[src/trunk]: src/sbin/dmesg Use new KERN_MSGBUF sysctl if running on a live k...

[simonb <simonb%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/3d470026777f
branches:  trunk
changeset: 487964:3d470026777f
user:      simonb <simonb%NetBSD.org@localhost>
date:      Fri Jun 16 00:20:23 2000 +0000

description:
Use new KERN_MSGBUF sysctl if running on a live kernel, and remove
setgid kmem bit from executable.

diffstat:

 sbin/dmesg/dmesg.c |  98 +++++++++++++++++++++++++++++++++--------------------
 1 files changed, 61 insertions(+), 37 deletions(-)

diffs (140 lines):

diff -r 2c04d86b1b52 -r 3d470026777f sbin/dmesg/dmesg.c
--- a/sbin/dmesg/dmesg.c        Fri Jun 16 00:18:09 2000 +0000
+++ b/sbin/dmesg/dmesg.c        Fri Jun 16 00:20:23 2000 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: dmesg.c,v 1.16 1998/07/05 08:56:54 mrg Exp $   */
+/*     $NetBSD: dmesg.c,v 1.17 2000/06/16 00:20:23 simonb Exp $        */
 /*-
  * Copyright (c) 1991, 1993
  *     The Regents of the University of California.  All rights reserved.
@@ -42,11 +42,13 @@
 #if 0
 static char sccsid[] = "@(#)dmesg.c    8.1 (Berkeley) 6/5/93";
 #else
-__RCSID("$NetBSD: dmesg.c,v 1.16 1998/07/05 08:56:54 mrg Exp $");
+__RCSID("$NetBSD: dmesg.c,v 1.17 2000/06/16 00:20:23 simonb Exp $");
 #endif
 #endif /* not lint */
 
+#include <sys/param.h>
 #include <sys/msgbuf.h>
+#include <sys/sysctl.h>
 
 #include <err.h>
 #include <fcntl.h>
@@ -54,7 +56,9 @@
 #include <limits.h>
 #include <nlist.h>
 #include <stdio.h>
+#include <stddef.h>
 #include <stdlib.h>
+#include <string.h>
 #include <time.h>
 #include <unistd.h>
 #include <vis.h>
@@ -76,11 +80,9 @@
        int argc;
        char *argv[];
 {
+       struct kern_msgbuf cur;
        int ch, newl, skip, i;
-       char *p;
-       struct kern_msgbuf *bufp, cur;
-       char *memf, *nlistf, *bufdata;
-       kvm_t *kd;
+       char *p, *memf, *nlistf, *bufdata;
        char buf[5];
 
        memf = nlistf = NULL;
@@ -99,38 +101,60 @@
        argc -= optind;
        argv += optind;
 
-       /*
-        * Discard setgid privileges if not the running kernel so that bad
-        * guys can't print interesting stuff from kernel memory.
-        */
-       if (memf != NULL || nlistf != NULL)
-               setgid(getgid());
+       if (memf == NULL && nlistf == NULL) {
+               size_t size;
+               int mib[2];
+
+               mib[0] = CTL_KERN;
+               mib[1] = KERN_MSGBUF;
+
+               if (sysctl(mib, 2, NULL, &size, NULL, 0) == -1)
+                       errx(1, "can't get size of msgbuf");
+
+               if ((bufdata = malloc(size)) == NULL)
+                       err(1, "couldn't allocate space for buffer data");
+
+               if (sysctl(mib, 2, bufdata, &size, NULL, 0) == -1)
+                       err(1, "can't get msgbuf");
+
+               /* make a dummy struct msgbuf for the display logic */
+               cur.msg_bufx =  cur.msg_bufs = size;
+       } else {
+               kvm_t *kd;
+               struct kern_msgbuf *bufp;
 
-       /* Read in message buffer header and data, and do sanity checks. */
-       if ((kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg")) == NULL)
-               exit (1);
-       setgid(getgid());       /* do now anyway */
-       if (kvm_nlist(kd, nl) == -1)
-               errx(1, "kvm_nlist: %s", kvm_geterr(kd));
-       if (nl[X_MSGBUF].n_type == 0)
-               errx(1, "%s: msgbufp not found", nlistf ? nlistf : "namelist");
-       if (KREAD(nl[X_MSGBUF].n_value, bufp))
-               errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
-                   nl[X_MSGBUF].n_value);
-       if (KREAD((long)bufp, cur))
-               errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
-                   (unsigned long)bufp);
-       if (cur.msg_magic != MSG_MAGIC)
-               errx(1, "magic number incorrect");
-       bufdata = malloc(cur.msg_bufs);
-       if (bufdata == NULL)
-               errx(1, "couldn't allocate space for buffer data");
-       if (kvm_read(kd, (long)&bufp->msg_bufc, bufdata,
-           cur.msg_bufs) != cur.msg_bufs)
-               errx(1, "kvm_read: %s", kvm_geterr(kd));
-       kvm_close(kd);
-       if (cur.msg_bufx >= cur.msg_bufs)
-               cur.msg_bufx = 0;
+               /*
+                * Read in message buffer header and data, and do sanity
+                * checks.
+                */
+               kd = kvm_open(nlistf, memf, NULL, O_RDONLY, "dmesg");
+               if (kd == NULL)
+                       exit (1);
+               if (kvm_nlist(kd, nl) == -1)
+                       errx(1, "kvm_nlist: %s", kvm_geterr(kd));
+               if (nl[X_MSGBUF].n_type == 0)
+                       errx(1, "%s: msgbufp not found", nlistf ? nlistf :
+                           "namelist");
+               if (KREAD(nl[X_MSGBUF].n_value, bufp))
+                       errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
+                           nl[X_MSGBUF].n_value);
+               if (kvm_read(kd, (long)bufp, &cur,
+                   offsetof(struct kern_msgbuf, msg_bufc)) !=
+                   offsetof(struct kern_msgbuf, msg_bufc))
+                       errx(1, "kvm_read: %s (0x%lx)", kvm_geterr(kd),
+                           (unsigned long)bufp);
+               if (cur.msg_magic != MSG_MAGIC)
+                       errx(1, "magic number incorrect");
+               bufdata = malloc(cur.msg_bufs);
+               if (bufdata == NULL)
+                       errx(1, "couldn't allocate space for buffer data");
+               if (kvm_read(kd, (long)&bufp->msg_bufc, bufdata,
+                   cur.msg_bufs) != cur.msg_bufs)
+                       errx(1, "kvm_read: %s", kvm_geterr(kd));
+               kvm_close(kd);
+               if (cur.msg_bufx >= cur.msg_bufs)
+                       cur.msg_bufx = 0;
+       }
 
        /*
         * The message buffer is circular; start at the write pointer