セキュリティ
前回はシステムコールをフックしてsshのパスワード入力のようすをモニタリングするというサンプロを取り上げました。今回はそれをさらに進めて、
次のスクリプトがそれを実施するためのスクリプトです
#!/bin/sh
##############################
# --- Process Arguments ---
#
opt_pid=0; opt_uid=0; opt_time=0; opt_timestr=0; opt_quiet=0; opt_debug=0
filter=0; pid=0; uid=0
while getopts dhp:qsu:v name
do
case $name in
d) opt_debug=1 ;;
p) opt_pid=1; pid=$OPTARG ;;
q) opt_quiet=1 ;;
s) opt_time=1 ;;
u) opt_uid=1; uid=$OPTARG ;;
v) opt_timestr=1 ;;
h|?) cat <<-END >&2
USAGE: shellsnoop [-hqsv] [-p PID] [-u UID]
shellsnoop # default output
-q # quiet, only print data
-s # include start time, us
-v # include start time, string
-p PID # process ID to snoop
-u UID # user ID to snoop
END
exit 1
esac
done
if [ $opt_quiet -eq 1 ]; then
opt_time=0; opt_timestr=0
fi
if [ $opt_pid -eq 1 -o $opt_uid -eq 1 ]; then
filter=1
fi
#################################
# --- Main Program, DTrace ---
#
dtrace -n '
/*
* Command line arguments
*/
inline int OPT_debug = '$opt_debug';
inline int OPT_quiet = '$opt_quiet';
inline int OPT_pid = '$opt_pid';
inline int OPT_uid = '$opt_uid';
inline int OPT_time = '$opt_time';
inline int OPT_timestr = '$opt_timestr';
inline int FILTER = '$filter';
inline int PID = '$pid';
inline int UID = '$uid';
#pragma D option quiet
#pragma D option switchrate=20hz
/*
* Print header
*/
dtrace:::BEGIN /OPT_time == 1/
{
printf("%-14s ","TIME");
}
dtrace:::BEGIN /OPT_timestr == 1/
{
printf("%-20s ","STRTIME");
}
dtrace:::BEGIN /OPT_quiet == 0/
{
printf("%5s %5s %8s %3s %s\n", "PID", "PPID", "CMD", "DIR", "TEXT");
}
/*
* Remember this PID is a shell child
*/
syscall::execve:entry
/execname == "sh" || execname == "ksh" || execname == "csh" ||
execname == "tcsh" || execname == "zsh" || execname == "bash"/
{
child[pid] = 1;
}
syscall::execve:entry
/(OPT_pid == 1 && PID != ppid) || (OPT_uid == 1 && UID != uid)/
{
/* forget if filtered */
child[pid] = 0;
}
/*
* Print shell keystrokes
*/
syscall::write:entry, syscall::read:entry
/(execname == "sh" || execname == "ksh" || execname == "csh" ||
execname == "tcsh" || execname == "zsh" || execname == "bash")
&& (arg0 >= 0 && arg0 <= 2)/
{
self->buf = arg1;
}
syscall::write:entry, syscall::read:entry
/(OPT_pid == 1 && PID != pid) || (OPT_uid == 1 && UID != uid)/
{
self->buf = 0;
}
syscall::write:return, syscall::read:return
/self->buf && child[pid] == 0 && OPT_time == 1/
{
printf("%-14d ", timestamp/1000);
}
syscall::write:return, syscall::read:return
/self->buf && child[pid] == 0 && OPT_timestr == 1/
{
printf("%-20Y ", walltimestamp);
}
syscall::write:return, syscall::read:return
/self->buf && child[pid] == 0 && OPT_quiet == 0/
{
this->text = (char *)copyin(self->buf, arg0);
this->text[arg0] = '\'\\0\'';
printf("%5d %5d %8s %3s %s\n", pid, curpsinfo->pr_ppid, execname,
probefunc == "read" ? "R" : "W", stringof(this->text));
}
syscall::write:return
/self->buf && child[pid] == 0 && OPT_quiet == 1/
{
this->text = (char *)copyin(self->buf, arg0);
this->text[arg0] = '\'\\0\'';
printf("%s", stringof(this->text));
}
syscall::read:return
/self->buf && execname == "sh" && child[pid] == 0 && OPT_quiet == 1/
{
this->text = (char *)copyin(self->buf, arg0);
this->text[arg0] = '\'\\0\'';
printf("%s", stringof(this->text));
}
syscall::write:return, syscall::read:return
/self->buf && child[pid] == 0/
{
self->buf = 0;
}
/*
* Print command output
*/
syscall::write:entry, syscall::read:entry
/child[pid] == 1 && (arg0 == 1 || arg0 == 2)/
{
self->buf = arg1;
}
syscall::write:return, syscall::read:return
/self->buf && OPT_time == 1/
{
printf("%-14d ", timestamp/1000);
}
syscall::write:return, syscall::read:return
/self->buf && OPT_timestr == 1/
