Detect when encryption failed to complete

For the case there encryption failes to complete because of a kernel
crash or the user power cycling the device, define a flag in the
crypto footer that says encryption is in progress.  Set it when starting
the actual encryption, and clear it when it successfully completes.

When the user is asked for the disk password, if the flag is set,
return a special error to the caller so the UI can know to tell the
user there is no valid data on the disk, and present a button to
wipe and reset the device.

Change-Id: I3723ec77f33437d94b3ac9ad5db0a5c950d11648

cryptfs.c

@@ -686,6 +686,13 @@ static int test_mount_encrypted_fs(char *passwd, char *mount_point)
     SLOGE("Error getting crypt footer and key\n");
     return -1;
   }
+
+  if (crypt_ftr.flags & CRYPT_ENCRYPTION_IN_PROGRESS) {
+    SLOGE("Encryption process didn't finish successfully\n");
+    return -2;  /* -2 is the clue to the UI that there is no usable data on the disk,
+                 * and give the user an option to wipe the disk */
+  }
+
   SLOGD("crypt_ftr->fs_size = %lld\n", crypt_ftr.fs_size);
   orig_failed_decrypt_count = crypt_ftr.failed_decrypt_count;
 
@@ -995,6 +1002,7 @@ int cryptfs_enable(char *howarg, char *passwd)
     /* Initialize a crypt_mnt_ftr for the partition */
     cryptfs_init_crypt_mnt_ftr(&crypt_ftr);
     crypt_ftr.fs_size = nr_sec - (CRYPT_FOOTER_OFFSET / 512);
+    crypt_ftr.flags |= CRYPT_ENCRYPTION_IN_PROGRESS;
     strcpy((char *)crypt_ftr.crypto_type_name, "aes-cbc-essiv:sha256");
 
     /* Make an encrypted master key */
@@ -1024,6 +1032,10 @@ int cryptfs_enable(char *howarg, char *passwd)
 
     if (! rc) {
         /* Success */
+        /* Clear the encryption in progres flag in the footer */
+        crypt_ftr.flags &= ~CRYPT_ENCRYPTION_IN_PROGRESS;
+        put_crypt_ftr_and_key(real_blkdev, &crypt_ftr, 0, 0);
+
         sleep(2); /* Give the UI a change to show 100% progress */
         sync();
         reboot(LINUX_REBOOT_CMD_RESTART);

cryptfs.h

@@ -34,6 +34,8 @@
 
 /* definitions of flags in the structure below */
 #define CRYPT_MNT_KEY_UNENCRYPTED 0x1 /* The key for the partition is not encrypted. */
+#define CRYPT_ENCRYPTION_IN_PROGRESS 0x2 /* Set when starting encryption,
+                                          * clear when done before rebooting */
 
 #define CRYPT_MNT_MAGIC 0xD0B5B1C4