From: Herbert Xu Subject: Re: [v4 PATCH 0/8] crypto: rsa - Do not gratuitously drop leading zeroes Date: Sun, 3 Jul 2016 10:46:11 +0800 Message-ID: <20160703024611.GA24340@gondor.apana.org.au> References: <20160622101432.GA30454@gondor.apana.org.au> <20160629102649.GA26987@gondor.apana.org.au> <20160629113125.GA27643@gondor.apana.org.au> <1997039.xp5G17Zq2C@positron.chronox.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andrzej Zaborowski , Tadeusz Struk , Linux Crypto Mailing List , Tudor Ambarus , Mat Martineau , Denis Kenzior , Salvatore Benedetto To: Stephan Mueller Return-path: Received: from helcar.hengli.com.au ([209.40.204.226]:47179 "EHLO helcar.hengli.com.au" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751993AbcGCCqk (ORCPT ); Sat, 2 Jul 2016 22:46:40 -0400 Content-Disposition: inline In-Reply-To: <1997039.xp5G17Zq2C@positron.chronox.de> Sender: linux-crypto-owner@vger.kernel.org List-ID: On Sat, Jul 02, 2016 at 07:55:59PM +0200, Stephan Mueller wrote: > > I re-tested that patch set and I still see the same issues as before, namely > that sigver does not work: Oops, somehow I conflated this problem with KPP. Does this patch fix it for you? ---8<--- Subject: crypto: rsa-pkcs1pad - Fix regression from leading zeros As the software RSA implementation now produces fixed-length output, we need to eliminate leading zeros in the calling code instead. This patch does just that for pkcs1pad signature verification. Fixes: 9b45b7bba3d2 ("crypto: rsa - Generate fixed-length output") Reported-by: Stephan Mueller Signed-off-by: Herbert Xu diff --git a/crypto/rsa-pkcs1pad.c b/crypto/rsa-pkcs1pad.c index 8ccfdd7..880d3db 100644 --- a/crypto/rsa-pkcs1pad.c +++ b/crypto/rsa-pkcs1pad.c @@ -456,49 +456,55 @@ static int pkcs1pad_verify_complete(struct akcipher_request *req, int err) struct akcipher_instance *inst = akcipher_alg_instance(tfm); struct pkcs1pad_inst_ctx *ictx = akcipher_instance_ctx(inst); const struct rsa_asn1_template *digest_info = ictx->digest_info; + unsigned int dst_len; unsigned int pos; - - if (err == -EOVERFLOW) - /* Decrypted value had no leading 0 byte */ - err = -EINVAL; + u8 *out_buf; if (err) goto done; - if (req_ctx->child_req.dst_len != ctx->key_size - 1) { - err = -EINVAL; + err = -EINVAL; + dst_len = req_ctx->child_req.dst_len; + if (dst_len < ctx->key_size - 1) goto done; + + out_buf = req_ctx->out_buf; + if (dst_len == ctx->key_size) { + if (out_buf[0] != 0x00) + /* Decrypted value had no leading 0 byte */ + goto done; + + dst_len--; + out_buf++; } err = -EBADMSG; - if (req_ctx->out_buf[0] != 0x01) + if (out_buf[0] != 0x01) goto done; - for (pos = 1; pos < req_ctx->child_req.dst_len; pos++) - if (req_ctx->out_buf[pos] != 0xff) + for (pos = 1; pos < dst_len; pos++) + if (out_buf[pos] != 0xff) break; - if (pos < 9 || pos == req_ctx->child_req.dst_len || - req_ctx->out_buf[pos] != 0x00) + if (pos < 9 || pos == dst_len || out_buf[pos] != 0x00) goto done; pos++; - if (memcmp(req_ctx->out_buf + pos, digest_info->data, - digest_info->size)) + if (memcmp(out_buf + pos, digest_info->data, digest_info->size)) goto done; pos += digest_info->size; err = 0; - if (req->dst_len < req_ctx->child_req.dst_len - pos) + if (req->dst_len < dst_len - pos) err = -EOVERFLOW; - req->dst_len = req_ctx->child_req.dst_len - pos; + req->dst_len = dst_len - pos; if (!err) sg_copy_from_buffer(req->dst, sg_nents_for_len(req->dst, req->dst_len), - req_ctx->out_buf + pos, req->dst_len); + out_buf + pos, req->dst_len); done: kzfree(req_ctx->out_buf); -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt