Found by: Coverity scan.
CID: 96643

Current code doesn't zero-out context completely. It's a minor issue
really as sha1 init already takes care of initing the context.

grub_pubkey_open closed original file after it was read; it set
io->device to NULL to prevent grub_file_close from trying to close device.
But network device itself is stacked (net -> bufio); and bufio preserved
original netfs file which hold reference to device. grub_file_close(io)
called grub_bufio_close which called grub_file_close for original file.
grub_file_close(netfs-file) now also called grub_device_close which
freed file->device->net. So file structure returned by grub_pubkey_open
now had device->net pointed to freed memory. When later file was closed,
it was attempted to be freed again.

Change grub_pubkey_open to behave like other filters - preserve original
parent file and pass grub_file_close down to parent. In this way only the
original file will close device. We really need to move this logic into
core instead.

Also plug memory leaks in error paths on the way.
Reported-By: Robert Kliewer <robert.kliewer@gmail.com>
Closes: bug #43601

	check.

To reproduce the problem, make sure you have a GPG public key available, build and install GRUB:
grub-install --debug --debug-image="all" --pubkey=/boot/pubkey.gpg --modules="serial terminfo gzio search search_label search_fs_uuid search_fs_file linux vbe video_fb video mmap relocator verify gcry_rsa gcry_dsa gcry_sha256 hashsum gcry_sha1 mpi echo loadenv boottime" /dev/sda
Sign all the files in /boot/grub/* and reboot.

'make check' results identical before and after this change.

TESTED: In a QEMU VM using an i386 target.

	Just "packed" doesn't always pack the way we expect.

	(grub_load_public_key): Likewise.
	(grub_verify_signature_real): Likewise.
	(grub_cmd_verify_signature): Likewise.

	We have only 92K of stack and using over 4K per frame is wasteful

	* grub-core/commands/verify.c (grub_load_public_key): Allocate on heap
	rather than stack.
	(grub_verify_signature_real): Likewise.

	Load gcry_dsa/gcry_rsa automatically.

	tampered with after verification was done.

	the first three hashes - they start with 1, not with 0.

	from the spec.

	operations to have intended shifts and not divisions.

	* grub-core/commands/verify.c (grub_cmd_list): New function.