From patchwork Tue Feb 1 00:34:13 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Biggers X-Patchwork-Id: 12731325 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 C0605C433EF for ; Tue, 1 Feb 2022 00:35:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230520AbiBAAfA (ORCPT ); Mon, 31 Jan 2022 19:35:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230510AbiBAAe6 (ORCPT ); Mon, 31 Jan 2022 19:34:58 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [IPv6:2604:1380:4601:e00::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C848C06173B; Mon, 31 Jan 2022 16:34:58 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 1C323B82CD0; Tue, 1 Feb 2022 00:34:57 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 76EBCC340F2; Tue, 1 Feb 2022 00:34:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1643675695; bh=Nh61dm4uORI3BdjRZX34AcWvRnvxLfYMB2NLPUBnTjI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=OEbZLtn+T/drz3k9MGa/Cz5dU/ZiDmNWU0zdxAq7mOejEeIVxpyeTRDXtydWEGJBL G3PyzOoe/OY7FvzLgl9fSkgFlH5MmOE5K1+rdh1NsA86qJcPLnqYSMmc/l+fn0SWXr PHgAgNrfmOoHVXfeXvD5vgpeI3+Ta76bxO5pv/NhWswxKyEbBv+3zG909k4PFSYqja 9kqgX/b67uVxgH79gDXjrtf4LtqkLRfoJLuX3Y64FeAwFDPIWfa6MnHFAHN8gG3TDJ x62H5LYGKeY5+DKm6468FfS5/mnmXGNbwpXEa+cOM0ZB5oJRNnClZztChXzbiXDhbd nKEWiz70Efvjg== From: Eric Biggers To: keyrings@vger.kernel.org, Jarkko Sakkinen , David Howells Cc: linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org, Stefan Berger , Gilad Ben-Yossef , Tianjia Zhang , Vitaly Chikunov , Mimi Zohar , stable@vger.kernel.org Subject: [PATCH 1/2] KEYS: asymmetric: enforce that sig algo matches key algo Date: Mon, 31 Jan 2022 16:34:13 -0800 Message-Id: <20220201003414.55380-2-ebiggers@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220201003414.55380-1-ebiggers@kernel.org> References: <20220201003414.55380-1-ebiggers@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org From: Eric Biggers Most callers of public_key_verify_signature(), including most indirect callers via verify_signature() as well as pkcs7_verify_sig_chain(), don't check that public_key_signature::pkey_algo matches public_key::pkey_algo. These should always match. However, a malicious signature could intentionally declare an unintended algorithm. It is essential that such signatures be rejected outright, or that the algorithm of the *key* be used -- not the algorithm of the signature as that would allow attackers to choose the algorithm used. Currently, public_key_verify_signature() correctly uses the key's algorithm when deciding which akcipher to allocate. That's good. However, it uses the signature's algorithm when deciding whether to do the first step of SM2, which is incorrect. Also, v4.19 and older kernels used the signature's algorithm for the entire process. Prevent such errors by making public_key_verify_signature() enforce that the signature's algorithm matches the key's algorithm. Also remove two checks of this done by callers, which are now redundant. Cc: stable@vger.kernel.org Signed-off-by: Eric Biggers Reviewed-by: Jarkko Sakkinen --- crypto/asymmetric_keys/pkcs7_verify.c | 6 ------ crypto/asymmetric_keys/public_key.c | 15 +++++++++++++++ crypto/asymmetric_keys/x509_public_key.c | 6 ------ 3 files changed, 15 insertions(+), 12 deletions(-) diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c index 0b4d07aa88111..f94a1d1ad3a6c 100644 --- a/crypto/asymmetric_keys/pkcs7_verify.c +++ b/crypto/asymmetric_keys/pkcs7_verify.c @@ -174,12 +174,6 @@ static int pkcs7_find_key(struct pkcs7_message *pkcs7, pr_devel("Sig %u: Found cert serial match X.509[%u]\n", sinfo->index, certix); - if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) { - pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n", - sinfo->index); - continue; - } - sinfo->signer = x509; return 0; } diff --git a/crypto/asymmetric_keys/public_key.c b/crypto/asymmetric_keys/public_key.c index 4fefb219bfdc8..aba7113d86c76 100644 --- a/crypto/asymmetric_keys/public_key.c +++ b/crypto/asymmetric_keys/public_key.c @@ -325,6 +325,21 @@ int public_key_verify_signature(const struct public_key *pkey, BUG_ON(!sig); BUG_ON(!sig->s); + /* + * The signature's claimed public key algorithm *must* match the key's + * actual public key algorithm. + * + * Small exception: ECDSA signatures don't specify the curve, but ECDSA + * keys do. So the strings can mismatch slightly in that case: + * "ecdsa-nist-*" for the key, but "ecdsa" for the signature. + */ + if (!sig->pkey_algo) + return -EINVAL; + if (strcmp(pkey->pkey_algo, sig->pkey_algo) != 0 && + (strncmp(pkey->pkey_algo, "ecdsa-", 6) != 0 || + strcmp(sig->pkey_algo, "ecdsa") != 0)) + return -EKEYREJECTED; + ret = software_key_determine_akcipher(sig->encoding, sig->hash_algo, pkey, alg_name); diff --git a/crypto/asymmetric_keys/x509_public_key.c b/crypto/asymmetric_keys/x509_public_key.c index fe14cae115b51..71cc1738fbfd2 100644 --- a/crypto/asymmetric_keys/x509_public_key.c +++ b/crypto/asymmetric_keys/x509_public_key.c @@ -128,12 +128,6 @@ int x509_check_for_self_signed(struct x509_certificate *cert) goto out; } - ret = -EKEYREJECTED; - if (strcmp(cert->pub->pkey_algo, cert->sig->pkey_algo) != 0 && - (strncmp(cert->pub->pkey_algo, "ecdsa-", 6) != 0 || - strcmp(cert->sig->pkey_algo, "ecdsa") != 0)) - goto out; - ret = public_key_verify_signature(cert->pub, cert->sig); if (ret < 0) { if (ret == -ENOPKG) {