From mboxrd@z Thu Jan 1 00:00:00 1970 Delivery-date: Mon, 03 Nov 2025 12:55:54 +0100 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by lore.white.stw.pengutronix.de with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.96) (envelope-from ) id 1vFtAA-00EqOb-0o for lore@lore.pengutronix.de; Mon, 03 Nov 2025 12:55:54 +0100 Received: from bombadil.infradead.org ([2607:7c80:54:3::133]) by metis.whiteo.stw.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1vFtA9-0000uJ-HQ for lore@pengutronix.de; Mon, 03 Nov 2025 12:55:54 +0100 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=4VjWcVXATZiVL4jEukkaAKWgrfBd3tNlnHS3C1jAsZI=; b=ZgindyHoZ7C+gNaD8bjyUlBEPe O7ngJhQ7axEWugYqLX08eDqLmlSJNoSz6X3vwz1JGdtueWBwH4HKWg4jCR0IkOrRjeHPVSdbHvyyY nvnNuot0zpMqydifEizxRaJ7oAnLqjBfPU6DNPIRrn/YxYtdyRhQowxxRxdQA4/7LHYHFlrlAvV0E fdtWfFhuxTGURfnyhv7TL3LEJNPf+F3tRVcpbfSF1onzCWGwpuZ/G8PsqqU4FkPeofNK3dg51Se5h gBSqSXTI7LSVVyVvUMCiBK+gpmyglVAMRk72+Haq/HcJhnfHK2b2sAuXsSYemA7pd5cepVYQ87c4N Wx1Hssmg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vFt9i-00000009n9M-0xD4; Mon, 03 Nov 2025 11:55:26 +0000 Received: from metis.whiteo.stw.pengutronix.de ([2a0a:edc0:2:b01:1d::104]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vFt9e-00000009n8r-3ftS for barebox@lists.infradead.org; Mon, 03 Nov 2025 11:55:24 +0000 Received: from ptz.office.stw.pengutronix.de ([2a0a:edc0:0:900:1d::77] helo=[127.0.0.1]) by metis.whiteo.stw.pengutronix.de with esmtp (Exim 4.92) (envelope-from ) id 1vFt9c-0000jZ-Fn; Mon, 03 Nov 2025 12:55:20 +0100 Message-ID: <45026e71-c901-428c-86b3-461c017db3f6@pengutronix.de> Date: Mon, 3 Nov 2025 12:55:20 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Sascha Hauer Cc: BAREBOX , Ahmad Fatoum References: <20251028-tlv-signature-v2-0-3bafce636ad7@pengutronix.de> <20251028-tlv-signature-v2-10-3bafce636ad7@pengutronix.de> <2249476f-03b5-404b-9a9b-feb69393ef1e@pengutronix.de> From: Jonas Rebmann Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251103_035522_925460_1571B7F7 X-CRM114-Status: GOOD ( 27.85 ) X-BeenThere: barebox@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "barebox" X-SA-Exim-Connect-IP: 2607:7c80:54:3::133 X-SA-Exim-Mail-From: barebox-bounces+lore=pengutronix.de@lists.infradead.org X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on metis.whiteo.stw.pengutronix.de X-Spam-Level: X-Spam-Status: No, score=-3.4 required=4.0 tests=AWL,BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_NONE autolearn=unavailable autolearn_force=no version=3.4.2 Subject: Re: [PATCH v2 10/17] common: tlv: Add TLV-Signature support X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on metis.whiteo.stw.pengutronix.de) On 2025-11-03 12:41, Sascha Hauer wrote: > On Mon, Nov 03, 2025 at 12:21:56PM +0100, Jonas Rebmann wrote: >> Hi Sascha, >> >> On 2025-11-03 11:02, Sascha Hauer wrote: >>> On Tue, Oct 28, 2025 at 07:03:15PM +0100, Jonas Rebmann wrote: >>>> Implement TLV signature using the existing placeholders for it. Use the >>>> existing cryptographic primitives and public key handling used for >>>> fitimage verification. >>>> >>>> Signature is verified and then must be valid iff CONFIG_TLV_SIGNATURE is >>>> enabled and a keyring is selected for the decoder. SHA256 hashing is >>>> hardcoded for now. >>>> >>>> As 16 bit are well sufficient to store the length of the signature >>>> section in bytes, reduce it to its least significant 16 bit and reserve >>>> the remaining 16 bit for future use. >>>> >>>> As sig_len where the only reserved bits left, and where zero-reserved, >>>> this leaves more wiggle room to still expand the format in the future. >>>> >>>> Signed-off-by: Jonas Rebmann >>>> --- >>>> common/Kconfig | 5 +++ >>>> common/tlv/parser.c | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++ >>>> include/tlv/format.h | 22 ++++++++++--- >>>> 3 files changed, 109 insertions(+), 5 deletions(-) >>>> >>>> diff --git a/common/Kconfig b/common/Kconfig >>>> index d923d4c4b6..663465443d 100644 >>>> --- a/common/Kconfig >>>> +++ b/common/Kconfig >>>> @@ -1122,6 +1122,11 @@ config TLV >>>> barebox TLV is a scheme for storing factory data on non-volatile >>>> storage. Unlike state, it's meant to be read-only. >>>> +config TLV_SIGNATURE >>>> + bool "barebox TLV signature support" >>>> + depends on TLV >>>> + select CRYPTO_BUILTIN_KEYS >>>> + >>>> config TLV_DRV >>>> bool "barebox TLV generic driver" >>>> depends on TLV >>>> diff --git a/common/tlv/parser.c b/common/tlv/parser.c >>>> index f74ada99d7..cbf45413dd 100644 >>>> --- a/common/tlv/parser.c >>>> +++ b/common/tlv/parser.c >>>> @@ -1,6 +1,7 @@ >>>> // SPDX-License-Identifier: GPL-2.0-only >>>> #define pr_fmt(fmt) "barebox-tlv: " fmt >>>> +#include "tlv/format.h" >>>> #include >>>> #include >>>> @@ -9,6 +10,80 @@ >>>> #include >>>> #include >>>> #include >>>> +#include >>>> + >>>> +static int tlv_verify_try_key(const struct public_key *key, const uint8_t *sig, >>>> + const uint32_t sig_len, const void *data, >>>> + unsigned long data_len) >>>> +{ >>>> + enum hash_algo algo = HASH_ALGO_SHA256; >>>> + int ret; >>>> + struct digest *digest; >>>> + void *hash; >>>> + >>>> + digest = digest_alloc_by_algo(algo); >>>> + if (!digest) >>>> + return -ENOMEM; >>>> + >>>> + digest_init(digest); >>>> + if (IS_ERR(digest)) { >>> >>> What you meant to do here is >>> >>> ret = digest_init(digest); >>> if (ret) { >>> ... >>> } >>> >> >> I used IS_ERR() here simply because that's how I saw it in >> common/image-fit.c. Will that need to be changed too then? > > I don't see that the return value of digest_init() is checked in > common/image-fit.c. > > Yes, we should consistently check the return value of digest_init(). > > Anyway, my point was that your IS_ERR(digest) is bogus. Oh indeed, common/image-fit.c uses IS_ERR(digest) for fit_alloc_digest() but digest_init() is unchecked. Will apply your suggestion for v3. >>>> + for_each_public_key_keyring(key, id, keyring) { >>>> + u32 spki_key = get_unaligned_le32(key->hash); >>>> + >>>> + if (spki_key == spki_tlv) { >>>> + count_spki_matches++; >>>> + ret = tlv_verify_try_key(key, spki_tlv_ptr + SPKI_LEN, sig_len - SPKI_LEN, header, payload_sz); >>>> + if (!ret) >>>> + return 0; >>>> + pr_warn("TLV spki %08x matched available key but signature verification failed: %pe!\n", spki_tlv, ERR_PTR(ret)); >>> >>> Not sure what this warning is about. Either it can happen that there are >>> two keys with the same hash in which case there's nothing to warn about, >>> or it can't happen and you would return an error here. >> >> When this happens, there is either a 32-bit hash collision, or >> something's broken, such as what we had last week, where ECDSA keys >> where incorrectly initialized, leading to signature verification to >> always fail even with a valid key. >> >> We can't error out here already because when we designed the TLV >> signature verification feature we specified that in case of spki hash >> collision, all matching keys must be tried. > > Ok, considering that a hash collision can happen we shouldn't warn about > it. > The odds of this happening are 1 in 2^32. It is much more likely that the underlying issue lays elsewhere. If no spki hash match occurs, there's a warning too: if (!count_spki_matches) { pr_warn("TLV spki %08x matched no key!\n", spki_tlv); return -ENOKEY; } The difference between: 'There was no matching key' and 'We had a key but failed to verify for dubious reasons' should clearly be reflected in the logs. Regards, Jonas -- Pengutronix e.K. | Jonas Rebmann | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-9 |