g13: Add commands --suspend and --remove.
authorWerner Koch <wk@gnupg.org>
Tue, 23 Feb 2016 13:32:46 +0000 (14:32 +0100)
committerWerner Koch <wk@gnupg.org>
Tue, 23 Feb 2016 14:40:28 +0000 (15:40 +0100)
commitf7968db30b0e0ccae038e354568accb0a05d877c
treeb6073b29d21a75ba7c7ef4f2849fd9474605d77f
parentf26867928c451443769fecc41c3283e077e8c49f
g13: Add commands --suspend and --remove.

* g13/g13.c (aSuspend, aResume): New.
(opts): Add commands --suspend and --resume.
(main): Implement dummy command aUmount.  Implement commands aResume
and aSuspend.
* g13/sh-cmd.c (cmd_suspend): New.
(cmd_resume): New.
(register_commands): Add commands RESUME and SUSPEND.
* g13/server.c (cmd_suspend): New.
(cmd_resume): New.
(register_commands): Add commands RESUME and SUSPEND.
* g13/be-dmcrypt.c (be_dmcrypt_suspend_container): New.
(be_dmcrypt_resume_container): New.
* g13/backend.c (be_suspend_container): New.
(be_resume_container): New.
* g13/suspend.c, g13/suspend.h: New.
* g13/mount.c (parse_header, read_keyblob_prefix, read_keyblob)
(decrypt_keyblob, g13_is_container): Move to ...
* g13/keyblob.c: new file.
(keyblob_read): Rename to g13_keyblob_read and make global.
(keyblob_decrypt): Rename to g13_keyblob_decrypt and make global.
* g13/sh-dmcrypt.c (check_blockdev): Add arg expect_busy.
(sh_dmcrypt_suspend_container): New.
(sh_dmcrypt_resume_container): New.
* g13/call-syshelp.c (call_syshelp_run_suspend): New.
(call_syshelp_run_resume): New.
--

The --suspend command can be used before a hibernate operation to make
the encrypted partition inaccessible and wipe the key from the memory.
Before --suspend is called a sync(1) should be run to make sure that
their are no dirty buffers (dmsetup, as called by g13, actually does
this for you but it does not harm to do it anyway.  After the
partition has been suspended a

  echo 3 >proc/sys/vm/drop_caches

required to flush all caches which may still have content from the
encrypted partition.

The --resume command reverses the effect of the suspend but to do this
it needs to decrypt again.  Now, if the .gnupg directory lives on the
encrypted partition this will be problematic because due to the
suspend all processes accessing data on the encrypted partition will
be put into an uninterruptible sleep (ps(1) shows a state of 'D').
This needs to be avoided.  A workaround is to have a separate GnuPG
home directory (say, "~/.gnupg-fallback") with only the public keys
required to decrypt the partition along with a properly setup
conf files.  A

  GNUPGHOME=$(pwd)/.gnupg-fallback g13 --resume

should then be able to resume the encrypted partition using the
private key stored on a smartcard.

The implementation is pretty basic right now but useful to me.

Signed-off-by: Werner Koch <wk@gnupg.org>
18 files changed:
g13/Makefile.am
g13/backend.c
g13/backend.h
g13/be-dmcrypt.c
g13/be-dmcrypt.h
g13/call-syshelp.c
g13/call-syshelp.h
g13/g13-syshelp.h
g13/g13.c
g13/keyblob.c [new file with mode: 0644]
g13/keyblob.h
g13/mount.c
g13/mount.h
g13/server.c
g13/sh-cmd.c
g13/sh-dmcrypt.c
g13/suspend.c [new file with mode: 0644]
g13/suspend.h [new file with mode: 0644]