From 79be093500791cc25cc31bcaec5a4db62e21497b Mon Sep 17 00:00:00 2001 From: Casey Schaufler Date: Mon, 7 Dec 2015 14:34:32 -0800 Subject: Smack: File receive for sockets The existing file receive hook checks for access on the file inode even for UDS. This is not right, as the inode is not used by Smack to make access checks for sockets. This change checks for an appropriate access relationship between the receiving (current) process and the socket. If the process can't write to the socket's send label or the socket's receive label can't write to the process fail. This will allow the legitimate cases, where the socket sender and socket receiver can freely communicate. Only strangly set socket labels should cause a problem. Signed-off-by: Casey Schaufler --- security/smack/smack_lsm.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) (limited to 'security/smack') diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index ff81026f6ddb..b20ef0602267 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -1860,12 +1860,34 @@ static int smack_file_receive(struct file *file) int may = 0; struct smk_audit_info ad; struct inode *inode = file_inode(file); + struct socket *sock; + struct task_smack *tsp; + struct socket_smack *ssp; if (unlikely(IS_PRIVATE(inode))) return 0; smk_ad_init(&ad, __func__, LSM_AUDIT_DATA_PATH); smk_ad_setfield_u_fs_path(&ad, file->f_path); + + if (S_ISSOCK(inode->i_mode)) { + sock = SOCKET_I(inode); + ssp = sock->sk->sk_security; + tsp = current_security(); + /* + * If the receiving process can't write to the + * passed socket or if the passed socket can't + * write to the receiving process don't accept + * the passed socket. + */ + rc = smk_access(tsp->smk_task, ssp->smk_out, MAY_WRITE, &ad); + rc = smk_bu_file(file, may, rc); + if (rc < 0) + return rc; + rc = smk_access(ssp->smk_in, tsp->smk_task, MAY_WRITE, &ad); + rc = smk_bu_file(file, may, rc); + return rc; + } /* * This code relies on bitmasks. */ -- cgit v1.2.3 From 81bd0d56298f93af6ac233d8a7e8b29aa4b094b7 Mon Sep 17 00:00:00 2001 From: Roman Kubiak Date: Thu, 17 Dec 2015 13:24:35 +0100 Subject: Smack: type confusion in smak sendmsg() handler Smack security handler for sendmsg() syscall is vulnerable to type confusion issue what can allow to privilege escalation into root or cause denial of service. A malicious attacker can create socket of one type for example AF_UNIX and pass is into sendmsg() function ensuring that this is AF_INET socket. Remedy Do not trust user supplied data. Proposed fix below. Signed-off-by: Roman Kubiak Signed-off-by: Mateusz Fruba Acked-by: Casey Schaufler --- security/smack/smack_lsm.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'security/smack') diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c index b20ef0602267..0e7703773a97 100644 --- a/security/smack/smack_lsm.c +++ b/security/smack/smack_lsm.c @@ -3780,7 +3780,7 @@ static int smack_socket_sendmsg(struct socket *sock, struct msghdr *msg, if (sip == NULL) return 0; - switch (sip->sin_family) { + switch (sock->sk->sk_family) { case AF_INET: rc = smack_netlabel_send(sock->sk, sip); break; -- cgit v1.2.3