Author: jamie
Date: Wed Oct 17 16:11:43 2018
New Revision: 339409
URL: https://svnweb.freebsd.org/changeset/base/339409
Log:
Add a new jail permission, allow.read_msgbuf. When true, jailed processes
can see the dmesg buffer (this is the current behavior). When false (the
new default), dmesg will be unavailable to jailed users, whether root or
not.
The security.bsd.unprivileged_read_msgbuf sysctl still works as before,
controlling system-wide whether non-root users can see the buffer.
PR: 211580
Submitted by: bz
Approved by: re@ (kib@)
MFC after: 3 days
Modified:
head/sys/kern/kern_jail.c
head/sys/kern/kern_priv.c
head/sys/kern/subr_prf.c
head/sys/sys/jail.h
head/usr.sbin/jail/jail.8
Modified: head/sys/kern/kern_jail.c
==============================================================================
--- head/sys/kern/kern_jail.c Wed Oct 17 14:51:43 2018 (r339408)
+++ head/sys/kern/kern_jail.c Wed Oct 17 16:11:43 2018 (r339409)
@@ -193,6 +193,7 @@ static struct bool_flags pr_flag_allow[NBBY * NBPW] =
{"allow.mlock", "allow.nomlock", PR_ALLOW_MLOCK},
{"allow.reserved_ports", "allow.noreserved_ports",
PR_ALLOW_RESERVED_PORTS},
+ {"allow.read_msgbuf", "allow.noread_msgbuf", PR_ALLOW_READ_MSGBUF},
};
const size_t pr_flag_allow_size = sizeof(pr_flag_allow);
@@ -3350,6 +3351,15 @@ prison_priv_check(struct ucred *cred, int priv)
case PRIV_PROC_SETLOGINCLASS:
return (0);
+ /*
+ * Do not allow a process inside a jail read the kernel
+ * message buffer unless explicitly permitted.
+ */
+ case PRIV_MSGBUF:
+ if (cred->cr_prison->pr_allow & PR_ALLOW_READ_MSGBUF)
+ return (0);
+ return (EPERM);
+
default:
/*
* In all remaining cases, deny the privilege request. This
@@ -3770,6 +3780,8 @@ SYSCTL_JAIL_PARAM(_allow, mlock, CTLTYPE_INT | CTLFLAG
"B", "Jail may lock (unlock) physical pages in memory");
SYSCTL_JAIL_PARAM(_allow, reserved_ports, CTLTYPE_INT | CTLFLAG_RW,
"B", "Jail may bind sockets to reserved ports");
+SYSCTL_JAIL_PARAM(_allow, read_msgbuf, CTLTYPE_INT | CTLFLAG_RW,
+ "B", "Jail may read the kernel message buffer");
SYSCTL_JAIL_PARAM_SUBNODE(allow, mount, "Jail mount/unmount permission flags");
SYSCTL_JAIL_PARAM(_allow_mount, , CTLTYPE_INT | CTLFLAG_RW,
Modified: head/sys/kern/kern_priv.c
==============================================================================
--- head/sys/kern/kern_priv.c Wed Oct 17 14:51:43 2018 (r339408)
+++ head/sys/kern/kern_priv.c Wed Oct 17 16:11:43 2018 (r339409)
@@ -62,6 +62,11 @@ static int unprivileged_mlock = 1;
SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_mlock, CTLFLAG_RWTUN,
&unprivileged_mlock, 0, "Allow non-root users to call mlock(2)");
+static int unprivileged_read_msgbuf = 1;
+SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_read_msgbuf,
+ CTLFLAG_RW, &unprivileged_read_msgbuf, 0,
+ "Unprivileged processes may read the kernel message buffer");
+
SDT_PROVIDER_DEFINE(priv);
SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv__ok, "int");
SDT_PROBE_DEFINE1(priv, kernel, priv_check, priv__err, "int");
@@ -104,6 +109,17 @@ priv_check_cred(struct ucred *cred, int priv, int flag
switch (priv) {
case PRIV_VM_MLOCK:
case PRIV_VM_MUNLOCK:
+ error = 0;
+ goto out;
+ }
+ }
+
+ if (unprivileged_read_msgbuf) {
+ /*
+ * Allow an unprivileged user to read the kernel message
+ * buffer.
+ */
+ if (priv == PRIV_MSGBUF) {
error = 0;
goto out;
}
Modified: head/sys/kern/subr_prf.c
==============================================================================
--- head/sys/kern/subr_prf.c Wed Oct 17 14:51:43 2018 (r339408)
+++ head/sys/kern/subr_prf.c Wed Oct 17 16:11:43 2018 (r339409)
@@ -1053,11 +1053,6 @@ msgbufinit(void *ptr, int size)
oldp = msgbufp;
}
-static int unprivileged_read_msgbuf = 1;
-SYSCTL_INT(_security_bsd, OID_AUTO, unprivileged_read_msgbuf,
- CTLFLAG_RW, &unprivileged_read_msgbuf, 0,
- "Unprivileged processes may read the kernel message buffer");
-
/* Sysctls for accessing/clearing the msgbuf */
static int
sysctl_kern_msgbuf(SYSCTL_HANDLER_ARGS)
@@ -1066,11 +1061,9 @@ sysctl_kern_msgbuf(SYSCTL_HANDLER_ARGS)
u_int seq;
int error, len;
- if (!unprivileged_read_msgbuf) {
- error = priv_check(req->td, PRIV_MSGBUF);
- if (error)
- return (error);
- }
+ error = priv_check(req->td, PRIV_MSGBUF);
+ if (error)
+ return (error);
/* Read the whole buffer, one chunk at a time. */
mtx_lock(&msgbuf_lock);
Modified: head/sys/sys/jail.h
==============================================================================
--- head/sys/sys/jail.h Wed Oct 17 14:51:43 2018 (r339408)
+++ head/sys/sys/jail.h Wed Oct 17 16:11:43 2018 (r339409)
@@ -228,9 +228,10 @@ struct prison_racct {
#define PR_ALLOW_QUOTAS 0x00000020
#define PR_ALLOW_SOCKET_AF 0x00000040
#define PR_ALLOW_MLOCK 0x00000080
+#define PR_ALLOW_READ_MSGBUF 0x00000100
#define PR_ALLOW_RESERVED_PORTS 0x00008000
#define PR_ALLOW_KMEM_ACCESS 0x00010000 /* reserved,
not used yet */
-#define PR_ALLOW_ALL_STATIC 0x000180ff
+#define PR_ALLOW_ALL_STATIC 0x000181ff
/*
* OSD methods
Modified: head/usr.sbin/jail/jail.8
==============================================================================
--- head/usr.sbin/jail/jail.8 Wed Oct 17 14:51:43 2018 (r339408)
+++ head/usr.sbin/jail/jail.8 Wed Oct 17 16:11:43 2018 (r339409)
@@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd August 20, 2018
+.Dd October 17, 2018
.Dt JAIL 8
.Os
.Sh NAME
@@ -549,6 +549,11 @@ option.
The jail root may administer quotas on the jail's filesystem(s).
This includes filesystems that the jail may share with other jails or
with non-jailed parts of the system.
+.It Va allow.read_msgbuf
+Jailed users may read the kernel message buffer.
+If the
+.Va security.bsd.unprivileged_read_msgbuf
+MIB entry is zero, this will be restricted to to root user.
.It Va allow.socket_af
Sockets within a jail are normally restricted to IPv4, IPv6, local
(UNIX), and route. This allows access to other protocol stacks that
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