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110 lines
3.2 KiB
Python
Executable File
110 lines
3.2 KiB
Python
Executable File
#!/usr/bin/env drgn
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# Copyright (c) Meta Platforms, Inc. and affiliates.
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# SPDX-License-Identifier: LGPL-2.1-or-later
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"""Dump the master key of a dm-crypt device that uses aes-xts-plain64."""
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import argparse
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import os
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from pathlib import Path
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import sys
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from drgn import cast, container_of
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from drgn.helpers.linux.block import disk_name, for_each_disk
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def crypto_skcipher_alg(tfm):
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return container_of(tfm.base.__crt_alg, "struct skcipher_alg", "base")
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def crypto_skcipher_ctx(tfm):
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return cast("void *", tfm.base.__crt_ctx)
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def crypto_lskcipher_ctx(tfm):
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return cast("void *", tfm.base.__crt_ctx)
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def aes_xts_ctx(tfm):
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AESNI_ALIGN = 16
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mask = AESNI_ALIGN - 1
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ctx = cast("unsigned long", crypto_skcipher_ctx(tfm))
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return cast("struct aesni_xts_ctx *", (ctx + mask) & ~mask)
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def aes_key_from_ctx(ctx):
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words = ctx.key_enc.value_()[: ctx.key_length / 4]
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return b"".join(word.to_bytes(4, "little") for word in words)
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def is_function(obj, name):
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try:
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global_ = obj.prog_[name]
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except KeyError:
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return False
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return obj == global_
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument("name")
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args = parser.parse_args()
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if "/" in args.name:
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device_path = Path(args.name)
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else:
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device_path = Path("/dev/mapper") / args.name
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name = os.fsencode(device_path.resolve().name)
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for disk in for_each_disk():
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if disk_name(disk) == name:
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break
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else:
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sys.exit("target not found")
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md = cast("struct mapped_device *", disk.private_data)
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map = cast("struct dm_table *", md.map)
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if map.num_targets != 1:
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sys.exit("dm table has multiple targets")
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ti = map.targets
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if not is_function(ti.type.map, "crypt_map"):
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sys.exit("target is not dm-crypt")
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cc = cast("struct crypt_config *", ti.private)
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if cc.cipher_string.string_() != b"aes-xts-plain64":
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sys.exit("cipher is not aes-xts-plain64")
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tfm = cc.cipher_tfm.tfms[0]
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exit = crypto_skcipher_alg(tfm).exit.read_()
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if is_function(exit, "simd_skcipher_exit"):
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cryptd_tfm = cast(
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"struct simd_skcipher_ctx *", crypto_skcipher_ctx(tfm)
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).cryptd_tfm
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cryptd_ctx = cast(
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"struct cryptd_skcipher_ctx *", crypto_skcipher_ctx(cryptd_tfm.base)
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)
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child_tfm = cryptd_ctx.child
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xts_ctx = aes_xts_ctx(cryptd_ctx.child)
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crypt_aes_ctx = xts_ctx.crypt_ctx
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tweak_aes_ctx = xts_ctx.tweak_ctx
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elif is_function(exit, "xts_exit_tfm"):
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xts_ctx = cast("struct xts_tfm_ctx *", crypto_skcipher_ctx(tfm))
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lskcipher_tfm = cast(
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"struct crypto_lskcipher **", crypto_skcipher_ctx(xts_ctx.child)
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)[0]
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cipher_tfm = cast(
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"struct crypto_cipher **", crypto_lskcipher_ctx(lskcipher_tfm)
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)[0]
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crypt_aes_ctx = cast("struct crypto_aes_ctx *", cipher_tfm.base.__crt_ctx)
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tweak_aes_ctx = cast("struct crypto_aes_ctx *", xts_ctx.tweak.base.__crt_ctx)
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else:
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sys.exit("unknown skcipher")
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print(aes_key_from_ctx(crypt_aes_ctx).hex())
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print(aes_key_from_ctx(tweak_aes_ctx).hex())
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if __name__ == "__main__":
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main()
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