From: Tadeusz Struk Subject: Re: [PATCH v6 6/6] crypto: AF_ALG - add support for key_id Date: Tue, 31 May 2016 10:44:03 -0700 Message-ID: <304aa8f1-ef22-3f2d-53e5-3c020f7ceb40@intel.com> References: <20160515041645.15888.94903.stgit@tstruk-mobl1> <20160515041719.15888.27170.stgit@tstruk-mobl1> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 8bit Cc: dhowells@redhat.com, herbert@gondor.apana.org.au, smueller@chronox.de, linux-api@vger.kernel.org, marcel@holtmann.org, linux-kernel@vger.kernel.org, keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, dwmw2@infradead.org, davem@davemloft.net To: Mat Martineau Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Hi Mat, On 05/25/2016 05:45 PM, Mat Martineau wrote: > > On Sat, 14 May 2016, Tadeusz Struk wrote: > >> diff --git a/crypto/algif_akcipher.c b/crypto/algif_akcipher.c >> index e00793d..6733df1 100644 >> --- a/crypto/algif_akcipher.c >> +++ b/crypto/algif_akcipher.c >> +static int asym_key_verify(const struct key *key, struct akcipher_request *req) >> +{ >> + struct public_key_signature sig; >> + char *src = NULL, *in; >> + int ret; >> + >> + if (!sg_is_last(req->src)) { >> + src = kmalloc(req->src_len, GFP_KERNEL); >> + if (!src) >> + return -ENOMEM; >> + scatterwalk_map_and_copy(src, req->src, 0, req->src_len, 0); >> + in = src; >> + } else { >> + in = sg_virt(req->src); >> + } >> + sig.pkey_algo = "rsa"; >> + sig.encoding = "pkcs1"; >> + /* Need to find a way to pass the hash param */ > > Are you referring to sig.digest here? It looks like you will hit a BUG_ON() in public_key_verify_signature() if sig.digest is 0. However, sig.digest is unlikely to be 0 because the struct is not cleared - should fix this, since public_key_verify_signature() will try to follow that random pointer. > Right, I need to have a local buffer for the digest here. >> + sig.hash_algo = "sha1"; >> + sig.digest_size = 20; >> + sig.s_size = req->src_len; >> + sig.s = src; >> + ret = verify_signature(key, NULL, &sig); > > Is the idea to write the signature to the socket, and then read out the expected digest (the digest comparison being done elsewhere)? Is that something that will be supported by a future hardware asymmetric key subtype? After the verify operation the output will be copied to the user, and the user needs to verify it. > > verify_signature() ends up calling public_key_verify_signature(), which currently expects to get both the digest and signature as input and returns an error if verification fails. The output of crypto_akcipher_verify() is discarded before public_key_verify_signature() returns so nothing ends up in req->dst to read from the socket. > > ALG_OP_VERIFY should behave the same whether using ALG_SET_PUBKEY or ALG_SET_PUBKEY_ID, and they aren't right now. > > If sig.digest is 0, verify_signature() could return the expected digest in the sig structure and skip the digest comparison it currently does. Then that data could be packaged up in req as if crypto_akcipher_verify() had been called. I don't know if this change confuses the semantics of verify_signature() too much, maybe a new function is required with all the requisite plumbing to the asymmetric key subtype. > We need to copy output to the user to verify because we don't have it. That will be consistent for both ALG_SET_PUBKEY and ALG_SET_PUBKEY_ID. Thanks for your comments and sorry for the delayed response. I'll will send v7 soon. -- TS