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>

1 files changed, 117 insertions, 0 deletions

diff --git a/g13/sh-cmd.c b/g13/sh-cmd.c
index 6ba4cd8c8..fe596f460 100644
--- a/g13/sh-cmd.c
+++ b/g13/sh-cmd.c
@@ -379,6 +379,121 @@ cmd_mount (assuan_context_t ctx, char *line)
 }
 
 
+static const char hlp_suspend[] =
+  "SUSPEND <type>\n"
+  "\n"
+  "Suspend an encrypted partition and wipe the key.\n"
+  "<type> must be \"dm-crypt\" for now.";
+static gpg_error_t
+cmd_suspend (assuan_context_t ctx, char *line)
+{
+  ctrl_t ctrl = assuan_get_pointer (ctx);
+  gpg_error_t err = 0;
+
+  line = skip_options (line);
+
+  if (strcmp (line, "dm-crypt"))
+    {
+      err = set_error (GPG_ERR_INV_ARG, "Type must be \"dm-crypt\"");
+      goto leave;
+    }
+
+  if (!ctrl->server_local->devicename
+      || !ctrl->server_local->devicefp
+      || !ctrl->devti)
+    {
+      err = set_error (GPG_ERR_ENOENT, "No device has been set");
+      goto leave;
+    }
+
+  err = sh_is_empty_partition (ctrl->server_local->devicename);
+  if (!err)
+    {
+      err = gpg_error (GPG_ERR_ENODEV);
+      assuan_set_error (ctx, err, "Partition is empty");
+      goto leave;
+    }
+  err = 0;
+
+  err = sh_dmcrypt_suspend_container (ctrl, ctrl->server_local->devicename);
+
+ leave:
+  return leave_cmd (ctx, err);
+}
+
+
+static const char hlp_resume[] =
+  "RESUME <type>\n"
+  "\n"
+  "Resume an encrypted partition and set the key.\n"
+  "<type> must be \"dm-crypt\" for now.";
+static gpg_error_t
+cmd_resume (assuan_context_t ctx, char *line)
+{
+  ctrl_t ctrl = assuan_get_pointer (ctx);
+  gpg_error_t err = 0;
+  unsigned char *keyblob = NULL;
+  size_t keybloblen;
+  tupledesc_t tuples = NULL;
+
+  line = skip_options (line);
+
+  if (strcmp (line, "dm-crypt"))
+    {
+      err = set_error (GPG_ERR_INV_ARG, "Type must be \"dm-crypt\"");
+      goto leave;
+    }
+
+  if (!ctrl->server_local->devicename
+      || !ctrl->server_local->devicefp
+      || !ctrl->devti)
+    {
+      err = set_error (GPG_ERR_ENOENT, "No device has been set");
+      goto leave;
+    }
+
+  err = sh_is_empty_partition (ctrl->server_local->devicename);
+  if (!err)
+    {
+      err = gpg_error (GPG_ERR_ENODEV);
+      assuan_set_error (ctx, err, "Partition is empty");
+      goto leave;
+    }
+  err = 0;
+
+  /* We expect that the client already decrypted the keyblob.
+   * Eventually we should move reading of the keyblob to here and ask
+   * the client to decrypt it.  */
+  assuan_begin_confidential (ctx);
+  err = assuan_inquire (ctx, "KEYBLOB",
+                        &keyblob, &keybloblen, 4 * 1024);
+  assuan_end_confidential (ctx);
+  if (err)
+    {
+      log_error (_("assuan_inquire failed: %s\n"), gpg_strerror (err));
+      goto leave;
+    }
+  err = create_tupledesc (&tuples, keyblob, keybloblen);
+  if (!err)
+    keyblob = NULL;
+  else
+    {
+      if (gpg_err_code (err) == GPG_ERR_NOT_SUPPORTED)
+        log_error ("unknown keyblob version received\n");
+      goto leave;
+    }
+
+  err = sh_dmcrypt_resume_container (ctrl,
+                                     ctrl->server_local->devicename,
+                                     tuples);
+
+ leave:
+  xfree (tuples);
+  destroy_tupledesc (tuples);
+  return leave_cmd (ctx, err);
+}
+
+
 static const char hlp_getinfo[] =
   "GETINFO <what>\n"
   "\n"
@@ -476,6 +591,8 @@ register_commands (assuan_context_t ctx, int fail_all)
     { "DEVICE",        cmd_device, hlp_device },
     { "CREATE",        cmd_create, hlp_create },
     { "MOUNT",         cmd_mount,  hlp_mount  },
+    { "SUSPEND",       cmd_suspend,hlp_suspend},
+    { "RESUME",        cmd_resume, hlp_resume },
     { "INPUT",         NULL },
     { "OUTPUT",        NULL },
     { "GETINFO",       cmd_getinfo, hlp_getinfo },