From: Mark D Rustad Subject: Re: [PATCH] crypto: rng.c: Cleaning up missing null-terminate in conjunction with strncpy Date: Sat, 26 Jul 2014 19:35:22 -0700 Message-ID: References: <1406384308-2269-1-git-send-email-rickard_strandqvist@spectrumdigital.se> Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: multipart/signed; boundary="Apple-Mail=_713D8B29-4C80-44BD-BC84-E5FBF798FF3D"; protocol="application/pgp-signature"; micalg=pgp-sha1 Cc: Neil Horman , Herbert Xu , "David S. Miller" , linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org To: Rickard Strandqvist Return-path: In-Reply-To: <1406384308-2269-1-git-send-email-rickard_strandqvist@spectrumdigital.se> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org --Apple-Mail=_713D8B29-4C80-44BD-BC84-E5FBF798FF3D Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii Rickard, On Jul 26, 2014, at 7:18 AM, Rickard Strandqvist = wrote: > Replacing strncpy with strlcpy to avoid strings that lacks null = terminate. >=20 > Signed-off-by: Rickard Strandqvist = > --- > crypto/rng.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) >=20 > diff --git a/crypto/rng.c b/crypto/rng.c > index e0a25c2..c3d4fb3 100644 > --- a/crypto/rng.c > +++ b/crypto/rng.c > @@ -65,7 +65,7 @@ static int crypto_rng_report(struct sk_buff *skb, = struct crypto_alg *alg) > { > struct crypto_report_rng rrng; >=20 > - strncpy(rrng.type, "rng", sizeof(rrng.type)); > + strlcpy(rrng.type, "rng", sizeof(rrng.type)); >=20 > rrng.seedsize =3D alg->cra_rng.seedsize; Not to pick on this patch in particular, but you need to be careful = about changing strncpy to strlcpy. Although strlcpy ensures termination, = it does not prevent information leakage - strncpy ensures that the = entire destination buffer is written. When leakage is a concern, it is = better to use strncpy and then to store a zero in the last location of = the buffer to ensure termination. These "simple" transformations can be risky - and many of these do not = represent any sort of problem when the source is smaller than the = destination. I hope information leakage is being considered. --=20 Mark Rustad, MRustad@gmail.com --Apple-Mail=_713D8B29-4C80-44BD-BC84-E5FBF798FF3D Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename=signature.asc Content-Type: application/pgp-signature; name=signature.asc Content-Description: Message signed with OpenPGP using GPGMail -----BEGIN PGP SIGNATURE----- Comment: GPGTools - http://gpgtools.org iQIcBAEBAgAGBQJT1GVqAAoJEDwO/+eO4+5urRYQALOCuZdPLRuvOZyVkEkzqLOE /IxV048SqzYO71GSnyD0WlVkrNZ3z9SzeuaTJOjRr4Z5jeWK29c2GlEzfE2JUtt1 goQYbvRBU3aQ/tCT460Y3XRDwiiXhsQoyIemOcoXz1IsvKidffMvYIjGamBdWeKY znjC1Ipw/jXeWHjSvnQdPh2hLA656XLrwX2vKLWsOhALPneTAGWzn4MjyposMsjc u245P8z1SY92RbwQi+PktG9/VaA2fMsfIaHj99hXoigx+sNE6EmzoISUsnNp1F1W wq0ZSrC9c+XDqxL7ivsHDtBq4u8ciCQKeTUuU85CuaCUoI/vSVKvUaEfVaesU/lL rmhd40NJLQHn3WqLcTy2PlqfKClA0QFhhKB1y7CoW7FdJ4mk3XaAc6PIyrtVsesq NKJMeeBdTQxczfvGPZUUtYsjXPf8qvkBMWJxgVnyKaCSVAxp0tVlpag4egd9t4ZT 3ZswTenZ0/yRTIDcr/05KZiMAPwyKz/aMOzwFkWSpBIJIVwBe8mxBpKxjtZW3dYX AOwxDHSaWC2wqxaeX6RWryu47GH6mV6Xf+QMss7A2+1mV/RpfT7bMeYHZ+3VteCl JKdWTslEaYnntKaKGf3iQ9302shmntgRKYqmwPYmhKZeNVEzSRvn/8TL9Z0Gaey3 5Z91eQjdsvxOV2YQkxNs =WCx+ -----END PGP SIGNATURE----- --Apple-Mail=_713D8B29-4C80-44BD-BC84-E5FBF798FF3D--