From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 70DCFFA373F for ; Sun, 23 Oct 2022 20:40:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229635AbiJWUki (ORCPT ); Sun, 23 Oct 2022 16:40:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56022 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229587AbiJWUkh (ORCPT ); Sun, 23 Oct 2022 16:40:37 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3B6185725A; Sun, 23 Oct 2022 13:40:36 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id A89F7CE0F28; Sun, 23 Oct 2022 20:40:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A1CFAC433D6; Sun, 23 Oct 2022 20:40:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1666557633; bh=Ase1ag2VU+E3ra79YOHGkuWXSUct//S7LLw1x5dUijM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=BnHvq8de4KkBrnnTJdp9P2IDrjbDwbEd3xG0OaJ+yOJJyUmQxzjxJjnM6zZg78pne Wl4L9nSgr1YLIGiAlxa2+tvFxHTxhOouHyQg+ATgDD4L6AkIQ3TMRQVmglEaARtEpP xPVBk4VEgE1Hq4AqCj41vda0tmK6g9FlXKpxx7vWMh3LJ7wzvzHWDlFyhAwcXWY0ay 8omPGhay4Fnw3cVp69nsW7btriy5i8K1pZMEEJjYI69NAhOR/AKVmvqL+qz6pkRNtg l9nDcFiwnyaIe9zK2u2wBNuFABv83xMOqtIOabZAop0NLc0SWfI044UeFXoh/pNenO l32+MbekzUSBA== Date: Sun, 23 Oct 2022 23:40:25 +0300 From: Jarkko Sakkinen To: Nikolaus Voss Cc: Mimi Zohar , David Howells , James Morris , "Serge E. Hallyn" , Yael Tzur , Cyril Hrubis , Petr Vorel , linux-integrity@vger.kernel.org, keyrings@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6] KEYS: encrypted: fix key instantiation with user-provided data Message-ID: References: <20221019164526.B70DF1C59@mail.steuer-voss.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20221019164526.B70DF1C59@mail.steuer-voss.de> Precedence: bulk List-ID: On Wed, Oct 19, 2022 at 06:38:20PM +0200, Nikolaus Voss wrote: > Commit cd3bc044af48 ("KEYS: encrypted: Instantiate key with > user-provided decrypted data") added key instantiation with user > provided decrypted data. The user data is hex-ascii-encoded but was > just memcpy'ed to the binary buffer. Fix this to use hex2bin instead. > > Old keys created from user provided decrypted data saved with "keyctl > pipe" are still valid, however if the key is recreated from decrypted > data the old key must be converted to the correct format. This can be > done with a small shell script, e.g.: > > BROKENKEY=abcdefABCDEF1234567890aaaaaaaaaa > NEWKEY=$(echo -ne $BROKENKEY | xxd -p -c32) > keyctl add user masterkey "$(cat masterkey.bin)" @u > keyctl add encrypted testkey "new user:masterkey 32 $NEWKEY" @u > > However, NEWKEY is still broken: If for BROKENKEY 32 bytes were > specified, a brute force attacker knowing the key properties would only > need to try at most 2^(16*8) keys, as if the key was only 16 bytes long. > > The security issue is a result of the combination of limiting the input > range to hex-ascii and using memcpy() instead of hex2bin(). It could > have been fixed either by allowing binary input or using hex2bin() (and > doubling the ascii input key length). This patch implements the latter. > > The corresponding test for the Linux Test Project ltp has also been > fixed (see link below). > > Fixes: cd3bc044af48 ("KEYS: encrypted: Instantiate key with user-provided decrypted data") > Cc: stable@kernel.org > Link: https://lore.kernel.org/ltp/20221006081709.92303897@mail.steuer-voss.de/ > Reviewed-by: Mimi Zohar > Signed-off-by: Nikolaus Voss > --- > Changes > ======= > v6: - fix checkpatch warnings > v5: - explain security issue in commit message, add Reviewd-by > v4: - change "Link:" address > v3: - use generated random key in example, reformat commit message > v2: - clarify commit message, add example to recover old/broken keys > - improve example in Documentation/security/keys/trusted-encrypted.rst > - add link to ltp patch > > Documentation/security/keys/trusted-encrypted.rst | 3 ++- > security/keys/encrypted-keys/encrypted.c | 6 +++--- > 2 files changed, 5 insertions(+), 4 deletions(-) > > diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst > index 0bfb4c339748..9bc9db8ec651 100644 > --- a/Documentation/security/keys/trusted-encrypted.rst > +++ b/Documentation/security/keys/trusted-encrypted.rst > @@ -350,7 +350,8 @@ Load an encrypted key "evm" from saved blob:: > > Instantiate an encrypted key "evm" using user-provided decrypted data:: > > - $ keyctl add encrypted evm "new default user:kmk 32 `cat evm_decrypted_data.blob`" @u > + $ evmkey=$(dd if=/dev/urandom bs=1 count=32 | xxd -c32 -p) > + $ keyctl add encrypted evm "new default user:kmk 32 $evmkey" @u > 794890253 > > $ keyctl print 794890253 > diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c > index e05cfc2e49ae..1e313982af02 100644 > --- a/security/keys/encrypted-keys/encrypted.c > +++ b/security/keys/encrypted-keys/encrypted.c > @@ -627,7 +627,7 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, > pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n"); > return ERR_PTR(-EINVAL); > } > - if (strlen(decrypted_data) != decrypted_datalen) { > + if (strlen(decrypted_data) != decrypted_datalen * 2) { > pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n"); > return ERR_PTR(-EINVAL); > } > @@ -791,8 +791,8 @@ static int encrypted_init(struct encrypted_key_payload *epayload, > ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv); > } else if (decrypted_data) { > get_random_bytes(epayload->iv, ivsize); > - memcpy(epayload->decrypted_data, decrypted_data, > - epayload->decrypted_datalen); > + ret = hex2bin(epayload->decrypted_data, decrypted_data, > + epayload->decrypted_datalen); > } else { > get_random_bytes(epayload->iv, ivsize); > get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen); > -- > 2.34.1 > Did you check that this passes "checkpatch.pl --strict"? Your earlier version did not. BR, Jarkko