From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELvCqQXVxQAWt0dx1hjvmVvCOEd9bfN8SJvYzWQKUWPrs6qmYJ0dcVo6UzkUZESbJVsXYAAz ARC-Seal: i=1; a=rsa-sha256; t=1521033475; cv=none; d=google.com; s=arc-20160816; b=yx9d7z0Ic4F88jG9gIb1e6HJCDRShKg0EulR7cvRDk/4tSoBOgBeUuB3OrKAYwAJ/l ce9n/FFR/mvWK9ApNBQDcGKwn83ve/ir9Yk0TIsUJf8zxHxUjv4uifQUEXUCoIkb5Zfj LlKEjLE1DlrPIG9/zSZlsIrtt1HdMryvEo/hwqzeWG8H6k2Tr6lIteRAR/XxKmmQvFWu iZk/DnzU55+TDpS7vl5GrFfSRz6dxvOStf8q5EvDhW94G0Ox4XTpPLTxYEKHzOWI1vsO SRuc0n7ZJq2qMtoPtNKZrB81j9yJ0hQ7ozM5P0Qxm/cy/NR5aAm8/HIKyFdchqPpksFy sT1A== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=message-id:date:subject:cc:to:from:dkim-signature:delivered-to :list-id:list-subscribe:list-unsubscribe:list-help:list-post :precedence:mailing-list:arc-authentication-results; bh=iITzaUcfAaEIVDvCIBFgWh/44XucP90daGxl2vB0D0M=; b=W7I3m1Nfv4LcE1iDk4E8Ls9FEioN9kTEC/Z0GI80CkQS2A2y4bt0gJnWUqoLL7JMMC nL+rA4mbuKheIDyWYcqiX9BSHxlO4B1mwNgO8dJzgnLN21Hpp6wtf3yNiIa6SH+C46hR 1Q3WPyOBaCOYqt+KAzdAUtCep66qAbuL3spoZqlx8gLZ2JS1YQ7tmclWuTzYy8xx9GnP eDwg1SADQlQAyisvCZPjrB/GeLX8iNzjJNxXSsVCnmplkjY1gjD5T2agVLy0t1kFUiGW 2PBFoTpsVXz8ksEe3A7urpTvpqIUzrB/6lSZ/3WONOAixCqj7pENc8tuFa4OeAE86IsY roMg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Az9dyYXA; spf=pass (google.com: domain of kernel-hardening-return-12594-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-12594-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=Az9dyYXA; spf=pass (google.com: domain of kernel-hardening-return-12594-gregkh=linuxfoundation.org@lists.openwall.com designates 195.42.179.200 as permitted sender) smtp.mailfrom=kernel-hardening-return-12594-gregkh=linuxfoundation.org@lists.openwall.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm List-Post: List-Help: List-Unsubscribe: List-Subscribe: From: Salvatore Mesoraca To: linux-kernel@vger.kernel.org Cc: kernel-hardening@lists.openwall.com, linux-crypto@vger.kernel.org, "David S. Miller" , Herbert Xu , Kees Cook , Salvatore Mesoraca Subject: [PATCH] crypto: ctr: avoid VLA use Date: Wed, 14 Mar 2018 14:17:30 +0100 Message-Id: <1521033450-14447-1-git-send-email-s.mesoraca16@gmail.com> X-Mailer: git-send-email 1.9.1 X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1594919197404593745?= X-GMAIL-MSGID: =?utf-8?q?1594919197404593745?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: All ciphers implemented in Linux have a block size less than or equal to 16 bytes and the most demanding hw require 16 bits alignment for the block buffer. We avoid 2 VLAs[1] by always allocating 16 bytes with 16 bits alignment, unless the architecture support efficient unaligned accesses. We also check, at runtime, that our assumptions still stand, possibly dynamically allocating a new buffer, just in case something changes in the future. [1] https://lkml.org/lkml/2018/3/7/621 Signed-off-by: Salvatore Mesoraca --- Notes: Can we maybe skip the runtime check? crypto/ctr.c | 50 ++++++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 42 insertions(+), 8 deletions(-) diff --git a/crypto/ctr.c b/crypto/ctr.c index 854d924..f37adf0 100644 --- a/crypto/ctr.c +++ b/crypto/ctr.c @@ -35,6 +35,16 @@ struct crypto_rfc3686_req_ctx { struct skcipher_request subreq CRYPTO_MINALIGN_ATTR; }; +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS +#define DECLARE_CIPHER_BUFFER(name) u8 name[16] +#else +#define DECLARE_CIPHER_BUFFER(name) u8 __aligned(16) name[16] +#endif + +#define CHECK_CIPHER_BUFFER(name, size, align) \ + likely(size <= sizeof(name) && \ + name == PTR_ALIGN(((u8 *) name), align + 1)) + static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key, unsigned int keylen) { @@ -52,22 +62,35 @@ static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key, return err; } -static void crypto_ctr_crypt_final(struct blkcipher_walk *walk, - struct crypto_cipher *tfm) +static int crypto_ctr_crypt_final(struct blkcipher_walk *walk, + struct crypto_cipher *tfm) { unsigned int bsize = crypto_cipher_blocksize(tfm); unsigned long alignmask = crypto_cipher_alignmask(tfm); u8 *ctrblk = walk->iv; - u8 tmp[bsize + alignmask]; - u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1); u8 *src = walk->src.virt.addr; u8 *dst = walk->dst.virt.addr; unsigned int nbytes = walk->nbytes; + DECLARE_CIPHER_BUFFER(tmp); + u8 *keystream, *tmp2; + + if (CHECK_CIPHER_BUFFER(tmp, bsize, alignmask)) + keystream = tmp; + else { + tmp2 = kmalloc(bsize + alignmask, GFP_ATOMIC); + if (!tmp2) + return -ENOMEM; + keystream = PTR_ALIGN(tmp2 + 0, alignmask + 1); + } crypto_cipher_encrypt_one(tfm, keystream, ctrblk); crypto_xor_cpy(dst, keystream, src, nbytes); crypto_inc(ctrblk, bsize); + + if (unlikely(keystream != tmp)) + kfree(tmp2); + return 0; } static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk, @@ -106,8 +129,17 @@ static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk, unsigned int nbytes = walk->nbytes; u8 *ctrblk = walk->iv; u8 *src = walk->src.virt.addr; - u8 tmp[bsize + alignmask]; - u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1); + DECLARE_CIPHER_BUFFER(tmp); + u8 *keystream, *tmp2; + + if (CHECK_CIPHER_BUFFER(tmp, bsize, alignmask)) + keystream = tmp; + else { + tmp2 = kmalloc(bsize + alignmask, GFP_ATOMIC); + if (!tmp2) + return -ENOMEM; + keystream = PTR_ALIGN(tmp2 + 0, alignmask + 1); + } do { /* create keystream */ @@ -120,6 +152,8 @@ static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk, src += bsize; } while ((nbytes -= bsize) >= bsize); + if (unlikely(keystream != tmp)) + kfree(tmp2); return nbytes; } @@ -147,8 +181,8 @@ static int crypto_ctr_crypt(struct blkcipher_desc *desc, } if (walk.nbytes) { - crypto_ctr_crypt_final(&walk, child); - err = blkcipher_walk_done(desc, &walk, 0); + err = crypto_ctr_crypt_final(&walk, child); + err = blkcipher_walk_done(desc, &walk, err); } return err; -- 1.9.1