From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 44C8015252D; Mon, 6 Jan 2025 15:25:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736177119; cv=none; b=HdxDTRpLnfF+R9nif3gvrU/aXVXG8xrxFZ9obP/sRcCsqUXOUopiIskY/n8cFcwfz66cmvrSU+9PXgCaQBfAs2rANITfOsy7qsEZSZVs9OVgXGck+D1ZEj2zj6raBfnjlo4oycRMXrBOyXfhLyIt2E8JGGJOFYyHJIjKk833i+E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736177119; c=relaxed/simple; bh=03EjnzBpAtXmTACzUaPA0qMe5Uf/ZpN5tnS/0X4efDE=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=img16S96wojypeo9ETKVY4B4puqNbaBOx6F5Mi/mBHr7hfXYGOtIesnoXqplpHOsVhAT3MJwVwLxBUk3DCkUqQcdolihmRNNaAVhHM0QqhZ7pC3bWEkH7qbiAKMlLw6gLIqggCy0KCzAKUzr4slV+IIPoNMcfFMM5BSw9AFqnYc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=VOOm/kta; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="VOOm/kta" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C412CC4CED2; Mon, 6 Jan 2025 15:25:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1736177119; bh=03EjnzBpAtXmTACzUaPA0qMe5Uf/ZpN5tnS/0X4efDE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VOOm/ktaLCqRcby99beBvTon2mdoR4mW4ehrk0oMmHaXY4FNClDdYRb1HKOD1auLP edDyZMEd+HRLJ2qZXfx9E2gTSDbVgh3aSWXU41Wq2HkvWwbzq8zFaelFF+LnsbpoYv tJwwsZA/oE92XSNmGVIalavDnqdJB/xqpFeenBD8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Lukas Wunner , Stefan Berger , Jonathan Cameron , Herbert Xu , Sasha Levin Subject: [PATCH 6.6 025/222] crypto: ecdsa - Avoid signed integer overflow on signature decoding Date: Mon, 6 Jan 2025 16:13:49 +0100 Message-ID: <20250106151151.554572243@linuxfoundation.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250106151150.585603565@linuxfoundation.org> References: <20250106151150.585603565@linuxfoundation.org> User-Agent: quilt/0.68 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Lukas Wunner [ Upstream commit 3b0565c703503f832d6cd7ba805aafa3b330cb9d ] When extracting a signature component r or s from an ASN.1-encoded integer, ecdsa_get_signature_rs() subtracts the expected length "bufsize" from the ASN.1 length "vlen" (both of unsigned type size_t) and stores the result in "diff" (of signed type ssize_t). This results in a signed integer overflow if vlen > SSIZE_MAX + bufsize. The kernel is compiled with -fno-strict-overflow, which implies -fwrapv, meaning signed integer overflow is not undefined behavior. And the function does check for overflow: if (-diff >= bufsize) return -EINVAL; So the code is fine in principle but not very obvious. In the future it might trigger a false-positive with CONFIG_UBSAN_SIGNED_WRAP=y. Avoid by comparing the two unsigned variables directly and erroring out if "vlen" is too large. Signed-off-by: Lukas Wunner Reviewed-by: Stefan Berger Reviewed-by: Jonathan Cameron Signed-off-by: Herbert Xu Signed-off-by: Sasha Levin --- crypto/ecdsa.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) diff --git a/crypto/ecdsa.c b/crypto/ecdsa.c index 28441311af36..da04df3c8ecf 100644 --- a/crypto/ecdsa.c +++ b/crypto/ecdsa.c @@ -36,29 +36,24 @@ static int ecdsa_get_signature_rs(u64 *dest, size_t hdrlen, unsigned char tag, const void *value, size_t vlen, unsigned int ndigits) { size_t bufsize = ndigits * sizeof(u64); - ssize_t diff = vlen - bufsize; const char *d = value; - if (!value || !vlen) + if (!value || !vlen || vlen > bufsize + 1) return -EINVAL; - /* diff = 0: 'value' has exacly the right size - * diff > 0: 'value' has too many bytes; one leading zero is allowed that - * makes the value a positive integer; error on more - * diff < 0: 'value' is missing leading zeros + /* + * vlen may be 1 byte larger than bufsize due to a leading zero byte + * (necessary if the most significant bit of the integer is set). */ - if (diff > 0) { + if (vlen > bufsize) { /* skip over leading zeros that make 'value' a positive int */ if (*d == 0) { vlen -= 1; - diff--; d++; - } - if (diff) + } else { return -EINVAL; + } } - if (-diff >= bufsize) - return -EINVAL; ecc_digits_from_bytes(d, vlen, dest, ndigits); -- 2.39.5