Re: disable libc sys wrappers?

[Ted Unangst]

On 2020-07-09, Theo de Raadt wrote:
> > Added a -T option to ktrace for transparency. I got ambitious here and made
> > it take suboptions, anticipating that other transparency modifications may
> > be desired.
> 
> Please don't do that.

Here is a simpler version.


Index: lib/libc/dlfcn/init.c
===================================================================
RCS file: /home/cvs/src/lib/libc/dlfcn/init.c,v
retrieving revision 1.8
diff -u -p -r1.8 init.c
--- lib/libc/dlfcn/init.c       6 Jul 2020 13:33:05 -0000       1.8
+++ lib/libc/dlfcn/init.c       13 Jul 2020 17:36:04 -0000
@@ -114,6 +114,8 @@ _libc_preinit(int argc, char **argv, cha
                                    _timekeep->tk_version != TK_VERSION)
                                        _timekeep = NULL;
                        }
+                       if (issetugid() == 0 && getenv("LIBC_NOUSERTC"))
+                               _timekeep = NULL;
                        break;
                }
        }
Index: usr.bin/ktrace/ktrace.1
===================================================================
RCS file: /home/cvs/src/usr.bin/ktrace/ktrace.1,v
retrieving revision 1.30
diff -u -p -r1.30 ktrace.1
--- usr.bin/ktrace/ktrace.1     15 May 2019 15:36:59 -0000      1.30
+++ usr.bin/ktrace/ktrace.1     13 Jul 2020 17:38:22 -0000
@@ -37,13 +37,13 @@
 .Nd enable kernel process tracing
 .Sh SYNOPSIS
 .Nm ktrace
-.Op Fl aBCcdi
+.Op Fl aCcdi
 .Op Fl f Ar trfile
 .Op Fl g Ar pgid
 .Op Fl p Ar pid
 .Op Fl t Ar trstr
 .Nm ktrace
-.Op Fl adi
+.Op Fl aBdiT
 .Op Fl f Ar trfile
 .Op Fl t Ar trstr
 .Ar command
@@ -109,6 +109,8 @@ processes.
 Enable (disable) tracing on the indicated process ID (only one
 .Fl p
 flag is permitted).
+.It Fl T
+Disable userland timekeeping, making time related system calls more prevalent.
 .It Fl t Ar trstr
 Select which information to put into the dump file.
 The argument can contain one or more of the following letters.
Index: usr.bin/ktrace/ktrace.c
===================================================================
RCS file: /home/cvs/src/usr.bin/ktrace/ktrace.c,v
retrieving revision 1.36
diff -u -p -r1.36 ktrace.c
--- usr.bin/ktrace/ktrace.c     28 Jun 2019 13:35:01 -0000      1.36
+++ usr.bin/ktrace/ktrace.c     13 Jul 2020 17:37:06 -0000
@@ -100,7 +100,7 @@ main(int argc, char *argv[])
                                usage();
                        }
        } else {
-               while ((ch = getopt(argc, argv, "aBCcdf:g:ip:t:")) != -1)
+               while ((ch = getopt(argc, argv, "aBCcdf:g:ip:t:T")) != -1)
                        switch ((char)ch) {
                        case 'a':
                                append = 1;
@@ -140,6 +140,9 @@ main(int argc, char *argv[])
                                        usage();
                                }
                                break;
+                       case 'T':
+                               putenv("LIBC_NOUSERTC=");
+                               break;
                        default:
                                usage();
                        }
@@ -240,9 +243,9 @@ usage(void)
                    " [-u trspec] command\n",
                    __progname);
        else
-               fprintf(stderr, "usage: %s [-aBCcdi] [-f trfile] [-g pgid]"
+               fprintf(stderr, "usage: %s [-aCcdi] [-f trfile] [-g pgid]"
                    " [-p pid] [-t trstr]\n"
-                   "       %s [-adi] [-f trfile] [-t trstr] command\n",
+                   "       %s [-aBdiT] [-f trfile] [-t trstr] command\n",
                    __progname, __progname);
        exit(1);
 }