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 <[email protected]>

1 files changed, 39 insertions, 2 deletions

diff --git a/g13/backend.c b/g13/backend.c
index bb7bfcc02..dd2176834 100644
--- a/g13/backend.c
+++ b/g13/backend.c
@@ -198,7 +198,7 @@ be_create_new_keys (int conttype, membuf_t *mb)
 }
 
 
-/*  Dispatcher to the backend's create function.  */
+/* Dispatcher to the backend's create function.  */
 gpg_error_t
 be_create_container (ctrl_t ctrl, int conttype,
                      const char *fname, int fd, tupledesc_t tuples,
@@ -220,7 +220,7 @@ be_create_container (ctrl_t ctrl, int conttype,
 }
 
 
-/*  Dispatcher to the backend's mount function.  */
+/* Dispatcher to the backend's mount function.  */
 gpg_error_t
 be_mount_container (ctrl_t ctrl, int conttype,
                     const char *fname,  const char *mountpoint,
@@ -238,3 +238,40 @@ be_mount_container (ctrl_t ctrl, int conttype,
       return no_such_backend (conttype);
     }
 }
+
+
+/* Dispatcher to the backend's suspend function.  */
+gpg_error_t
+be_suspend_container (ctrl_t ctrl, int conttype, const char *fname)
+{
+  switch (conttype)
+    {
+    case CONTTYPE_ENCFS:
+      return gpg_error (GPG_ERR_NOT_SUPPORTED);
+
+    case CONTTYPE_DM_CRYPT:
+      return be_dmcrypt_suspend_container (ctrl, fname);
+
+    default:
+      return no_such_backend (conttype);
+    }
+}
+
+
+/* Dispatcher to the backend's resume function.  */
+gpg_error_t
+be_resume_container (ctrl_t ctrl, int conttype, const char *fname,
+                     tupledesc_t tuples)
+{
+  switch (conttype)
+    {
+    case CONTTYPE_ENCFS:
+      return gpg_error (GPG_ERR_NOT_SUPPORTED);
+
+    case CONTTYPE_DM_CRYPT:
+      return be_dmcrypt_resume_container (ctrl, fname, tuples);
+
+    default:
+      return no_such_backend (conttype);
+    }
+}