{
printf("%-20Y ", walltimestamp);
}
syscall::write:return, syscall::read:return
/self->buf && OPT_quiet == 0/
{
this->text = (char *)copyin(self->buf, arg0);
this->text[arg0] = '\'\\0\'';
printf("%5d %5d %8s %3s %s", pid, curpsinfo->pr_ppid, execname,
probefunc == "read" ? "R" : "W", stringof(this->text));
/* here we check if a newline is needed */
this->length = strlen(this->text);
printf("%s", this->text[this->length - 1] == '\'\\n\'' ? "" : "\n");
self->buf = 0;
}
syscall::write:return, syscall::read:return
/self->buf && OPT_quiet == 1/
{
this->text = (char *)copyin(self->buf, arg0);
this->text[arg0] = '\'\\0\'';
printf("%s", stringof(this->text));
self->buf = 0;
}
/*
* Cleanup
*/
syscall::exit:entry
{
child[pid] = 0;
}
'実行すると次のような結果が得られます。新しくシェル
% sudo ./shellsnoop PID PPID CMD DIR TEXT 14843 757 sh W $ 14843 757 sh R d 14843 757 sh W d 14843 757 sh R a 14843 757 sh W a 14843 757 sh R t 14843 757 sh W t 14843 757 sh R e 14843 757 sh W e 14843 757 sh R 14843 757 sh W 14844 14843 date W Mon Mar 13 17:50:13 JST 2017 14843 757 sh W $ 14843 757 sh R c 14843 757 sh W c 14843 757 sh R a 14843 757 sh W a 14843 757 sh R l 14843 757 sh W l 14843 757 sh R 14843 757 sh W 14845 14843 cal W March 2017 14845 14843 cal W Su Mo Tu We Th Fr Sa 14845 14843 cal W 1 2 3 4 14845 14843 cal W 5 6 7 8 9 10 11 14845 14843 cal W 12 13 14 15 16 17 18 14845 14843 cal W 19 20 21 22 23 24 25 14845 14843 cal W 26 27 28 29 30 31 14845 14843 cal W 14843 757 sh W $ 14843 757 sh R l 14843 757 sh W l 14843 757 sh R s 14843 757 sh W s 14843 757 sh R 14843 757 sh W 14846 14843 ls W FREEBSD-20170306.tgz sources typescript.txt 14846 14843 ls W Makefile typescript.gh typescript.xml 14846 14843 ls W commands typescript.html 14843 757 sh W $ 14847 9165 bash W [daichi@virt ~/Documents/lwt/20170313]$ 14847 9165 bash R p 14847 9165 bash W p 14847 9165 bash R w 14847 9165 bash W w 14847 9165 bash R d 14847 9165 bash W d 14847 9165 bash R 14847 9165 bash W 14847 9165 bash W /Users/daichi/Documents/lwt/20170313 14847 9165 bash W [daichi@virt ~/Documents/lwt/20170313]$ 14847 9165 bash R a 14847 9165 bash W a 14847 9165 bash R 14847 9165 bash W 14847 9165 bash R c 14847 9165 bash W c 14847 9165 bash R a 14847 9165 bash W a 14847 9165 bash R l 14847 9165 bash W l 14847 9165 bash R 14847 9165 bash W 14848 14847 cal W March 2017 14848 14847 cal W Su Mo Tu We Th Fr Sa 14848 14847 cal W 1 2 3 4 14848 14847 cal W 5 6 7 8 9 10 11 14848 14847 cal W 12 13 14 15 16 17 18 14848 14847 cal W 19 20 21 22 23 24 25 14848 14847 cal W 26 27 28 29 30 31 14848 14847 cal W 14847 9165 bash W [daichi@virt ~/Documents/lwt/20170313]$ 14847 9165 bash R q 14847 9165 bash W q 14847 9165 bash R u 14847 9165 bash W u 14847 9165 bash R i 14847 9165 bash W i 14847 9165 bash R t 14847 9165 bash W t 14847 9165 bash R 14847 9165 bash W 14849 14847 bash W bash: quit: command not found 14847 9165 bash W [daichi@virt ~/Documents/lwt/20170313]$ 14847 9165 bash R e 14847 9165 bash W e 14847 9165 bash R x 14847 9165 bash W x 14847 9165 bash R i 14847 9165 bash W i 14847 9165 bash R t 14847 9165 bash W t 14847 9165 bash R 14847 9165 bash W 14847 9165 bash W exit 14843 757 sh R e 14843 757 sh W e 14843 757 sh R x 14843 757 sh W x 14843 757 sh R i 14843 757 sh W i 14843 757 sh R t 14843 757 sh W t 14843 757 sh R 14843 757 sh W ^C %
このサイズのスクリプトになってくるとぱっと見で何をしているか理解するのはちょっと手間取りますが、
※ ここに掲載したサンプルスクリプトは"DTrace Dynamic Tracing In Oracle Solaris, Mac OS X & FreeBSD", by Brendan Gregg and Jim Mauro P.
勉強会
第61回 3月23日（木）19:00～FreeBSD勉強会：リキャップ・ザ・AsiaBSDCon 2017 ～日本語でふりかえるABC～
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