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authorJakob Kaivo <jkk@ung.org>2020-11-12 20:41:55 -0500
committerJakob Kaivo <jkk@ung.org>2020-11-12 20:41:55 -0500
commitfe54b7e117ffbc4830db24de2f7f820333ae0cf7 (patch)
treece7071634fc6014cc72a3496718e704fd869d65d
parent797cee95db1b164b0d0fd7de6d2947fc1dd669c8 (diff)
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+DeOneBook
+---------
+
+This program extracts encryption keys from eOneBook SD cards. Eventually I will
+add decryption as well, but for now it is enough to extract a key that can be
+used passed to `openssl` to do the actual decryption.
+
+Building
+--------
+
+If you have a system with a directly attached SD card reader (i.e. a device
+that appears as `/dev/mmcblk0` or similar, *not* as `/dev/sdb`), you can build
+a native version of the program with:
+
+ make
+
+If you do not (this includes all USB readers and some internal devices that are
+attached through an internal USB adapter), you'll need to cross-compile the
+tool to run directly on the eOneBook. First install a cross compiler. On
+Debian and Ubuntu systems, you can do this with:
+
+ sudo apt install crossbuild-essential-armhf
+
+Then build with the cross compiler:
+
+ make CC=arm-linux-gnueabihf-gcc
+
+Use
+---
+
+If you are using the native version, simply place an eOneBook SD card in your
+SD card reader, and run:
+
+ ./deonebook -G [devicename]
+
+Here, `devicename` is optional, and will default to `mmcblk0`. If your SD card
+has a different device name, specify it there. The encryption key will be
+presented in hexadecimal.
+
+For the eOneBook version, it's a little more complex. You'll need to prep the
+SD card to execute the program and save its output. First, make sure the SD
+card is not write-protected by moving the write-protect slider to the end of
+its slot nearest the pins of the card. Mount the SD card somewhere you can
+write to it, `cd` to that mount point, and run the following commands,
+replacing `$DEONEBOOKDIR` with the path to the compiled DeOneBook.
+
+***Be very careful with these commands, as if you lose or overwrite the
+original `.A001` file, you will not be able to use that SD card in your
+eOneBook anymore. You are strongly advised to back up the entire SD card
+before attempting this.***
+
+ mv .A001 eonebook # rename the official firmware
+ cp $DEONEBOOKDIR/deonebook . # copy over the key extractor
+ cp $DEONEBOOKDIR/extract.sh .A001 # copy over the extraction script
+
+Put the SD card in your eOneBook and open it up. When the official interface
+comes up, the key extraction is complete. Close the eOneBook and there will be
+a file called `eonebook.hex` containing the encryption key for that card.
+
+Decrypting
+----------
+
+Eventually this will be integrated into DeOneBook itself. For now, you can use
+the extracted key along with `openssl` to decrypt files. Replace `$KEY` with
+the hex key, either as printed with the native version or the contents of
+`eonebook.hex` from the cross-compiled version. Replace `$INFILE` with the name
+of an encrypted image (e.g. `002E`), and `$OUTFILE` with a path where you want
+the decrypted image to go:
+
+ openssl aes-128-cbc -d -iv 03030303030303030303030303030303 -K $KEY -in $INFILE -out $OUTFILE
+
+You can do a whole directory with something like:
+
+ for i in *E; do
+ openssl aes-128-cbc -d -iv 03030303030303030303030303030303 -K $KEY -in $i -out $i.gray
+ done