109,7 +109,7 @@ int os_open(const char *pathname, int os_flags)
         */
        flags |= O_CLOEXEC;
 
-       return open(pathname, flags, 0777);
+       return open(pathname, flags, 0644);
 }
 
 int os_close(int fd)
@@ -746,7 +746,7 @@ int os_write_ram_buf(const char *fname)
        struct sandbox_state *state = state_get_current();
        int fd, ret;
 
-       fd = open(fname, O_CREAT | O_WRONLY, 0777);
+       fd = open(fname, O_CREAT | O_WRONLY, 0644);
        if (fd < 0)
                return -ENOENT;
        ret = write(fd, state->ram_buf, state->ram_size);
@@ -791,7 +791,7 @@ static int make_exec(char *fname, const void *data, int size)
        if (write(fd, data, size) < 0)
                return -EIO;
        close(fd);
-       if (chmod(fname, 0777))
+       if (chmod(fname, 0755))
                return -ENOEXEC;
 
        return 0;