[Libguestfs] [PATCH nbdkit 2/3] server: Disallow -FD for stdin/stdout/stderr.

$ ./nbdkit ssh host=localhost /nosuchfile password=-0 --run 'qemu-img info $nbd' abc fcntl: Bad file descriptor The reason for this is that we close the file descriptor after reading the password. Closing stdin causes bad stuff to happen. --- docs/nbdkit-plugin.pod | 5 +++++ server/public.c | 4 ++-- 2 files changed, 7 insertions(+), 2 deletions(-) diff --git a/docs/nbdkit-plugin.pod b/docs/nbdkit-plugin.pod index 612688ab..7b8a5393 100644 --- a/docs/nbdkit-plugin.pod +++ b/docs/nbdkit-plugin.pod @@ -1249,6 +1249,11 @@ passed in a file. C<password=-> can only be used when stdin is a terminal. +C<password=-FD> cannot be used with stdin, stdout or stderr +(ie. C<-0>, C<-1> or C<-2>). The reason is that after reading the +password the file descriptor is closed, which causes bad stuff to +happen. + =head2 Safely interacting with stdin and stdout int nbdkit_stdio_safe (void); diff --git a/server/public.c b/server/public.c index dafdfbae..2e36e43a 100644 --- a/server/public.c +++ b/server/public.c @@ -433,8 +433,8 @@ nbdkit_read_password (const char *value, char **password) if (nbdkit_parse_int ("password file descriptor", &value[1], &fd) == -1) return -1; - if (fd == STDIN_FILENO && !nbdkit_stdio_safe ()) { - nbdkit_error ("stdin is not available for reading password"); + if (fd == STDIN_FILENO || fd == STDOUT_FILENO || fd == STDERR_FILENO) { + nbdkit_error ("cannot use password -FD for stdin/stdout/stderr"); return -1; } if (read_password_from_fd (&value[1], fd, password) == -1) -- 2.25.0