From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vlad Yasevich Subject: Re: [PATCH] sctp: add verification checks to SCTP_AUTH_KEY option Date: Mon, 25 Aug 2008 21:24:41 -0400 Message-ID: <48B35B59.2020208@hp.com> References: <20080825164440.GA504@kernel.sg> <12196959323990-git-send-email-vladislav.yasevich@hp.com> <48B35561.2010001@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net, netdev@vger.kernel.org, linux-sctp@vger.kernel.org, security@kernel.org To: Eugene Teo Return-path: Received: from g5t0009.atlanta.hp.com ([15.192.0.46]:26539 "EHLO g5t0009.atlanta.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752812AbYHZBYo (ORCPT ); Mon, 25 Aug 2008 21:24:44 -0400 In-Reply-To: <48B35561.2010001@redhat.com> Sender: netdev-owner@vger.kernel.org List-ID: Eugene Teo wrote: > Vlad Yasevich wrote: >> The structure used for SCTP_AUTH_KEY option contains a >> length that needs to be verfied to prevent buffer overflow >> conditions. Spoted by Eugene Teo . >> >> Signed-off-by: Vlad Yasevich >> --- >> net/sctp/auth.c | 4 ++++ >> net/sctp/socket.c | 5 +++++ >> 2 files changed, 9 insertions(+), 0 deletions(-) >> >> diff --git a/net/sctp/auth.c b/net/sctp/auth.c >> index 675a5c3..1fcb4cf 100644 >> --- a/net/sctp/auth.c >> +++ b/net/sctp/auth.c >> @@ -80,6 +80,10 @@ static struct sctp_auth_bytes *sctp_auth_create_key(__u32 key_len, gfp_t gfp) > > This should be __u16 key_len. > >> { >> struct sctp_auth_bytes *key; >> >> + /* Verify that we are not going to overflow INT_MAX */ >> + if ((INT_MAX - key_len) < sizeof(struct sctp_auth_bytes)) >> + return NULL; > > Shouldn't this be UINT_MAX? But then if you are going to change > sctp_auth_create_key() to accept __u16 key_len, then it should be > USHORT_MAX. > I'd rather keep it a u32 since this function is not only for userspace, but for creating a generated key. Yes, UINT_MAX makes more sense. >> /* Allocate the shared key */ >> key = kmalloc(sizeof(struct sctp_auth_bytes) + key_len, gfp); >> if (!key) >> diff --git a/net/sctp/socket.c b/net/sctp/socket.c >> index bb5c9ef..afa952e 100644 >> --- a/net/sctp/socket.c >> +++ b/net/sctp/socket.c >> @@ -3144,6 +3144,11 @@ static int sctp_setsockopt_auth_key(struct sock *sk, >> goto out; >> } >> >> + if (authkey->sca_keylength > optlen) { >> + ret = -EINVAL; >> + goto out; > > Is there a better upper bound check? Hm... optlen - sizeof(struct sctp_authkey) is more accurate. There is really no other bound. -vlad > >> asoc = sctp_id2assoc(sk, authkey->sca_assoc_id); >> if (!asoc && authkey->sca_assoc_id && sctp_style(sk, UDP)) { >> ret = -EINVAL; > > Thanks, > Eugene >