audit not catching accept call from a 64bit sshd

Thu Jan 15 20:25:21 UTC 2015

On 2015-01-15 09:25, Steve Grubb wrote:
> On Tuesday, January 13, 2015 03:16:25 PM hsultan at thefroid.net wrote:
>> Hi,
>>
>> So I'm a bit dumbfounded by what I'm seeing on my Ubuntu 14.04 
>> Server
>> LTS :
>>
>> ubuntu at ip-172-31-37-137:~/test$ sudo netstat -anop |grep sshd
>> tcp        0      0 0.0.0.0:22              0.0.0.0:*
>> LISTEN      1406/sshd        off (0.00/0/0)
>>
>> Using file I verified that it's a 64bit process :
>>
>> ubuntu at ip-172-31-37-137:~/test$ file /usr/sbin/sshd
>> /usr/sbin/sshd: ELF 64-bit LSB  shared object, x86-64, version 1
>> (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24,
>> BuildID[sha1]=00e04495db18849d9fa69d05f3626e66c6a6d4e1, stripped
>>
>> I then ran strace on it, and launched a telnet to 127.0.0.1 : 22
>>
>> ubuntu at ip-172-31-37-137:~/test$ sudo strace -p 1406
>> Process 1406 attached
>> select(7, [3 4], NULL, NULL, NULL)      = 1 (in [3])
>> accept(3, {sa_family=AF_INET, sin_port=htons(58853),
>> sin_addr=inet_addr("127.0.0.1")}, [16]) = 5
>> fcntl(5, F_GETFL)                       = 0x2 (flags O_RDWR)
>> pipe([6, 7])                            = 0
>> socketpair(PF_LOCAL, SOCK_STREAM, 0, [8, 9]) = 0
>> clone(child_stack=0,
>> flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
>> child_tidptr=0x7f95cba7db10) = 6224
>>
>> Clearly it is calling the accept system call.
>>
>> Next I look at the audit infrastructure to see what it gives me :
>> ubuntu at ip-172-31-37-137:~/test$ sudo auditctl -l
>> LIST_RULES: exit,always arch=3221225534 (0xc000003e)
>> syscall=accept,accept4
>>
>> Then I use my own tool to catch every msg from the netlink (using
>> audit_get_reply) port and display each and every msg that has a 
>> struct
>> audit_reply->len > 0 , as well as audit msgs from 
>> netfilter/conntrack.
>> Just to make sure that my audit code/settings are correct, I launch 
>> a
>> telnet to port 22, and another one to port 631 (cups), and here's 
>> what I
>> see :
>>
>> audit(1421190014.387:45784): audit_enabled=1 old=1 auid=1000 ses=16
>> res=1
>>      [NEW] tcp      6 120 SYN_SENT src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 [UNREPLIED] src=127.0.0.1 dst=127.0.0.1 
>> sport=22
>> dport=58860
>>   [UPDATE] tcp      6 60 SYN_RECV src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 src=127.0.0.1 dst=127.0.0.1 sport=22 
>> dport=58860
>>   [UPDATE] tcp      6 432000 ESTABLISHED src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 src=127.0.0.1 dst=127.0.0.1 sport=22 
>> dport=58860
>> [ASSURED]
>>   [UPDATE] tcp      6 120 FIN_WAIT src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 src=127.0.0.1 dst=127.0.0.1 sport=22 
>> dport=58860
>> [ASSURED]
>>   [UPDATE] tcp      6 30 LAST_ACK src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 src=127.0.0.1 dst=127.0.0.1 sport=22 
>> dport=58860
>> [ASSURED]
>>   [UPDATE] tcp      6 120 TIME_WAIT src=127.0.0.1 dst=127.0.0.1
>> sport=58860 dport=22 src=127.0.0.1 dst=127.0.0.1 sport=22 
>> dport=58860
>> [ASSURED]
>>      [NEW] tcp      6 120 SYN_SENT src=127.0.0.1 dst=127.0.0.1
>> sport=40478 dport=6031 [UNREPLIED] src=127.0.0.1 dst=127.0.0.1
>> sport=6031 dport=40478
>> [DESTROY] tcp      6 src=127.0.0.1 dst=127.0.0.1 sport=40478 
>> dport=6031
>> [UNREPLIED] src=127.0.0.1 dst=127.0.0.1 sport=6031 dport=40478
>>      [NEW] tcp      6 120 SYN_SENT src=127.0.0.1 dst=127.0.0.1
>> sport=36764 dport=631 [UNREPLIED] src=127.0.0.1 dst=127.0.0.1 
>> sport=631
>> dport=36764
>>   [UPDATE] tcp      6 60 SYN_RECV src=127.0.0.1 dst=127.0.0.1
>> sport=36764 dport=631 src=127.0.0.1 dst=127.0.0.1 sport=631 
>> dport=36764
>>   [UPDATE] tcp      6 432000 ESTABLISHED src=127.0.0.1 dst=127.0.0.1
>> sport=36764 dport=631 src=127.0.0.1 dst=127.0.0.1 sport=631 
>> dport=36764
>> [ASSURED]
>> audit(1421190031.663:45785): arch=c000003e syscall=43 success=yes
>> exit=15 a0=b a1=7f84aee66f7c a2=7fff960572fc a3=7f84ad2b67b8 items=0
>> ppid=1 pid=22048 auid=4294967295 uid=0 gid=0 euid=0 suid=0 fsuid=0
>> egid=0 sgid=0 fsgid=0 tty=(none) ses=4294967295 comm="cupsd"
>> exe="/usr/sbin/cupsd" key=(null)
>> audit(1421190031.663:45785): saddr=02008F9C7F0000010000000000000000
>> audit(1421190031.663:45785):
>>
>> I never see the accept call for sshd ... even though connection is
>> established, but I see the one for cups. The machine is pretty much
>> idle, so there should be no msgs dropped.
>>
>> Any idea what could be the reason ? I just can't see what I could be
>> doing wrong here.
>
> Make sure you have both a 32 and 64 bit rule. That's all I can think 
> of. Also,
> check to see if you have audit=1 on your kernel boot parameters. 
> There is a
> chance that sshd is starting before auditd and then its marked 
> inauditable.
> But, it works fine on my system.

Thanks that did it, not sure how I missed that, should have been 
obvious :(

Hassan